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First stereo tube amp build advice
First stereo tube amp build advice
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Old 12th November 2020, 10:04 PM   #1
Tom Kamphuys is offline Tom Kamphuys  Netherlands
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Default First stereo tube amp build advice

Hello all, newbie here.

I am contemplating building my first stereo hifi tube amplifier. I've been reading up on (guitar) tube amplifiers, watched way too many youtube clips and have (succesfully) built two guitar amps (Marshall JTM45 and JCM800). Despite that I find it hard to get started in the hifi amp world and that is the reason for this post.

I've got lots of question, but I'll limit myself to a few. Here they are: What amp do you guys suggest I should build? Are there any informative build threads or sites? Any must read books, articles or websites? I've read both tube preamp book by Merlin Blencowe and the power amp book by Richard Kuehnel.

Any advice is welcome. Thanks in advance.
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Old 12th November 2020, 10:08 PM   #2
rayma is offline rayma  United States
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You'll need this. And no carbon comps. Audio amplifiers are very different from guitar amps,
since they are not supposed to add distortion or coloration.
http://hifisonix.com/wordpress/wp-co...ound-Loops.pdf

Last edited by rayma; 12th November 2020 at 10:19 PM.
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Old 12th November 2020, 10:12 PM   #3
nigelwright7557 is offline nigelwright7557  United Kingdom
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Guitar amps tend to not use global feedback so the sound is more rich.
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Old 12th November 2020, 10:19 PM   #4
invaderzim is offline invaderzim  United States
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What speakers will it power? Room size? How loud do you like your music to be able to go? What type of music do you prefer? Is a kit okay or do you want it completely from scratch? Budget range?
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Old 12th November 2020, 10:22 PM   #5
Tom Kamphuys is offline Tom Kamphuys  Netherlands
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Quote:
Originally Posted by rayma View Post
You'll need this. And no carbon comps. Audio amplifiers are very different from guitar amps,
since they are not supposed to add distortion or coloration.
http://hifisonix.com/wordpress/wp-co...ound-Loops.pdf
That pdf should keep me busy for some time...

Btw, no carbon comps in my guitar amps; only metal oxides (power supply) and metal films.
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Old 12th November 2020, 10:26 PM   #6
painted is offline painted  Luxembourg
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My suggestion is to start with a proven concept, like an EL84 push pull. Choose your speakers with easy crossovers, big caps suck the life out of the scarce 2x 12W/ch. A 30W/ch EL34 push pull might come next. If you are brave try a proven SE design, 300B is popular for 8W/ch.
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Old 12th November 2020, 10:29 PM   #7
nigelwright7557 is offline nigelwright7557  United Kingdom
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Here is a picture of a 80 watt valve amplifier i designed.
Not quite finished in the picture.
12ax7 front end.
12au7 phase splitter.
Four EL34 in output stage.
Someone on ebay made the chassis for me.

Click the image to open in full size.
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Old 12th November 2020, 10:37 PM   #8
Tom Kamphuys is offline Tom Kamphuys  Netherlands
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Speaker have yet to be bought. Advice on them is also welcome. Room is L shaped; Total is 6m x 8m, the leg I'm sitting in is 4m x 3.5m. It would be nice if the music would have some oompf, but I don't wanna upset my neighbours. My favorite music is blues and rock. My JTM45 was a kit I tweaked, my JCM800 was completely scratch build. I like that thought. Budget range is a couple of hundred euros for the amp, keeping in mind I also have to buy some speakers.
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Old 12th November 2020, 10:56 PM   #9
OldHector is offline OldHector  Sweden
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I think a Tubelab SPP or Tubelab SSE are good starting points. They are not complicated, so you can understand the philosophy of tube hifi, and they can be adapted to different tubes, and budgets.
I built the SPP, then I built it again point-to-point, so you can take a proven design, and learn how to adapt it to be built in a traditional way, sharing the bulk of the expensive components.

The hardest part is making a presentable and electrically safe case. Bearing that in mind, there are some very reasonable Chinese origin kits that are complete, e.g. Boyou, and a lot of discussion here on improvements.

Another tack is to buy something classic in need of attention, e.g. Quad 2’s, and get them running, learning along the way.

It is a hobby that satisfies all of the senses, and benefits from lots of skills.
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Old 13th November 2020, 03:59 AM   #10
Eli Duttman is offline Eli Duttman  United States
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Tom Kamphuys,

You want speakers with a reasonably flat impedance curve, as tube amps do not exhibit the gargantuan damping factors seen in SS amps.

Paul Joppa has provided the community with a useful rule of thumb, for mating amps and speakers. Joppa's Rule states that for "typical" listening spaces an amp speaker combo should be capable of producing 102 dB. SPL peaks at a 1 M. distance.
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