adapting unreg PSU to Brian's boards

[Jimmy D.]

I need some help retrofitting Brian's kit with the unreg PSU. I'm using one transformer with 2 secondaries. Brian's rectifier board and chip board uses a PG+, PG-, V+, and V-. Carlos schemo uses only V+,V-, and ground. How do I adapt using Brian's boards for PS and the chip board?

[Greg Erskine]

Hi Jimmy D.

Brian's kit PSU is a unreg PSU with a very small cap. If you want to increase the capacitance then it has to be in parallel with the existing cap. Also, the "snubber(tm)" is also in parallel with the exisiting cap.

I recommend NOT to connect PG+ and PG- at the PSU PCB because it is already connected at the amp PCB and earth loop will occur. If you decide to connect PG+ and PG- you will need to cut a track on the amp PCB.

By coincidence, this link in another recent thread, should help explain what I was saying above, but keep the common separate.

http://www.tnt-audio.com/clinica/ssps2_e.html

[Jimmy D.]

Originally posted by grege
Hi Jimmy D.

Brian's kit PSU is a unreg PSU with a very small cap. If you want to increase the capacitance then it has to be in parallel with the existing cap. Also, the "snubber(tm)" is also in parallel with the exisiting cap.

I recommend NOT to connect PG+ and PG- at the PSU PCB because it is already connected at the amp PCB and earth loop will occur. If you decide to connect PG+ and PG- you will need to cut a track on the amp PCB.

By coincidence, this link in another recent thread, should help explain what I was saying above, but keep the common separate.

http://www.tnt-audio.com/clinica/ssps2_e.html

Thank you for the response. I don't see that the link addresses my specific question though. If I parallel the 2 caps on the PS board, the large caps will be in reverse polarity?? And if I don't connect the PG+ and PG- leads to the chip board, it appears from the schemo that the 1500 uF caps will be floating.

Someone in this forum had posted a pic at one time doing the same thing but I can't find.

[HawkeyeStoob]

I second Jimmy D’s request for a little more info.

I have a very basic understanding of electronics diagrams. Any detailed pictures of the PSU with BrianGTs boards where I could see the layout, wiring, and hookup would be very helpful.

Craig

[fireman]

Originally posted by HawkeyeStoob
I second Jimmy D’s request for a little more info.

I have a very basic understanding of electronics diagrams. Any detailed pictures of the PSU with BrianGTs boards where I could see the layout, wiring, and hookup would be very helpful.

Craig

Me too. My kits sound good but as with most DIYer, I'm always looking to improve my toys and this sounds like a very good option.

[dw1narso]

With my fully respect to Peter Daniel and Brian for the board rev 2 that they design,

with my fully respect to Carlosfm for his effort to introduce the advantage of using high-capacitance-snubbered-unregulated-PSU,

here is the combination of both...

I hope I do not break someone's copy right...

REgards,
---
David

[dw1narso]

Sorry,

a little mistake... 10uF should be 100uF. I revise the drawing...

And I forgot to mention... other connections (from PSU board to amp board) should be kept the same.

And, as Carlosfm said, 10,000uF (drawn as 10mF) is a starting value... for 2x18Volt transformer, I believe 15,000uF (or 2x 6,800uF or 2x 8,200uF) will be better. For higher voltage transformer like 2x22Volt or 2x25Volt one, 10,000uF will be sufficient.

Bigger than 20,000uF is not reasonable at all...

Regards,
---
David

[Jimmy D.]

Thank you David! This is much easier that what I was going to do. I have 2 questions:

Why is the snubber shown at the chip board?

Is the orientation of both snubbers correct? C8 and R4 on Carlos schemo look reverse to what you have.

Jim D.

[SheldonD]

Sequence matters not whether C or R on snubber, as long as they are in sequence.

[dw1narso]

Hi Jim D.,

just back from a looong holiday...

Happy New Year 2005....

Sorry, I don't have internet connection at all at my place at that time

Sheldon already answer your question...

However, if it is really matter... (as some has found that it "sound" different... but you might not...) ... yes.. I wrongly draw the sequence of the R-C snubber. So I attach the revised one.

I put the snubber on the the chip board, and not on the PS board, because... theoretically... the best location to put the snubber is as close as possible to the gain device..., which in this case is the chip.
But... it might be does not really matter whether you put it on the PS or chip board... (see... a strange "un-exact" thing on this supposed to be "exact" world...)

BUT..... may I suggest something... this is based on what I found on the last two weeks...

If you follow the forum... I have some gripe about the GC initial sound... as you can see on the thread below:

Burning in GC, results and problems

The fact is... after my GC burned for about 150 hours... my complain about the "attack" has been surprisingly solved by it's own...

My GC do not sound "sweet" any longer... it has the "attack" and "speed"... really... has it... without any modifications (no hi-cap, no snubber, no zobel...etc.)

So before you made any changes... please burn the GC first...

And if you want to modify, please do it one by one... burn it to know the result... before making other changes...

REgards,
---
David