Hi Marcin,

This isn't speculation on my part - I explained how I arrived at this conclusion here:  http://www.computeraudiophile.com/content/How-can-influence-SQ (conclusion at the bottom).

The 'analogue -> AD -> AES -> PC -> AES -> DA -> analogue' chain sounds identical to the direct feed from the analogue source.

Furthermore, XX playing a 24/192 recording of the analogue source also sounds identical to the analogue source.

ERGO... my PC is OK. Nothing more to be done here.

Where I still have some work to do is in optimising the playback of 16/44.1 files via XX.

But look, I can easily change the number of cores from the BIOS - I'm currently using 2 and not 4. I'll happily try 1 core once I have some time.

Cheers,
Mani.

Yep, got the case. Will report my findings when I'm back in the UK later this week.


Interesting question! Actually, I'm very chilled right now. I've proven to myself that my hardware is transparent. This is so nice to know this. No more messing around putting PCs together, playing around with interfaces and/or digital cables. This is cool.

But I'm still waiting on Peter's findings regarding AP... If it's currently working as he intended, then that's fine. But for whatever reason, it no longer 'works' with my DAC. Don't get me wrong, it still sounds good. But I'm just losing the 'body' and 'weight' of instruments and music in general. Maybe this has always been the case and I've only just realised...

Mani.

Thanks Peter - I'll do this when I'm back home later this week. I'm really interested in hearing what you think of these digitised vinyl files.

Mani.

I've finally gotten my act together and done the things that I've been threatening to do for a while: 1) determine how transparent my 'PC chain' really is and 2) compare QAP applied to a 16/44.1 file recorded from vinyl vs. a native 24/176.4 file from the same vinyl.

You can read the results of 1) here http://www.computeraudiophile.com/content/How-can-influence-SQ (conclusion at the bottom).

Well 2) has just been really interesting. Firstly, I never knew how good 16/44.1 could be! It's pretty difficult to distinguish it from the source or the 24/176.4 file... but there is a small difference. The 24/176.4 file however is, to my, my wife's and to some friends' ears, identical to the source. Another surprise was how much better my 16/44.1 file sounds than the CD rip that I have (which happens to be HDCD-encoded).

But one thing I have verified for myself is that the current QAP (with Peak Ext) seems to be changing the sound. The native 16/44.1 and 24/176.4 files sound rich and full, like the analogue source. QAP on the 16/44.1 file sounds slighty 'thinner' in comparison.

[Peter, I'm happy to send you these two files - if you're interested, let me know how I can do this.]

Mani.

PS. All listening was done with HDCD-encoding in XX switched off, Adaptive mode and with the buffer set to 4096.

Peter, yes I used the exact same files as before: Beethoven Piano Concerto No4 in G major Op58 - Andante con moto.

I would be cautious about these findings, if it were not for the fact that the 192 file is identical.

EDIT:

But maybe you're asking for more info on actual procedure? Nothing complicated. I just set 'peak hold' on and play the whole track. So, these are just the peak signals at the various frequencies.

Mani.

Well, QAP has CERTAINLY changed!

Have a look at the spectra graphs that I posted earlier this year: http://www.phasure.com/index.php?topic=1017.0

Now have a look at the three graphs below:

The first shows the 192 file. This is exactly the same as it was before.

The second shows the 96 file with DAP applied. You can see that DAP does a really good job of recreating info above 48KHz.

The third shows the 16/44.1 file with QAP applied. It is different from before. There is a lot less HF content. How this could lead to a thinning of the sound, I have no idea...

(I still can't get QAI to play for more than 30 secs or so.)

More later...

Mani.

My comments apply more generally to 0.9z vs. 0.9y. With the latter, I simply never had an issue with AP.

I've (finally) finished making up some cables that will allow me to record from analogue. What I want to try is recording the same track at 16/44.1 (with and without Peak Extend) and at 24/176.4. This is what I'll then do:

1) Tune the 'XX chain' playing the native 24/176.4 file until it sounds as close as possible to the analogue source going through the 'A-D/D-A chain'. This will entail playing with all the variables in XX, my PC, the PCI/firewire interface, power and cables. The biggest issue I have here is that I am going to have to use a vol control for the A-D/D-A chain. To make it consistent, I will use the same vol control for the XX chain and set the XX vol to -0.0. (The vol control will be an Audio Synthesis ProPassion connected to the power amp via 0.5m cables.)

2) Find the configuration in XX that gets the two 16/44.1 files closest to the 24/176.4 file.

Then I think I'm done.

Mani.

4xAP seems to work well with HDCD.exe. This doesn't sound thin to me. Maybe I'm just losing the plot...

Unfortunately, I can't make a direct comparison with the HDCD decoder in my DAC as I now use the XX vol control and have no preamp in the chain (one of the best improvements in the sound of my system BTW, and I was a die-hard anti digital vol guy, until I tried what Peter's been suggesting all this time).

Mani

Hi Roy,

Yes, I saw the thread and I agree with you - 1024 seems to be the sweet spot.

I've been all over the place lately with buffers, as I've been trying to improve my AES connection. What totally amazes me is that everything seems to matter, down to the voltage of the AES connection. In some instances, 32 samples is better, in others 1024 is better. With 4xAP, taking it right up to 4096 helps, but doesn't solve the issue IMO.

FWIW, the comparisons that I mentioned were done with the buffer set to 1024. I'll change my sig...

Mani.

I'm not sure if this is particular to 0.9z-1, but I now have an 'issue' with the sound of Arc Prediction. When it was first released, I thought it was a revelation, exposing detail that just wasn't there on 16/44.1 material.

However, I've just done a pretty thorough listening session and have come to the conclusion that AP is making everything sound too 'thin'. The body, weight and substance of instruments is definitely diminished. I have three versions of the same track from Linn Records - 16/44.1, 24/96 and 24/192. Without going into all the permutations that I've tried, I can say that 4xAA on the 16/44.1 sounds sounds closer to the 24/192 version than 4xAP does. Furthermore, the native 24/96 sounds closer to the 24/192 than 2xAP does.

Peter, what has changed with AP? Anything? I really hope we can come up with something, because right now, I can't listen to it...

I did do a few tests with RME's Digicheck, but couldn't see anything that obviously points to a thinning of the sound. (There is however an HF 'click' on pressing play with 4xAP - and perhaps intermittently throughout the track also.)

Mani.

Marcin, thanks for posting this. I've just ordered one of these and will let you know how it works.

I went for the low-powered version because I think 38W is enough to power my single RME AES card. Also, I want to use a linear AC-DC 12V supply, which itself will be powered by an AC-DC-AC regenerator. All this with a view to getting the cleanest 5V AES signal out of the RME card.

Including shipping and VAT, this solution has cost more than I was hoping for - around €275! But it might be worth every penny...

Mani

The Pass amp was the '100W SS single-ended class-A amp' that I mentioned in the first post of this thread. It's not an integrated though - it's a 50Kg stereo power amp.

It's a laid back amp, and sounds very nice when matched with the right speakers. I've managed to get very good sound using it to drive a pair of Celestion SL600 speakers. But with the electrostatics, the Hypex is better. The reason why I'd never mentioned the Hypex before was simply because up until that point I'd never tried it with the Quads.

Incidentally, one of the guys who was over at my place has dropped me an email. He says about the Quad 2805 speakers, "Hi-Fi World's measurements show a 6ohm average with a low of 3.2 ohms and a high of 12 ohms."

Mani.

Before I got the Quads, I was multi-amping a pair of Wilson-Benesch Chimera speakers (yes, also gathering dust in my basement!) with a total of eight UcD700HG amps. Of course, you'd think that 700W into 4ohms for tweeter is total overkill. Yes, but boy did they sing with this sort of power on tap. In any event, the Hypex amps are mighty fine up top as well as down below.

Mani.

Hi earflappin,

You know, I shouldn't be talking to a 'sinner'. Now if you could find a way to get your MH working with XX, then all will be forgiven...

I can't find any impedance curves for the 2805s. One of the guys who was over at my place (very knowledgeable) doesn't believe they have the same sub-1ohm of earlier ESLs at high frequencies. Powerful as they are, I don't think the Hypex UcD700HG amps are very happy at sub-4ohm impedances.

Mani.

Hi Marcin,

No, I've never heard a Tripath, and as Telstar's pointed out, there'd probably be no point with the Quads. But I've owned ICE-powered amps before and actually still have a PS Audio somewhere - it's OK, but the Hypex UcDs are in another league altogether.

Mani.