Hi Erik,

I have a friend who has the new Citypulse 2.03e USB DAC and is very impressed by it feeding his Trends amp.

Regarding speakers, Stephen Mejias really likes his PSB Alpha B1 monitors: http://www.psbspeakers.com/product.php?pId=69&sId=4

Try to give these a listen if you can! At 91dB in-room sensitivity and nominal impedance of 6-ohms, they should be a great match with the Trends amp!

Good luck and keep us posted!

Vinnie

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I have a friend who has the new Citypulse 2.03e USB DAC and is very impressed by it feeding his Trends amp.

I have some USB-equipped DACs in for review and I am finding that they are extremely sensitive, not only to the computer used to drive them but also to the audio program used. iTunes on both PC and Mac seems to be the most consistent, but I get anomalous results from Windows Media Player 9 (running on XP Service Pack 2 on a 2.4GHz PC). I have wasted hours playing with Windows control panel settings to try to trouble-shoot the problems, which look to me like the effects of SRC. What has been your experience?

John Atkinson
Editor, Stereophile

Quote:

Quote:
I have a friend who has the new Citypulse 2.03e USB DAC and is very impressed by it feeding his Trends amp.

I have some USB-equipped DACs in for review and I am finding that they are extremely sensitive, not only to the computer used to drive them but also to the audio program used. iTunes on both PC and Mac seems to be the most consistent, but I get anomalous results from Windows Media Player 9 (running on XP Service Pack 2 on a 2.4GHz PC). I have wasted hours playing with Windows control panel settings to try to trouble-shoot the problems, which look to me like the effects of SRC. What has been your experience?

John Atkinson
Editor, Stereophile

Hi John,

I do not own a USB dac and in the past I have not tried many different combinations of computers and software with USB dacs to notice a pattern, but I will say that I have NEVER had trouble using iTunes with USB dacs (ripping to WAV or Apple Lossless files and setting the Error Correction to "ON") with my PC. I really like the iTunes interface for ripping, playback, burning, obtaining tag info and album artwork, etc.

FWIW, I believe Gordon Rankin of Wavelength Audio prefers a Mac and iTunes (based on what I have been reading on audioasylum's computer audio forum) with his USB dacs. This is a good place to post your question to see what others are experiencing.

Best regards,

Vinnie

John,

I am delighted that you are working on a review of USB equipped DACs! I am extremely curious as to what you will find. In particular I hope you are checking out Benchmark's latest as well as PS Audio's.

Many believe that Windows KMixer modifies the bit stream and that one must use kernel streaming to bypass KMixer on XP to get bit-for-bit transfers. This bypasses both Windows' volume control and KMixer. Foobar2000, a freeware audio player for Windows, includes kernel streaming and may be good to try.

On the other hand, Benchmark's Elias Gwinn offers the following:

"Here is a summary of what kmixer does to audio:

CONDITION 1: One audio stream is sent through audio through kmixer at a time

RESULT: kmixer streams the audio bit-transparently (when using usbaudio.sys) - that is, bit-for-bit, what goes in, also comes out. We have tested and proven this using a test function called 'Bittest' by Audio Precision.

CONDITION 2: Two audio streams of same sample rate are sent through kmixer

RESULT: kmixer streams both without problems, ASSUMING THE SUM OF THE AUDIO STREAMS DOES NOT ECLIPSE 0 dBFS!! Just like any digital mixer, if the sum of the audio eclipses 0 dBFS, digital clipping will occur, which is not popular among audio enthusiasts. However, if it does not eclipse 0 dBFS, there should be no problems. This was confirmed by playing a 'Bittest' stream with one app and a silence (all 0's) stream with another. The result was bit-transparency. NOTE: When multiple audio streams are summed in kmixer (even 16-bit audio streams), the result will be a 24-bit audio stream. THIS IS WHAT WE WANT, assuming we have a 24-bit device to receive it.

CONDITION 3: Two audio streams with different sample rates are sent through kmixer

RESULT: kmixer will up-sample the lower sample rate to the higher one. The higher one remains unaffected. This conversion is not very good though, and should be avoided. It is easily avoidable, however, as long as only one audio stream is playing at a time, or they are of equal sample-rates."

As to iTunes, he offers:

"iTunes:

You must be careful of a few things:

1. iTunes volume control should always be set to 100%, as volume reduction in iTunes causes severe distortion. This is because volume calculations will result in 24-bit words, even if the audio was initially 16-bit (due to remainders after division). iTunes will then truncate to 16-bits, instead of dithering or simply passing 24-bits

2. iTunes will convert the sample-rate of any audio with different sample-rates then that set in QuickTimes preferences (yes, QuickTime preferences affects iTunes!!) Be sure that sample-rate corresponds to the sample rate of the audio you are listening to.

3. For the purest audio playback, do not use the "sound check" or "sound enhancer" features in iTunes. All of these DSP and/or audio plug-ins in all media players should be avoided to obtain faithful playback."

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I am delighted that you are working on a review of USB equipped DACs! I am extremely curious as to what you will find. In particular I hope you are checking out Benchmark's latest as well as PS Audio's.

Currently I have the Benchmark, the Bel Canto DAC3, and the Musical Fidelity XDACv8.

Quote:
Many believe that Windows KMixer modifies the bit stream and that one must use kernel streaming to bypass KMixer on XP to get bit-for-bit transfers. This bypasses both Windows' volume control and KMixer. Foobar2000, a freeware audio player for Windows, includes kernel streaming and may be good to try.

I wondered about the Windows kmixer, having read the long thread on the Head-Fi forum. I have downloaded Foobar and will try it out tonight.

Thanks -- JA

John Atkinson
Editor, Stereophile

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I wondered about the Windows kmixer, having read the long thread on the Head-Fi forum. I have downloaded Foobar and will try it out tonight.

I think you'll enjoy Foobar-- it looks a little barebones, but has some really nice features (the resampling is surprisingly good if your hardware supports it, and there are all sorts of plug-ins for just about any purpose you can imagine. Crossfeed in particular is nice for headphone listening.) If it only did HDCD like Windows Media. Sigh. Probably the best PC music player software, IMHO. (I tend to stick to iTunes on my Mac, and like Aqualung and xmms in Linux)

Lionel