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name773 3rd July 2005 01:26 AM

headphone amp psu

i'm interested in building the heaphone amp depicted here, and i was wondering what kind of power supply you guys recommend. it says 12-0-12 to 20-0-20 dc, so there's some room to move. would a simple linear supply suffice, or should i go regulated? i have an easy source for 1-5A 24vct transformers, so i prefer any design that can use those, but i can find other transformers if need be.

thanks in advance for your help (even if it is a link to another thread)

name773 3rd July 2005 03:27 AM

ok, some candidates:

possibly the regulator from the second post in this thread looks good, has the right voltage out, etc. i have a 30-0-30 @2A trafo lying around, maybe i could use this preregulator with 27V zeners to get the line into the 24-30v range that reg uses, 16.2 on the out is great

this reg uses the 7{8,9}15 regulators, so i'd like to avoid it, but it would be easy to build. optionally i could go with the updated version that uses the lm3{1,3}7 (also undesireable, but just how bad are those?) simply for the ac detection circuit that would let me put a relay on the output to avoid turn on/off thumps. i would use the old version if thumps aren't a problem with the amp i listed in the first post, any ideas on if that would be an issue? i will be using the amp to drive grado sr80s if that helps any.

another option is the sulzer reg, but the only one i've seen a schematic for doesn't list the input/output voltages. i'll look for one that does

edit: i'm also very much in favour of a simple amplifier type circuit used in conjunction with a voltage reference, more to keep the voltage steady than to reduce noise (i value the simplicity here, and i like discreet circuits). i'll be looking for a schematic of one of these too, but if anyone wants to butt in with a link before i've found it, i'd be much obliged

jwb 3rd July 2005 04:22 AM

The Jung regulator is usually used instead of the Sulzer. It is the same idea but more highly evolved (and more parts, naturally). I used four Jung-like regulators in a headphone amp and was pleased with the results. Note however that my amplifier differed substantially from the one you are building.

The usual output of the super-regulator types is 13.8V, which is twice the voltage of the common LM329 6.9V reference.

You could do worse than the LM317 types of regulators. They are certainly easy to understand and will not surprise you. They are also cheap.

As for the AC detection, you can make such a thing with a '555 timer, a relay, and 6 passive parts. Don't let such a simple consideration dictate your choice of power supply design.

name773 3rd July 2005 05:49 AM

very nice :nod:

thanks for the tips

in the process of looking for a discrete shunt reg for the voltage i'm looking at and ~200ma, i stumbled upon this nice reg, i think i'll use it in conjunction with the ac detector dealy from your amp (if that's all right). where does the +vcc for the turn-on delay come from, just anywhere on the power line that's under 18v?

(spelling discrete properly greatly aided my search :cool: )

name773 4th July 2005 03:52 AM

just got an reply from the author of the amp, it draws ~1A per channel. i'll fish around for something (capacitance multiplier looks neat), maybe go to another design entirely

jwb 4th July 2005 06:14 AM

1A per channel is ludicrous for a headphone amplifier. Do you really want to have heatsinks sufficient for 60W in a headphone amp?

name773 4th July 2005 08:24 AM

not really, no

maybe he thought i was asking about a different amp... anyway, i think i'll just look for a different design (maybe something cheap and easy just for kicks)

thanks for your help anyway

name773 4th July 2005 10:33 PM

well he said the power supply should be ~1A/ch, so that's probably a peak draw, give it headroom and the like. i'm going to browse schematics/threads and attempt to piece together a headphone amp with an opamp frontend and a bipolar transistor output.

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