Building something better with a Chinese SE EL34B Amp DIY Kit - diyAudio
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Old 12th February 2011, 12:04 AM   #1
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Default Building something better with a Chinese SE EL34B Amp DIY Kit

There have been a couple of threads that have some discussion about this kit, but I thought I'd pull a few thoughts together here. It may be simpler for future readers to have the links and a few pictures in one thread.

To start: The 'kit' is sold via eBay and is titled 'SE EL34B Amp DIY Kit' - a search will turn it up

It's been discussed here and also over there

The 'kit' comes with a schematic and non-matching layout diagrams. In this thread there was a strong recommendation (from Eli Duttman and Ezequiel) for a different SRPP circuit, using 6SN7 tubes (the kit has octal sockets/cutouts).
Link to the recommended circuit:
1.000.000 de Circuitos Eletrônicos Audio: SRPP 12AU7 / EL34 SE
That's what I built.
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File Type: gif Ezequiel SRPP EL34.gif (8.8 KB, 1152 views)
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Old 12th February 2011, 12:07 AM   #2
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It all worked out fine in the end, but I wouldn't recommend this kit, at all.

Shipping was expensive but fast, and the packing was fairly good (the usual Chinese crumbling styrofoam beadboard...).
Attached Images
File Type: jpg Fast and expensive DHL shipping.jpg (188.9 KB, 789 views)
File Type: jpg kit contents_1.jpg (61.9 KB, 749 views)
File Type: jpg kit contents_2.jpg (57.6 KB, 739 views)
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Old 12th February 2011, 12:09 AM   #3
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A few problems were obvious right away.....
No hole for the PT, and holes for the OT leads were too small to fit grommets (no grommets in kit...)
Stainless chassis - I hate working with stainless....but it is nice and shiny..
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File Type: jpg chassis I got.jpg (46.1 KB, 723 views)
File Type: jpg chassis I needed.jpg (37.4 KB, 218 views)
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Old 12th February 2011, 12:11 AM   #4
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Output transformers didn't fit inside the OT covers.....so I had to do a workaround with tab bending and lockwashers under the machine screw heads...
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File Type: jpg OT and cover don't match.jpg (22.4 KB, 231 views)
File Type: jpg OT kludge.jpg (40.5 KB, 231 views)
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Old 12th February 2011, 12:19 AM   #5
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The kit recommendation was for a buss-style build.
These can be very nice-looking (and sounding, if you do them properly) but I haven't had much luck on the couple of occasions I've done a build with a buss.

I just slapped in some lug strips and got to work. Some of the extra lugs came in handy later, when I was 'adjusting' the PS to give the correct (lower) B+. (added another RC section).
I added switches for the NFB and also a 'Pentode/Triode' switch.
BTW- I didn't use any of the caps or resistors that came with the kit. The quality looked a bit suspect and the electrolytics were all radial-style, which I don't use with point-to-point wiring.

Not a very neat wiring job, but it works. Fortunately, it doesn't have to look pretty to sound pretty!
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File Type: jpg wiring_1.jpg (104.1 KB, 346 views)
File Type: jpg grounds.jpg (119.6 KB, 375 views)
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Old 12th February 2011, 12:23 AM   #6
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Switches and chassis top....
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Old 12th February 2011, 12:24 AM   #7
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For testing, it's quite useful to take a few minutes building a 'frame' to support the chassis when it's inverted...
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File Type: jpg test frame.jpg (37.8 KB, 348 views)
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Old 12th February 2011, 12:27 AM   #8
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Something else which wasn't included in the 'kit' was a bottom cover. I really think all projects should have these, for safety's sake.
A piece of aluminum plate from the local recycling yard and some cutting and drilling later....
BTW, save those perforated steel bottom covers from old gear - they make good drilling templates. Just clamp to your new work and head for the drill press.....
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Old 12th February 2011, 12:32 AM   #9
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I also cut a couple of hardwood end plates to use instead of the supplied particleboard items, and made a matching knob.

I'm happy with the results- it sounds very good, and is dead-quiet when the music stops.

I ended up using EL34s (Russian equivalents), some NOS 6SN7s I had on hand, and a 5R4GYB rectifier.

The power transformer is right at its limit - hot enough that I don't want to keep my hand on it for more than a few seconds - so I put the supplied PT cover on the shelf for another project.
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File Type: jpg finished front.jpg (140.5 KB, 303 views)
File Type: jpg finished top.jpg (105.1 KB, 318 views)
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Old 12th February 2011, 01:15 AM   #10
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Nice work. I'm sure your efforts will help those unfortunate souls who bought one of these and don't know what to do with their unfinished amp.

jeff
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