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Old 17th January 2011, 04:19 PM   #1
ads2 is offline ads2  France
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Default Dual Mono boards with only one transformer.

Hello,
I have the Dual Mono boards (2 PSU and 2 amplifiers) from Brian Gt.
Finally I decided to buy only one Transformer 2x25V 300VA.
Does it make any improvement if I use the 2 PSU boards instead of one, with only one transformer ?
each PSU board have 2 caps of 10.000uF.

Regards

Armindo
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Old 17th January 2011, 06:02 PM   #2
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It comes down to an improvement in the bass region vs. a higher likeliness of ground loops.

You could use one power supply with double the capacitance.
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Old 17th January 2011, 10:23 PM   #3
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I'm not an expert, but it seems that the best success is a 1:1 of trafos to PSU boards.

it seems ok to have multiple amp modules draw off the same PSU board but having multiple PSUs on one set of diodes or 1 trafo could cause ground loops.

like PB said, double up on the bulk storage caps on the central PSU.
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Old 18th January 2011, 07:16 AM   #4
ads2 is offline ads2  France
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Thanks for your reply.
How do I double ? should I put the caps in serial or parallel ?
Regards
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Old 18th January 2011, 07:28 AM   #5
sandyK is offline sandyK  Australia
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I can't speak for chipamps, but I had been running a dual PCB Class A HA from one PSU and a single JLH PSU addon , then I changed to dual PSUs and dual JLH PCBs running off a single outboard 18-0-18 30VA transformer. There was an improvement in soundstage etc.
Later, a friend (DIYAudio member) told me that he had even better results when using dual transformers as well. Eventually, I did what he suggested and changed to dual mono type construction. There appeared to be a further improvement in channel separation, and as my friend suggested, t just sounded more "right"
Sandyk
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Old 18th January 2011, 07:44 AM   #6
ads2 is offline ads2  France
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Sandyk,
Dual mono was what I planed to do first, but my problem now is double :
- cost of 2 transformer
- my case is only 230x280 mm, and not a lot of space...not sure it would be safe to put the boards very near to transformers.
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Old 18th January 2011, 05:09 PM   #7
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Quote:
Originally Posted by ads2 View Post
How do I double ? should I put the caps in serial or parallel ?
In parallel.
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Old 18th January 2011, 06:32 PM   #8
ads2 is offline ads2  France
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thanks Pacificblue
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Old 19th January 2011, 11:17 AM   #9
AndrewT is offline AndrewT  Scotland
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Hi,
if you use a centre tapped transformer for your single Bridge Rectifier then you must have ONE Main Audio Ground.
This Main Audio Ground must be shared between all channels.
This seems to have fewer problems if you have one PSU.

If you have a dual secondary transformer you can either have a single PSU & single Bridge Rectifier as above
or
using twin Bridge Rectifiers you have the option to have an Audio Ground dedicated to each channel. This requires. dual secondary, two sets of dual Bridge Rectifiers, two sets of Smoothing Capacitors and two sets of Disconnecting Network to tie in the Safety Earth.
Each channel must strictly follow star grounding and must use low loop area for all flow and return pairs.
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Old 19th January 2011, 12:01 PM   #10
ads2 is offline ads2  France
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AndrewT,
Hummm . It seems that there were a misundersting due to my bad English...

In fact I should have shortly a dual secondary transformer (2 x 25V 300VA). (bought it for 30 Euros delivered)

I have in my hands the dual secondary transformer, 2 amp board http://www.chipamp.com/images/lm3886amp-parts.jpg and 2 power supply board http://www.chipamp.com/diyaudio/snubber.jpg also here http://www.chipamp.com/images/ps-rev3-sch.gif

Normally, with one dual secondary transformer, we use 2 amp boards + 1 power supply board. like this http://www.chipamp.com/images/lm3886amp-assembly.jpg

But I have 2 Power supply boards (and don't plan to use 2 transformers). So my question was, instead of using only one power supply board, won't it ne better to use both power supply boards (connected to the same dual secondary transformer).

Sorry again for my bad English
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