Amp No 46

[Cressy Snr]

Another transformer coupled headphone amp I've been putting together over the last week or so:

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Being an HPA, it needs DC heaters of course, which I've yet to do but despite the heater hum it sounds good, though not yet as good as the 1626 HPA.
It uses a 6N6P cascade per channel and the OPTs are from a WAD Pre II.
Mr I sent me these transformers many years ago, so it's about time I got around to doing something with them.

Next job is to put in a raw DC supply transformer and feed the output to one of my Rod Coleman regs.

[Cressy Snr]

OK
DC plus Rod Coleman reg is lashed up and everything is quiet

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How the feck I’m supposed to get that lot in the box is another matter entirely

[Cressy Snr]

Well of course, the SMPS supply would not go in the box, so it ended up on top. I’ve left enough length of wire underneath, so the top can be hinged up, in order to change the valves.
With the Coleman reg, the amp is completely silent when idling, which it would be of course

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In combination with the RTZ DAC it all sounds jolly good!
I’ll have to find some sort of holey cover for the switcher.

[Cressy Snr]

Audio cct:

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[Cressy Snr]

Power supply:

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[Mike H]

Very good.

I have a couple of notebook PSU's so would have used one of those.

[Cressy Snr]

Aye, I could have got a notebook PSU in the box, but the only one I’ve got is an 18V one off an ancient IBM ThinkPad; too high.
I’m still on the hunt for some kind of cover for the fugly thing on top of the box.

Meanwhile the 1626 headphone amp is due a refurbish, with purple Rexine applied to the top plate.

[pre65]

with purple Rexine applied to the top plate.

That's nice.

[Cressy Snr]

Found a small piece of gold, anodised, aluminium mesh, so made a cover for the raw DC switching supply to the Coleman heater regulator in the box. I’d have preferred silver but it’ll do:

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[Cressy Snr]

Here's a push-pull headphone amp I picked up on the web. I might try it out or might do my own version with 6H30s. I'll probably build as is to see what it sounds like before going for heftier outputs.

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[andrew Ivimey]

Weird! Onwards...

[Cressy Snr]

Well, I built the push-pull HPA:

Mounted the “Lazy Man” CCS regulator chips on a piece of aluminium, screwed to the heatsink plate for the Rod Coleman DC heater reg. New tagboard and perspex plate for a pair of B9 sockets too. Power supply simplified to one 470uF followed by R to 2200uF C.

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Not a lot of components in the circuit:

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Turned up the heater voltage to 7V to accommodate a pair of Philips Miniwatt PCC88

Full interior view showing 2uF motor run cap bypassing final 2200uF power supply electrolytic and stupid, overkill output transformers.

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[Cressy Snr]

Schematic:

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Inexplicably, I found myself out of LM317 reg chips, but I had a few TL783C, so used 2 of these instead.
I must say, it sounds very good.

EDIT
I suppose, technically this is amp #47. Jeez!

[Cressy Snr]

Push-pull 1626s? Well it’s going to have to be isn’t it.

And push-pull 6080/6AS7s as I have the necessary custom wound Sowter output transformers from around 2007.

[Cressy Snr]

Here's the power supply for the headphone amp. All very simple:

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