Stereo Tube Amp Kit....

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311Sam
Junior tube assistant
Posts: 1
(3/6/04 3:34 am)
  Stereo Tube Amp Kit....
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 Im looking for a stereo tube amp kit and im having trouble finding one. Im wondering if anyone has any info? I am trying to stay under $400 total. Im looking for a kit that has good documentation, the main board, and a few parts. Any info accepted!


Thanks for the help,

Sam
 
Andy Poupart
Senior tube assistant
Posts: 127
(3/6/04 3:47 am)
  Re: Stereo Tube Amp Kit....
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 I don't know of any kits, but you can build a simple stereo single-ended amplifier for way less than $400. You don't need a board, either. There are so few parts that you can build it point to point with a couple of terminal strips.

I built a really nice-sounding stereo amp using 6S4A triodes and 6JD8 SRPP drivers, from a design at this web site:

boozhoundlabs.com/6s4hifi/

Total cost was well under $100
 
Tyrannocaster
Junior tube assistant
Posts: 49
(3/6/04 8:08 am)
  100? Probably not...
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 A PT and two OT's for less than a hundred bucks? Not if you want anything strong enough to actually push some speakers. It's true that one to five watts can be quite loud through efficient speakers, but most of us need more than that for actual listening purposes.

Of course it's different if you already have stuff around and can recycle, but that's not really fair when you start quoting costs - everybody doesn't have a full parts bin; I know I sure don't.

Using those little Hammond 125 OT's is cheap (but two of them will still set you back seventy bucks or so, leaving only thirty for your PT and you still have to get your tubes, chassis, sockets and other components), but they only go down to 150 hz - not great for hi-fi.
 
Tiny Daddy
I will work on all amps
Posts: 526
(3/6/04 10:13 am)
  Re: Stereo Tube Amp Kit....
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 Easy to build:
www.geocities.com/tinydaddy2000/

Get hammond transformers and chassis. Tube socket holes may be cut with a large step-drill except for the output tubes, if they are octal you may want to buy a punch such as Greenlee.
 
Tyrannocaster
Junior tube assistant
Posts: 50
(3/7/04 8:19 am)
  Mullard plans
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 There is a widely available book of reprints of schematics and articles from the fifties that Mullard put out called "Tube Circuits for Audio Amplifiers" which contains the info for building an EL 34 based power amp. You could build a pair of these (using a common PT) and I'm betting it would sound darn good.
 
Andy Poupart
Senior tube assistant
Posts: 129
(3/7/04 6:12 pm)
  Re: Mullard plans
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 Hey, spend all you want on a hifi amp. The little 6S4A-based amp I built using Hammond 125s sounds great. It's true that I had a power transformer that I reused. The rest of the parts, including sockets, terminal strips and filter caps came out of my "parts bin". I bought aluminum foil-in-oil caps. The tubes were cheap. If you're starting from scratch maybe you'd have to spend $150. Maybe not.

I built a couple of high efficiency speakers using full range MCM drivers. The amp sounds very nice indeed. I use it in my office at work. It's not going to rattle the rafters, but it substantially improves the experience of listening to mp3s on my iPod. It has good low end for such a little amp and considering the Hammond OTs, surprisingly so. So don't knock those little Hammond single ended OTs. They're cheap and they sound just fine, thank you very much.
 
311Sam
Posts: 2
(3/7/04 8:15 pm)
  re
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 well the problem is that i dont think i fully understand how these tube amps work. Thats why i was wanting a kit with good documentation so that away i could learn as i build. The plexi 50 sure looks nice. I like all the controls it has. How hard would it be to add a second channel to it?
 
Andy Poupart
Senior tube assistant
Posts: 130
(3/7/04 11:55 pm)
  Re: re
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 Okay, now I'm confused.

I thought you wanted to build a stereo hifi amp, for listening to CDs and so on. If you want to build a guitar amp, there are lots of kits available. I'd start with something simple like a Fender 5E3 kit, or a tweed Champ. A quick Google search will throw up a bunch of kit vendors.
 
311Sam
Posts: 3
(3/8/04 1:17 am)
  stereo amp
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 yea i want a stereo hifi amp. Im just saying that the plexi looks nice but its only one channel. A 2 channel guitar amp wouldnt sound good as a stereo amp?
 
Tiny Daddy
I will work on all amps
Posts: 536
(3/8/04 8:11 am)
  Re: stereo amp
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 2-channel guitar amp usually means there are 2 preamps but only one power amp. The 2 preamps are voiced differently. For Hi-Fi you don't want "voicing". The difference is, a guitar amp/guitar is a system for producing the music whereas Hi-Fi amps are reproducing music, an entirely different thing. Suggest you get a vintage stereo amp and fix it up. Look on eBay.
 
ernie jr
Junior tube assistant
Posts: 72
(3/8/04 1:19 pm)
  amp kits
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 you could look under "dynaco" on ebay. there are kits as well as fixer uppers
good luck
ernie
 
Andy Poupart
Senior tube assistant
Posts: 131
(3/8/04 1:23 pm)
  Re: stereo amp
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 A hifi amplifier is designed to operate as linearly as possible, and to have a fairly wide frequency response, well into the teens of KHz. A guitar doesn't produce any significant frequencies above something like 3 KHz. As a result, guitar amps aren't designed to reproduce high frequencies. And many of them are designed to operate in a non linear fashion. Not at all what you'd want for hifi.

Directly heated power triodes are very linear tubes. It is possible to build a simple pair of single-ended amplifiers using a pair of triodes, each driven by a twin-triode small signal tube in some configuration (the 6DJ8 is very popular). The circuits are very simple and the amp will sound very transparent and will image better than anything you've ever heard (I'll bet).
 
311Sam
Posts: 4
(3/8/04 2:36 pm)
  Re: stereo amp
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 well thanks for the info everyone. I have been looking on ebay for one to overhaul. Dynaco seems like they got some good ones. What were some other good manufacturers of tube amps back in the days?
 
Tiny Daddy
I will work on all amps
Posts: 539
(3/8/04 11:57 pm)
  Re: stereo amp
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 Dynaco, Heathkit, Harmon-Kardon, McIntosh, Marantz, HH Scott
Some of these used selenium rectifiers that need a bit of re-design for silicone diodes. And there are reliability and safety improvements to be made. And of course some were better than others.
 
311Sam
Posts: 5
(3/10/04 5:00 am)
  Re: stereo amp
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 dang it. the more i look at these amps on ebay the more i want to build one myself. Hmm, guess i better start reading...
 
 
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