6AS7 Headphone amp layout

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colin.hepburn
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6AS7 Headphone amp layout

Post by colin.hepburn » Thu Oct 11, 2007 7:36 pm

hi All
first run attempt at my 6as7 h/amp layout and wiring looks OK i think but i may have mist something if anyone can see any mistake's pleas point them out :P
Cheers
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Post by Nick » Thu Oct 11, 2007 7:56 pm

Looks alright with a quick check. But a couple of questions

What are the resistors from the input (I assume) the seem to be between the input and the pot?

Also I would not earth like that. I would take both 0v from teh phono input, to the star point you have on the left of the amp, then take a wire from that to the external power supply 0v. I suspect you run the risk of hum doing what you have done.

Likewise, I would take the resistor from the pot wiper to ground, direct to the same start earth point, as you are joining them to the 0v from the capacitor negs, they will see the charging current from the caps, its not much but more than it needs to be.

You need to think about 0v lines, as not some abstratc zero point, but a conductor carrying current, and make sure that any voltages induced by that current are kept from signal.

And to take that farther, maybe you could haveseperate 0v from the caps -ve's as the first cap will be passing a lot of nasty charging currents, the ov from this will contain those current, so any voltage induced in that bus bar will induce those spikes into the second cap, as it shares the same bit of copper.
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Post by colin.hepburn » Thu Oct 11, 2007 8:17 pm

Hi Nick
Thanks for the pointers on the ov earth side those two resistors are for the shunt pot i put them there on my other h/amp as its easier to change them for different types to try a/b other resistors
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Post by Nick » Thu Oct 11, 2007 8:35 pm

Fair e nuf.
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TX regulation for both TXs

Post by colin.hepburn » Sat Nov 03, 2007 1:14 am

Hi All
Well I'm about to put a psu together in Duncan’s PSU II for my Headphone Amp I have two options of TX
TX 186-0-186 @290 mA or 270-0-270@200 mA both with
Choke x2 10H @160ohms for 200volts B+
RC.LC.LC.RC
Not sure whether to go valve rec or SS also not sure how to work out the TX regulation for both TXs I guess it about 15% can anyone advice me on how I get this and what the general feeling is for valve rec versus SS rec I have read somewhere that valve recs can slow the amp down
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Post by Nick » Sat Nov 03, 2007 11:37 am

I have read somewhere that valve recs can slow the amp down
Yep, and SS rect can make the amp sound edgy. Problem is both and both true and false. Taking a suply that works well with a vac rect and putting in SS will make a worst supply and vice-versa.

Try both options in PSD, using the components you have, and once you get the B+ you need, see how they react to step change loads.

I would pick the one with the fastest response, with the least overshoot, and the smoother change in level.
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Post by colin.hepburn » Sat Nov 03, 2007 12:08 pm

Thanks nick
ill give that a go so what about setting the regulation for the TX should i just set it too 15%
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Post by Nick » Sat Nov 03, 2007 2:36 pm

Wel, its not perfect, but why not measure the DC resistance of the secondary, and use that, it won't be exact, as the primary resistance should also be part of it, but it will give you something to start with.
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