Monday, February 27, 2017

Enter the Tweed, or, How I Learned To Stop Worrying And Love The High Power Twin

You know how sometimes you get a wild hair and decide you want something really outlandish? This is what I ended up with and thereby hangs a tale.

One time I stumbled over some of Hartley Peavey's musings about some of the amps he'd built over the years, one of which was the Peavey "Vintage" series. The very early ones were all tube and they're kind of hard to find. I've only seen pictures of them, and they included a 2x12, a 4x10, and a 6x10 towering monster. All three were 100w of all tube power including the out of production 6C10 triple triodes.

What you had, essentially was a 100w tweed Bassman with reverb. Now who wouldn't like that?

I couldn't find one for love or money so I said to myself "Well, I'll just make one, won't I."

So I got in contact with J.D. Newell and he figured he could cook up a 4x10 cabinet that could house a High Power tweed twin chassis.

Somewhere along in there I acquired a chassis and transformers from Mojotone and started constructing the chassis.

I also acquired two new Eminence  Legend 12 inch speakers on the recommendation of a friend of mine. About then the project became a high power tweed twin. I built the eyelet board and sourced the parts, most of which I had and built about 90 per cent of it, and the cabinet and speakers were sitting in my living room.

I used quality parts throughout, Heyboer  iron, F&T and Mojotone capacitors, and choice power and rectifier tubes from my stash: a Mullard rectifier and RCA black plate 6L6GCs.

I also incorporated some changes to the screen and grid resistors. After the first run I changed the Switchcraft jacks for Cliff jacks with a substantial reduction in noise.

All was assembled including a bracket to support the power transformer. It saves a lot of effort to assemble this amp upside down.

How's it sound? Loud as hell, but the speakers are not broken in at all. It sounds purty bright but will mellow with time.

On to  the next project-reviving my Marshall Club and Country. Stay tuned.

There matters stood until last weekend when I finished the wiring, adjustable bias control, and jacks. The first run was uneventful.

UPDATE: I've found some follow on buzzing that appears to be circuit related so it'll have to come out and get on the scope to locate the source of discomfort. Stay tuned.

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