Simple, good quality DAC

[Elso Kwak]

Hi Lucas,
The DAC I demonstrated in 't Harde was:
AD8561->CS8412 with Wildmonkeysects loopfilter-> ASR->TDA1543 (NON-OS)-> discrete-opamp IV->discrete outputbuffer.
I posted the powersupply (triple darlington with LM329) for the TDA1543 on this forum. The digital supply is with LT1086 and LT1033. The analog supply is with Jung like regulators (opamp driving a series pass transistor). All analog supply is referenced to one LT1021-5.
I also posted the general idea of the IV and ouput buffer including third order low-pass filter.
I am sorry, well I am not , further schematics are NOT available.

[Fin]

Hi all

I know I'm a few months late on this one but hope that someone can still help me.

I have a Philips CD624 which uses a SAA7323 bitstream dac. The onboard opamps, which for part of the low pass filter, can be bypasssed. I think it is a voltage output at this stage.

Does anyone have a design for an alternative filter arrangment to use here?

Regards

Fin

[Kochkurov Maxim]

I have thought about the upsampler approach but gave up when I realised the upsamplers like CS8420 and AD1890 - 1893 have a digital filter "on board".

I used many asynchronous sample rate converters as digital filters but only AD1896 (SRC4193) was suitable for Hi -End audio. This IC in synchronous mode provide very clean and detail sound (likely NPC SM5842 digital filter) despite the fact that it has passband ripple 0.015 dB against 0.00002 dB of the SM5842. The CS8420 is absolutely useless for audio because it has very hardly sound and tendency to signal dropouts.

[slbender]

Mr. Daniel and others,

I design tube amps and simple transistor audio stuff, so I defer to those who really know their CD players. I have a Cambridge Audio D-500SE, which I seem to recall uses a Philips CDM, but mostly Sony chips after it. The output board (PS Regs, DAC, several R-C audio filters, Audio OP Amps, Digital output) was in some way defective, beautiful sound from one channel; disastrous distortion from the other. I replaced the audio IC's, it was no better. I replaced the coupling caps and other 'lytics, the problem remained the same. All this soldering despite using a temp-controlled soldering iron, and careful technique, eventually destroyed the board, as I suspect its made with 1/2 oz. copper and too thin traces, most of the redone thin copper traces lifted. I have the schematics for this Cambridge Audio unit, but for none of the other units I will mention.

I'd like to replace this board DAC/OP Amp Output board with something else, preferably something of high quality, simple or using existing "junker" boards I that I already have...


1) I have the main board and PS of an early Proton CD Player which used an early Philips CDM; two TDA-1540 DAC chips (Circa 1987?) and older OP Amps.

2) I have the main board and PS from a Marantz CD-48 which uses a TDA-1549 and JRC-4560D, plus another JRC-4560D for the headphone amp; the Cambridge Audio 500SE lacked a headphone amp and jack; the CD-48 also has a digital out, like the Cambridge Audio did.

3) Two made in China, Circa 1992 KLH Digital HA-2000 home theater units with 6 channels of TA-2020 plus a universal type DVD/CD decoder DAC board, both lasers in the players are quite dead, one might have a working optical out.

4) Two stand alone DVD/CD players KLH digital model KD-1220's which work and also have a similar universal decoding board to above unit #3.

5) Several broken Spectrasonic 7" LCD screen DVD/CD portable players, having some universal decoding DAC; and discrete audio output stages (and really small speakers).

6) One or two working UJDA720 DVD/CD-Writer drives from notebook computers.

I'm sure within the seven unit types above I can connect the signals going to the Cambridge Audio DAC chip to a circuit entering another DAC chip and get proper audio out, even if I have to switch out OP amps and / or caps to make it better.

Exactly which one to best attempt to use, that I am unsure...

Unit #5 would appear to be the most recent in manufacture only a few years old, so maybe it has the best chips inside, also the discrete audio stages may be better than OP Amps. The boards in #5 and #6 would appear to be smaller and would likely make the process easier than some of the others where the boards are about 2 to 5 times the size of the original Cambridge board. Luckily 'bout 1/3 of the Cambridge Audio unit is empty inside, so room to "grow" for a bigger board... The #3, #4, #5, #6 don't have PS Regulators on their DAC/Audio boards, I seem to recall that the Cambridge Audio board contained diodes, caps, and two or three regulators along with the DAC and audio stages.

If more info on the chips present in various devices is needed, I can rip 'em open and jot down numbers and makers.

I also have some PDF-1703/1704 chips, a DAC or two from Crystal from a few years back, LT1083, LT1084, and LT1085 pairs in various versions, as well as some LT1115, NE5532, NE5534AN, and OP-xxx OP amps somewhere.

I'd appreciate comments from all who feel qualified!


-Steven

Originally posted by Peter Daniel
I just modified my Marantz CD-94 and as a stand alone unit it is better than used as a transport feeding my recent CS8420/PDF1704/parallel PDF1704 DAC. I'm still using original PS inside the player, while my DAC had 8 transformers and at least 13 local PS based on LT 1035/1085 (or whatever numbers) chips.

The only thing I did to Marantz was bypassing digital filter, simplifying output stage to a single OPA627 per channel, removing DC reducing resistors network right at DACs output, changing all electrolytics to HFQ and Cerafines, adding local bypassing (Goudreu triplets). Well, the results are impressive and that player is producing the best bass I've heard so far. Sometimes simple ways are better indeed.