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-   -   Proximity of toroid PT from Gainclone boards (http://www.diyaudio.com/forums/chip-amps/135876-proximity-toroid-pt-gainclone-boards.html)

limono 3rd January 2009 10:42 PM

Proximity of toroid PT from Gainclone boards
 
I'm contemplating stereo 3886 gainclone in stainless steel enclosure with toroid in the middle. With transformer in the middle I have ~2.5" from sides to which I'd like to attach Power chips. Any chance for hum free amp in this enviroment?
regards, l

pacificblue 4th January 2009 01:17 PM

That is a question of Trial-&-Error. As a rule of thumb there should be a minimum of 20..30 mm, which translates to 0.8..1.2". The more the better.

One advantage of toroids is their narrower stray magnetic field compared to other transformers. And there are examples, where toroids are used very near to the audio components without problems.

On the other hand we have seen threads, where the transformer had to be put into a separate case, because it would couple into the audio signal at any distance.

By the way, the original Gaincard uses the transformer in a separate enclosure.

limono 4th January 2009 04:01 PM

OK ! Thanks
That's what I've thought. It (the amp ) supposed to be a gift for a girl so less "boxes" the better.
Regards, L

MJL21193 4th January 2009 04:31 PM

Hi,
You may try shielding:

http://i412.photobucket.com/albums/p...Picture538.jpg

This is not a GC but you get the idea. The shield is grounded to the chassis and seems to effectively block (or limit) effect from the toroid.
May be more work than you want to do but something to keep in mind.
:)

pacificblue 4th January 2009 11:50 PM

Don't expect too much of shielding a transformer. At those low frequencies you need an extremely efficient shielding material like mu-metal, which is hard to get by and extremely expensive.

MJL21193 5th January 2009 12:20 AM

Quote:

Originally posted by pacificblue
Don't expect too much of shielding a transformer. At those low frequencies you need an extremely efficient shielding material like mu-metal, which is hard to get by and extremely expensive.

Oh, it has an effect all right. Anytime you put a conductive barrier between a magnetic source and an area you want to protect, there will be some reduction. It may not be 100% or even close to that but it beats doing nothing at all.
I can say that if a quiet amp is important to you, every effort to reduce noise and hum are well worth it.

Ted205 5th January 2009 09:12 AM

i agree. I've used a sheild between the psu section and the audio with success.

Trial and error is the way forward though. Better to build the chassis around the amp imo

limono 5th January 2009 02:42 PM

One picture worth a 1000 words
 
2 Attachment(s)
Steampuck gainclone

MJL21193 5th January 2009 03:03 PM

Re: One picture worth a 1000 words
 
Quote:

Originally posted by limono
Steampuck gainclone

Where's the heatsink going to go?

limono 5th January 2009 03:28 PM

The stainless steel chassis is covered with riveted tick copper strips. I'll just screw chip amps to the flat alu plates and the plates to the sides od chassis and the whole chassis will be a heat sink. Should be enough .Original Gaincard doesn't seem to have excessive heat sinks.
Regards, L


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