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.

I'm not sure I know who you mean Gerard. I know my wife would be interested though...

Mani

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.

Hey Peter, debunk away!


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.

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?


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.

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.

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.

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.

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.

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).

Hi Brian, thanks for jumping in so quickly. It's getting late here, but I'm tempted to swap the mobos out right now, knowing that there'll be no software installing to be done.

Cheers, Mani.

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/µs) 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.

Nick, Brian, (or anyone else who may have an opinion),

I'm ready to go ahead and replace my Asus mobo with the ASRock mobo. A quick question beforehand though:

Did you find that you could use the same HDD/Win8 install or did you create a new HDD/Win8 install for the new mobo. The former would be great, the latter a right royal PITA.

Now just let me know...

Cheers, Mani.

Nice Peter. Thanks.

A few questions:

1)


So, when will this become a reality in XX/multi-channel-NOS1?

2) For now, would it be possible for me to apply similar LF DSP with my Swing MkIIs, do you think? Maybe too much work and not possible without your 'secret alignment tricks'?

3) Where do headphones fit into all this? My golden reference are still my AKG K-1000 headphones. I can substitute the speakers directly with these, i.e. they can (need to) be driven by the power amp. I've found them invaluable in giving me an idea of how the music should really sound. Single FR driver, no x-overs, no DSP, no standing waves, nada. And still easily the best sound I've ever heard.

Mani.

Hey Peter, I think that was the case for the original MkI Swings. Mine are a pair of MkII Swings, which I'm sure only have a single 15" driver per side. I'm not sure why Bert went this route for the MkIIs...

Mani.