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iceman 6th September 2003 03:53 PM

25W almost finished
I'm almost finished with my amp now. I should put the headphone amp in the case to, then I'm finished.
What I wonder is:
Should I use the transformer i use to the 25W Amp (18-0-18 before rectifie) and regulate the power to headphone-amp(-+ 5-15 V) withex:lm7812 & lm7912 or should i use a seperate PS to the headphone ?

JOE DIRTŪ 6th September 2003 04:49 PM

I would leave the headphone amp separate to avoid crosstalk in the enclosure especially if its compact


sam9 6th September 2003 05:24 PM

If the headpone amp is based on high performance opamp(s) or another Self based design, the curcuit itself should be pretty much resistant to cross talk via the PS. I would take care that that amp input signal wiring and both in and out signal wiring for the headphone amp be shielded.

Using the same transformer makes sense with the following provisos. I've read that to get good results the power rails should be at least 3V higher than the regulator output. The next ios unlikely to be an issue but . . . . Are you going to use the headphones and power amp at the same time? If so, be sure the VA rating is just a smidgen greater than needed. Not much headphones don't draw that much current, just be sure you aren't already "at the edge".

Jan Dupont 6th September 2003 05:30 PM

I will go with sam9:nod:

Use the sam transformer with seperate bridge and caps for each amp. No need to make space for yet another toroid/transformer.

iceman 6th September 2003 06:33 PM

Thanks for the answer/reply

I go for the same transformer for both amp's.

Joe Dirt:No it's not compact. the case is width=19" and height=2UH deep=10". Lot of space

Sam9: The headphone amp is based on OPA2134, and it's not my design. I think people call it "cmoy"
And no, i dont use the headphone and amp at the same time.
I gonna put a switch to select speaker/headphone

sam9 7th September 2003 12:26 AM

The OPA134 has pretty good power supply rejection. So long off PCB wiring keep input signals away from the power supply and other signal sources you are not likely to have a problem.

iceman 8th September 2003 03:57 PM

2 Attachment(s)
Joe Dirt:
Here's a picture of the amp inside.
I draw a line where i want to put the headphone-amp.
As you can see there is lot of space in the case.

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