Optimal supply design for UCD and Zappulse modules

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#101
An externally hosted image should be here but it was not working when we last tested it.


Picture of my Zappulse,not finished cabinet but playing.I use a 2*50V 1000VA trafo and LC Audio soldered two bigger capacitors on their Predator PSU to handle the bigger trafo.2*15000 80V.Unfortunally the right channel died but i`m going to have a new on the warranty.This amp really plays nice and very powerful,and for the money nothing can compare.
/ Sven-Åke
 
#102
I heve made an intresting experience....

I have made 1 UcD400 and 3 UcD180 stereo amps...

one of the UcD180 is equipped with 2 Rifa PEH200 22000µf 63V caps fed from a700 VA trafo via 2 rectifier bridges...

the other two UcD180 has the same trafo but 4 rectifier bridges feeding 2*15000µf 63V BHC ALP20A153DF063 per UcD module...
http://194.205.122.12/servlet/AdminBHC?purpose=spec&partNo=ALP20A153DF063

There is a big sonic differance between them... the one with BHC caps sound much better!
Tighter bass, clearer, more open mids and great high's without "sssss-sounds"...

I have tested this together different people on Dynaudio Contour 3.4, B&W 802 and Carlsson OA51.3... Chord and Vincent pre-amps. Same result on all equipment...

I will replace the Rifa PEH 200 in the first UcD180 as soon as possible...

The difference between the amps, besides the cap-brand is that in the one with Rifa PEH200 the two UcD modules share the PSU, and the one with BHC caps only "share" the trafo since it has 2 rectifier bridges and two caps per module...
How big is the impact of this difference...?
And PEH - total of 44000µf, BHC total of 60000µF...

I will also test this on my UcD400... A friend of mine is building a 400 with the same components as mine and I will wait until he is done so that we can check that they sound the same... then I have a something to compare with when I modify my 400 with new caps...

/Stefan
 
#103
Originally posted by OA51 There is a big sonic differance between them... the one with BHC caps sound much better!
Tighter bass, clearer, more open mids and great high's without "sssss-sounds"...
Click to expand...

Same here.

I first tested my UcD180 module with big tanks BC 114 10000UF and after with BHC ALC 10 S 1080 DF (the special ones from Shuro).

Better with BHC specialy the bass (less boom boom).

The sound is also better without film caps in // with big caps (better medium).

Tested with Dynaudio BM15.
 
#104
How do you wire one transformer to 4 rectifier bridges? I think I already posed this question and was told that it shouldn't be done?

I assume that you wire each pair of bridges in parallel to your one transformer. It's not obvious why rectifying the same rails more than once should be of any benefit... Perhaps because the current through any one rectifier is lower...? (Do you have bypass caps around the rectifiers?)

Interesting...
 
#105
Each pair of bridges in parallel to one transformer yes...
(actually it is two 1*33 V transformers)
Bypass caps around all rectifiers...

I did it to minimize the current through the rectifiers since I wanted to use fairly high µF (60000µF)

I don't know... but there might be some benefit in respect of channel crosstalk or one module having some kind of impact on the other since the modules share only the trafo...

Regards

/Stefan
 
#107
Glad to hear this.

I instaled 2*22000 uF/63V BHC ALS40 caps (if I recall well) on my 4 channel UCD180 amp (I only use as stereo amp for now) and I also found tremendous, perfectly controled bass impact and a very dynamic presentation with morbid midrange and sweet highs.
I've never heard a Krell amp but I can't imagine it will be much better than this!

I use Tannoy D500 speakers.

It seems like they worth the money spent on them.
 
#108
BHC do a massive range of stuff... In general I assume that main differences in the range is the type of terminal yes? However, does one want the low ESR versions or the high ESR versions...?

Curiously the range of ESR values varies quite significantly depending on the "style" of connector.
 
#116
stef1777 said:
Why 80V?

UcD400 is rated for 60V max and standard power transformer will give you around 55V.
Click to expand...

Mine measure about +-57 VDC. I wont pretend to know anything about this, but to me it seems to be quite close to the 63V maximum of most caps. So I would choose 80V (or anything above 75V or whatever) to get a good lifetime from the caps.

But maybe I shouldn't worry about that...
 
#118
Yeah, I think it sound practice to give yourself some safety margin on the cap voltage rating, 20% minimum as a rule of thumb.

You design for a 10% mains overvoltage @unloaded condition to bring the rails as close as possible to the 63 volt limit of the module (when the protection kicks in) in order to get the most out of it..

What if you had a bit of a dc offset for some reason and the caps started pumping up, or a "real" mains surge? If they didn't explode they'd easily be permanently damaged.

You can find BHC caps here

http://www.thlaudio.com/

They seem to have fair prices what they do give prices on, and people have said they're great to deal with, even though their order process seems like a true pain! At least they can get you what you want.

Regards
 
#119
richie00boy said:


I think I'm (and classd4sure) playing Devils Advocate here, but it's possible that the fact that one was shared PSU and the other almost dual mono causes the differences, not the caps.
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Yeah, it just isn't a good A vs B comparison, too many other factors that are different.

However, I'm sure the two caps will have a different sound.. I remember reading at some website the other day a "review" of the different characteristics (sonically) each type of cap had, Rifa Vs BHC Vs a few others... I wish I could remember where it was..
 
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