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Old 18th June 2002, 11:44 AM   #1
Geoff is offline Geoff  United Kingdom
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Default DAC - Upgrade or replace?

This is my first foray into the Digital forum so please be gentle with me. My current CD player (Marantz CD-94 Mk2) has a CDM1 transport and dual TDA1541A/S1 dac chips in a balanced configuration.

It is time for an upgrade and I have been considering various options. I have the full service manual for this unit and am quite comfortable with determining suitable modifications for the analogue and power supply circuits. However, this design is now over 13 years old and I am wondering if there are any, more recent, dac chips that would offer a significant improvement in performance.

Basically, my current options are to either improve the analogue/power supply sections of the existing circuit or to replace the complete dac. I would welcome any views, opinions or alternative suggestions from those members with more experience of digital design than myself.

Geoff
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Old 18th June 2002, 04:23 PM   #2
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Have you read any of my rantings? Look for the "Jocko CD80" thread for starters.

Jocko
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Old 18th June 2002, 08:22 PM   #3
Geoff is offline Geoff  United Kingdom
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Jocko

Thanks. I usually avoid rants, particularly those that degenerate into something of slanging match, preferring instead a well reasoned presentation of facts and opinions. Despite this, I had in fact read every thread containing a reference to the TDA1541 before starting this thread and so was well aware of your dislike for this particular device.

However, my understanding from the many posts in other threads was that there did not appear to be a clear-cut concensus agreeing with your view. Surely, as with analogue, the circuit topolgy has an effect on the overall sound quality, not just the type of dac chip used? In this respect, is it not possible for an older dac chip in an optimised circuit to sound better than a more recent design in perhaps a less than perfect layout?

To put this into context, I am currently unemployed and do not have the funds available to purchase the components, and a quality pcb, required for a more modern dac unless the result is likely to be a significant improvement in performance.

It is a pity that up-dated (improved?) dac chips are not pin-compatible, drop-in replacements, like many IC op-amps, since this would make my choice of options much easier.

So, back to my original query. I have dual TDA1541A/S1 dacs operating in balanced mode, followed by an analogue stage that can be easily improved upon. I would still welcome alternative opinions as to the best course of action to achieve an audible benefit, bearing in mind that further upgrades can be undertaken at a later date when funds permit.

Geoff
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Old 19th June 2002, 04:04 AM   #4
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You can replace the I/V stage with something other than an op-amp, and they do sound much better. No, they will never be a match for newer DAC sets, but you can devise a simple discrete I/V for little cash outlay and improve things quite a bit. Trust me.......I have worked on more CD players than most people have seen.

Jocko
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Old 19th June 2002, 02:04 PM   #5
ergo is offline ergo  Estonia
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Geoff

I have a Philips CD610 cd player that I use at the moment. I was not as fortunate as you and the player had TDA1543 DAC inside... I went for a solution that I'm listening currently which involves using the Philips player as transport and I take the I2S signal from decoder IC and run a non oversampled (yes Jocko, I know your opinion of this: ) ) DAC configuration with PCM1702 DAC's.

Anyway, what I'm trying to get at is that during the process of all this it appeared that the digital filter SAA7220 is a part to keep your eye on. Even though I didn't need it I left it in as the spdif out in this player was formed by this IC. Then when studing the power supply lines and all sorts of RF crap it appeared that this IC was a real winner in crap generating department. It creates a lot of crap into both, power supply lines and all over the player as RF noise. So one suggestion would ceratinly be to get rid of this one or decouple/shield it very well.

**

I also already have a TDA1541A/S1 in my partbox but I haven't had the time and energy to make it into something jet. So I would be very interested in your result, especially in analog stage and power supplies, so if you have the time please give us some feedback on your efforts also.

Regards
Ergo
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Old 19th June 2002, 05:22 PM   #6
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Default SAA7220

YES! It is a crap generator. And also the clock generator, too.

1702s work......so do 1704s.......AD1862s.........

'7220 puts a zero in the response which is a main component of the "crap" this pair produces that causes me to hate them so much. Which is why heavy filtering of the analog signal is necessary.

Speaking of clocks.......don't take that 680 pF cap off of the '1541.

Jocko
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Old 27th June 2002, 08:51 AM   #7
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Hi Geoff,

I think that the TDA1541 is still a great DAC, especially if a zero-oversampling, passive IV conversion approach is adopted. Both tweaks are cheap, reversible and easy to implement.

I think it would be very worth your while (and money) to try the approaches and THEN evaluate the sound and whether changing the DAC/CDP is required.

At the end of teh day, it is your ear that must guide, and in my mind there is a sufficient number of positive reviews of the zero-oversampling approach to suggest that it merits investigation, regardless of what the "thought police" may say...

I have posted an extensive set of mods in the Tweakers asylum forum. Search under Ryan and 1541.

Regards
Ryan
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Old 27th June 2002, 03:28 PM   #8
Geoff is offline Geoff  United Kingdom
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Ergo

Thanks for your useful input and warning about the 7220. I will certainly take your information (and Jocko's follow-up) into account when reaching a decision. The CD94Mk2 has reasonable power supply isolation, with three separate transformer windings for the analogue, +/-12V and +5V rails. The usual ic volt regs for the digital but, much to my surprise, a discrete transistor regulator for the analogue.

Ryan

Thanks for your information, it's good to get alternative opinions. I found it difficult to accept that that the 1541 could be all bad (despite Jocko's rants :-) since Sugden (of Class-A fame) use this dac chip in their fairly recently designed, top-of-the-range, 'Masterclass' CD player. I very seldom visit the Asylum but I will do so now and have a look at your posts.

Geoff
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Old 3rd July 2002, 02:54 PM   #9
dice45 is offline dice45  Germany
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Quote:
Originally posted by Jocko Homo
[B]You can replace the I/V stage with something other than an op-amp, and they do sound much better. No, they will never be a match for newer DAC sets, but you can devise a simple discrete I/V for little cash outlay and improve things quite a bit. ...
Geoff and Jocko,
although almost ignorant concerning digital, i have to second that. Never heard a DAC or CDP soound musical with an opamp doing the I/V job. BTW, the most musical sounding digital i heard were setups using a signal transformer doing the I/V conversion with a vacuum tube driven from the the trannies secondary. So if yo have an unused microphone input trannie lying around, it would be worth a try.

Before i forget it, the things did ot use SPDIF, data and clock lines were separated and the DAC's oscillator was the ultimate master clock.
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Greets,
Bernhard
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