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Old 13th July 2011, 05:17 PM   #101
Bobken is offline Bobken  United Kingdom
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Quote:
Originally Posted by Peter Daniel View Post
Guys, sorry for all the confusion, but it also looks like I made an error drawing the schematic: Pushing the limits Regulator
Hi,

I am also sorry that I didn't notice this error in the reversed wiring of the diode, but because I entered this thread long after the diag was posted I just didn't think to check specifically on any details like that.

I did see that the overall structure looked OK, and this still doesn't explain why maartentje has this problem when merely the resistor and mosfet are used alone, which until the further revelations today, was apparently the problem.
This is still a puzzle to me, unless perhaps he is using depletion-mosfets which were already damaged in some earlier trials, which again shows how important it is to explain any problems fully and the history at the first opportunity.
From what was said, I naturally assumed that the latest (and only - until today) trials have been made with new & unused BSP129s straight off the reel for this 2-component hook-up.

The resistor and diode are both correctly positioned as Peter mentioned in this other thread.

Regards,
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Old 13th July 2011, 06:30 PM   #102
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Originally Posted by Bobken View Post
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.......
Hi Bob,

Thanks for you help and knowledge.
I bought 50pieces unused brand new from:

Search Results : Get wholesale retail and high quality products at wholesale prices and buy online from China wholesaler and China supplier right here., SAVE 60% OFF our lower Ebay Prices by Shopping in our Store!

$0.40 a piece. Seems like they are the fake ones.

Since the BSP129 is hard to find i have to find a suitable replacement.. currently looking in to datasheets for the DN2540 and DN3525. If the tolerances from these are not as good as the BSP129 i just have to match the resistor with each fet.

Best regards,
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Old 13th July 2011, 06:54 PM   #103
Bobken is offline Bobken  United Kingdom
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Originally Posted by maartentje View Post
Hi Bob,

Thanks for you help and knowledge.
I bought 50pieces unused brand new from:

Search Results : Get wholesale retail and high quality products at wholesale prices and buy online from China wholesaler and China supplier right here., SAVE 60% OFF our lower Ebay Prices by Shopping in our Store!

$0.40 a piece. Seems like they are the fake ones.

Since the BSP129 is hard to find i have to find a suitable replacement.. currently looking in to datasheets for the DN2540 and DN3525. If the tolerances from these are not as good as the BSP129 i just have to match the resistor with each fet.

Best regards,
Hi,

Its a real bummer I know, but looking at the pics of your devices they are not the same as the Infinion parts which I have ever used because the body is a bit different on close examination from what I can see, and the markings are also not quite the same.

Isn't it possible to obtain any from Newark right now, as Peter suggested?

Personally, unless as in my stated instance where there was commercial time-pressure, I would still go for the BSPs. They are smaller neater devices and yet still very easy to solder manually. Their size helps a bit in keeping to a tight layout which you do need to watch-out for especially with these op-amps which are very fast current feedback devices and don't like much stray capacitance around them.

If you cannot wait if there are supply problems now with BSPs, set the DN2540 mosfets up in a rig with a pot so you can measure the current output and adjust for each device to suit your requirements. Then you can measure the pot's value and select a close value fixed resistor.

IIRC, I needed to use something like close to 30R for some of those I tested to achieve a suitable current for the 8+v reg, which is around 80mA from memory to avoid unnecessary heat being developed. The TDA's need around 55mA and you need a margin for losses in the circuit as well as an operating margin to cover for any rogue TDAs.

Regards,

Bob.
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Old 13th July 2011, 07:05 PM   #104
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Quote:
Originally Posted by Bobken View Post
Hi,

Its a real bummer I know, but looking at the pics of your devices they are not the same as the Infinion parts which I have ever used because the body is a bit different on close examination from what I can see, and the markings are also not quite the same.

Isn't it possible to obtain any from Newark right now, as Peter suggested?

Personally, unless as in my stated instance where there was commercial time-pressure, I would still go for the BSPs. They are smaller neater devices and yet still very easy to solder manually. Their size helps a bit in keeping to a tight layout which you do need to watch-out for especially with these op-amps which are very fast current feedback devices and don't like much stray capacitance around them.

If you cannot wait if there are supply problems now with BSPs, set the DN2540 mosfets up in a rig with a pot so you can measure the current output and adjust for each device to suit your requirements. Then you can measure the pot's value and select a close value fixed resistor.

IIRC, I needed to use something like close to 30R for some of those I tested to achieve a suitable current for the 8+v reg, which is around 80mA from memory to avoid unnecessary heat being developed. The TDA's need around 55mA and you need a margin for losses in the circuit as well as an operating margin to cover for any rogue TDAs.

Regards,

Bob.
Hi,

Newark is out of stock and to be expected in October 2011. The DN2540 comes in a TO-92 or SOT-89 so that will be small enough (plenty in stock at mouser.com). Around 80mA for the TDA, how much for the CS8412? 40mA?

Best Regards,
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Old 13th July 2011, 07:15 PM   #105
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If there is a problem sourcing suitable components for shunt regulator, you can as well go for a series regulator we've been using initially, the difference isn't really that big: Pushing the limits of TDA1543 NOS DAC
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Old 13th July 2011, 08:46 PM   #106
Bobken is offline Bobken  United Kingdom
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Originally Posted by maartentje View Post
Hi,

Newark is out of stock and to be expected in October 2011. The DN2540 comes in a TO-92 or SOT-89 so that will be small enough (plenty in stock at mouser.com). Around 80mA for the TDA, how much for the CS8412? 40mA?

Best Regards,
Oh! that's a nuisance, but as Peter has said the series reg is also quite good, although I do prefer the shunt version, myself. The samples of DN2540 I received were T0220 devices which are a bit more clumsy than what you mention, so maybe size is not an issue here.

I don't have the data-sheet to hand whilst typing this but IIRC each of the two PS for the CS8412 chip needs around 20mA, but you should check this for yourself. Assuming this to be so, between 35 & 40 mA for each reg should be fine, but IIRC the circuit-losses with the lower-voltage regs are not reduced directly proportionally to the reduced output voltages.

Ideally, as with any new or even a change to any design, you need to do the calculations for total current requirements etc to avoid potential starvation problems, and this requires the known and likely circuit losses to be derived. Then you can finalise the correct value resistor to use between gate & source of the device.

For example, lost across the 470R to ground from AD811 pin 3 there will be around 12mA (8.4v less 2.5v at pin 3 : divided by the resistance of 470R).

Similarly across the series pair of resistors connected to pin 2, around 6mA I guess (8.4/1428), and so-on. Allow a bit for the chip itself which won't be much anyway and for that lost across the ZVN mosfet and you are virtually there. I usually add a margin of maybe 30-40% on top of what I calculate when all are added together for safty's sake, but too high current is merely wasteful and unnecessarily generates excessive heat.

You never know until you try and make some direct comparisons, but a DN 2540-based reg might even sound better than a BSP-based one in this circuit.

Very few of these choices are entirely set-in stone in reality, although almost any change will affect the sonics in some way or another, even though the meter-reading-only 'experts' will not agree with this comment.

I usually use an LT1009 for my 2.5v current diode in this circuit, which has good specs and is readily available over here, but Peter has found that his choice which I have used before also works well for him. As already mentioned, with very simple reg circuits like this the overal sonic result is more-dominated by the type and value of the associated caps surrounding the reg circuit, and these do have a profound effect on the final sounds.

This is where the real challenges begin, to get the best overall balanced results with no parameters being ignored (at least be me), and it is surprising how the results can and will be changed if you are a sensitive/acute listener with a good and highly-revealing system.

However, where I have talked specifically about certain regions in this DAC circuit and mentioned definite component choices/values, I think that you can be pretty certain that it will be hard to improve very much on what I have found works best, during the past nearly 5 yrs of extremely intensive trials and listening tests.

I've done enough 'hogging' for a few days now I reckon, but I hope that it has helped a few members, so I'll take a break unless something major crops up, and will get back to my other interests for a while.

Regards,
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Old 14th July 2011, 02:25 PM   #107
le´flu is offline le´flu  Germany
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Hi Bob,
thanks allot for writing so detailed about your changes.
I will describe what i did until now, maybe you would help me
going one step ahead, ´cause i want to hear the differences.

By the way, what amplifier and speakers do you listen with?

So from spdif i´m goint directly into the cs8412 reciever via
75ohm Caddock MK132 (+ = pin 9, - = pin 10)
pll filter is R6 = T2352 1k2, C11 BG NX 0,52uF. PSU is still the
old one.

So were to go next? Change pll filter? Do you still have in mind
what the sonical difference between 1k2 + 0,52 and your latest
pll filter is? I´m asking because it takes some time to get new
resistors from TI ;-)

Thanks for sharing all your ideas and findings (as well big thank
you to Peter)

Greetings ulf
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Old 15th July 2011, 03:16 PM   #108
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Originally Posted by le´flu View Post
PSU is still the
old one.

So were to go next?
PSU should be priority: everything starts there and optimizing PS brings usually most noticeable changes.

That also makes the circuit more revealing so any subsequent mods are easier to evaluate.

You may also consider changing I/V resistors to Caddocks TF020 and maybe coupling caps, although it's hard to find something better than BG NS. Sure, other caps maybe more impressive initially, but BG Ns in a right setup are so smooth and natural...
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Old 16th July 2011, 09:29 AM   #109
le´flu is offline le´flu  Germany
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Hi Peter,
thanks for advice. So i´ll start collecting all parts for the three powersupplies.
Unfortunately farnell-germany doesn´t have bsp129 on stock.
As to the output-coupling i allways wanted to try teflon. My preamp
has 47k log pot at the input so i think 220n for the teflons will do, right?
Did you change the IV-resistor or is it still the original value?

Greetings Ulf
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Old 16th July 2011, 05:01 PM   #110
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Default Modifying a Magnavox CDB-262 or any other Mag with the TDA 1543

Peter,

I am a newby to this forum and have been spending hours looking up information about the Magnavox units after hearing a Philips CD80 and a Magnavox CDB 560. Absolutely amazing sound from 20 year old CD players.
Those units are, however, very rare whereas the Mags with the TDA1543 have good prices and seem to be available in thrift stores and on eBay.

Have you or any of your friends or customers used all or part of your TDA1543 DAC to mod a Magnavox CD Player with the very nice CDM 4/19 laser assembly and the TDA 1543?
If you have any information on implementing your mod in a Mag CD player it would certainly be appreciated. If there is more information on diyaudio could someone point me in the right direction.
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