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sundaycyclist 1st February 2015 11:53 AM

Boyuu EL34 A9 Tube Amp
Hi all

I'm new on here and I'm hoping someone can help me. I bought (maybe foolishly) a Boyuu EL34 A9 amplifier as a kit. I'm used to building electronic kits with good plans but the Boyuu comes with a schematic wiring diagram only which I'm finding difficult to interpret. There are very few photos of the internal wiring of the A9 availalbe. My main problem is the connections to the two front pots; then the rear input/output panel and, importantly, the mains input.

Does anyone have the ability to post/send photos of the inside of one of these amps? Or does anyone know someone that can build it for me for a fee?

Thanks in appreciation of some help.


VictoriaGuy 1st February 2015 07:06 PM

Can you post some pictures, especially of the schematic?

Where are you located? If you want in-person help or somebody to build it for you, that would help.

It might be cheaper to sell the kit on to another user, and just buy a pre-built amp.

However, from what I saw with Google Image search (in 30 seconds), it doesn't look like a very complex circuit. You can learn how to read (and build from) a schematic, with a bit of work. So don't give up!

mdamp 1st February 2015 08:07 PM

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Originally Posted by sundaycyclist (
I'm new on here and I'm hoping someone can help me.

Hi I brought some months back from china a voltage amplification tube: 6N9PJ 2.
power output tube: Shuguang EL34B 2.
rectifier tube: 5Z3PJ 1. KIT
I had a few problems with the schematic it came with but after a few googles got it working, then after I heard it running I chanced the whole thing and re-did the schematic, did away with the 6N9P and replace with 12ax7 and changed the whole setup and sound wow 100% the punch now from bass is that "punch" and excellent high end as well. just a thought this was the schematic that came with the kit. sound ok but again what a total difference replacing the preamp side for 12ax7.

sundaycyclist 1st February 2015 09:50 PM

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Thanks for the replies so far.

I've spent some time looking at photos on the web and at the schematic (which is below) and I reckon I understand most of it. I'm not happy with the mains fuse housing so I'll buy a better one at Maplin. I'm still not clear on the input/output and volume board connections but I'm more confident that I can work those out now.

Keep the info coming.


sundaycyclist 1st February 2015 09:51 PM

Oh, and by the way, I'm in Basingstoke in Hampshire.

Celsius 1st February 2015 11:57 PM

Celsius 1st February 2015 11:58 PM

mdamp 2nd February 2015 12:04 AM

2 Attachment(s)
This is my finished revamp EL34B Amp with 12ax7 the bass is excellent I would forget the 6N9P my self. good luck with it tubes are fun to play around with.

goldenbeer 2nd February 2015 09:03 AM


Originally Posted by celsius235 (

Paralleled 6SL7 at the input, not a good idea. Miller capacitance will roll off treble.:nownow:

UL operation without feedback has high Zout, will give wobbly bass.:(

Maybe some will appreciate the "tube sound", I call it effects box. ;)

ygg-it 2nd February 2015 10:26 AM


Originally Posted by celsius235 (

A part the missing 10K grid stopper resistor, the scheme is identical to my (ex) EL34B + 6N2 SE Tube Amplifier with 5Z4P rectifier.

They just changed the rectifier and drivers tubes (I don't know if tranformers too).

Very good construction, see all my mods for which I have put the KT66.

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