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Old 4th September 2005, 07:44 AM   #1
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Default Convert a non-valve amp to a Valve (tube) Amp

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

Cheers
Sean
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Old 4th September 2005, 08:45 AM   #2
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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:
http://www.ampage.org/ or search the forum for a good schematic.
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Old 4th September 2005, 08:51 AM   #3
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...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.
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Old 4th September 2005, 10:48 AM   #4
SY is offline SY  United States
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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."
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Old 4th September 2005, 01:25 PM   #5
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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
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Old 4th September 2005, 01:55 PM   #6
amperex is offline amperex  United States
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Default no

Answere is no. Perhaps a line fuse holder, power cord or the power switch is about as compatible as it gets.
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Old 4th September 2005, 02:36 PM   #7
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Ye of little faith, us who doth believe Fred Nachbaur hath came to this Earth shall show yonder way:
http://www.dogstar.dantimax.dk/tubestuf/gallery3.htm



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Old 4th September 2005, 04:12 PM   #8
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Tim,

That's 1 heck of a link!



All,

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?
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Old 4th September 2005, 04:26 PM   #9
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Quote:
Originally posted by Sch3mat1c
[B]Ye of little faith, us who doth believe Fred Nachbaur hath came to this Earth shall show yonder way:
http://www.dogstar.dantimax.dk/tubestuf/gallery3.htm
That's the way to do it! - throw all the insides away, and build a valve amp in the space left

It's hardly 'converting' though?.
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Old 4th September 2005, 05:36 PM   #10
igge is offline igge  Sweden
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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.
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