Conversion Amp Projects!

[Cygnus X1]

I've done a few, now have a lot yet to do.
I have a friend that squats ebay, and sends this stuff to me to work on.

Heres one:



Here's the auction:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=300303180110
2x6L6, 5V4 recto, some funky preamp octals (6SJ7, 6SC7's).
I baked it in slowly and it is a nice sounding little 50 watt.
Don't know exactly what I'll end up doing with it.

Another one, a Lafayette.
Again, really odd tubes. 7C7's, 7B4, 7GOK what...a pair of 6L6's, and a 5U4G rectifier. I redid all the electro caps and it is playing on my bench right now. Also put the required 3-prong cord on it.
A little noisy-there's a bunch of old wax caps in it. But not bad at all.
It has a very Tweed Bassman vibe to it, cathode biased 6L6GB's.
I ended up replacing the Atom caps with newer NOS Sprague Black, and Tan Beauties.
Made it much quieter and gave a sparkle to the tone.



Then there was the Grommes monoblock I just finished building a TD 5C3 into. Sounds good!
I haven't taken a pic yet, but it doesn't look a whole lot different from the original:


Oh, and the Copper clad Gulbransen that I turned into a Spitfire. A kick butt little amp!
I built a combo cab for it and it has an old 16ohm 10" alnico in it. Pic of the first build...



I also have a Hammond AO-14(?) and a Baldwin organ
to play with ideas for.

My biggest issue is having to buy all these electrolytic caps.
Even if they power up ok, they are all time bombs.
I've been hoarding them up.
And-what to do with all these octals, when most of the conversions I want to build involve 9 pin mini's. Is there an off the shelf plate that will fit in an octal hole?

Great fun!

[rudutch]

I have a stomberg Carlson "musak" amp I need to put a tone stack in and get some volume out of,
I think it is 8-10 watts, breaks up on '2'
lotsa weird tubes in that one as well

[Cygnus X1]

OH!

And how could I forget this one...
The Sunn 5E3.
I am seriously considering putting this into a worthy cabinet and doing something else altogether with the Sunn.






And also this one yet to do:
It's a schoolhouse mono turntable with another pair of 6L6's and some other oddball octals inside:

[Gris]

My first amp was a mono turntable 2x6V6. It sounded like the best , tightest 5E3 you ever heard. Those were the sh*t for square dance calling. Throw on a record, plug in your mic and dosey doe, LOL. That's what my grandma used it for. She used to call dances directly across the street from where the Allmans would play their dances. I'd watch my hero Dickie, then run across and wait for Gramma to get done to 'steal' the amp. Ahhh, memories. Thanks for posting!

[Cygnus X1]

I haven't done anything to that turntable yet.
I don't have a needle for it-just the 78 side works on it.
It works, I just have it buried under a pile of boxes.

Yes, I remember something like it being used at the square dances my parents used to attend.

[Gris]

Try plugging a guitar straight into the 'mic' slot with a good extension speaker. It might sound great as is!

[Cygnus X1]

I did that-it did sound ok, nothing special.
I didn't want to run it very long with those old caps in it.

I do the very slow variac "break in" routine advocated on the antique radio sites.
But I only do it to analyze what is there.
Those caps never last-even after that very long and tedious process.
I'm still too impatient-it takes me 10 hours to get it done.
I tend to ramp it up towards the end.

[jerryjg]

your one groovy dog! I have two conversions. An old Lafayette amp that was voiced to a Fender Pro..tubes changed from el34's to 6l6's by a good tech. Very well done and sounds crisp and clean.
Another is a Bogen CH-100 and sounds very Marshally. Runs weird expensiove tubes.7199's i think.not sure.
I'd leave the turntabel amp as a dual funcion thingie-dont wreck that cool tt!

[Cygnus X1]

I have left the Califone alone-I can still get a stylus for it.
It's a mono TT, but still, kind of hip the way it is.

Wow it has been a very busy year!

I left out about a half dozen 40's-50's radios I have.
One is good enough to restore in itself.
AM, but what a tone monster-it just sounds so warm and sweet. I think it is a Philco, but the tags are long gone.
Even got a couple of car radio's that have 6V6's in them.
Very cool stuff.

I have to compile a list of what I have built, converted, etc.
I have sold just one-but have only tried to sell two.
It is indeed addictive.

[jerryjg]

I have left the Califone alone-I can still get a stylus for it.
It's a mono TT, but still, kind of hip the way it is.

Wow it has been a very busy year!

I left out about a half dozen 40's-50's radios I have.
One is good enough to restore in itself.
AM, but what a tone monster-it just sounds so warm and sweet. I think it is a Philco, but the tags are long gone.
Even got a couple of car radio's that have 6V6's in them.
Very cool stuff.

I have to compile a list of what I have built, converted, etc.
I have sold just one-but have only tried to sell two.
It is indeed addictive.

WOOF! WOOF WOOF!!

[refin]

Not a conversion,but my dad had an old Silvertone mono reel to reel from the '50s.........all tube of course.I used to plug my guitar into that and it BAKED.Same with my cousin,borrowing a tube record player from church so we could jam.Both of these situations were in the late '60s/early '70s.

[Cygnus X1]

Here's about 2/3 of what I have:
Not included are a Traynor Custom 80, another Cygnus SEL,
and a half dozen tube radios and TV's.

[Cygnus X1]

Left to right, top to bottom it is this:
Lafayette PA amp. kind of like an early bassman.
THE Prtototype Single Ended Lead, Cygnus amp-the only amp I ever need besides a Deluxe Reverb. It is essentially a high gain little Marshall.
Top right: Baldwin organ chassis-no plan yet.
Middle left: Another very rocking PA amp- a Masco. Google it. It is nice. Just needs a cap job. Then another Baldwin piece-the reverb amp. And another hefty pice of iron. A Hammond AO-something, probably 30 watts. No plan yet.

Tough to see, bottom left-a 5E3 Tweed Deluxe. Then mid bottom is a Gulbransen built into a Matchless Spitfire. My second favorite build next to the SEL.

Last, bottom right, is the Grommes 5C3.
It looks great, and sounds even better than the 5E3, IMO.
The 5e3 was always just too loud for home use.
The older octal 5C3 fits what I like, but it will be going back to the buyer.
It was a challenge to build it into such a small package.
Then I shot myself in the foot for one simple wire linking up the power tubes.
After all of the other attention bird-dogging the simple problem-it came out simply great.

[Cygnus X1]

I forgot to add this pic.

[Cygnus X1]

And some fresh builds-various versions of the Cygnus Lead Amp.

[Fedora]

Hey Cygnus, I have a couple of big old Atwater Kent radios. Could these be converted into guitar/bass amps? I read somewhere that radios are tough to convert because it's hard to isolate the amp circuitry from the radio circuitry. Wadda you think....I know next to nothing about this stuff. So maybe that rules me out from the get go.

[Cygnus X1]

Sometimes the radios are better off as cool looking shells that will hold the parts you will have to sub in.

I keep my eye out for those-appearance is everything.

The majority of the cool looking wood cabinet radios have veneer issues.
If it looks good, has enough real estate to work with...then it might be worth a shot!

[Kap'n]

Heres one:

Virtually every chassis I've run into that looks like that uses some variation of the "Hi-Fi" schematic from RC-19, page 361.

When you strip all the crap out, the B+ ends up close to 500VDC, but there's not enough current for 6L6's.

[jerryjg]

Theres some point where you should leave rats nests like this alone. Just isnt worth the time and trouble. I hope your friend doesnt buy any more of these to fix up. When i gave my tech an amp to fix, it looked reasonably sensible.

[Cygnus X1]

Theres some point where you should leave rats nests like this alone. Just isnt worth the time and trouble. I hope your friend doesnt buy any more of these to fix up. When i gave my tech an amp to fix, it looked reasonably sensible.

HEY!
That is the rat's nest I built into it after stripping everything out!


It's a Spitfire circuit-true PTP.
And it is one of the best sounding little amps I've built so far.

[Cygnus X1]

Virtually every chassis I've run into that looks like that uses some variation of the "Hi-Fi" schematic from RC-19, page 361.

When you strip all the crap out, the B+ ends up close to 500VDC, but there's not enough current for 6L6's.

Too many times true.
The Masco PA amps were built quite close to the old Bassmans.
Harp players search these ones out for the fat tone and "just right" breakup.
It sounds pretty good as is and I'll just have to see how close I can get to a JTM45 when I get it on the bench.

Sometimes the iron can be used.
Other times it turns out to be just another chassis with some useful holes.

[Fedora]

Here are the radios I was talking about. They stand about 40" tall so they are pretty big.
I was thinking sort of a "parlor amp". Something cool looking that could sit in the living room. It may not really be sturdy enough to take the vibration...I dunno, just sort of thinkin out loud.
They are nice looking old radios though. I'm pretty good at woodworking so refinishing and veneer issues aren't that big of a deal.

[Cygnus X1]

Those are very cool!
I've looked at a few at the antique stores-tempting.

The interior woodwork is generally very solid.
As long as you do a good job with the veneer and trim it ought to sound good.

[Kap'n]

Warning - field coil speaker in that radio.

[Cygnus X1]

Warning - field coil speaker in that radio.

I was thinking about mentioning that Kap'n.
There is someone out there using field coil old tech to vary speaker responsiveness, as opposed to playing with B+ (K. O'connor circuits) in order to bring down volume while ostensibly keeping the tone of the amp.

I'm more in the Holistic camp-good tone comes from a combination of "all of the above".

Pertaining to the vintage radios-yeah, the OT would have to go, as well as the speaker. I'd say the PT would be pretty much useless as well.
A very nice looking shell to work with, and SOME of those radios had good wood.
Stromberg Carlson is one to look for.

[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://soundclick.com/share.cfm?id=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:

[Kap'n]

Looks nice.

Soundclick isn't working.

[Cygnus X1]

Looks nice.

Soundclick isn't working.

Thank you Kap'n.
Fixed the link.

http://soundclick.com/share.cfm?id=10302876

[Kap'n]

Sounds nice.

[Cygnus X1]

Going to post this one backwards.
They always ask for sound clips, I'll do that first, and backwards.
Never apologize for anything (is what they say), but there is a running high frequency noise on the recording that isn't coming form the amp, it's somewhere between the mic and the PC.
Too lazy to look it up, I just wanted to record.
It's in all the clips.

So here is the prototype Cyg-30 (I estimate the wattage).
2x6L6GC, 5U4GB rectifier, 2x12AX7, 12AU7 PI.
Iron is 1950's Masco power and Hammond organ output transformer.

Preamp is nearly the same as the Cygnus-7.
PI section is paraphase, output is cathode biased.

So, all in all, a little vintage, a little modern mixed in together.

High gain first:
http://www.soundclick.com/player/sin...ongID=10488576

Clean:
http://www.soundclick.com/player/sin...ongID=10488577

And dirt:
http://www.soundclick.com/player/sin...ongID=10488575

There is anoise issue in the background beyond that mic problem, just some fine tuning to do.
But I feel the tone is there.
Guitar is Sinster's Gift, his homebrew LP loaded with Stephens Design VL3 Proto bridge and PF Star neck, rolled back to about 70% volume and tone (you'll hear the transitions).
High gain is all VL3 Proto bridge full on.

[refin]

Going to post this one backwards.
They always ask for sound clips, I'll do that first, and backwards.
Never apologize for anything (is what they say), but there is a running high frequency noise on the recording that isn't coming form the amp, it's somewhere between the mic and the PC.
Too lazy to look it up, I just wanted to record.
It's in all the clips.

So here is the prototype Cyg-30 (I estimate the wattage).
2x6L6GC, 5U4GB rectifier, 2x12AX7, 12AU7 PI.
Iron is 1950's Masco power and Hammond organ output transformer.

Preamp is nearly the same as the Cygnus-7.
PI section is paraphase, output is cathode biased.

So, all in all, a little vintage, a little modern mixed in together.

High gain first:
http://www.soundclick.com/player/sin...ongID=10488576

Clean:
http://www.soundclick.com/player/sin...ongID=10488577

And dirt:
http://www.soundclick.com/player/sin...ongID=10488575

There is anoise issue in the background beyond that mic problem, just some fine tuning to do.
But I feel the tone is there.
Guitar is Sinster's Gift, his homebrew LP loaded with Stephens Design VL3 Proto bridge and PF Star neck, rolled back to about 70% volume and tone (you'll hear the transitions).
High gain is all VL3 Proto bridge full on.

Sounds great---are you selling these?

[Cygnus X1]

Sounds great---are you selling these?

Thanks refin.

I ought to sell some!
Have more amps than guitars...and I have over a dozen of those.
Some are gifts, horse-trading, that "30 Watt" is spoken for as a trade trinket for a pickup maker.

[Bill Moore]

I didn't have the money in my sock drawer for your last Cygnus run, I hope I do for the next!

[Cygnus X1]

Thanks Bill.
Still have a lot of vintage iron for conversions.

I'm toying with some ideas for Hi-Fi too.

[Cygnus X1]

Pix of that 30 watt cathode biased high gain monster I posted above (with sound clips).
I used the head cab and gutted chassis of a 35 dollar Univox 1236 bass head.





Original gut shot:



And this is what it started as...not really a great sounding amp at all, I decided to gut it out and sent the parts to a Uni fan...

[Cygnus X1]

Man....<Yawn>...OK, how about a "cleaned up" nasty clip to wake everyone up.

Bring it on Monday!

http://www.soundclick.com/player/sin...ongID=10535520

[Skip]

Man....<Yawn>...OK, how about a "cleaned up" nasty clip to wake everyone up.

Bring it on Monday!

http://www.soundclick.com/player/sin...ongID=10535520

Sounds good... Monday look out!

[refin]

Nice tones!
How does the 30 watter do with blues---any clips?

[Cygnus X1]

Nice tones!
How does the 30 watter do with blues---any clips?

Thanks!
More will be on the way.

[Cygnus X1]

TIME FOR AN UPDATE!

OK, I'm stoked, really stoked...

One of those old organ amps is really a great stereo power amp.
Ever fall asleep, wake up, and in the "in between foggy time" yields an undeniable thought and destiny?
Well I guess all that great Thanksgiving food did that to me.
(I did something for myself, but it's just for today...)

First, a closeup pic...post 34 upper right.


Now here is what it is.
I don't know!
Apparently a pro grade Baldwin amp because I can't find anything about it amongst the many consumer organ amp forums or sites.
So it's (4) x 6L6, with (2) 12AX7 for the phase inverters.
But EVERYTHING is split, she is true stereo.
One to drive the pedals, the other for the "main".
The only thing that would be needed to make this a true stereo amp is equal output transformers.

As it is...close enough to drive with my stereo tuner, EQ, and the old Teac Model 2 mixer.
SWEET sounding, far better than the SS amp I have, and the separation is simply awesome.
So figure 50 watts per side through the 6L6GC's, into some inefficient but tough and good sounding PA speakers.
I'm in heaven for now.