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Old 13th July 2008, 03:51 PM   #1
Phobos is offline Phobos  Italy
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Default Modifying a fenice into a headphone amp?

I was wondering if it is worth it to use a Fenice as a headphone amp, with some modifications.
I made a little research and it seems that output transformers are necessary with Class T designs and the only site that i could find that sells them (specifically made for this use) asks three times the price of a Fenice board for a pair. Is there a way to get good OP Transformers? Would it be better to modify the headphones and get 2 separate grounds? Then i would just need resistances across the outputs of the amp right?
I would be looking to use this amplifier with Beyerdynamics DT 770 or DT 990, that have a minimum of 250 Ohm resistance with a bump of 300 in the bass region.
Any suggestion will be greatly appreciated.
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Old 13th July 2008, 06:06 PM   #2
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Default Re: Modifying a fenice into a headphone amp?

Quote:
Originally posted by Phobos
Would it be better to modify the headphones and get 2 separate grounds?
No, it would be better to build or buy a proper headphone amp.
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Old 13th July 2008, 06:43 PM   #3
Pano is offline Pano  United States
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Mr. Anonymous one is quite correct!

I've used the Fenice boards, even used to modify and sell them. Very nice board, but not the best thing for headphone use.

Yes, you will have to modify your headphones ofr seperate grounds.

No, you will not need output transformers.

Yes, you will need massive attenuation. It can be done with a dedicated L-Pad.

But even after all that attenuation, there will still be some ultrasonic noise left. Maybe not enough to hurt you, but I certainly would not sit under a pair of heaphone with it all day.

You will get much better results with one of the more "normal" headphone projects or kits.
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Old 13th July 2008, 10:30 PM   #4
Phobos is offline Phobos  Italy
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Mh ok i see your points.
Can somebody suggest me a very simple Class A amplifier then? Possibly one that runs on 12v?
12 v because it is easy to get a good quality PSU, and simple since it would be my firtst diy?

BTW the output transformers i mentioned where used to avoid separating the grounds, wich seems to be imperative with tripath based amps.

Currently i'm using Sony HDR 7506 (64 Ohm) directly plugged into the line out of my audio card that is a +4 dB, but i don't think it would work with 250 ohm cans :P
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Old 13th July 2008, 11:28 PM   #5
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If for some odd reason someone really wanted to use the fenice or some other BTL amp as a headphone amp; you don't have to use output transformers. You could also just use one of the outputs for each channel (+ or -) with a DC blocking output capacitor. I still don't recommend this though.
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Old 14th July 2008, 02:00 PM   #6
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Quote:
Originally posted by Phobos
Mh ok i see your points.
Can somebody suggest me a very simple Class A amplifier then? Possibly one that runs on 12v?
Almost all headphone amps run on 12V. I've built the PIMETA, it's class A and very simple to build:
http://tangentsoft.net/audio/pimeta/

The Minił is tiny, high-powered and sounds very good, I've heard:
http://www.amb.org/audio/mini3/

If you want something heavier-duty, there's lots of very good designs - and designers - at the DIY part of http://headwize.com .
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Old 15th July 2008, 08:38 AM   #7
Phobos is offline Phobos  Italy
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THX, i like the PIMETA and looks cheap and easy enough to be my first project, it runs on 12v and can be biased in class A... now i just have to find time to do it...
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