25W almost finished

iceman · 6th September 2003, 02:53 PM

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 DIRT® · 6th September 2003, 03:49 PM

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

DIRT®

sam9 · 6th September 2003, 04:24 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, 04:30 PM

I will go with sam9

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, 05:33 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 · 6th September 2003, 11:26 PM

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, 02:57 PM

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.

6th September 2003, 02:53 PM	#1
iceman diyAudio Member Join Date: Jun 2003 Location: Gothenburg	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 ? __________________ "Quis custodiet ipsos custodes?"

6th September 2003, 04:30 PM	#4
Jan Dupont diyAudio Member Join Date: Apr 2003 Location: Copenhagen, Denmark	I will go with sam9 Use the sam transformer with seperate bridge and caps for each amp. No need to make space for yet another toroid/transformer. __________________ Free Schematic and Service Manual downloads www.audio-circuit.dk, Company: www.dupont-audio.com, Joint venture: www.DupontMantra.com

6th September 2003, 05:33 PM	#5
iceman diyAudio Member Join Date: Jun 2003 Location: Gothenburg	Thanks 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 __________________ "Quis custodiet ipsos custodes?"

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6th September 2003, 03:49 PM	#2
JOE DIRT® diyAudio Member Join Date: Apr 2003 Location: Brantford, ON	I would leave the headphone amp separate to avoid crosstalk in the enclosure especially if its compact DIRT®

6th September 2003, 04:24 PM	#3
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	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".

6th September 2003, 11:26 PM	#6
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	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.

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