There may be, but I think the slight increase in LF output via DSP has already fixed the issue. The boogie factor is now there in spades.


I think you're right Alain - what I'm probably missing is the harmonic distortion low down that I'm so used to. Perhaps I should bypass the internal amps and use an external tube amp... OR just get used to accurate bass reproduction... haha.

Mani.

Thanks for your thoughts guys.

Of course, listening through headphones (or more accurately 'head speakers', in the case of the K-1000s), could never be mistaken for the real thing, whilst with (the very best) speakers it could. But when I talked about the 'sound' of my AKG K-1000 headphones in my previous post, I really meant 'tone'. There is a 'colour', a 'liquidity' to the tone with the K-1000s that I find simply intoxicating... And I'd love to have it in my speakers.

Sorry for causing the misunderstanding.

Mani.

Thanks Peter.

Here's something that John Swenson wrote on CA:

"First off, USB is not one signaling standard, there are currently 3 in use, the one in use for a large percentage of DACs at the moment is the high speed standard, so I will cover just that.

HS mode runs at 480 Mbs, at this speed over normal human cable runs(measured in meters not mm) the "signal integrity" (SI) at the receiver can vary GREATLY. The spec allows for a very wide range of SI at the receiver, this means the receiver circuit has to be good enough to recover the data over this wide range of SI.

This receiver is NOT just a simple logic gate input. It uses a multiphase clock at 480MHz, some use 8, some 9 and the ones I worked with use 12 phases. This means there are twelve clocks, each at 480MHz, but slight delays between clocks. These different phases are generated by digitally controlled delay lines with 1/2ps resolution, you read that right, one half pico second resolution. Each of these clocks controls a very fast ADC with a few bits resolution. Thus every "bit" on the incoming analog signal is sampled 12 times, the digital representation of these analog values go into some DSP circuitry that tries and figure out where the "edge" actually is amongst all the noise, jitter and reflections on the wire.

If the SI is pretty good this determination is pretty easy, if the SI is not good, it has to work harder to figure out where the edge is. Part of this process is continuously tweaking the frequency of the clocks AND adjusting the exact delays of each of those phases to get the best data to the DSP block. Even though the clocks are 480MHz, the rate at which the frequency and delays are adjusted is right in the middle of the audio range. The worse the SI the more tweaking goes on.

Lest someone thinks this is USB only, this sort of thing is the basis for ALL high speed serial interfaces. USB HS is actually the simplest because it has to be dirt cheap, others do even more complex feedback on the input parameters. You really don't want to know what goes on in a thunderbolt receiver!

All of this processing to track the input signal generates lots of noise on the power traces and ground plane of a board. Even with very careful circuits and board layout some of this gets through to the DAC chip and its clock, which CAN change the output signal. Note: none of this actually changes the bits, that input circuit IS good enough to recover the actual bits. It is the consequences of the heroic measures taken by the receiver to get those bits in the face of poor SI that can affect the sound.

Measuring this stuff is not easy, frequencies are high and amplitudes are low. I don't have anywhere NEAR good enough test equipment at home to do this justice (we are talking about at least $50K, I can't afford that!!) and if I tried to use the stuff at work, I wouldn't be working, so a book full of graphs proving all this is not going to be coming from me anytime soon.

Gordon just got some equipment that CAN show this so sometime in the future you might be seeing some data from him.

I hope this helps a little bit in understanding how a USB cable may change the sound of a DAC.

John S."

I think the NOS1a has eliminated this as a cause for differences in SQ between different USB cables. But I'm posting this as a reminder of how complicated this all can be.

Mani.

And another point while I remember it...

I also tried the mobo USB port vs. the Silverstone card. The Silverstone card was much better than the mobo... but only with its bracket still attached.

So in summary, the best sound I achieved was this:

- SS card with its bracket attached (i.e. non-isolated)
- 5m 'standard' USB cable

Both these findings were total shocks for me and the exact opposite of what I expected (so no placebo here).

Oh and in case it matters, I have never touched the black cable within the NOS1(a) itself.

Mani.

I came to the conclusion that USB cables now matter greatly (with the NOS1a) about 3 weeks ago. I wasn't even looking for differences but just stumbled upon them. I was experimenting with where I could place my PC and NOS1a, and had pretty much resigned myself to having them both sitting exactly between my speakers in my main room. I then decided that it would be better to have the PC in the corner of the room, which would require a 3m (or so) USB cable. I got out my (very) expensive 3.5m USB cable, plugged it it and immediately thought WTF?... this sounds way worse than the 'standard' 1m cable I had been using!

I then went through a bunch of USB cables (all cheap printer cables) of various lengths, and they all seemed to have a slightly different sound. Unfortunately, with the way things were situated, I couldn't try a 0.5m length - maybe Paul (Scroobius) can share his findings with short lengths when he tries one. But what I did try was a long 5m USB cable. And you know what? It sounded way better than any other cable I had tried. So with my setup, there isn't a clear inverse correlation between length and SQ. If I had to hypothesize, I'd say, generally, the shorter the USB cable, the better... BUT...

... Very long USB cables (getting to the edge of the USB spec) may sound even better. I know they are very different animals, but I've found exactly the same thing with spdif/AES3 cables. The longer (~5m) cables sound better than shorter ones. For these types of digital cables, the practice actually matches the theory - they are terminated (or should be) so RF reflections come into play. As for whether the same theory would apply to USB cables, I have no idea.

Oh and BTW, I get absolutely zero USB errors showing in the USB Control Panel with the 5m USB cable.

I think Peter's advice of trying a few 'standard' (i.e. non-audiophile, non-expensive) USB cables of different lengths is bang on. So my strong recommendation is to buy a bunch of 'standard' cables from 0.5m to 5m lengths and give them a go. I mean, why not? The outlay should be no more than 20 Euros max, right?

Mani.

Hey Jud, thanks for sharing... I really do appreciate your thoughts.

Yep, I'm all for simply listening and enjoying the music, and seeing where that takes me. Definitely. And I think I'm nearly in a position to be able to do this, now that I have a tonal balance I'm happy with.

I suppose one of my biggest 'issues' is that I already have (have had for a while now) a system that I totally love the sound of - my vinyl digitization setup in my little 'studio' in my basement. Essentially, a pair of BD-Design mono amps driving a pair of AKG K-1000 headphones. This is my reference sound, the one I've been striving to emulate through speakers for quite a few years now (with different amps). So, I know the exact sound I'm looking for... and I generally know how far away (and in which 'direction') I am from getting it. When it's too far, I find it really hard to simply listen and enjoy the music through speakers.

Blessings and curses...

Mani.

Just a quick update on this...

I've finally settled for an increase of 1.7dB in the LF. Doesn't sound like much, but it totally changes the impact the music has. Bass lines and percussion really start driving the music forward. After 30-60 minutes of listening I realise that my neck muscles are hurting through all the involuntary head jiving.

But the bass 'quality' still takes getting used to. It's so lean and fast with absolutely no artificial 'bloom/fat' whatsoever. This is great from a rhythm perspective, but from a tonal perspective, it's difficult getting used. I'm totally convinced this lack of bloom is due to lack of distortion, which is a good thing. But I don't know... sometimes an oil painting is more gratifying than a photo...

Mani.

Hey Kjell, well done on your design choice(s). The first thing my wife said was that yours look much better than mine. But I think she was referring to the whole look and feel of your room - very, very nice indeed.

I also went for a minimalist approach and originally had the PC and NOS1a in my basement. But right now they're both in my main room, as I test a few things out. I'm pretty confident that I'll be able to return the PC to the basement, but depending on my interconnect findings this week, I may have to keep the NOS1a in the main room. We'll see...

Mani.

I haven't had much time to play around with things lately, but will be testing a few interconnects (various lengths and models) this week. Will let you know how I get on...

Mani.

I'm currently working in Germany and I have to say that I didn't get much sleep last night with all the car horns being blown into the early hours.

I also couldn't get the image out of my head of that little boy in the crowd (about the same age as one of my sons) crying his eyes out in total confusion and desperation. I imagine this experience was akin to loosing his parents in the supermarket. I had to switch the TV off at half time because I just couldn't watch the humiliation any more.

But hats off to the German team for playing well.

Mani.

Hey Todd, thanks for sharing your thoughts. It's always nice when someone arrives at the same findings as yourself totally independently.


Well I hope it was either of the first two and not the last. But in any case, it's nice to know that someone finally listened to me. Now if only I could have the same effect on my wife


Haha...

Mani.

Yep, I think the LF is just a little too prominent at +2dB. But at least it's 'clean' LF, so even though it needs taking down by 0.5dB, it still doesn't interfere with the enjoyment of the music in any way.

Mani.

I've just played Satty her favourite Bhangra track and she's more than impressed.

Happy household...

Mani.

No, not repairing my windows (hardware or software  ), but really enjoying the sound now. I've just increased the output of the LF by 2dB (takes just seconds to do via USB cable into speakers) and...

... WOW!!!

This is bass like I've never heard before. (Nick/Paul, all the criticisms that we all had have totally disappeared. On a good dance track, my chest is thumped to pieces.) I'm going to keep things like this for a while, but may reduce it by 1dB if I feel it's too overwhelming.

Oh, I'm really, really happy now. 

Mani.

So, who's still been using this recently? I know it isn't compatible with the new Custom filter, but I just wondered if anyone had been using it with AP.

Overall, I think it's a great idea - to prevent overs as a result of the filtering, even if the source material itself has no clipping. But PE seems to have fallen by the way side.

Just wondered...

Mani.