• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Recommended inexpensive tube amp to build?

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#22
Here too
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#26
I use a wood box and 6061 Al plate 3 or 4mm thick (3/16 or 5/32 if you measure inch). I like the look and I absolutely hate working with steel, stainless is impossible to work with unless I am in a machine shop settings with the right tools. 4mm has all the strength you'll ever need and spreads the heat uniformly among all the components.

Using the lasagna pan is a bit ridiculous and pushing it way too far. 🤣
 
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#30
$100 problem is the cost of audio transformers. I agree SE EL84 is best bet if you have highly sensitive speakers. What speakers are you using? Magnavox Stereo SE EL84 are about $70 on eBay. I would rebuild the amp though with new capacitors and use Russian K40Y-9 coupling capacitors. These amps sound excellent. Needs phono preamp if you use vinyl with a stereo selector input switch.

GE 6BQ5 and JJ E83CC are best sounding tubes.
 
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#31
A real 6BQ5 is a Beam Power tube.
A real EL84 is a Pentode tube.

Some marketeers decided to Dual-Mark their tubes as 6BQ5 / EL84, or as EL84 / 6BQ5.
That is because the data sheet specifications are almost identical.

Your sound may vary.

Whenever possible, I use JJ tubes. I just drive over to Eurotubes.com and pick up which tube types I need.
 
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#32
Tubesaregreat said:
Magnavox Stereo SE EL84 are about $70 on eBay
Click to expand...

OPTS are good, not pretty, with all the other circuitry gone, the PSU trafo is decent. Valves, sockets are often reuseable, if you aren’t concerned with pretty the chassis as well

And if you are lucky reselling the speakers can pay back the cost of the console.

Fun to disassemble them and figure out how theybuilt them.

dave
 
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#33
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#35
I do a wooden frame with an 1/8” 6061 aluminum top plate. It’s easy to use hole saws to make tube holes and it’s easy to mount all the transformers. I get remnants from my local metal supply place for $2 a pound! It cuts easily on a table saw with a carbide blade.
 
#36
6A3sUMMER said:
A real 6BQ5 is a Beam Power tube.
A real EL84 is a Pentode tube.

Some marketeers decided to Dual-Mark their tubes as 6BQ5 / EL84, or as EL84 / 6BQ5.
That is because the data sheet specifications are almost identical.
Click to expand...
I'm sorry, GE begged to differ.

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So did RCA:

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and Tung Sol:

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If you have some unused vintage 6BQ5, go ahead and use them. They'll be better than many of the Russian 6P14P and Chinese 6P14 often sold as EL84. However, I have seen and heard lots of good things about the JJ EL84.
 
#40
Interesting.
Ah, the 7189A. I should have hoarded them 40 years ago when Philips ECG ceased production. A beam tetrode in EL84 drag, rated for 415V plate and screen in ultralinear operation, max dissipation 15W combined plate and screen grid. I wish they were still plentiful.

I had a Dyna ST35. It came with 7189A in it. They eventually wore out. At the time, I was wondering why so many replacement EL84s burned up in that amp.
 
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