Converting a 100w 6l6 to a 200w?

[WORMDIRT]

Seriously, how hard would it be, really?
Please refrain from the "Don't do it" stuff, and the 2 word answers.
I'm genuinely interested in how you would do this.

[martin manning]

Buy two.

[matt h]

(deleted)

[WORMDIRT]

May or may not be feasible depending on the circuit and components.

Chances are a lineout mod into a SS amp for some assistance would be easier, cheaper, and less likely to kill a n00b.

This is the route I am currently taking.
I'm not worried about doing it and dying or anything, I just never really thought about what it would actually take. A new tranny, a new filter supply...

[matt h]

(deleted)

[WORMDIRT]

D) Some of the Above
E) All of the Above
F) None of the Above


Honestly--without specifics, it's impossible to say.

[IMG:638:339]http://i60.tinypic.com/4jx9jq.gif[/img]

What else qualifies for specifics?
I have enough amps I love to make 1 of them into a bastard.

Specifics on me?
I work with industrial electronics (I guess) by trade
I've done a few filter cap jobs, tube socket replacement,
tranny wiring etc
So I'm not too stressed about the leg work, I just don't have allll the theory down to be able to do this completely unassisted.

[lord preset]

New power transformer and new output transformer and run four KT88s. Take a look at the Hiwatt Dr201 to see how it was done. They ran 650v on the plates and 410v screens to get 200+ watts. Basically everything except the preamp section will need to be reworked. If your 100 water is tube rectified that will have to go (I think). So it's a lot of work and expense but it can be done.

[matt h]

(deleted)

[vibratoking]

Financially, I think you'd be better off selling that amp and building another. It's not worth converting that amp.

Maybe take a look at the Marshall Major. I can't figure out why you need a 200W amp, but to each his own.

There's a few good tinnitus threads here.

[roberto]

Sell this and build a new one, it's cheaper.

[Stevem]

first off why is it you want, or feel you need 200 watts?

doubling a amps rms wattage cost near 4 times as much as it did to get the first 100 watts by the time all is said and done!!!

[potatofarmer]

Apart from the cost, there's no way to know if the chassis will support the weight of the new transformers or have enough room for the power tubes to be happy. KT88 ask for, what, 4" center to center?

All this work to gain a measly 3dB. You can get the same increase in loudness by doubling the number of speakers you're using. Got a 2x12? Buy a 4x12. Buy a pair of 8x10 fridges. Or just buy more efficient speakers. Or do both. I'd love to hear a full 8x12 stack of EVM12Ls. I don't think I'd hear much else after that.

Speakers are ultimately the weakest link, as far as loudness goes. They're expensive, they're heavy, and they're hard to transport. This is what's happened to bass amps in the past couple of decades. People only want to carry a single 4x10 or 2x12 cab, so the manufacturers pick speakers with voice coils that can handle hundreds of watts without burning up. The only problem is that as the power handling goes up, the efficiency goes down, so you're getting the same "not loud enough" volume, but making a whole lot more heat to do so. Check out some of the bass guitar forums: you can find dozens and dozens of threads where people ask "Is 500W enough to gig with?" and people say "no".

Efficient speakers, and lots of them.

[lord preset]

Actually potatofarmer's point about KT88 spacing might rule them out for this particular amp. Pics of the Sundown indicate that socket spacing will be too tight to work. As for why someone would want a 200 watt amp, there may not be any compelling reasons to have one but some times we just want what we want. Nothing wrong with that and in truth few of us "need" a 100 watt amp either and there are plenty of those being built. So if Kt88s are impractical in this case the OP could still look at a voltage doubling high plate/low screen scheme like that used by Music Man Amps and the Hiwatt DR201 to squeeze something close to 200 wats out of 4 El34s or 6l6gcs. The MusicMan RD100 got what is reportedly a true 100 watts RMS out of 2-6l6. You would still have to order a custom spec PT and OT and they would still have to fit the chassis but it may get be workable.

[Zippy]

Line out >> Satellite amp.

A 200W amp may not be as heavy as two 100W, but it feels pretty close to it. I know I'll never consider working on another one.

[Phil_S]

I 2nd what Matt says about clicking that schematic. It opened Flash player in such a way that it loaded down my CPU and nothing wanted to run. Don't click it. Who knows what trash landed in my temp folder as a result. I'll be checking on that after I finish writing this.

Without passing judgment on the wisdom of doing it, as others have said:
1) You need room for two more octal sockets (or possibly 4 more octal sockets) and remember to consider the required spacing between tubes.
2) New power transformer that has double or more on the mA rating on the high voltage secondary and additional capacity for the filament supply. Actual spec will depend on the choice of tube. The physical size is very unlikely to fit the footprint of the existing.
3) New output transformer and can handle double the output and with a primary impedance matched to the tube choice. (If you are doing this, you are no longer restricted to 6L6's.) This is also not likely to fit within the footprint of the existing.
4) Select the tube type that suits the reworked amp best.

Plan on spending $500 for new transformers. I might be off $100+/-.

All of this suggests to me you'll need a new chassis to make it all fit (maybe $40 for a blank you drill yourself or $100 for a predrilled chassis.)

Once you get into a chassis transplant, the suggestions to get a different amp or just build one from scratch start to make sense.

You might be able to shoehorn a pair of KT-120's onto the existing chassis, but I doubt the existing transformers will support them in milking the maximum power out of them, which will be 120W for the pair, if all other conditions are supporting that, which is doubtful. Besides, the perceived volume difference will be quite small.