6V6 Headphone Amp

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Paul Barker
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#16 Re: 6V6 Headphone Amp

Post by Paul Barker »

Yes when it splits it doesnt decouple, scrap the vr tube split it,and use two resistors before the two caps. 105/channel current = R, V x channel current x 4 = wattage.

The VR doesnt regulate it just wastes voltage. Looks pretty.
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Nick
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#17 Re: 6V6 Headphone Amp

Post by Nick »

I have mixed feeling about the VR in that position, but the one thing it can do that a couple of resistors wont, is to allow a lower DC supply impedance. On demand the VR can deliver more current that a resistor without effecting the output voltage.
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#18 Re: 6V6 Headphone Amp

Post by simon »

Interesting discussion, it's a long long long time since I've used VR tubes. Is there any merit in stacking two VR105s as a shunt instead?
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#19 Re: 6V6 Headphone Amp

Post by Nick »

Yep, you get actual voltage regulation and lowish source impedance, and if you load the shunt with a CCS you also get good noise rejection (though I would include a small resistor in series with the CCS as a CCS will tend to look more like a capacitor at VHF)
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#20 Re: 6V6 Headphone Amp

Post by simon »

Just trying to get my head around how that would look. Say a "typical" DN2540 (or pair) CCS on top of 2xVR105, with the top of the CCS connected to the 330R and output node? Or perhaps as a sink under the VR tubes?
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#21 Re: 6V6 Headphone Amp

Post by Nick »

No, input from cap after the choke, 20R resistor in series with CCS of your preference, that to VR tube. zobel across the VR, maybe 330r and 0.1uf, then to first stage of the amp.
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#22 Re: 6V6 Headphone Amp

Post by Cressy Snr »

Alright you nitpicking buggers! :mrgreen: :D :lol:

I've re-worked the front end and the power supply. The VR tube is no more.
There are now two RC filters at the end of the power supply; one per channel, feeding the input stage.

The input tube is now a 6H30P, running at just over 13mA per side. There are no bypass caps across its cathode resistors.

I had to up the rectifier output to a 5U4G in order to maintain the same voltages at the power stage, because of the 26mA worth of extra draw from the 6H30P.

I also ended up converting the amp to a single input as I was sick of the selector switch playing up. I'm fed up of building unreliable equipment.

I'm going to have a clear out of resistors and switches, because a lot of them are knackered beyond saving. Resistor leads are too short half the time from being used in a million different circuits, which means piecing the bloody things out with bits of wire and shrink down sleeving. Bits fall off switches at the most inopportune moments. Building with new bits is the way to go, I think. I mean resistors and switches aren't exactly expensive.
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Mike H
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#23 Re: 6V6 Headphone Amp

Post by Mike H »

izzy wizzy wrote: Fri Jul 05, 2024 9:31 pm I've always wondered why folk feed each channel with a wire and cap essentially putting those two caps in parallel. Are the two caps in parallel and that's the purpose or is there something else happening that I'm missing?
To me it looks like each amplifier has its own V+ cap, close to itself, each with a wire from the PSU, which are 'X' long - so kinda makes sense to have the cap close to the o/p stage - is the sort of thing I would like to do. But if you draw the PSU only and show the 2 caps, it looks a bit odd.
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#24 Re: 6V6 Headphone Amp

Post by Mike H »

See now he's changed it so the 'wires' now have resistance.
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#25 Re: 6V6 Headphone Amp

Post by simon »

Nick wrote: Sat Jul 06, 2024 5:18 pm No, input from cap after the choke, 20R resistor in series with CCS of your preference, that to VR tube. zobel across the VR, maybe 330r and 0.1uf, then to first stage of the amp.
I missed the resistor - so as a shunt "module", after the 470uF cap and before the output, 10R-CCS-2xVR105s-ground. Correct?

Sorry to be part of the derail Steve :-).
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#26 Re: 6V6 Headphone Amp

Post by Nick »

Yes, that's it.
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#27 Re: 6V6 Headphone Amp

Post by Nick »

To me it looks like each amplifier has its own V+ cap, close to itself, each with a wire from the PSU, which are 'X' long - so kinda makes sense to have the cap close to the o/p stage - is the sort of thing I would like to do. But if you draw the PSU only and show the 2 caps, it looks a bit odd.
But to me, this is exactly the type of thinking that drawing it like that will encourage, and I think that that's the point Izzy was trying to make. The drawing encourages you to think like that and thinking like that makes you draw it like that. IMHO, there should be absolutely no inferred physical layout inferred from a drawing, unless its separately and clearly written.
is the sort of thing I would like to do
Yes, but you do that because you think it would make a difference, so you keep doing it. Why would it make a difference? the internal inductance of the cap will be far higher that the short length of wire. It creates a dogmatic way of thinking, I prefer to analyze all such beliefs and work out why I think the way I do, and if there is any real justification other than "feels".
it looks a bit odd.
Get over it, I find that sort of thing similar to setting the TV volume to 27 instead of 25 or 30. It feels wrong because of "reasons". But keep doing it, and 28 and 29 and 26 and after a bit you find you get rid of that bit of unconscious bias.

Or if you want it to be two caps, draw it as two caps.

But of course the above is just me, others will be different, that's ok as well.
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#28 Re: 6V6 Headphone Amp

Post by simon »

This thread has reminded me just how much I love the glow of VR tubes. I'm not sure why I stopped using them really.

I suppose the question is, regarding the R-CCS-VR shunt stack, is a separate shunt reg better anyway?
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#29 Re: 6V6 Headphone Amp

Post by Mike H »

Thanks Nick, that's very interesting!


And yes I am guilty of trying to maintain my computer volume at 50% .. :oops:
 
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#30 Re: 6V6 Headphone Amp

Post by Cressy Snr »

I've spent the last couple of days building a passive control unit for the headphone amp out of a new(ish) selector switch and my Khozmo 'Red" 10K shunt stepper. I tested the unit with the volume pot still in place on the HPA and turned up full, to make sure I was happy with the performance before removing the pot altogether so that the HPA is now purely a power amp.
PowerAmpMode.jpeg
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The passive control unit can be seen on the right of the photo. Obviously it needs a top and bottom making up, to hide the innards.
The only label I had of sufficient length to cover the holes left in the front panel of the HPA was the '45' logo from the old 2 watter from a few years ago.

I must say I'm quite enjoying these head-fi experiments. Flea power single-ended jobs seem to make stonking headphone amps :)
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