Valve amplifiers coming on – you too can have one of these.


David Davis

Libertarians ought to be looking for other things to do as we enter The New Dark Age. I am not sure how we will be able to power machines like that I have created below, after the Lights Have Gone Out: lots of chicken-shit for biogas I expect, and highly-restricted viewings/listenings of the stuff, as methane in sufficient quantity is available to drive the Honda 2KW-generator (fast, high-eating-rate-chickens required, and someone who knows about motors in pumps.)

Yesterday, the Steel Beast made its nearly final journey to its hopeful owner. (Valves obviously taken out for lifting and transport, as it weighs about 59Kg and we can’t afford even one 12AX7 breakage, let alone one of the 8 matched KT88s.)

After some false-starts and terrible oscillation, it functions now (almost) perfectly on both sides. Still some AC mains hum to smooth out.

I will build you one of these, similar to that shown but with an all-metal case not a ceramic embedded tile which was a pain and a torment to me, for £2,750 for labour and all parts, including the specially wound set of 4 transformers. And you’ll have to have more modern meters, not that rare pair out of Avro-Lancasters. It would have been more than that price ideally, about £3,600 taking time into account, but there’s a recession on and I need the dosh.

You can power 4, 8 or 16-ohm speakers from the transformers, as you decide. The feedback is adjustable by yourself, for you to vary the colour-tone of the sound. HT voltage and current is avilable for up to 160 watts RMS per side if you wanted a Glastonbury-gig-job, but I’d initially build it for 20 watts at less than 0.6% harmonic distortion.

You will have to arrange your own collection, as I don’t think couriers’ delivery vans have strong enough springs.

It will of course work using 8 6L6, or EL34, or 5881/6550, with the correct bias system changes. Personally, I’d like it best with 6L6s, at about 50 watts a side and 0.8% to 0.9% distortion, with 585V at the anodes: quite hard and bright and tight, but also bassy, with restricted midrange.

I also like to build transistorised stuff, which of course is much much cheaper and lighter, and uses less pounds of chicken-shit-per-hour, as there are no heaters to power. But you don’t like that do you.

 

Off home

Off home

 

 

 

First burn-in

First burn-in

The light comes on!!!

The light comes on!!!

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5 responses to “Valve amplifiers coming on – you too can have one of these.

  1. Pingback: Valve amplifiers coming on

  2. They look magnficent. Do you do guitar amps too? You might want to consider it since there’s proper money in boutique valve gear now that digital modeling rigs are the rage.

  3. The problme was the Williamson-type (but a wee bit different) output transformers. I had to design them from first principles.