New DAC

Hi,

There are a number of Kits out there, Thomas in Hong Kong is probably best choice, but his approach to business is problematic, as it is a sideline and his main job often keeps him away for a week or two at a time. His Kit may soon get more professional marketing and support though.

http://www.diyaudiocraft.com/

Purely schematics for one, if you can make use of them and work out the few errors drawn in....

http://www.fortunecity.com/rivendell/xentar/1179/projects/adagio/Adagio.html

(the slight greeking of values/numbers is intentional, the project is STRICTLY for advanced DIY'ers, who can work out the details for themselves, according to their taste)

This probably was the first ever on the net at least and has done much to popularise Non-Os & TDA1541....

There have been later ones, I believe Pedja Rogic's one might be a good choice:

http://users.verat.net/~pedjarogic/audio/tda1541a_dac/tda1541a_dac_rev.htm

Naim Fiends could replace the Tube or Op-Amp stage with circuitry derived from Naim Phonostages BTW....

Past that I will say that geting a TDA1541 working well (non-os or not) is a magnitude more difficult than a TDA1543 or 1545, this is quite challenging.

Ciao T

 

Ah yes the diyaudiocraft one, forgot it was a 1541. This is quite popular on diyaudio if you do some searching.

 

So does this dac ignore the clockin your transport and re clock? Tempted (for the price) to build one and fit it inside the copland rather than outboard. Could I use the power supply from the copland internal dac to power this?

 

Hi,

Not quiet. There are four general options for DAC Side Reclocking of the Data to the DAC WITHOUT letting the DAC actually clock the Transport.

1) Secondary PLL

(PLL = PhaseLockedLoop a way to syncronise a given clock like 12.228MHz for digital audio with a lower rate clock like the S/P-DIF frame-clock)

Every PLL will have a cutoff frequency, below this frequency any change in input frequency (jitter) is passed on, chages with a higher frequency will be progressively suppressed as the frequency goes up. Funnily enough, Multibit DAC are really only sensitive to audio band and slightly above jitter, any jitter above the sample rate is suppressed anyway.

Most receivers PLL cannot reject jitter in the audio band (Cirrus Logic Parts suppress jitter above 10KHz with a slow falling slope, meaning at 44KHz there virtually no jitter attenuation) as it is required to lock onto a 44.1 or even 96KHz datastream which requires a quick response.

A secondary PLL can have a much slower response with a lower corner. Such a PLL can be analogue or digital. The kind of syncronous memory buffer as used by Lavry is actually a digital PLL, an analogue version is used in the earlier Audio Synthesis DAX.

A slight modification of this is a scheme I call 2-Speed PLL, where the original PLL in the receiver is slowed down severely once lock has been achieved so that the corner frequency is very low. I am still working very slowly on that, for DIY it would likely take just a few parts and could be fitted to any CS8412/14 et al equipped DAC. Maybe more another time, but corner frequencies for the PLL in the 10Hz region are possible.

2) Asyncronous output clock

Some receivers like various Cirrus Logic Parts (and possibly the DIR1703 from BB) support certain modes where an external clock is used to clock the data out of the receiver. The assumption is that the application circuit will take care of adjusting either the input or output clock to match.

If a free running oscillator is used (DDDAC1543 and the StormDigital DAC discussed elsewhere use this) there is no syncronicity and if both clocks differ enough in frequency the system will either drop or repeat a single sample in an interval determined by the difference between the clock frequencies (the larger the clock difference the more frequent the dropped or repeated samples).

In such an application it would be wise to fit identical clock generators with a very narrow specified frequency tolerance (2 - 5 ppm) to both DAC and Transport (making it strictly a DIY solution), a single frame will be dropped/repeated only every few seconds or so, which should be completely irrelevant.

If the difference is large (as much as 5000ppm from nominal have been recorded with cheap players which would cause a dropped/repeated frame every 25mS appx. if my math is on the money) there may very well be audible problems.

The above would seem best for DIY use, if you can live with a single sample rate and modify the transport. I suspect one could use the various frequency status pins to select a range of clocks for the output but the whole thing becomes VERY messy.

3) Memory Buffer and free-running output clock

This is really a variation of 2), except here we do not just buffer a single sample, but a large number of samples, so that we do not get dropped/repeated samples at all if the buffer is large enough.

Chord seemingly uses this principle, but it is all a question (again) of how much difference between the clocks you want to allow and you need buffer as much as the possible lost samples and have twice that amount of memory.

Morgan Jones worked out that around 16 - 32MB would be needed IIRC, this was long ago.

4) Asyncronous Reclocking

This is actually an interresting one, it has been first (AFAIK) introduced by Kusonoki San, it has since gained a lot of popularity. What it does is to use a free-running oscillator with a frequency not at all related to the sample frequency and use that to reclock the critical (latch enable) clock. The "Monica/Monica2" uses this principle, as do many others.

As a result jitter is actually NOT AT ALL reduced, instead it is shifted in terms of level (peak-peak jitter becomes invariably a constant, namely the clock cycle of the re-clocking clock) and the entire jitter spectrum is shifted, by producing in effect a beat-frequency effect between the two clocks.

The resulting interactions are unpredictable and it is obvious that selecting the highest practical clock frequency (how about 125MHz - this BTW gives still 8nS or 8000pS peak-peak jitter). I suspect the principle is similar to what Altman Micro uses in the Jisco/PCI products, but I cannot be sure.

' '

So, what is the bottom line? Unless you use a secondary PLL you are invariably inviting a number of problems. The audibility of these depends on a number of factor and may be from "non at all" to "bad".

If you fit a seperate DAC internal you are better off tapping the actual I2S signal on the Coplands PCB, prior to the Digital Filter and using that. Much lower jitter, easy re-clocking from the clock source in the Copland etc.

If you can use the existing supply depends on the supply specification, if there is enough spare capacity and the correct voltages available this may very well be a good option.

Ciao T

 

Thanks T, The copland has 2 int power supplies one for digital and one for analogue so I would imagine there is enough power just depends on the voltages then.

 

I've built both T's valve output based TDA1541 and Pedja's with AD844 used as a common base
Both designs sound excellent, obviously T's is harder to build because you have to make it from scratch

 

Hi
I have the Monica2 silver wired and fed by a Nuuks SMPS and also a Shek unit that I've again silver wired and rehoused using his regulated PSU,I have been chopping and changing for a couple of months now and find they're quite different,Shecks DAC is more forward and Monica2 seems a little more laid back,Madeleine Peyroux is a great CD for comparison.I'm totally undecided,just waiting for a Bottlehead Foreplay which is gonna run with a Charlize to help me decide
Rob

 

Okay so what do you guys think THE BEST DAC out there is that you can get either as a kit or an assembled board? Not just NOS but anything and any price.

 

The best digital replay I've heard was with dCS.

 

Hi,

This depends upon application and requirement, as I pointed out previously (as with so much else).

If you application is recording/monitoring/mastering in a studio you need a DAC that allows the use of wordlength above 16Bit, high sample rates and is "neutral" to a fault.

If your application is home replay using CD's as source you need a DAC that is designed/voiced to obtain the best from the Media and there I find some excellent recording DAC's missing.

For CD Replay the best I have heard include Audio Note Japan (Kondo) Hibari/Ongaku DAC, Zanden Model 5000, Marantz DA-12/Philips LHH-1000 (must be refurbished), Wadia's top of the range stuff. I found dCS wanting in use strictly for CD Replay, but not much.

Note that I feel that a "neutral" textbook DAC as such does not neccesarily serve most CD's well at all.

Hence the various "crazes" like upsampling, non-oversampling, digital filters with high pulse fidelity etc (non-os and pulse-true filters share a lot in terms of the resulting signal, techincally & sonically).

As non of these technologies are truely a universal panacea for CD replay my view is that they should be all available for use depending on need, personal preference etc., though I PERSONALLY fin Non-Oversampling TDA1541 DAC's to give the result I prefer most of the time.

The result is that the upcoming CD Player I am working on with friends will feature a TDA1541 which has been optimised first and foremost for non-oversampli ng operation but includes options for 2X & 4X Oversampling using standard digital filtering and upsampling to 48/96/192KHz witrh options for smoothing (dither) also selectable, so depending on the recording you select what replay processing is most suitable.

Ciao T

 

T, thank you for your 1541 recommendations. They all seem to require more effort/knowledge than I can muster for the forseeable future. Anything off the shelf you can recommend that doesn't use tubes, or should we wait for the fruits of your own efforts?

 

Thorsten, I did actually mean what DIY DACs are THE BEST. But you obviously like the 1541 in which case I want to know the same as Markus; are there any off the shelf ones around? Or off the shelf DIY ones, if you know what I mean.

I know you probably think modding my DEQ2496 is the best option for me, and I agree it would be the cheapest and probably best sounding way for me to go but I would rather get something I can sell again later if I want to. I doubt a modded DEQ2496 would sell for any more than a standard one. So if I can get a super-duper board to stick in the d02 case and use its power supply then I think that sounds good.

I think the Django looks good too but I want to wait until I have got a DAC first before I spend money on the pre.

 

Hi,

Sorry for that, but it's a little like the pre 2K situation with type 45 (or RE604, R120 et al) output valves, you could find them, they where not even really expensive, but most seemed to require more effort/knowledge than "they" could muster.

Now they are "high fashion".

I'm afraid I am rather much like the JubJub Bird of Lewis Carrols "Hunting of the snark", MY TASTE IS AGES AHEAD OF FASHION (OR BEHIND) OF FASHION.

The TDA 1541 is sufficiently long obsolote to cut the same furrow.

Any Philips, Marantz, Rotel, Cyrus, Arcam (other may apply) CD-Player marked "4 times Over Sampling" and "16Bit" build pre 1990 or so should have the right guts and can be switched to non-os with 3 cut PCB traces and 3 wire bridges (or be made switchable), Naim made some Players using TDA1541 too...

My own efforst are not really recommended as the "IT", they derive from my personal delusions and prejudices, plus a lot of "giving the market what it wants".

I can say that the results will be exceptional, expensive, but worth it. But then I would, wouldn't I?

Ciao T

 

Hi,

I have not build/listened to most, so don't ask me for a definite answer.

BUT, my recommendations would be like that:

"Neutral DAC, completely unsuited for CD Replay"

K & K Audio "RakDac"

"Best sound on CD but unsuited to monitoring Duties"

Tubelover Dual TDA1541 DAC Kit with SRPP Tube Output.

Personal opinion BTW, not the gospel, no direct experience with either, but much with very similar devices/designs.

You had to ask.

Ciao T

 

Just googled the tubelover ad it didn't get a thing. Where can that be found?

 

http://www.diyaudiocraft.com/

Ciao T

 

Cheers

 

Liteaudio DAC-60 is right up there with the best.
LINK