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Old 18th August 2004, 09:06 AM   #1
supra is offline supra  Australia
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Default Non-Oversampling TDA's

I've just spent the best part of 3 weeks playing around with TDA1543 and TDA1541 Non-oversampling Dacs and would like to make some observations and welcome any dissention or agreement. This thread may be useful for those contemplating getting into a DIY DAC.

I've been happy with a heavily modified Rotel 965 for a long time- to my ears it is more organic and less brittle than most contempory machines, but acquiring a Metaxas MASDAC with the UltraAnalog 23400 chip showed me that the Rotel really is very compromised.
Unfortunately the Masdac is beset with a noise problem and will only play when it is in the mood, and getting it repaired is impossible as Metaxas wont release circuits or provide any back-up.

There is something about the UltraAnalog chip that is just "right" and I can hear why it was so highly regarded for so long. I have heard that there were some reliability problems with it, and maybe that was the reason for it's demise, or maybe Wadia just wanted the design crew as they bought UltraAnalog out and then let the brand die.
If anyone has a circuit for a simple UltraAnalog Dac I would love to see it.

The TDA chips attracted me as the basis of a DIY DAC, mainly because of the good reputations for sound and the availability of information about them.

To get a feel for the different chips i bought one of Scott Nixon's DACKIT with a single TDA1543 , I purchased an assembled board from Scott and just had to enclose the board and provide sockets and a wall PSU.

The LITE DAC-AH from www.diyclub.biz is incredibly inexpensive for a completed ready to go dac - it uses 4 paralled TDA1543 with an OPA602 op-amp output stage.

Getting a TDA1541 DAC was a bit more difficult- there are published PCB's available , but I couldn't find any actually for sale. I settled on the www.diyaudiocraft.com Double TDA1541 kit.

I received the Lite DAC-AH first and was quite frankly dissapointed with it at first- for the price it is very good, but in very critical terms it sounded congested and dead- it displayed all the hallmarks of a conventional opamp output stage so I quickly bypassed the output stage and ran it unbuffered direct and cap coupled . Much more alive and less vieled but still a bit rough around the edges- so to be fair to it I connected it up to a spare transport and left it running for 3 days.
When I came back to it I received a very pleasant surprise for it was much better- almost smooth and quite listenable.
The BG coupling caps I used may even take longer to settle in, so I've still an open mind on this one.

Then i received the DACKIT from Scott Nixon in the US (Can I just take a short break to observe that on day 3 of the Olympics Australia with 20 million people has the same medal tally as the US with how many million? Perhaps that can be put down to the McDonalds culture and media propaganda that keeps TV screens on "reality" TV)
The assembled DACKIT PCB is a bit expensive for what you get, but a bargain in terms of sound quality. And bear in mind that you can get it going in under an hour with a minimum of skills.
It is a bare CS8414-TDA1543 with simple cap coupling to the output. It doesn't have a real low output Z so is best used with tube amps- which suits me just fine.
It's very transperant, lively and very revealing. A touch too revealing maybe- mine had Rubycon ZA caps, BG's might be better, but that will be taste, system dependent- most people would be very happy with The DACKIT.

The Double TDA1541A kit from www.diyaudiocraft.com arrived and looks very impressive - a very professional double sided board with gold plated through-plating mounting holes (a good DC soldering station and an equally good de-soldering gun is an absolute necessity)and good quality audiophile parts.
The manual is not the best , but it's not beyond most- the surface mount CX8414 freaked me out so I went for a DIL CS8412.
The output is quite low though and you cant use this direct, and I have some very high gain tube preamps here, which soon proved this point.

I tried 3 different types of output gain/buffers. First up was a parafeed step up trans- I was after simplicity, with the ability to tailor the frequency response both up top (for filtering) and in the bass. This was possible as the trans I used had very wide bandwidth, and parafeeding enables quite a range of variables.

I then tried a tube buffer, and finally Pedja Rogics 844/j-fet buffer stage.

This really got the Dac cooking! I'm an unashamed tube/transformer freak but this little SS gain stage was simply cleaner and more dynamic. It seems the output of the DAC is very load dependent- I've been told a high impedance load is not ideal for the TDA1541 and in my opinion, the tube gain stage, which was a very high quality unit, just didn't sound as competent as the AD844/2SK369.

Unfortunately, as good as it sounds, there is still a bit of high frequency noise present- I dont know if this is typical of the non-oversampling TDA1541and although I've been building tube gear for a long time I'm not much of an expert on digital.
At the moment the only filtering is a 1000p cap on the Dac output- Pedja's design has an optional further filtering cap on the output which I have yet to try.
Anyone with any suggestions on removing the HF noise very welcome!

So what's the verdict?

The TDA1541 has a cult following and I can hear why- it has a very natural sound and has also a sense of dynamics that is also best described as natural, rather than forced or electronic.

The TDA1543 is a detail machine, very transperant , very revealing, yet quite listenable and enjoyable.

Pedja seems to hear the same as per his quote from his web site:

".....it was interesting to note that though the TDA1541A is smoother (some claim it is the most analog sounding digital part ever made) and the TDA1543 is obviously a rougher performer that additionally could get into the saturation by the sonic content where TDA1541A stays soft, the TDA1543 has more liveliness and transparency. Then, with TDA1541A necessity for sin(x)/x compensation becomes more obvious. Hence I can, without any problem, understand both those claiming the TDA1541A is a higher class chip and those who opt for the TDA1543; I also understand those who describe the situation as a matter of taste."

I have to say though that I think the UltraAnalog 23400 kills both of them- and it probably should as it was just about impossible to buy it in a machine that didn't cost many thousands of dollars in it's heyday, plus the fact that I believe it was really a hybrid and virtually handmade- it certainly sounds remarkable to my ears.

But at the end of the day there is still that damn digital lack of true realism- it sounds very good, but there just isn't that freedom from constraint you get with a great vinyl system. The ease and flow just isn't there.

I think the problem isn't so much the DAC, but the whole gain/filtering process that follows. My experience with 30 years of building tube preamps and power amps is that any filter is bad news, whatever it's origins or components.

The CD system really is flawed . Like politics, it is really quite depressing. Thankfully I still have all my vinyl for when I want to listen to a more MUSICALLY dynamic , more organic and natural reproduction of music.
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Old 18th August 2004, 10:24 AM   #2
supra is offline supra  Australia
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Default HF Noise

BTW I solved the HF Noise problem- it was a human error in assembling the PCB. Hard to find but easy to fix.
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Old 20th August 2004, 01:54 AM   #3
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For the double TDA1541a kit from diyaudiocraft, you can increase the output simply by changing the I/V resistors (R28, R39, R47 and R48) to higher value, say 47ohm. Higher value has better punch and dynamic, but at the expense of higher distortion and has a coarser texture.

I am also a builder for the kit, but I found exactly the opposite to your observation. I like the tube gainstage much better than AD844. The AD844 sounds a bit electronic and lifeless, whereas the 6C45Pi sounds faster, detailed and with more emotion to the music. The 6DJ8 SRPP tube option is very smooth, a bit too smooth for my taste. So I settled in the 6C45 and tweaked the power supply by converting the cap (C5) after the 6X4 to 47uf Balckgate, the 2 cap (C3 and C43) to 10uf Solen MKP bypassed with ERO 0.1uf MKP1841. This has improved the sound a lot. I also use ERO 0.47uf MKP1845 as the output cap after the 6C45.

Please give this baby a couple hundred hours for it to break in, then you might have a different verdict.

I like vinyl but I am too lazy in cleaning up the vinyl, especially in the humid weather of Hong Kong summer.
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Old 22nd August 2004, 02:51 AM   #4
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Talking Non-Oversampling TDA's

hi michael,

does your friend collect the kits already.
I post to him over three days by EMS.

If U feel that the tube PCB is not better than the AD844.

Pls try to remove the L3 & L4 ( filter) of the TUBE PCB. The HF will increase more but will still less electronic sound as AD844.
Pls try and tell me that which different. &......... U said the
HF Noise problem- it was a human error in assembling the PCB. Hard to find but easy to fix.
Pls email to me or share to others in this forum where it was. I need to improved when I re-print the PCB's Film.

thanks

thomas
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Old 22nd August 2004, 02:53 AM   #5
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Talking Non-Oversampling TDA's

hi,

I said remove the L3 & L4 of the Tube PCB means every L3 & L4 use a copper wire as a jumper to connect them.


thanks

thomas
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Old 22nd August 2004, 07:56 AM   #6
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I must agree with cmt42001- after messing around with a few values, the 6c45pi buffer is markedly better than the 844 stage, which I found full of punch, particularly in the bass, but very electronic- sounding.
I also tried some very nice English 6DJ8 Mullards in the alternate buffer config, but missed the holographic effect of the 6c45's.
The initial config using the i/v resistors at 22R is too low in my opinion, with a somewhat flat soundstage and rather lacking dynamics. Things improve greatly with even a small tweak of these values. I settled on [for the moment] 27R, and the soundstage moves forward, out of the speakers. I went to 33R, but the sound got too grainy for my liking.
I did find the bass a touch light using the 0.47uF ERO's and now have 10uF MKT's there, which improved it greatly.
Overall, I'm pretty happy with the way the 1541 sounds- it is like what everyone has said: a very analogue- sounding chip. Now, whether a dual chip config is better than a single one is another argument again! javascript:smilie('')
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Old 22nd August 2004, 12:46 PM   #7
Pedja is offline Pedja  Serbia
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Guys, get serious and if you use AD844 as common base stage, use it the way it must be used or do not use it. At least, be aware of the way you use it.

It does not sound electronically at all, nothing even close to that.

Pedja
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Old 22nd August 2004, 10:31 PM   #8
t. is offline t.  United Kingdom
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Quote:
Originally posted by Pedja
Guys, get serious and if you use AD844 as common base stage, use it the way it must be used or do not use it. At least, be aware of the way you use it.

It does not sound electronically at all, nothing even close to that.

Pedja

I'll second that, after trying different output stages tube and op-amps Pedja's idea of using the AD844 as a common base was easily the best in my system.
I use three different amps buffered/regulated GC,kit88 tube amp and Avondale power amp with modded Nac pre.
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Old 23rd August 2004, 01:54 AM   #9
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Quote:
Guys, get serious and if you use AD844 as common base stage, use it the way it must be used or do not use it. At least, be aware of the way you use it.
Pedja,

I agree with your comments that AD844 need a careful implementation for I have built three before using different parts, and I thought that AD844 was great until I heard the 6c45 tube stage. You are RIGHT that I do not use AD844 anymore and I would not look back.

l have also tried the OPA660 common based stage and I think the AD844 is a bit electronic-sounding, while the OPA660 is better in the sense that it is warmer and natural sounding. Afterall it is a matter of taste and it might reflect the sonic signatures that different manufacturers have.

Who am I to judge who is serious...??

Tim,

I also found that 0.47uf is bit bass thin, so I use two in parallel (0.47uf x 2) and the bass and mid improves.

Please try the Riken RMG resistors in the I/V position, and it will smooth out the sound a lot (dale is a bit rough). At present I used the 12ohm Vishay S102 and it sound wonderful, with more texture and bass than RMG (12 ohm is fine with me as I have the 99db fullrange speakers).

Recently I got hold of the new EH 6C45Pi Gold pin version and it sounds better than the standard grade. The bass has the same punchy but clean notes, but the mid and high is smoother. That wonderful holographic effect is about the same for both version. The gold pin version is more natural.
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Old 23rd August 2004, 01:57 AM   #10
ss1 is offline ss1  United States
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Hello Supra,
I have the lite dac-ah. How did you bypassed the output stage? Where did you installed the bg coupling cap? Which bg did you used (bg n,std, etc)? If you can share some info,it would be helpful.
thanks
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