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Ultimate Audio Playback => Chatter and forum related stuff => Topic started by: manisandher on September 16, 2013, 10:07:03 pm



Title: Trying to eliminate noise totally
Post by: manisandher on September 16, 2013, 10:07:03 pm
I didn't know where to put this, so thought I'd just place it in a new thread.

OK, I bought a new amp today. Yeah, my wife is ecstatic - I already have the BD-Design monos, the Sauermann monos, the Berning 300B and the Sanders Magtech... and now I go ahead and buy another 'expensive' amp. She's totally ecstatic. The only reason I'm still alive is because I promised I would sell at least one of my other amps. (Anyone looking for one?)

So why did I do it? Well, it's an amp that I've wanted for a while. It's another valve amp. It's a Tube Distinctions Soul 15 - a 15wpc single-ended amp with an ultra-wide bandwidth solid-state driver stage (>MHz, slew rate >600V/Ás) and a single KT88 output valve per channel. Overall bandwidth is 7Hz-150KHz +/- 0dB. Yep that's correct, totally flat. Actually, the bandwidth has been limited by the designer because the amp is prone to picking up radio stations otherwise.

Unlike the Berning SET, the Soul 15 is a floating design - signal ground is NOT connected to PE.

But I've got a noise issue. With my 115dB/w horns, there is noise (just) audible from the listening chair. There's a little bit more noise than when using the BD-Design or Sauermann amps, both of which use balanced connections. Rather than being upset, I see this as a great opportunity to try to eliminate noise totally from my system.

I've identified a couple of things that affect the noise massively:

1. If I disconnect just one RCA cable (from NOS1 to amp), the noise virtually vanishes.

2. If I disconnect both RCA cables, the noise really does vanish. Nada, nothing, even with my ear inside the horn!

These two data points suggest to me that the amp itself is very quiet. (Remember, this is a single-ended valve amp driving 115dB horns!) But something happens when connected to the NOS1. The amp designer believes there is some sort of ground loop being generated in the NOS1 between the left and right channels, and hence why the noise is almost totally eliminated when just one RCA cable is disconnected.

I've tried my other NOS1 and both generate pretty much the same amount of noise.

Anyone have any ideas as to what I could try to eliminate this noise? Any help would be much appreciated.

(In case it helps, I'm using a 'regular' USB cable. I've also tried another PC with a 1m 'regular' USB cable, and the noise is pretty much identical.)

Cheers, Mani.


Title: Re: Trying to eliminate noise totally
Post by: CoenP on September 16, 2013, 10:20:32 pm
Hi mani,

Your nr1 observation indeed points to a (ground) loopproblem between left and right channel.

This is about the internals of the NOS1, I guess Peter will jump in soon.

Dit you try to redo the offset of the NOS1?

Regards, Coen


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 16, 2013, 10:45:31 pm
Hi Coen, thanks for your thoughts. I'll liaise with Peter and see what we come up.

Cheers, Mani.

PS. Are you familiar with Tube Distinctions? The designer, Anthony Matthews, worked with Tom Evans for a while, and apparently is the real mastermind behind the Linear A/B amps (along with another guy called Peter Chappell).


Title: Re: Trying to eliminate noise totally
Post by: CoenP on September 16, 2013, 11:32:34 pm
Before I forget: a loop needs to be closed so there must be a connection between left and right channels in the (new) amp too.

So this can't be solved without the complete picture including the connections in your amp.


Regards, Coen

P.s. i am not familiar with the brand. I'll look into it.
[ edit i removed a useless sentence]


Title: Re: Trying to eliminate noise totally
Post by: Scroobius on September 17, 2013, 08:29:25 am
Hi Mani - just to say that my experience was that I had to separate the left and right channel grounds in my GC amplifier to get low noise levels. With them connected there was a lot of noise. Not sure if you said that yours were connected or not inside your amp.

Paul


Title: Re: Trying to eliminate noise totally
Post by: PeterSt on September 17, 2013, 09:12:17 am
Mani, ignorant me here :

Your GC should not produce noise, and your Sauermann shouldn't either. This has been talked through before.
Careful about the "shouldn't" because I obviously did not have those both physical same amp sets here. But the same for their design, yes.

To me this tells that you have a general other problem *first*, no matter you can't find/solve it.
Of course this does not prove that this other problem is playing a role here, but it can.

Peter


Title: Re: Trying to eliminate noise totally
Post by: PeterSt on September 17, 2013, 09:40:26 am
This is about the internals of the NOS1, I guess Peter will jump in soon.

Ok, not that soon, but now I'll give it a try.

Quote
Dit you try to redo the offset of the NOS1?

So, what about this ? Anything changed ?

Apart from that, yea, blame the poor NOS1. But I don't see how that could happen with the NOS1 as the cause. I think it will or can be related though ...

Signal ground is "obviously" connected in the NOS1 for both channels. This is because ground is created from the differential setup. Call that floating, but with an absolute 0V point.
Now, nothing tells that the same happens at the other end, especially not with the design of that amplifier. Well, if I judge correctly of course;

So, floating ground. Ok, but what is the ground reference then, and how is it created ? It's not a differential design as far as I can tell from this distance (I didn't look up specs or anything), so, floating yes, but absolute 0V how ?
Besides this, anything with a gnd and plus will lift the gnd somewhat. So, even when intended as 0V it will be somewhat higher. At least that is what I think.

Side note : I ever saw it happening anywhere that the DC Offset as measuered in the NOS1 changes. So, as you know yourself, we measure it here and I ask every customer to "get close to that", and all come up with the exact same (but give it a few 0.1mV difference which already happens because of longer warming up; we usually don't give it that much time.).

So, midpoint creation within the NOS1 is stronger than what the other side implies inherently. This is prone to groundloops maybe. But "in" the other side (I think).
And thus my cautious conclusion is that the groundloop emerges inside you amp.
(hey, I must blame something, right ? :))

What I would try first, and now assuming that both channels inside the amp are separated for their floating ground (hard to imagine, but I think it can exist) is connecting the input gnds of the amp by means of a short wire (like 10cm between the both input terminals). If normal RCA you can just use the outside of the connector, assumed they are metal. But check with a multimeter whether both ends are connected through this means. Anyway, you'll find your way.

Alternatively you can do this on the NOS1's side (but I don't think that will help).
Or both sides.

When this helps, it is again my cautious conclusion that both generated grounds in the amp are not equal;
When this can be proven (or admitted by the manufacturer), "we" can consider whether the now noise free solution is the solution at all. Thus, better make those channels equal ?

What you can also try (when the above does not help) is applying a separate ground wire (per channel) of thicker gauge and of shorter length than the interlinks. Can't make a difference ? suprise yourself. Well, hopefully.
So, apply these in parallel over the interlinks. Again connecting them to the outside of the interlink connectors would be the most easy, but they must be connected to the gnd wire in the cable again.

Let us know what happens ...
Peter

PS: Advice of another kind : stop buying amps and keep your wife.




Title: Re: Trying to eliminate noise totally
Post by: Leo on September 17, 2013, 10:07:27 am
Well up to now he has been buying some great amps.... :)


Title: Re: Trying to eliminate noise totally
Post by: CoenP on September 17, 2013, 10:49:28 am
I think you amp has only one powersupply. Signal grounds of both channels should come together there.

Next to the experiments Peter suggested, I propose to look into screening of the amp and cable. If the amp is floating wrt the chassis, you can ground the chassis and strongly reduce the influence of outside EM inside the box. Same thing for the interlinks (did you experiment with different ones?).

If this doesn't bring relief the noise source is likely inside one of the boxes. Probably some oscillation as result of parasytics (unintentional inductance and capacitance) in the loop.

Regards, Coen


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 17, 2013, 03:00:29 pm
Thanks for all the ideas guys.

To start off with, I've just checked the NOS1's meters and they read -5.0mV and -0.5mV respectively. Is a relative offset of 4.5mV acceptable? I guess it is. (I can't remember what the respective values were when I received the upgraded NOS1 back from Peter.)

The other thing that I've noticed is that the power transformer of the amp is humming. According to the designer, this simply should not happen - it's dead quiet at his place. And furthermore, the noise coming out of the speakers is identical in quality to the sound of the transformer!

I'm going to proceed with the hypothesis that the humming transformer is cause of the noise through the speakers and will try a few things to see if I can reduce the humming. The main suspect right now is my dedicated mains rings with its two 5KVA balanced transformers. I'll try feeding everything off the house mains and see what happens.

Incidentally, the power supplies of Bert's amps hum loudly also. But the Sauermann and Sanders amp PSs don't. The Berning has a switch-mode PS which makes no audible noise, even with your ear close up. Yet the noise from the speakers even with the Berning is uncannily similar to that from the Soul amp that I'm currently using.

Thanks again for all your thoughts. If this post triggers some more, I'd love to hear.

Mani.


Title: Re: Trying to eliminate noise totally
Post by: CoenP on September 17, 2013, 03:14:30 pm
Haven't we heard this all before?

I think your PC PSU is prime suspect of creating DC on the mains.

Did you allready pull the plug of the PC out of the powerbar? Is there still noise?

With a couple of HV diodes and some caps you can create a "DC blocker" (google for that). Some brands using big toroids (which are very susceptible to DC) have those on board.

regards, Coen


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 17, 2013, 03:37:10 pm
Coen, I think things are a bit more complicated...

With everything running off the house mains, the noise is still exactly the same. And here I'm using my the other music PC from my office (totally different PSU, and absolutely no noise in my office system, even with preamp at full gain and ear next to Genelecs).

I've tried a Kemp DC blocker too and it makes absolutely zero difference.

Next on my list is to bring in my Sanders amp in and see what happens. Noise is quoted as 'More than 110dB below rated output'. The Sanders is the only amp I have with both RCA and XLR inputs, so might prove interesting.

Mani.


Title: Re: Trying to eliminate noise totally
Post by: CoenP on September 17, 2013, 03:53:16 pm
Ok,

Having more than one amp makes perfect sense now!

So: All transformers humming on an isolated mains supply and not on the normal mains..... How does the isolation xformer sound, does it ham/rattle too?

Regards, Coen


Title: Re: Trying to eliminate noise totally
Post by: Nick on September 17, 2013, 04:05:22 pm
Mani hi,

I remember reading superb reviews of the Soul amplifier in HiFi+ a few years ago. Have to say I really liked the ideas behind the amp design, IIRC it has number of very high performance power supplies for vairious roles in the amp.

Definatly on my list of amps to try after a lottery win  ;)

Nick.


Title: Re: Trying to eliminate noise totally
Post by: CoenP on September 17, 2013, 04:56:24 pm
Coen, I think things are a bit more complicated...

With everything running off the house mains, the noise is still exactly the same. And here I'm using my the other music PC from my office (totally different PSU, and absolutely no noise in my office system, even with preamp at full gain and ear next to Genelecs).

I've tried a Kemp DC blocker too and it makes absolutely zero difference.

I may have misread your post.

So your regular office system (at a different location?) is dead silent. If you move that pc to the "gand room" and put everything on the mains, you do have noise. Probably all amps are dead silent with shorted inputs (nothing but the speakers connected) or do the powertransformers hum?

This PSU humming could very well be the cause of the groundloop noise since the left and right channels are likely to be connected together in the vicinity of the magnetic fields (either from the x-former or psu caps).

Is your main rigs ring circuit braker connection ok?

Regards, Coen


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 17, 2013, 05:02:06 pm
A quick update...

Right, just tried the Sanders Magtech and the Sauermann monos, and...

Run off house mains

Sanders power supply dead quiet (low bias class AB amp, with little load at idle). There's only the slightest bit of hiss coming from the horns, and absolutely no other noise of any character - with ear 1m or so from horn. My feeling is that a little hiss from 115dB horns at 1m is acceptable. (Perhaps Peter's/Bert's horns have this too, but they're both just too old to hear it!) RCA or XLR makes no difference.

Sauermann supply has slight hum when ear pressed against PS (class A mono amps, each PS drawing ~250W at idle). A little more hiss through speakers than Sanders amp, but maybe this is down to perhaps extra gain (not sure).

Run off dedicated hifi circuit

Exactly as above. Absolutely no difference whatsoever! Phew!

*************************

So, there maybe something up with my new amp and it'll be going back to its maker, Anthony Matthews, tomorrow. I say 'new' but it's actually 9 years old now. Apparently, it's been sitting in storage for most of these 9 years and perhaps some things are just resettling on its re-exposure to prolonged active service. Anthony will give it a thorough going over and we'll proceed from there (see next post).

Mani.


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 17, 2013, 05:16:09 pm
I remember reading superb reviews of the Soul amplifier in HiFi+ a few years ago. Have to say I really liked the ideas behind the amp design, IIRC it has number of very high performance power supplies for vairious roles in the amp.

I really, really hope Anthony can find something amiss and get the Soul working acceptably with my horns. I have to say that hearing the Soul in my system, even with the noise issue (which quite frankly wouldn't be an issue at all on 99.9% of systems) I don't want to have any other amp in my system. Not the Sauermann, not the BD-Design, not the Sanders... OK, maybe the Berning if I had to (it comes pretty close). And this is absolutely no judgement on these other amps - they're all great. But to my ears, they don't have the 'magic' that the Soul (and to a lesser degree the Berning) has. For me, at least, it's going to be single-ended valve amps and horn speakers for ever from now on. If the Soul comes good, it may be a keeper for life. As for speakers... I'll definitely be buying a new pair next year.

Nick, if the Soul does come back 'fixed' (I hope and pray) you're welcome to take a listen. I think it'll be well worth your while. But maybe hold off until I get the new speakers sorted out. There are currently three on my radar - Bert's new Orelinos, the Tune Animas and a bespoke pair of horns (which I'd rather not disclose anything about right now). I'm taking a listen to the Animas tomorrow and have really high hopes - they're exactly the sort of design that sits well with me.

Mani.


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 17, 2013, 05:23:32 pm
Probably all amps are dead silent with shorted inputs (nothing but the speakers connected) or do the powertransformers hum?

This PSU humming could very well be the cause of the groundloop noise since the left and right channels are likely to be connected together in the vicinity of the magnetic fields (either from the x-former or psu caps).

Yep, this may well be the issue. The thing is though that with the Berning there's also a similar noise profile coming from the speakers.. but of course no audible PSU noise, as it's an SMPS. Maybe they're two totally unrelated issues that just manifest themselves in similar symptoms?

Is your main rigs ring circuit braker connection ok?

Hmmm, I think so. If it weren't, wouldn't I expect more issues with my other big PSU amps like the Sauermanns? (Although of course these have totally separate PSUs.)

Mani.


Title: Re: Trying to eliminate noise totally
Post by: Scroobius on September 18, 2013, 09:00:05 am
Hey Mani - just managed to get a quiet few moments this morning to read about the Soul amp. I had not come across it before and I have to say it looks very interesting indeed. I hope the noise problem gets sorted I would be very interested to hear it sometime.

Cheers

Paul


Title: Re: Trying to eliminate noise totally
Post by: PeterSt on September 18, 2013, 09:50:51 am
Hi Mani,

In the other topic - the one where you put up a drawing from your mains situation and earthing - I asked you to measure the DC offset of (by now whatever) ring. I don't think you understood that (because as far as I am concerned I did not see you do that, although you sure measured "something".

Notice that because of your transformer situation you have "created" ground there, which btw should be absolute zero, but maybe is not. So, with this in mind, hold the one ring against the other for its PE. Use the one for reference against the other (which is which does not matter). At first you undoubtedly should see something, meaning : when devices are connected and on power. Or the other way around : when nothing is connected on either ring, you should see no offset. But if you do, your transformers do not create an absolute zero. Well, assumed you measure an earth pin situation against a transformer situation. The earth pin should show zero in "absolute" sense anyway. Remember, when nothing is connected.

One other thing not so obvious (but I think I mentioned that before too) : maybe switch off the BD30 amp in your Swings. This, with the notice that these speakers just emerged before I came up with my crazy ideas that such speakers - even with their 115dB - should be totally silent, while at that time nothing was silent in my own room, nor Bert's. It is about the latter of course, and how the BD30 performs or influences. We just didn't know and thus check at the time (which for Bert and me were times with a TVC passive preamp which actually produces unacceptable noise (at full volume).
So, just a thought on this latter.

Regards,
Peter


Title: Re: Trying to eliminate noise totally
Post by: PeterSt on September 18, 2013, 10:01:21 am
One more thing but probably worth nothing much :

I have been looking at the specs of your latest new/old amplifier, but I was not impressed by anything but the fairly good (commercial) outlay of the "design". Well, maybe I could have written it, because in the end it says nothing much but good spirit from the designer with further no guarantee. Example : Today's amplifiers quote 'better than 0.3% THD" (I do this by heart now, maybe it was even 3%). This as an indirect reference to the sh*t out there back at the time, while NO specs are presented from the amp itself. Strange ...
The only thing which kept me up was the "in the microvolts" noise. Still it slipped my mind that this can also be 900uV, right ? If so, that's 42dB more noise than your NOS1 shows (7-8uV).
Notice that I made up the 900uV ad it can well be less, but this happens when the specs concerned just are not there (plus my notice that a heading "Specs" for sure is there).

Of course I don't want to debunk you precious new child, but I thought a small warning was in place. It is by now not the most modern, not saying that it can't be good. But I do say that while we today try to utilize the best SQ from the lowest noise, this design doesn't tell anywhere that it suits that.
Of course I heard you say that without interlinks it is dead quiet, but that doesn't tell all. Example : I create my own ground reference which is way off (what about a few Volts). Without connection it can be "inherently" quiet. But now connect it to something with a normal 0V reference and your interlinks will sparkle. See ?

Another serious hint : please don't like sound of which it is clear to you that it's driven by noise. You will be lost forever.
Oh, of course you are allowed to like it (forever) but now don't try to remove that noise. I mean, I hope it is clear to you that this noise "makes" the sound. So, remove that and you will put the amp to eBay again (the charme of it will be gone).

Still hope this helps and that you won't shoot me !
Peter


Title: Re: Trying to eliminate noise totally
Post by: PeterSt on September 18, 2013, 10:22:14 am
I have another hopefully more constructive tip, but it is a (very) long shot (and doesn't fit much in the complete picture, but alas) :

The other day I ran (pretty sure it was by private mail) into another person who couldn't solve his hum/noise;
In the end he solved that by replacing the tubes (don't ask me whether recitifiers or main).

I don't know how this works but I have the hunch that Coen will be able to work out something about this. Anyway for me it will be interesting to learn how old(er) tubes can imply something like a groundloop (which sure is how it came to me in that particular stuation). Is something half-shortcutting or so ?

Peter





Title: Re: Trying to eliminate noise totally
Post by: CoenP on September 18, 2013, 12:26:23 pm
Could very well be.

Tube noise problems are usually related to emmission and oscillation. The latter can couple into any suitable wire and cause hiss or pfff into a circuit.

I also had AM radio in my circuit once. This was the result of a breadboard layout (acting as antenna) and dirty tube pins/socket that act as a rectifier. Connecting -unshielded and ungrounded wires to an amp is like introducing antennas feeding the circuit.

Especially triodes with their inherent feedback and large grid capacitances are prone to oscillation (in fact many triodes are designed for hf oscillation pruposes). This varies with age, contact condition, circuitlayout etc. No simple answer available.

Regards, Coen


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 18, 2013, 05:39:52 pm
Of course I don't want to debunk you precious new child, but I thought a small warning was in place. It is by now not the most modern, not saying that it can't be good. But I do say that while we today try to utilize the best SQ from the lowest noise, this design doesn't tell anywhere that it suits that.

Hey Peter, debunk away!

Another serious hint : please don't like sound of which it is clear to you that it's driven by noise. You will be lost forever.
Oh, of course you are allowed to like it (forever) but now don't try to remove that noise. I mean, I hope it is clear to you that this noise "makes" the sound. So, remove that and you will put the amp to eBay again (the charme of it will be gone).

I totally accept this. There is a certain 'characteristic sound' to all the single-ended amps (valve and solid-state) that I've owned - a deep & resonating bass, a sweet, if somewhat recessed, top end and overall a very laid-back sound. Maybe my calling this 'magic' is a bit OTT. But certainly, they sound very different to regular push-pull amps. Is this down to noise? Maybe. In which case, the noise has a nice effect on the sound.

BUT... there's no way I would be happy with this. I want a nice, natural sound WITHOUT noise. To this end, the Soul has gone back to its creator. He will have a look at it. If he can reduce the noise significantly, I'll take it back. If not, he'll return my money and we'll move on.

Thanks for the advice Peter... as always.

Mani.


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 18, 2013, 05:44:48 pm
No simple answer available.

Thanks for your thoughts Coen.

It presents a bit of a dilemma I think. Single-ended valve amps tend to be low-powered, so need high efficiency speakers. But these are ruthless with noise, as I'm finding. So the only way to go is to switch to push-pull... which kind of defeats the purpose IMO.

Mani.


Title: Re: Trying to eliminate noise totally
Post by: Gerard on September 18, 2013, 06:05:09 pm
Quote
he'll return my money.

I know who  :love: you again.  ;)


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 18, 2013, 06:44:14 pm
I'm not sure I know who you mean Gerard. I know my wife would be interested though...

Mani


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 18, 2013, 06:51:09 pm
I'm trying to eliminate the noise 'totally'. But how totally is 'totally'?

I've got a 1KHz track recorded at 0dB FS. With the Sauermann monos I can still hear this track over the amp's (white) noise with XX set to -120dB! OK, that's with my ears right next to the 115dB horn.

So, are the Sauermann monos quiet enough, or do I need to work on getting their noise down further???

Mani.


Title: Re: Trying to eliminate noise totally
Post by: AlainGr on September 18, 2013, 06:59:53 pm
Quote
he'll return my money.

I know who  :love: you again.  ;)
Hi Gerard,

It's been a long time ! :)

Alain


Title: Re: Trying to eliminate noise totally
Post by: Gerard on September 18, 2013, 07:15:38 pm
Quote
he'll return my money.

I know who  :love: you again.  ;)
Hi Gerard,

It's been a long time ! :)

Alain

@ Mani
Quote
my wife is ecstatic
  :rofl:

@ Alain You are right.... Sorry...  :)


Title: Re: Trying to eliminate noise totally
Post by: AlainGr on September 18, 2013, 07:31:57 pm

Quote from: Alain
It's been a long time ! :)

Alain
@ Alain You are right.... Sorry...  :)
No problem at all, just happy to see you again :)

Alain


Title: Re: Trying to eliminate noise totally
Post by: Gerard on September 18, 2013, 07:34:45 pm

Quote from: Alain
It's been a long time ! :)

Alain
@ Alain You are right.... Sorry...  :)


No problem at all, just happy to see you again :)

Alain

Well that is nice from you to say....  :thankyou:


Title: Re: Trying to eliminate noise totally
Post by: Flecko on September 18, 2013, 07:46:51 pm
Hi Mani,

the first thing you should look at is an amplifier with low gain, because the gain defines how strong your amp will amplifiy the noise of your dac. Especially with the ultra high efficiency of your horns I would exclude anything above ~25db. 15-20db could be a good value to look for. The noise of the amp itself is normally no problem.
My personal way to get noise down is to have speakers with not so high efficiency (90db) an amp with low gain (21db) and a volume poti. With my poti fully opened I can hear a noise up to 30cm distance "ear to speaker". If I set the poti to listening levels the noise is so low I just can hear it with my ear directly at the membrane. "Hearing" is in a way exaggerated because I have to try very hard to hear it at all, it is more I imagine there must be a noise and maybe "yes" there semes to be something. (I have not made any earthing tweaks)

Greetings
Adrian


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 18, 2013, 07:58:40 pm
Hi Flecko, thanks for your thoughts. But see next post...

Mani


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 18, 2013, 08:47:03 pm
Arghhh!

I'm an idiot, and I admit it.

When I've been comparing amps in the past, one of the things I haven't been doing is adjusting the gain of the bass amp in the speakers. What I did today was to try all the amps (minus the Soul) but adjust the gain of the speakers' bass amp to get a nice balance. Without doing this, the SS amps can sound too anemic, and it's no wonder that I've preferred the low-powered SE valve amps, with their larger bass 'bloom'.


But what's perhaps more striking is the fact that the amps have different levels of noise in this order (from most to least):

1. Soul (15wpc DC-coupled valve SE)
2. Berning (5wpc DC-coupled valve SE)
3. Sauermann monos (40wpc class A PP)
4. Sanders (~500wpc class AB)
5. BD-Design monos (~100wpc gainclones - currently with input caps)

Stupidly, I've never tried the BD amps with the Swing speakers for any prolonged period of time until today. Why? Well firstly because of the aforementioned anemic sound (not their fault as I wasn't adjusting the bass gain). But also because one of the PSU transformers has always hummed from the day I received the amps. Bert immediately sent me a couple of replacement trannies to try, but to this day I've not gone ahead and taken the soldering iron out to do this.  I've now got the BD amps in the system and one of the trannies still hums a little, but nowhere near at the level of hum from the single Soul trannie.

I really am an idiot. With the bass gain much higher than 'normal', I really like what I'm hearing from the BD amps. I've said before that the BD amps are simply the cleanest sounding amps I've ever heard. But with the bass gain increased to a nice balance, they're very sweet and musical too.

As mentioned, they're also easily the quietest amps I've tried with the Swings. What's interesting is that the channel with the quiet PSU has virtually no noise coming out of the horn (or the powered bass driver for that matter). I really mean virtually nothing. With my ear in the horn, I can hear just a little hiss. That's all.

However, the channel with the humming trannie has humming noise coming out of the horn and bass. At a pretty low level, but it's still audible from a couple of meters away.

So I'm now wondering whether I even have a 'global' noise issue. Maybe I don't! Perhaps the issue is simply noisy PSUs? This would also explain why the BD amps are quieter than the Sauermann amp. The former are class AB and draw virtually nothing at idle, whilst the latter are class A, so the trannies are working overtime even at idle. (Edit: I think the Sauermann monos have a higher gain also.)

Of course, the next step will be to eliminate the noisy trannie from the single BD amp. I should have some time this weekend to try this and will report back.

As for the Soul, well I will only take it back now if it is as quiet as the BD amps. They are now my new reference.

Mani.


Title: Re: Trying to eliminate noise totally
Post by: CoenP on September 18, 2013, 08:47:58 pm
No simple answer available.

Thanks for your thoughts Coen.

It presents a bit of a dilemma I think. Single-ended valve amps tend to be low-powered, so need high efficiency speakers. But these are ruthless with noise, as I'm finding. So the only way to go is to switch to push-pull... which kind of defeats the purpose IMO.

Mani.

Push pull will "eliminate" power supply noise, which is the most common source of noise in tube amps (so not originating in the tube itself). SE has hardly any power supply noise rejection so your Soul amp addresses this firmly with a tightly regulated supply according to the rap on the site. Nothing wrong here.

Good tubes used within their ratings generate very little noise. You can make a practcally noise free MM amp with tubes and a little care. Power tubes add very very little noise themselves, and the driver and voltage amp are allready dealing with a firm signal.

A well designed SE amp can be completely silent.

Regards, Coen


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 18, 2013, 08:51:51 pm
Thanks Coen. I will remind Anthony of this if he comes back and says his amp is as quiet as it can be.

Cheers, Mani.


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 19, 2013, 12:17:56 am
I've got a 1KHz track recorded at 0dB FS. With the Sauermann monos I can still hear this track over the amp's (white) noise with XX set to -120dB! OK, that's with my ears right next to the 115dB horn.

Haha. I didn't try any lower with the Sauermanns, but with the quiet channel of the BD amp, I can hear the tone with XX's vol set to -144dB!!!

Weirdly, as the attenuation gets very high, the tone starts coming and going. At > -132dB attenuation, it seems to be riding on a 1-2Hz modulation.

Now, I have no idea if XX's vol control is at fault here. Or maybe there's some sort of 'Nick effect' going on - the house is 130 years old, so ghosts can't be ruled out.

Mani.


Title: Re: Trying to eliminate noise totally
Post by: Nick on September 19, 2013, 12:38:10 am
I've got a 1KHz track recorded at 0dB FS. With the Sauermann monos I can still hear this track over the amp's (white) noise with XX set to -120dB! OK, that's with my ears right next to the 115dB horn.

Haha. I didn't try any lower with the Sauermanns, but with the quiet channel of the BD amp, I can hear the tone with XX's vol set to -144dB!!!

Weirdly, as the attenuation gets very high, the tone starts coming and going. At > -132dB attenuation, it seems to be riding on a 1-2Hz modulation.

Now, I have no idea if XX's vol control is at fault here. Or maybe there's some sort of 'Nick effect' going on - the house is 130 years old, so ghosts can't be ruled out.

Mani.

Mani hi,

That is the breakthrough suspected I2S de modulation noise I get as well. I can hear it with music playing at -144db vol particularly music with a strong beat. I also use a 0db 1khz tone teach for testing. I don't get the modulation that is interesting.

Do you know what the gain is of you Sauremann amps are my bridged gainclones are about 36db IIRC. I wonder if amp gain it important.

Regards,

Nick.

Ps hears another test try playing the music / test signal into the NOS with the NOS turned ON but with switch 2 turned OFF ( eg the DAC board not powered on). Can you hear anything ?


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 19, 2013, 10:31:26 am
Nick, I'll try this over the weekend.

Mani.

Edit: Not sure of the gain of the Sauermann or BD amps.


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 19, 2013, 10:38:46 am
Slightly off topic...

I'm interested in understanding the mechanism that causes the bass to change its quality with different amplifiers. Generally, the more powerful amps have a tighter and more controlled bass. This is exactly as one would expect. HOWEVER... the amps are not driving the 15" bass driver directly. They are driving the in-built gainclone amp, which increases the LF gain by I guess 15dB or so to match the MF/HF horn sensitivity. Presumably, this in-built amp has a very high damping factor.

So how is it that the bass quality can change so much when none of the amps are even 'seeing' the bass driver? Any thoughts anyone?

Mani.


Title: Re: Trying to eliminate noise totally
Post by: PeterSt on September 19, 2013, 01:57:17 pm
Mani,

Because the first amp (like the Soul) acts like a pre-amp for the second (the BD30 in your case). And the pre-amp determines the sound ...
(largely)

Peter


Title: Re: Trying to eliminate noise totally
Post by: PeterSt on September 19, 2013, 02:23:24 pm
And Mani, there is one aspect of huge importance (but neglected by about everyone - ehm, including you because I already told it two weeks or so ago) :

When you change the volume of the bass section like it can be done with the Swings, you will be molesting the crossover (and not a little bit). Or the other way around : don't do that but connect a "first amp" with different gain than the one previously connected - same story.

Sad point to make : you won't know the "reference" hence what the exact (and I mean EXACT) gain must be, because the Swing comes with the bass amp only. So I said it : this is neglected by most ... if you know what I mean. But not anymore (if you know what I mean) because it is clear now.

So for example : That Orelino speaker comes with all the amplification for a reason; it guarantees that the XOver is still as how I tuned it (or we tuned it).
Get it now ? Please do, because it is crucial.

If you tune that volume you shouldn't watch for bass but watch the music in the XOver area. Not that this is really feasable (for 100% good result) but it still is better than "just watch the bass").
What you also can do (or maybe should do) is get yourself a radioshack SPL meter, hold it at 1 meter or so exactly between the top and bottom horn, create a 285Hz test signal, play that and let someone else slowly turn the bass volume. When the output is the highest the XOver should be at its best.
This, assumed that the XOver midpoint for the Orphean horn is 285 Hz indeed, which I don't know. But most probably so.

When you found the highest output, do the same for 400Hz and 110Hz but now hold the SPL meter in front of the respective horns. First of all the level of both should be the same as were you ended with the volume balance. If it is not, than or the XOver just can't be made well at all because the both slopes are not equal and you are in bad luck.
Still you can attempt now to make the levels equal for the both frequencies from the respective horns, and after this look at the 285Hz again (if it is that at all) in the middle of both horns like before. Now you have the levels right (and mangling those for the better means subjective ears) but the XOver will be wrong. To what degree (haha) will be shown by the SPL meter. Don't be shocked when you see 10dB or more less output.

When you can't make any sense out of it at all, switch the plus/minus from the bass section (not sure whether that is easy to do) and start all over. Better now ? then leave it at that.

Notice that you can create a sort of best of worse by lowering (not highering) the bass volume, which may let rise the 285Hz level. Don't let it rise more than the level from the Orphean. So, now envision that you are creating an upwards going graduate level from bass to mid. Not the best, but also no hole in the Xover.

All right, from now on you will never forget how important this is, because you will see the results yourself.

Super large disclaimer :
Although this may help somewhat, it is a method of nothing which starts with not knowing the exact XOver midpoint and the necessary guarantee that the slopes of both filters are equal. What it sure will teach you is how wrong it is for whatever listening situation.

Have fun (or maybe better drop the whole subject ?),
Peter


Title: Re: Trying to eliminate noise totally
Post by: PeterSt on September 19, 2013, 02:32:52 pm
That is the breakthrough suspected I2S de modulation noise I get as well. I can hear it with music playing at -144db vol particularly music with a strong beat.

I don't agree Nick and I'm araid it is too hard to explain it. For me it is proven that this is not Mani's case, just because I saw it coming reading his posts. At least I see it "happening" because of no change in that level occurring anymore from -120dBFS and down. This is where the resolution of the chip stops but the glitching always continues. Remember ?
It nicely mimics the frequency - each frequency (zero crossing).

Your i2s story is true too, but don't tell me why nobody but you is bothered by this. So, everybody should perceive the tone like Mani has it (because of glitching), but no way this 30 or so uV will get profound when music plays through it at 100dB more of level (and 2V or whatever is in order).
The i2s situation is a totaly different one (call it a 2nd issue), but accidentally implies a very similar behavior.

Ok, I just helped with this going (too much) off topic. So let's not do that. There's a topic for that so we can continue it there when needed.

Regards,
Peter


Title: Re: Trying to eliminate noise totally
Post by: Nick on September 19, 2013, 04:48:23 pm
Peter hi,

I didn't post the suggestion that Mani is getting I2S de-modulation breakthrough until until he mentioned the test tone can be heard at -144db.

Haha. I didn't try any lower with the Sauermanns, but with the quiet channel of the BD amp, I can hear the tone with XX's vol set to -144dB!!!

For me it is proven that this is not Mani's case, just because I saw it coming reading his posts. At least I see it "happening" because of no change in that level occurring anymore from -120dBFS and down. This is where the resolution of the chip stops but the glitching always continues.

From -122db to -144db I also get more or less constant volume of breakthrough but the characteristic of sound "improves" moving from -144db to -122 db as the I2S pulse width modulation effect starts to happen above -144db. What Mani is hearing could could still be either DAC glitch or I2S demodulation. The way to establish if it is I2S demodulation is there is to try playing music with the DAC board turned off. If the sound is still there this really points towards I2S demodulation being involved because with no power on the DAC chips so glitching cannot happen. This is why I asked Mani to try the test with his DAC section off.

(Sound withe the DAC board off will be quieter because the gain of the IV board is also switched off)

Regards,

Nick.



Title: Re: Trying to eliminate noise totally
Post by: Flecko on September 19, 2013, 08:19:33 pm
Quote
I wonder if amp gain it important.
Yes it is. In general most of the noise you hear comes from the source and not the amp itself. The noise of the source is amplified by the amp in relation to the gain value.
That is why the list from mani...
Quote
1. Soul (15wpc DC-coupled valve SE)
2. Berning (5wpc DC-coupled valve SE)
3. Sauermann monos (40wpc class A PP)
4. Sanders (~500wpc class AB)
5. BD-Design monos (~100wpc gainclones - currently with input caps)
...could be misleading because the gain of the amps is not known. So you do not know how much the noise from source is amplified and hence you cannot say anything about the general quality of the amps. I do not know how much the noise of the amp itself playes a role with 115db speaker but from what I have experienced with normal speakers it can be totally neglegted.


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 19, 2013, 08:57:55 pm
In general most of the noise you hear comes from the source and not the amp itself.

This may well be the case in most systems, but not with mine. I have two passive vol. controls - one RCA the other XLR. I can put them between the NOS1 and the various amps and the noise through the horns doesn't change at all with the control set to 0 vs. max. Remember, the noise out of the NOS1 is in the single-digit ÁV range.

Mani.


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 19, 2013, 09:14:07 pm
Because the first amp (like the Soul) acts like a pre-amp for the second (the BD30 in your case). And the pre-amp determines the sound ...
(largely)

Sure, any 'preamp' is going to matter. But I always thought that the control the power-amp has over the driver is a larger factor.

Mani.


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 19, 2013, 09:18:31 pm
What you also can do (or maybe should do) is get yourself a radioshack SPL meter, hold it at 1 meter or so exactly between the top and bottom horn, create a 285Hz test signal, play that and let someone else slowly turn the bass volume. When the output is the highest the XOver should be at its best.
This, assumed that the XOver midpoint for the Orphean horn is 285 Hz indeed, which I don't know. But most probably so.

When you found the highest output, do the same for 400Hz and 110Hz but now hold the SPL meter in front of the respective horns. First of all the level of both should be the same as were you ended with the volume balance. If it is not, than or the XOver just can't be made well at all because the both slopes are not equal and you are in bad luck.
Still you can attempt now to make the levels equal for the both frequencies from the respective horns, and after this look at the 285Hz again (if it is that at all) in the middle of both horns like before. Now you have the levels right (and mangling those for the better means subjective ears) but the XOver will be wrong. To what degree (haha) will be shown by the SPL meter. Don't be shocked when you see 10dB or more less output.

When you can't make any sense out of it at all, switch the plus/minus from the bass section (not sure whether that is easy to do) and start all over. Better now ? then leave it at that.

Notice that you can create a sort of best of worse by lowering (not highering) the bass volume, which may let rise the 285Hz level. Don't let it rise more than the level from the Orphean. So, now envision that you are creating an upwards going graduate level from bass to mid. Not the best, but also no hole in the Xover.

All right, from now on you will never forget how important this is, because you will see the results yourself.

Thanks Peter. I was actually thinking of getting a calibrated mic (Earthworks, or something) and using the RME software to capture some 20-20 sweeps. But I'll look into your approach too. Thanks again.

Mani.


Title: Re: Trying to eliminate noise totally
Post by: Flecko on September 19, 2013, 11:01:09 pm
Quote
I have two passive vol. controls - one RCA the other XLR. I can put them between the NOS1 and the various amps and the noise through the horns doesn't change at all with the control set to 0 vs. max. Remember, the noise out of the NOS1 is in the single-digit ÁV range.

If feared you will tell this, so I used the word "general" before my statement :) That is an impressive performance and interesting to know it is possible.


Title: Re: Trying to eliminate noise totally
Post by: manisandher on September 20, 2013, 07:32:15 pm
A quick update on the Tube Distinctions Soul 15 amp. Anthony Matthews got back to me. He checked the amp out and according to him, everything is working as normal. He suggested, and I agreed, that the Soul probably isn't the best match for my 115dB speakers. It just isn't quiet enough. He has given me a full refund.

It's a shame because it had a really nice quality to its sound. But if this was down to noise, then I'd rather not have it. In any event, the BD-Design gainclones are dead quiet (well, one channel at least) and are sounding seriously nice with the Swings. I'm going to have a crack at replacing the one noisy trannie this weekend. I'll report back on whether this affects the (slight) noise coming from the horn.

Mani.


Title: Re: Trying to eliminate noise totally
Post by: PeterSt on September 20, 2013, 07:36:17 pm
Everybody who hold on will finally get there ...

But don't forget to listen to music !
:)
Peter


Title: Re: Trying to eliminate noise totally
Post by: Flecko on September 26, 2013, 08:47:32 pm
I just made a comparison between the noise of my AudioNET Amp1 V2 and my Linnenberg Amp 2S. If the volume poti is turned down, with the AudioNET amp I still hear noise from the speakers, if I have my ear in about 20 cm away from it. In the same configuration the Linnenberg is totally silent. This is the first time I realised there can be such a difference of amplifier noise. My 90db/w speakers are quite new to me and I always used speakers with low sensitivity so I would correct my statement. If the speakers have a sensitivity about 80db/w, amp noise can be neglected but from 90db/w up, definitely not.

Greetings


Title: Re: Trying to eliminate noise totally
Post by: PeterSt on September 27, 2013, 08:36:52 am
Hi there Adrian,

I hope it doesn't come too much as a surprise, but you should always listen to the noise at full gain. And I'm afraid you will have other thoughts about it all then.

This is not about whether noise can be tuned down by means of attenuation because the signal/noise relation will stay the same. It also is not about the noise not being able to hear so sound will be good. It is about the noise not allowed to destroy the signal. So set all to full gain, listen to the noise you peceive then, and envision how that noise mangles with the signal at any level.

And not to forget please : Were it for the audibility of noise, I perform the gag with 115dB sensitivity.

Hope this helps (better SQ, maybe not your mood :)),
Peter


Title: Re: Trying to eliminate noise totally
Post by: Flecko on September 28, 2013, 08:23:40 am
Quote
I hope it doesn't come too much as a surprise, but you should always listen to the noise at full gain.
No it is not a surprise. This experiment should show me if I  can hear the noise of my amplifier.
At full gain I hear the noise of my DAC. I guess this cannot be reduced without a new design?

Quote
It is about the noise not allowed to destroy the signal.
Do you mean in the digital domain or how is the analog signal destroyed independently from SNR?

Quote
Were it for the audibility of noise, I perform the gag with 115dB sensitivity.
That is impressive. Is see my approach as the first step to what you have already achieved. I like the simplicity of the concept of low gain amp, volume poti and not to high efficiency speakers. I am glad to be informed by all of you, so amplifier noise is on my list now too.

Quote
(better SQ, maybe not your mood Happy)
;) Well, lets say I have nothing against better sound quality. At the moment there are so many things I can try (the noise problem beeing one of them). It is a lot of fun!

Greetings
Adrian


Title: Re: Trying to eliminate noise totally
Post by: manisandher on October 10, 2013, 04:18:25 pm
Just a quick update and probably a final wrap-up of this thread...

You know, sometimes you only know how much something means to you once you've been without it for a while. Well last week I decided to try all the amps I had lying around to see which to stick with until my Orelino speakers arrive. And there's absolutely no question about it, the Sauermann monos are the amps. I blame the bloody bass controls on the back of the Swing speakers for creating a bunch of '"red herrings" for me. I've got Nick and Paul (Scroobius) coming over next weekend, and although there won't be time to swap amps around (and I don't really have the inclination to either), I hope they agree that the Sauermann/Swing combo provides a pretty nice sound.

Mani.