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Old 12th July 2011, 05:02 AM   #91
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Quote:
Originally Posted by Greg Stewart View Post
Very useful reply. I get that there is a high level of synergy at play here and that changing topology and/or component choices will not produce the demonstrated and desired performance.

And I get that my 'I2S-connected, sound-card mounted, TDA1543 DAC-only' version will be a journey into un-charted territory. Still, I suspect it will be a worthwhile journey & I will start with as close of a clone of the unit as presented here, shorn only of the SPDIF front-end.

On updating my Peter Daniel DAC kit to this level while keeping it un-balanced, I still have a few questions...

1. Did you retain the 74ACT86 used for providing balanced data signal inputs into the DACs? That would seem to not be needed for an un-balanced implementation.

2. What coupling caps do you recommend?

I had intended to do both my 'sound-card DAC-only' version and the upgrade of my PD kit to a standard as close as possible to topology & components as laid out here. Looking it over, the Black Gate 2200uf/35v FK's and 1000uf/50v N's are going to be the hardest to obtain... Black Gates in general are getting to be very rare and those are going to be very rare. Luckily, I have the rest of the BG's needed in my dwindling stock.
It certainly shouldn't prevent you from trying the DAC directly with I2S sources. In fact I will be trying it soon with m2tech USB-I2S adapter board.

A good example of updating stock DAC kit to this level while keeping it un-balanced was presented here: Pushing the limits of TDA1543 NOS DAC

The guy still calls me and raves how good it all sounds

To keep it a reasonable cost I used MIT RTX caps and they seem to work fine. With single ended version the 74ACT86 is not needed.
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Old 12th July 2011, 06:03 AM   #92
leflu is offline leflu  Germany
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Hello Peter and Bob,
im still loving the sound of my 1543-DAC and am always interested in
even making it better.
When upgrading with your regulators, as BG-N 10uF/50V are hard to find,
whats an alternative for this cap in the regulators?
Bob, you referred to the importance of the pll at the inputchip. What are
the actual parts to use here?

greetings Ulf
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Old 12th July 2011, 10:52 PM   #93
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Quote:
Originally Posted by Bobken View Post
Hi,

I can assure you that this circuit when completed exactly as designed does work, and very well in this DAC.

I can only reiterate that your best chance is to *complete the entire circuit as shown by Peter* using the correct value components, and unless the components are down on spec the results must be OK.

I did mention earlier that resolving problems when there is a departure from the published design is not what I wish to spend my time on, but looking back at your original comments that placing a finger on the device seems to enable it to pass some current, suggests to me that you may have some stability problems here.

The added capacitance to ground resulting from the applied finger could be affecting this instability, although I have not experienced any such problems with any of these BSP129 devices myself - unlike the associated AD811 which is very sensitive to stray capacitance through poor layouts.
In this regard (and I don't wish to be overly critical here) that layout you show is rather a mess anyway, and when constructing the entire circuit you will need to keep all components very tightly together with minimal lead lengths etc, or you will have all kinds of problems for sure.

It is now after 1.00 AM here in the UK and I need some sleep now, but please don't expect others to resolve your problems for you unless you are fully-prepared to take the sensible advice given to you.

Regards,
Quote:
Originally Posted by Peter Daniel View Post
You need to build the regulator circuit exactly as posted, the complete version, then we can discussed the results.
Hi,

Thanks for your inputs. I build the entire DAC and regulators as posted. When i turned it on the first time there where no voltage showing up on all 3regulators, that's why i build a dummy current source with the BSP129.

After further investigation today i notice that my BSP129's don't perform as the INFINEON or Siemens datasheets says. Both are different from each other. For both of them they can work with a 0 Vgs and still show current (Ida) between 80-150ma depending on the brand. My ones which i don't know the brand of unfortunately does not perform this way and needs a positive Vgs.

Any suggestions on where to get the infineon BSP129's?

Best regards,
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Old 13th July 2011, 12:32 AM   #94
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I got mine from Newark
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Old 13th July 2011, 02:50 AM   #95
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Quote:
Originally Posted by leflu View Post
When upgrading with your regulators, as BG-N 10uF/50V are hard to find,
whats an alternative for this cap in the regulators?
You may check this post for possible substitutes, looks like Elna Starget is a good candidate: Finally, an affordable CD Transport: the Shigaclone story
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Old 13th July 2011, 10:18 AM   #96
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Can 1:1 600R transformers be used on output, avoiding caps. I currently have two on the output of my cs4398 converting it to balanced out.
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Old 13th July 2011, 11:55 AM   #97
Bobken is offline Bobken  United Kingdom
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Quote:
Originally Posted by maartentje View Post
Hi,

Thanks for your inputs. I build the entire DAC and regulators as posted. When i turned it on the first time there where no voltage showing up on all 3regulators, that's why i build a dummy current source with the BSP129.

After further investigation today i notice that my BSP129's don't perform as the INFINEON or Siemens datasheets says. Both are different from each other. For both of them they can work with a 0 Vgs and still show current (Ida) between 80-150ma depending on the brand. My ones which i don't know the brand of unfortunately does not perform this way and needs a positive Vgs.

Any suggestions on where to get the infineon BSP129's?

Best regards,
Hi,

I am sorry to hear this, especially as you said that you have 50pcs of them. In view of what you now say they must be fakes, which on reflection is perhaps not too surprising, because a 'genuine' BSP129 does not behave like that.
Had you mentioned earlier (when I first commented on the other reg components) that you had already tried 3 complete reg versions with identical problems, it would have saved some time and head-scratching perhaps, and I would have asked about their source as I did suggest the possibility of devices being out-of-spec.

For some obscure reason, since I have been using these depletion mosfets I have noticed worldwide shortages from time-to-time, a matter I mentioned to Peter when I first suggested that he might like to try this circuit in his DAC. At that time he also found they were not readily available, and the lead times at the UK distributers I checked for him were all for several months delays.

Around the time when I first used BSP129s I was involved in a commercial design with a tight deadline, and I had to abandon my intentions to use the devices as none were available and lead times were unacceptable then.

I obtained a batch of the only practical alternatives I was aware of, Supertex DN2540, but on checking the entire batch their parameters varied so much that the current-setting resistor would need to vary by 200% from the two extremes! This would result in the unacceptable complication and additional costs of measuring each individual device and selecting resistors on test, so they are not my preferred choice for this requirement.
IIRC, several of their parameters were substantially different as well from BSPs, and as an example I recall that the current-setting resistors needed to be considerably higher values for similar currents than the values I use in the BSP-based regs.

During the time when I have been using BSP129s, I have never seen any genuine devices offered for sale other than the Infineons, and I have done a lot of searching around. Accordingly, I would be wary of anything of unknown pedigree as it seems that whenever any devices are scarce or still popular after their discontinuation, there are unscrupulous vendors around who will take advantage of the fact.

Some years ago Peter, myself, and many other Forum members were 'taken-in'
with a group buy of discontinued dual J-Fets, but due to the integrity and efforts of the organiser who had himself been duped, most of us received most of our money back.

Hopefully, you will be able to recover your outlay, but as a favour to other members please tell us where they were obtained so they can avoid falling into the same trap.

Regards,
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Old 13th July 2011, 03:04 PM   #98
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Guys, sorry for all the confusion, but it also looks like I made an error drawing the schematic: Pushing the limits Regulator
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Old 13th July 2011, 03:11 PM   #99
Bobken is offline Bobken  United Kingdom
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Quote:
Originally Posted by leflu View Post
Hello Peter and Bob,
im still loving the sound of my 1543-DAC and am always interested in
even making it better.
When upgrading with your regulators, as BG-N 10uF/50V are hard to find,
whats an alternative for this cap in the regulators?
Bob, you referred to the importance of the pll at the inputchip. What are
the actual parts to use here?

greetings Ulf
Hi Ulf,

The PLL filter is a region I was intending to go into, anyway, so now is a good time to make some comments.

When I began trials with alternative components here, I was aware of the reasons for Peter's choice, IIRC mainly based on the popular "wildmonkeysect"
filter which had been adopted by many previous experimenters.

I had also researched all the comments I could find associated with this particular combination of components, and began to realise that it seemed everyone had more-or-less just followed this concept having found that it sounded better than the stock data-sheet suggestions. This was never likely to satisfy my curiosity, so I ignored what I had already become aware of, and started my own experiments based on the original parts chosen.

I have always been a fan of Black Gate caps (probably the first - or nearly so - to espouse their benefits and you only need to read some of my earlier postings on this Forum to see that!), and like Peter I decided initially to try BGs as he had done for the main PLL cap C11 on his original schematic.

In spite of being enthusiastic about their use in audio circuits which stems from discovering that nothing else gave me similar sonic satisfaction, BGs are not perfect electrolytics but there are none better in my view so this seemed a safe choice initially. I soon discovered that in opposition to the frequent suggestions and seemingly accepted-wisdom of my predecessors, increasing this cap's value excessively was a big mistake. I had seen comments about caps up to 1uF being touted, together with either very low-value series resistors (R6 on the orig. schematic) or even no resistor at all, until the circuit failed to lock onto the incoming digital-stream!

However, my ears soon told me that this was not the way to go as increasing the cap's value gave a fat slow sound as if everything was over-damped, and the entire life was missing from the sound. To cut a long story short (unusual for me!) after many months of intense trials together with hundreds of different resistor choices, I reached the conclusion that anything much above 0.2uF was just not good for the desired results, and this value was a problem with BGs. A particular problem here is that this region is sensitive to picking-up unwanted interference (although not quite as serious a problem as some had made-out) and virtually all other HQ caps had awkward lead-arrangements and/or were physically large and unsuited to this application.

I tried many other caps but nothing came close to the superbly clean BG 'sound', and as most of my 100+ stock of NX HiQ 0.1uFs measured at around 0.125uF I tried a couple of 0.47 NX HiQs in series to begin-with which was quite good. I also tried many other combinations of 3 in series & some in parallel etc BGs, but finally settled-on a pair of 0.1 in parallel which actually measure closer to 0.25uF jointly, a bit higher than I would really like. A single 0.1 is certainly superior sonically in most respects to going higher than around 0.2uF, but although many times since the original basic choice was made I have changed this cap's value again out of curiosity, I always come back to the 0.25-ish combination after a while.

This is again an example of needing to make the best out of what components are available and sounds good in the particular application, and unenlightened nay-sayers will doubtless criticise these situations severely, and say that this is just making matters harder than is necessary. Before anyone is tempted to do this, they should LISTEN to the results with what I have found to be the best (so far), and if they still believe that they have a better alternative I would be delighted to know what that is.

The other smaller cap (C10) is a real dilemma for me, mainly as I don't know of any cap made which is in the correct region of values and which 'sounds' as good as I prefer, and which is not far too large in size to be suitable here.

Additionally, according to the finest references I can find on PLL filters (mostly in Dean's Book) the earlier-suggested 3300pF C10 is far too low in value technically to do much good, anyway. It needs to be around (just under, actually) 10 times smaller than C11, ideally, if these sources are correct and in normal applications this cap is not specifically intended to change the filter's slope as much as overcome issues due to the resistor R6.

Also, this concept of making the filter 3-poles came originally from the later Crystal data-sheets which clearly state that the component-values etc do not apply to the earlier chips like the 8412 and I am less sure that the same concept is very effective with this earlier design.

******I don't know what just happened here, but as this is unfinished I didn't intend this to be shown yet, and I don't know how to withdraw it without losing the info. I will continue on another posting!!.
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Last edited by Bobken; 13th July 2011 at 03:21 PM. Reason: ****-up with the send button!
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Old 13th July 2011, 04:16 PM   #100
Bobken is offline Bobken  United Kingdom
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[QUOTE=Bobken;2637827]Hi Ulf,


Part 2.

Whatever, I have still been unable to find any suitable caps to try in this region which don't immediately spoil the entire sonic results to my ears although a tiny plastic-film Wima was the best, or rather the least damaging to the sound, out of all those I tried of a substantial value. Going smaller in values I like the high-rise polystyrene types which have a small footprint and 5mm lead-spacings, but as yet I don't find much (if any) sonic benefit when adding these, so for now I am still avoiding this cap altogether.

Moving on to R6, the short answer here is that I would not use any other type than a naked Vishay (TX2352 or the slightly better TX2575) after 'listening' to dozens of other choices here. The change in the sound is quite marked and for example using the same-values of Vishay (non-nude) like S102 is very poor in comparison, even though they are the same bulk-foil concept albeit with a molded surround.

As to values, actually I am still experimenting here and this value gets changed quite frequently as it is a handy means to tailor the resultant sounds, and this again can be fairly drastic. Going too low in value provides a lacklustre effect in comparison as if the extreme upper frequencies are being truncated. This would be similar to a low-pass analogue filter where the -3dB point is lowered a little, although I confess that I don't know why it should particularly affect the HF more than any other frequency in the digital stream, and it is perhaps unintuitive. It becomes a tame sound somehow for want of a better sonic discription, but going higher in value for R6 one starts to hear more-obvious distortion effects typical of jitter. This can appear to be more lively but there is far too much distortion in this circuit already, and for me I would rather not add to this if it is avoidable.

On this subject, of course the HF is troublesome anyway due to the way we use this TDA chip, and checking with a 'scope shows that over a few kHz, sine waves are getting badly distorted to the extent that had I seen this first, I would not have believed that the results were even worthwhile listening-to. This is another regrettable problem with these kinds of DAC, of course, but they can and do sound quite extraordinary in spite of all of their technical shortcomings.

A conclusion I have reached more-recently is that there is an 'optimum' breakpoint for this PLL filter to sound at its best, and from my experiments the R-C time-constant I have reached by hundreds of hours of empirical trials happens to be very close to the Crystal Data-sheet recommendation.

Presently, with my C11 value I am working in the region around 180R for R6, and Peter's choices are perhaps not-coincidentally very close to this same time-constant, also apparently judged by ear.

I can readily hear changes of less than 10 Ohms here for R6, which surprised me a lot being such a small percentage variation, but again this is the nature of this particular rather 'touchy' circuit where we are trying to get the very best perceived sonic results out of a (sometimes!) bad bargain.

There is possibly some merit in exploring a separate clock/PLL filter sometime, but so far I have enjoyed the challenge of avoiding further complications to the circuit, and some others including Peter don't always agree that these are an overall improvement. Besides, I might lose the opportunity of using this region to 'tune' the results I guess, and that would spoil the challenge and probably some of the fun, and because other caps are not perfect in this design, the tuning facility is quite useful.

Regards,
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