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Old 16th December 2011, 04:15 PM   #4071
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Quote:
Originally Posted by -ecdesigns- View Post

Power supply module still needs to be designed. I am currently testing pre-filtered common mode power supplies.
Well John.. we (I) are eagerly waiting...

Is it similar to the pre-regulator and capacitor multiplier parts of the schematic you posted earlier, which are then followed with a post-reg locally at the TDA ?
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Old 17th December 2011, 08:01 PM   #4072
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Quote:
Originally Posted by -ecdesigns- View Post
hi dady,



The latest DAC module is the TDA1541A-MK8 with a single TDA1541A(S2). I posted concept schematics on this thread.

Power supply module still needs to be designed. I am currently testing pre-filtered common mode power supplies.
Hi, John,

In briefly looking at your common-mode regulator (a need for which, I very much agree) it appears to me that it doesn't so much reject common-mode noise as it converts difference-mode noise into common-mode. Which would be great for circuits which inherently tend to reject common-mode noise, such as complementary symmetry, balanced circuits, and transformer-coupled circuits. Was that your design objective, or do you have a different view of what the regulator is actually doing?
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Last edited by Ken Newton; 17th December 2011 at 08:30 PM.
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Old 18th December 2011, 08:45 AM   #4073
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Default Common mode power supply schematics

Hi studiostevus,

Quote:
Well John.. we (I) are eagerly waiting...
This year I have been busy building a new workshop, so I had very little time for audio projects. This workshop has now been completed.

Yesterday I completed common mode power supply schematics and routing of the PCB. The module will hold 5 separate common mode power supplies and fits on a euro size PCB.

Quote:
Is it similar to the pre-regulator and capacitor multiplier parts of the schematic you posted earlier, which are then followed with a post-reg locally at the TDA ?.
Capacitance multipliers are located on the power supply module, pre / post regulators are on the MK8 DAC module.

I attached common mode power supply concept schematics. When combining it with the MK8 schematics I posted earlier (post #4008 on page 401) you can see how I split up the power supply sections.
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File Type: jpg MODPWR2.jpg (192.8 KB, 814 views)
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Old 18th December 2011, 09:20 AM   #4074
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Hi Ken,

Quote:
Was that your design objective, or do you have a different view of what the regulator is actually doing?
Common Mode - attenuation to signals that appear identically on each of the wires going through the filter
Differential Mode - attenuation to signals that appear on just one of the lines.

Based on this, the new power supply should be called common mode power supply unless I am missing something.

Anyway, main function is placing a high impedance in both feed and return (GND). So the impedance between the mains and the powered circuit is high. With a conventional power supply, the return line (GND) has low impedance.

By placing a high impedance between mains and circuit, the effect of mains interference and ground loops can be greatly reduced.

Other objectives are very low noise, low output impedance and unconditional feedback stability under complex dynamic loading.
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Old 18th December 2011, 10:16 AM   #4075
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Thanks John, very interesting!

I am currently running on Salas shunts, and playing around with the local decoupling of the power supply lines. What are your findings there? I see you only use a 1uF acrylic at the tda.

I have tried combinations of
-1uF acrylic smd
-22 uF BG STD
-270 uF Oscon SEPC

Not sure what I like best...
-22uF BG only --> seems like things are missing
-22uF BG + 1uF SMD --> added smoothness
-22uF BG + 1uF SMD + 270 uF Oscon --> Added bass
-1uF acrylic SMD only --> listening to it now, it seems very bass-heavy, but also liquidy smooth. I am not sure if I like the amount of bass... on the other hand it's quite analog now. It's less transparent though

What do you think?

Last edited by studiostevus; 18th December 2011 at 10:18 AM.
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Old 19th December 2011, 09:30 AM   #4076
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Those acrylic caps also take quite a while to 'settle down', or break-in - detail comes up, everything gets 'cleaner', including the fat bass - patience required, maybe 50-100hrs - similar thing with the B32529 Epcos ones.
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Old 19th December 2011, 09:51 AM   #4077
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Thanks James.
They have now at least 50 hrs under their belt, I'd say. It's not entirely unpleasant, this fat bass. Especially since the mids are very smooth as well, and it sounds like vinyl.

I am just not sure whether I am listening now to the TDA or to the caps...
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Old 19th December 2011, 10:13 AM   #4078
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I do tend to go a bit over the top at times & if you don't mind doing something quite ridiculous, add a couple more of those 1uFs in parallel to pins 13 & 18 so there is 4uF on them! I have 4uF of the Solen FCs there and I quite like the effect - no fat bass but quite heavy enough and very clean.

Also a bit outside the box, I've also got 2uF on all the other decoupling pins ...

The caps aren't particularly expensive but a bit more than 2 cents!
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Old 19th December 2011, 10:18 AM   #4079
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Well... I don't think it is not uncommon to put a bit more uF on the MSB pins.. you see that in most designs with TDA1541a. I think John even started out like that, but went away from it again...

What do you do on the power supply decoupling? (pins 28, 26, 15)
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Old 19th December 2011, 10:48 AM   #4080
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Just the 1uF of the Epcos caps - this one of mine is still pretty basic - a long way to go yet. Playing with EUVL's Cen o/p stage, etc and looking forward to trying John's new power supply design - love the humble C multiplier cct - use it on power amp supply rails sometimes.
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