More Conversion Amp Projects

[Cygnus X1]

Scored a lot of iron last Monday...answered a CL ad about an organ and met a guy that used to work on these but really doesn't have time to do it anymore.

...Right when I said I was clearing my bench of old projects!

I didn't pay much, but here is what I have:
Hammond AO 88, working, complete with reverb amp and springs.
Another as of yet unidentified 2x6L6 organ amp.
Rauland-Borg PA amp, 2x12AX7, 6AV6, 2x6L6-now working.
Univox 1236 Bass head, 12AU7, 12AX7, 12AU7, and 2x6L6.
Was not working, I tracked down a bad cathode resistor and now it works.

Once I tackle the remaining organ amp I'll have four amps to turn into...great stuff!

The Cyg-7 is on hold for a while until I get these out of my blood.

[warlok]

I know you've built your own from scratch but do you buy these and convert them into guitar amps? Or just use them for components? Not being an amp guy, I wouldn't know the first thing to do with them..

[Cygnus X1]

Thank you warlok.
Sometimes they get parted out, all of these are working so they will be converted.

Some very nice transformers and other parts make them great platforms.
The last was a Conn organ amp, and it is LOUD.
Very nice.

[warlok]

Your interest in these has peaked my interest a bit. Don't know if I'll ever try on my own but ya never know. My question is.. Does this fall into the theory that an amp is an amp? Like the circuits and components of these are the same type or similar to what's used in guitar amps?

[Hellbat]

Your interest in these has peaked my interest a bit. Don't know if I'll ever try on my own but ya never know. My question is.. Does this fall into the theory that an amp is an amp? Like the circuits and components of these are the same type or similar to what's used in guitar amps?

Essentially yes. Input - increase signal - output.

Most of these amps are designed to produce a clean, flat signal. Swap a resistor here, a capacitor there, drop in higher gain pre-amp tube equivalents and they can make fine guitar amps.

[Cygnus X1]

Hellbat is dead-on.
One of the best features is the quality of the transformers in these amps.
Organ power amps are usually far overrated for a guitar amp, and they are big.
Reason for that is the other accessories they are designed to drive.

Often the output transformers are the same interleaved designs on paper bobbins that the vintage
Marshall and Fenders had.

Not all tube amps are suited for conversion.
If you luck up on a stereo rig, leave it as is or refer it to a hifi aficionado.

I have settled on the first conversion-the Univox bass head will be completely gutted and converted into a JTM45.
GZ34 recto, probably with power scaling.

[warlok]

Holy crap. Saw some on ebay... How many tubes do these things need.. lol

[Cygnus X1]

Holy crap. Saw some on ebay... How many tubes do these things need.. lol

Depends on what you're looking at.
Some use a zillion relatively useless 12AU7's for the tone generating circuits.

Buying from ebay really chews into the price due to shipping.
I buy local whenever I can.

[warlok]

I was just looking for research as I've never even seen an organ amp before. I'd need a lot more research before I looked at trying it out. That's what some were, 12au7's and a bunch of other tubes I've never heard of. Definitely need some more in depth knowledge of the circuits to have one of these projects be feasible. But I'm getting interested in learning more. Seems like a cool hobby.

[Cygnus X1]

Best way to learn is read up, buy a kit, gather the tools.
Join a good tube amp builders site or three and ask a lot of questions.
Dave Hunter wrote a great book for both beginner and intermediate
builders/modders.
Stay away from Gerald Weber and Aspen Pittman.
Old, and some of the material is inaccurate.
They were just spreading the misinformation that was common back then.

Good website to browse: http://www.geofex.com/tubeampfaq/taffram.htm

[Mazz]

Pics when you finish please Cyg? or pics of your old projects would be good, I'm quite interested in project stuff most of the time.

[Cygnus X1]

Just search for my amps for the original builds.

A couple older ones:

Tweed Deluxe 5C3:
gromees5c3fr1.jpg

Copper coated chassis Gulbransen organ amp into a Matchless Spitfire:

spitfireundersidefi4.jpg

[Cygnus X1]

Took some parts and pieces and made a Matchless Spitfire amp.
Happy new conversion amp day!

Sound clip is clean, dialed down, but if you listen closley you'll hear what she has in store:
http://www.soundclick.com/player/sin...ongID=10302876

Used a power transformer from an old RCA console stereo that was already hacked up.
Output transformer from the "sidecar" portion of a honkin' huge Baldwin organ chassis that drove (2) EL84's at 8 ohms.
So after looking at several schems (including 18 watt TMB etc), I settled on a Spitfire.
Things got sloppy on the power transformer/choke side, and the OT, but that's where it also ran the quietest.

Pic:

SpitfireFEB2011Small.jpg

[Twitch]

Impressive as always cyg.

[Cygnus X1]

Thanks Twitch.
I need to wheel it up to give an idea what it sounds like a true rawk volume.

Sunday night is a little tame around here.