[Paul Meakin]

Thanks; that was a good read.
 
Quote:

Hi Paul. What measured greatly in my decision going for the (PCM1704-based) Reference 7 is conveyed by LessLoss, in their web page explaining why they chose the PCM1704 chip for their DAC 2004 MkII.
 
The reason I trusted Audio-gd's top PCM1704 implementation is easily understandable from most users' very positive feedback throughout this thread. This was certainly the best PCM1704 DAC my sub-€2000 budget could buy.

 

 

[LarsHP]

Here's another positive review of the Ref 7.1 DAC:
 
http://www.headfonia.com/the-flagship-audio-gd-pcm1704-based-ref-7-1/

 

[SP Wild]

I only have the Reference 7 and not the 7.1.  But my comparison between the Bryston and 7 was similar, but slightly different to the review.  Definitely agreed about the channel separation and fine ambiance being noticeably better on the 7 and that the 7 is indeed at a higher performance envelope than the Bryston, but it stops there.
 
Its funny how both are in similar price brackets, but to me they are not in the same league.
 
I was going back to my roots for the last week, using only my DIY mid-level dac (better than dacmagic) and my first ever headphone amp, the XcanV3 and running my K701s.  I think the 7 and Phoenix combo has ruined me for good, just with my K701s - the mid level stuff sounded significantly veiled to me.
 
 

 

[tim3320070]

A few more Ref 7.1 and Ref-5 are for sale now.

 

[shamu144]

I ordered my Ref 7.1 a couple of month ago, and expect to receive it any day now (apparently has shipped from China)... Grab those while you can.
 
Quote:

A few more Ref 7.1 and Ref-5 are for sale now.

 

 

[Audio-Omega]

I thought they had stopped making Reference 7.1 completely.  

 

[LarsHP]

I thought they had stopped making Reference 7.1 completely.  

That was what Kingwa said, but apparently he got hold of some PCM1704UK chips.

 

[haloxt]

They have some spare pcm1704uk's in case they need them for repairs. Even if they buy no more of these chips, they may release occasional pcm1704 dac's over the next few years to help sell spare parts they keep on hand for warranty repair. And since they keep upgrading so rapidly, I wouldn't be surprised if they have to release some promo priced mix and match gear to help liquidate excess cases or components.

 

[lmswjm]

Just wondering about how much sonic improvement the 7.1 is over the Reference 1. Has anyone done any comparisons?

 

[tim3320070]

Currawong went from the Ref-1 to the 7.1- try him

 

[dukja]

I am looking for the output impedance of Ref-7 (not 7.1) to build a custom passive volume control for it.  Anyone may have this number? 
 
I googled it and found some number from about 20 ohm to 33 ohm.   I would really appreciated it you have it somewhere.
 
Thanks!!

 

[jimmychan]

Quote:

I am looking for the output impedance of Ref-7 (not 7.1) to build a custom passive volume control for it.  Anyone may have this number? 
 
I googled it and found some number from about 20 ohm to 33 ohm.   I would really appreciated it you have it somewhere.
 
Thanks!!

 
 
I guess you have to ask Kingwa.

 

[IPodPJ]

Quote:

Just wondering about how much sonic improvement the 7.1 is over the Reference 1. Has anyone done any comparisons?

I had the 1, the 7, and now the 7.1.  The differences are very apparent, especially if you have a quality source.
As everyone knows, the DSP-1 module is on its 5th iteration.  It's claims of making a source clock non-important are just not true.  In fact, I am using a modified Transporter with two Audio-gd JZ1 clocks, dual torroidals, and an Audio-gd power supply (all with upgraded caps).
I determined this after trying multiple sources, and most recently because I discovered an interesting feature about the Transporter.  When you are doing the initial setup you have the option for digital output of either "digital passthrough" or "word clock on digital output".  When you select word clock on digital output the quality is far superior in every way.  There are a lot of theories as to why this could be, from the people on the Squeezebox forums I've spoken to about it, but I won't get into that, since the passthrough feature was intended to just pass through whatever word clock signal was coming from whatever input is being fed into one of the Transporter's input jacks.  What is important is that the word clock on digital output is including the generated word clock data from the Transporter which in my case is being generated by the Audio-gd JZ1 clocks.  In my Transporter, everything is disabled except the digital output:  the internal DAC is disabled, the original clocks have been removed, the original transformers have been removed, and the analog outputs have been disabled.
 
To make a long story short, the DSP-1 can perform very well, but only if fed with an accurate/stable word clock (and word clock refers to the signal, not to be confused with a master clock which generates the word clock, and can be either an internal clock circuit or an external device).  Don't expect to get world class performance out of your Ref 7.1 (or any other Ref model) if you are feeding it a word clock generated by a poor quality oscillator.  What do I consider a poor quality clock?  An oscillator with greater than 2ppm stability (you want it to be less than 2ppm... the JZ1 are about 1.5ppm... the uber expensive Antelope Audio Rubidium oscillator is rated at 0.05 parts per BILLION), and a clock with high jitter.  Ideally you want a TCXO (a thermally controlled oscillator), which regulates the temperature inside a miniature oven.  Oscillators are very sensitive to temperature fluctuation, and this is also one reason why a digital source sounds better after it has had time to warm up.  You also want multiple fixed frequency oscillators as opposed to a single, variable frequency one.
 
I'm sure some will disagree with me, but digital designers won't:  a clock circuit is far more important to the end result than the type of DAC chips used (assuming the DAC chips are of level playing field and are capable of accepting the same bit rate and sample rate.)

 

[krumme]

PPM is normally defined as a diviation from a known frequency. You are in no position to hear if the music is whatever minicule diviation slower or faster. What you can hear - is jitter. When the frequency changes. When you place your crystal in an owen its because you need precise absolute frequency, not because of jitter - even though owen crystals normally have the same good qualities for jitter. If you want to minimize jitter make sure the crystal is not micro-shaking. Make sure your dac is place the right way then, and add fx. some sticking white stuff with anti shaking effect on the clocks themselves (cant remember the name). The effect is better than even the most expensive cables in the world, and it cost next to nothing.
 
To understand jitter you need at least a spectral view of it. Fx. if there is a lot of low frequency jitter, typical 1-bit dacs, with capacitor loading of the clock, can filtrate the high frequency jitter away, but the low frequency jitter for the wordclock goes into the dac. That can give bad sound. Combine it with an unclean, unliniar and slow power supply, fx. from an standard regulator and your 1-bit system fails giving both boring and unpleasant sound. If there is one place in the audio world, where you can hear the effect of standard regulators its for the 1-bit dac and your clock generator . Basicly the 1-bit is just your powersupply amplified using your clock and ground as a reference.
 
Now your expensive multibit dac is intrinsic less sensitive to jitter.And i wouldnt mind giving it a less clean power supply also. But today the cost of 1704 is so high, so it really doest matter that much to improve the quality of the ps.
 
All this data manipulation done today is ofcourse a very ineffective way of dealing with jitter, if we use a transportet. If you use a transporter, the clocks should be in the dac, and syncronized back to the transport. In the old days with cd players that was not a problem. But the separation of transport and dac, created a huge industri wit work - also for us hobbyist
 
http://forum.allaboutcircuits.com/showthread.php?t=40034
 
 
 
 
Quote:

I had the 1, the 7, and now the 7.1.  The differences are very apparent, especially if you have a quality source.
As everyone knows, the DSP-1 module is on its 5th iteration.  It's claims of making a source clock non-important are just not true.  In fact, I am using a modified Transporter with two Audio-gd JZ1 clocks, dual torroidals, and an Audio-gd power supply (all with upgraded caps).
I determined this after trying multiple sources, and most recently because I discovered an interesting feature about the Transporter.  When you are doing the initial setup you have the option for digital output of either "digital passthrough" or "word clock on digital output".  When you select word clock on digital output the quality is far superior in every way.  There are a lot of theories as to why this could be, from the people on the Squeezebox forums I've spoken to about it, but I won't get into that, since the passthrough feature was intended to just pass through whatever word clock signal was coming from whatever input is being fed into one of the Transporter's input jacks.  What is important is that the word clock on digital output is including the generated word clock data from the Transporter which in my case is being generated by the Audio-gd JZ1 clocks.  In my Transporter, everything is disabled except the digital output:  the internal DAC is disabled, the original clocks have been removed, the original transformers have been removed, and the analog outputs have been disabled.
 
To make a long story short, the DSP-1 can perform very well, but only if fed with an accurate/stable word clock (and word clock refers to the signal, not to be confused with a master clock which generates the word clock, and can be either an internal clock circuit or an external device).  Don't expect to get world class performance out of your Ref 7.1 (or any other Ref model) if you are feeding it a word clock generated by a poor quality oscillator.  What do I consider a poor quality clock?  An oscillator with greater than 2ppm stability (you want it to be less than 2ppm... the JZ1 are about 1.5ppm... the uber expensive Antelope Audio Rubidium oscillator is rated at 0.05 parts per BILLION), and a clock with high jitter.  Ideally you want a TCXO (a thermally controlled oscillator), which regulates the temperature inside a miniature oven.  Oscillators are very sensitive to temperature fluctuation, and this is also one reason why a digital source sounds better after it has had time to warm up.  You also want multiple fixed frequency oscillators as opposed to a single, variable frequency one.
 
I'm sure some will disagree with me, but digital designers won't:  a clock circuit is far more important to the end result than the type of DAC chips used (assuming the DAC chips are of level playing field and are capable of accepting the same bit rate and sample rate.)

 

 

[Kingwa]

The PCM1704 can support 192KHz at 8X oversampling, the PCM1704 pfd is so conservative declare PCM1704 have max 768KHz input support but we have test it can support 1.536MHz as high as the ES9018 declare.
Later once I have time, I will try to test if the PCM1704 can    support 384KHz input at 8X oversampling , Wadia had said the PCM1704 can support 2.82 MHz (352K at 8X oversampling) but we want to  proof-test.
If had an I2S output device, simply modify the RE7.1 had the I2S input socket, then can playback with 192KHz .
But we have not plan develop the RE7.1 support 192K through SPDIF input. Because we consider the SPDIF interface DIR9001 is the most neutral chip we can applied.