Just got the PS Audio Perfectwav DAC -- Amazing

I don't know why you guys are not talking about this, but I think that the real issue with using the DAC to attenuate the volume is whether that is achieved by analog or digital methods.

If it is done digitally, then you are definitely losing original bits from the songs. Lossy. Think mp3. No surprise if you lose "3D", and you're probably losing something in the 2D and 1D and 4D and 23D as well, whatever that means. Lossy. Worse with more and more attenuation, and if you're bringing it down from 100 to 60ish then you can forget about hifi.

If the attenuation is done via analog, then of course it depends on how well it is done. Now that is precisely what a preamp is suppose to do! A good one should do it well, and if the DAC outperforms it then we are talking about one hell of a great DAC (or one lousy pair of interconnect cables).

I know that the squeezebox attenuates by digital manipulation; I'm pretty sure that the Transporter does the same thing. This thread will shed some light on this,

http://forums.slimdevices.com/showthread.php?t=30916

Basically, you want to listen to the slimdevice gadgets at maximum volume and attenuate with something else; or use them to get the 1s and 0s into whatever DAC you like, and then go through there to, once again, a preamp.

Anything else and you're asking for lossy data. Mp3s, maybe nice mp3s, but still mp3s. The whole point of flac gets tossed into the bitbucket.

I have no idea what the PS Audio dac does to achieve this. If it trumps a preamp, then it's a better preamp than that preamp. If it trumps all preamps, then it's a hell of a preamp (well, except for its lack of non-digital inputs!). But if it does it digitally, then it's lossy. The fact that their web site does not mention this issue is not encouraging,

http://www.psaudio.com/ps/products/description/perfectwave-dac?cat=

since it is a clear big selling point and they should be explicit on the method (sadly, the logitech transporter site does not mention it either). For $3k, I would expect one hell of a volume knob...

Redbook CDs are 16bit. Most of the current DACs upsamples to 24bits. So there are 8 bits for attenuation without lossing any bits when a Redbook CD or CD ripped file is played.

However, if you have a downloaded HiRes file starting at 24bit, then any attenuation via digital will lose information. i.e. you don't have the full 24bit resolution after attenuation.

This is the case for the Transporter. (read it from the slimdevice forum). I don't know how PS does it.

Let's hope that the 32bit DAC chips will become popular. Then we have 8 bits to play with when we play 24/192 files.

IMO for a DAC->amp combo (via analog volume control) to beat a DAC-pre-amp combo, it has to have superior power supply and ability to drive diffult loads in the analog section. There aren't too many DACs built that way. (may be the Theta Gen 8)

I don't know why you guys are not talking about this, but I think that the real issue with using the DAC to attenuate the volume is whether that is achieved by analog or digital methods.

Good point...

The following has been copied from the PS Audio Forum:

Is the PWD perfect? Not entirely but close. Used in the last 50% of its volume setting (where any serious listening would be) you get a “free lunch” so to speak.

Can you expand on this Paul? Is that the loudest or quietest 50% percent? Why is there a difference? Also, the Slimdevices Transporter had a bug which occasionally caused full-volume output. I’m sure you’d never release a product with a bug, but that brings up a more interesting point. A product like this is probably going to benefit firmware updates. How will this be handled? An Ethernet port would have been nice (I’m sure it’ll be on the PWD II…)

The loudest 50%. The volume control is such that the loudest 50% is handled without any loss of data (it’s a digital volume control meaning it is just doing math and not an extra element in the audio chain). In the lower 50% there is a small data loss but we have this setup so for any serious listening you’re way outside of this area,
For updates, all PerfectWave products will be easily field upgradable by the customer.
Paul McGowan - 27 January 2009 01:10 PM

Hi folks, I haven’t participated in this forum for a while and just re-registered.
I’m assuming from your statement that the output level of the PWD in the lowest 50% of the VC’s range is relatively low and would produce a low volume level with the average amp and speaker combination, lower than a “serious listening” level. A logical and appropriate choice, although difficult (actually impossible) to get right with every amp and speaker combination, particularly with very high sensitivity speakers. Am I correct?
It popped into my head that given that the output stage of a DAC is similar to a preamp, that your Gain Cell level control could be used as the volume control in the PWD. Seems obvious, but things are rarely as simple as they ought to be, and there are likely many reasons why this was not done. Just wondering…

Absolutely this would be a perfect place for a Gain Cell except we don’t need one since the digital attenuation scheme obviates the need for a Gain Cell. Here’s the deal. The output of the DAC is an analog output stage (discrete type in ours) and has very little gain. It’s near a gain of 1 and is really there as an output driver and balanced device to lower any common harmonics - and to isolate the IV stage. A Gain Cell makes the most sense when you have a large dB change you want to effect as in a preamp.

The only thing cleaner than a Gain Cell is this simple output stage and the digital attenuation scheme we’re using.

For this reason, I listen through my preamp because I tend to do a lot of listening in the evening under the 50% "level." I have driven the amp direct via the PWD at levels well above the 50% range with exceptional results.

Ben

I have a new question... How does the PWT compare to the Linn Klimax DS. Granted the Linn KDS is ~7x the price ($20k) but I want to know how much of that is just for the 'Linn' name / hype. I find it hard to believe that the KDS could be that much better considering it's 2 years old and digital streaming technology is relatively new.

Furthermore Linn provides almost no specs about the KDS (DAC, how it processes the info etc). Maybe the PWT description is all marketing but things like native mode etc seem pretty legit and I doubt the KDS has them.

Danyal,

That is exactly the question I'd like answered. Very little mention of Linn on here, though they were the first high-end audio company to adopt this technology, and they seem to have truly embraced it. (For the sake of argument, I'm allowing Slim Devices no high-end pedigree, unlike ModWright).

For my money, Linn 'get' the benefits of this architecture better, and have made excellent efforts to explain it (though there's a lot to it and I'm techier than most). Their products seem more focused to me, as a direct result. They have always integrated an ethernet port with the DAC. The Klimax and Akurate DS both use the same DAC as the PS, the Wolfson WM8741 (though Linn use 2). Actually the PS blurb says it uses the WM8741 and the WM8742 in the same paragraph, which is poor. The Majik DS and entry-level Sneaky DS uses a single WM8740. I'm not perfectly sure, but believe Linn's implementation is to upsample always.

Interestingly, and confusingly, Linn talk very highly of their digital volume control, and the benefits of a signal path unencumbered by a preamp. But, they only have digital volume on their two lower models. It's a mixed message, and you have to wonder whether they have an eye on the inevitable harm done to pre-amp sales. One thing's for sure: analog or digital, attenuating reduces the s/n ratio, so it's 'lossy' either way. But it's entirely confusing(though tempting) to equate this with lossy compression, which is doing different things to different frequencies.

Price wise, I think the equivalent to a PS + bridge would be an akurate ds, but you need a pre-amp with the akurate. I have yet to do a single listening test, but looking forwards to comparing PS and Linn one day.