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Old 6th January 2007, 10:45 PM   #1
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Default my first amp (transformers???)

Hi!
I have been browsing these forums and lots of other sites for the whole day and last night too, trying to figure out what transformer(s) I should buy for my first DIY project, a "gainclone" based on the parts list from the chipamp.com kit PDF file!

They have a drawing for a power supply with two rectifier bridges and from what I have gathered, I will need either a transformer with two secondary windings, or two transformers.

I have read (somewhere) that these things are supposed to sound better with lower voltages, so I am considering the following options:

(btw I am SUPER poor)

2x - Triad 16V CT @ 6.25A
2x - Triad 25V CT @ 2.0A
1x - Avec 2x18V, 160VA

Which of these will work? Which is best? Is there another power supply I can build that only needs one center tapped transformer?

BTW, the chip is the LM3886

I'm super excited, but I'm on a scraping budget and the most I wanted to pay for transformers was $40!

Micah Fitch
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Old 6th January 2007, 11:07 PM   #2
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man, by avec I totally meant avel
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Old 7th January 2007, 02:57 AM   #3
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Get a 24VAC 6A Transformer. Will do the job - even better if it is 24-0-24 or 24-0 24-0

Just use the basic design on http://www.chipamp.com for the PSU.
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Old 7th January 2007, 07:55 AM   #4
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That's the one I am using, and it has two bridge rectifiers (8 diodes). I can use a single center tapped transformer with that?

How many VA should I aim for?
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Old 7th January 2007, 08:04 AM   #5
AndrewT is offline AndrewT  Scotland
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Hi,
Centre tapped uses just one bridge rectifier (four diodes).
Dual secondary can be wired to mimic centre tapped
or
can use dual rectifiers with single smoothing cap after each rectifier.

Some chipamp PCBs are designed to only use dual secondaries and dual rectifiers.
These can usually be modified to use a centre tapped transformer.

Check the chipamp data sheet and identify what voltage you need to suit your speakers.

Check what you are getting on the PSU/chipamp PCB and buy the appropriate transformer.

for single channel or two channel amplifier, I suggest VA=1.5times total output power.

for multi channel
VA=1.5times most power channel + total of all other channels. IF all the amps run at the same voltage.
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regards Andrew T.
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Old 7th January 2007, 07:26 PM   #6
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Default well the 25 volt @ 2 amp one is SUPER cheap right now...

thanks, that is very helpful!

I just have one question:

would any of the transformers I mentioned above come in useful for future audio projects, either alone or in pairs?

the reason I ask is because that 25 volt 2 amp transformer is on sale for $3.50!

is that a good deal, and would it be usefuL?
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