Convert a non-valve amp to a Valve (tube) Amp

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I'm new to the site, and I've searched and havn't seen this discussed.
I have no real working knowledge of electronics so I decided to start slow rebuilding an old amplifier, a Yamaha HY-10G III 25W with 8" speaker.
It's a cheap combo that I figured if possible, a great start off project. I am willing to buy and spend money on what's necessary to convert this non-tube amp into a working Tube Amplifier.
However, what I would like to know before I get started is if this is possible, converting a non-valve to a valve amp?
I'm sure it is by purchasing the able parts, but is it also possible to use what I have and add on?

Any information is greatly appreciated

Tubes and Transistors work very different. For example Tubes need high Voltages and an output transformer.
I am afraid you can "recicle" only the loudspeaker and the box, to convert you amp.
You need a schematic(KT88 or EL34 or 6L6 or KT66 or 807 single ended, or EL84 pushpull or others) and make a complete tube amp. If you chose a single ended schematic(KT88 or EL34 or 6L6 or KT66 or 807) and don't want to buy an expensive output transformer, you can use a good commercial transformer 220V-6V 100VA(if loudspeaker is 4ohm), with less sound performances.

Btw you have to buy also a new transformer for supply voltages for tubes, or, for cheap construction, use some commercial transformers: for example 2 transformers 220V-12V. Wiring them properly you will have 220V AC that give you about 300V DC for B+(with solid state bridge), and also you have 12V for filaments.
See: or search the forum for a good schematic.
...ehm, sorry!
I realized only now that you come from US. You have 110V transformers...
BTW, for output transformer 110V-3V 100VA can do the job.
For B+ you can use 2 transformers 110V-12V, and an auto-transformer 110V-230V if you can find(some adapter 110V-230V are auto-transformers).
Be careful with the right power of transformers.

Just my 5cents.
You're asking for a way to turn a Toyota into a steam locomotive.

If you want a tube amp, I'm afraid you'll have to either build from scratch or start with a tube amp. Best to start reading up first, since tube amp construction is not cheap and is potentially dangerous (high voltages). You do NOT want to do that with "no real working knowledge of electronics."
Please, please, take what the other posters have said to heart. For the most part, tubed circuitry works at high voltages. Those voltages equal danger. There is a tried and true dictum of always working with 1 hand in a pocket. FOLLOW IT!

You MIGHT be able to safely cobble some tubed circuitry into that "sand box". The 6GM8/ECC86 twin triode is atypical in that it is designed for low voltage service. You will need an external source of heater power. A 6.3 V. filament trafo might work, but be prepared for hum trouble.

In another recent thread, I suggested the 6GM8 for buffer (cathode follower) duty in the automotive environment. Take a look at that thread, as it will give you some idea of what can be done at low voltage.
Automotive Thread

That's 1 heck of a link! :)


I ran a Google search on the Yamaha piece in question. It's a guitar amp. FOR SURE, some glowing glass is badly needed. The tone has got to improve with something as simple as a 6GM8 SRPP as the 1st gain block.

I did not spot any FREE sources for the Yamaha schematic. Can anyone provide a link?
Here's a link to a Yamaha guitar tube amp schematic: it's the T50/T100. The schematic works for both the 50 watt (T 50) & 100 watt (T 100) versions. Apparently this particular guitar amp is considered legendary. Yamaha T50/T100

And it is possible to reuse more parts in a solidstate guitar amp for conversion into tubeamp than some here has suggested. Filter caps, diodes, pots, on/off switches, ceramic caps, etc. I reused most on-board components in my 10 watt Kustom solidstate guitar amp when I converted my Marshall JCM800 2205 into an AX84 Hi-Octane.

Good luck, and have fun cranking that mother when it's finished.:D

thanks for the link.

I can't believe the help I've recieved in such short time. Great forum man.

New tubes are in from post and used Jensen P8R-4, scrounged an output transformer (25W) from a Studio 65 Amplifier and have half a book on valve circutry (other half has been burned).
75% ready to get started.

As they do in shows like Monster Garage or as was done in the Marshall or Carlsbro drabs 45 years ago.
"I'm going to turn this Toyota into a Steam Locomotive."

Information, input, opinion and or advice is always greatly appreciated

Ye of little faith, us who doth believe Fred Nachbaur hath came to this Earth shall show yonder way:
Fred's Vacuum Photo Gallery



And you actually think someone with "no working knowledge of electronics" can pull off something like this? The thread is about what the OP can do, not what can be done by a pro. IMHO, he should do a LOT of reading to get some knowledge, look at Fender schematics to get a feel for how the circuit goes together and go from there. I don't see any point of doing this unless you know what is doing on. If you only are a player then no, you don't need technical knowledge. But if you want to be a builder, then you should. Just my 2 cents.
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I have done this just to see if possible - donor amp was headed for the tip. The guy throwing it out used it at his next Church gig - I recognised the sound while still in the car park unloading my own gear.
You do have to know a bunch of electronic stuff to be able to recognise what you can re-use, modify or re-purpose. As well as the hi voltage safety requirements.
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If you need more literature on valve/tube technology, I have a large collection of that in pdf-format (Adobe Acrobat) . I could make them available on my website for download, if you like.

Here's the link to the the folder on my server where my pdf documents on tube/valve technology can be found.
tube circuitry books/tube data books


Just FYI, I can't access this link. Tried through IE11 and Chrome. No dice.
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