i got free transformers + amps! i need some suggestions!!

so my landord tells me (about 5 minutes after i tell him i flaked on rent for a week and im sorry bout that) hes got all this old audio gear and loves the fact that i do repairs out of the basement. says hes got some old peavey tweed amp, some wierd tube pa, and some old bogen pa.
ok sounds good free stuff!
so he drops off the 'wierd tube pa' and its this HUGE Dukane PA that looks AWESOME! im going to post pics when i can, its so rad looking.
anywho its got 4 decent sized, decent weight input transformers! about as big as the darkgrey version of the Ampex350 input tranny. heavy core im sure. anybody around have any specs on them?
so this chassis HAS to be used for something. the output tranny is suitable for 100w output (dont know @ what ohms but i HOPE it can do 4) and a huge power tranny. the idea i had was an svt style preamp into a quad 6550 output section, again similair to an ampeg SVT. it would need an auxillary filament tranny, as the current draw on 6550 heaters is rediculous. it would also have a line amp in it for keyboards.
so i guess my questions are:
1) does anybody have any specs on these input trannies? they are marked Dukane Model 3A55 - Dukane Corporation St. Charles Ill --- octal socketed with a steel (i guess) can over them (shield)

2) does anyone have schematic/specs/something on the amp itself? its a Dukane 1B45-A - has 4 6L6's on the output. im most concerned with the output tranny as its not as large as the partridge on an SVT, but still bigger than any Fender or marshall. i hope the taps are ok off the pwr transformer for what im looking at doing!

3) anyone have any ideas on the amp setup itself? i not much of a guitar player - oh wait - im not a guitar player, but own one and alot of pedals - and do alot of noise stuff so as long as the amp sounds good as an amp, has alot of bass - and punishes the crowd, im ok. **i DO need a really nice line amp, something with some character (all tube ofcourse, all of this is all tube i should mention) and with a summing section for the guitar preamp that would go into a phase splitter and current driver for the 6550 (svt used a 6C4 if i remember correctly) also i have alot of knobs that i can do - one idea i thought of on the guitar pre was the ability to alter the cathode resistor on one of the more intrussive gain stages in the guitar preamp, giving me the ability to control the linearality of the tube's operation. Scott Hampton gave me a lengthy description on how rad this mod is, though he did it on the phase splitter of his marshall (and the summing buss on his console, an awesome option indeed!). i donot want this option on my line stage. just some character and good tight bass on the line section.

4) PSU for this thing has to be oil caps and filter chokes. screw that electrolytic crap. only problem is ive never worked much with filter chokes and big oil caps! i dont know what values are normal! i have access to a large supply but whatever someone can think of as good values would be most appreciative!

this is the biggest diy project ive thought of, and i never thought i would build an amp, everything is just falling too perfect into place for this to happen. im trading the peavey tweed amp for parts and a yamaha 2x15@4ohm cabinet!

sorry for the HUGE lengthy post, usually im limited to short lines and quick questions.
thanks for your time everyone
-bryan sours

Stick with 6L6. You won't get significantly more watts with 6550 on the same transformers, the sound won't be "wow!" different, and 6550 do draw a lot more heater power.

6L6GC is more available and cheaper. Is a good tube.

6550 make sense when you want 60-100 watts/pair. But sticking with the current power transformer you are never going to see 150-200 watts from this beast.

It is possible that two 6550 can replace four 6L6GC. I'd have to see supply voltages and driver details to guess.

100 watt PA rating for quad-6L6GC is pretty rad already. 50 watts AB1 is cooking in 2-6L6GC, and PA amps were usually derated. They may have abused the old AB2 rating that claimed 47 watts for a pair of original-recipe 6L6. But AB2 tends to be nasty at full power.

hmm...
im so excited over this project im scanning the thread like mad before i run off to the shop.
anyhow you really dont think the 6550 will be much of an improvment in sound? i mean im looking for bass reproduction at its best, and i love the svt sound, but the B-15/18 amps - did they use 6L6?
ive just seen too many 6L6 amps, and im looking for something more...exotic/unique in this design (granted im taking already used designs for the preamp/poweramp i still think this thing will be its own beast in the end)
i definately want this thing to growl, but mostly in the guitar pre - im still gonna use this amp for a keyboard amp sometimes. im sure the stock output tranny will have its own 'growl'.
have you ever used a PA off this series? im just guessing @ the 100W rating since i see 4 6L6 / i have very little info on these.
i always look forward to your posts PRR
thanks again
-bryan

> im just guessing @ the 100W rating

Don't guess. Before you go off half-cocked, study this beast. PA amps almost always have power rating and impedance info clearly marked on the back panel. I have seen quad-6L6 making 30 watts. The model number you posted dosn't find any info in my search, so you are going to have to study it to find out what you got.

Does it smoke when you plug it in? (I would expect it might, so do it outside with a long cord so you can unplug it without getting burned.)

Here ya go:
x
x

x
x

x
x

:guinness: :guinness: :guinness: :guinness:

thanks for the info!
any clue as to how they sound?

prr: how can i figure out the approx pwr output? its not labeled on the rear, only the outputs (75v, common, 25v, cntr tap, 25v)
i better know before i start using that output tranny.
thanks!
-bryan

That poor transformer! Oh, well, I guess sacrifices must be made! CJ, did you see the show on the history channel, about how the Russians reverse engineered 3 of our B-29's they "aquired"? They kept 2 planes flying, and totally disassembled the other one, and created their own version of it . (The Tu-4.) Scary thing is, that was pretty much what accelerated the cold war!
Talk about DIY! They couldn't reproduce the tires, so they sent spies over here to get them off the surplus market! (Who needs the internet!?) Of course, it makes you wonder, now that we do have the internet, who is building what! (Hopefully, it's all audio related!) :green: :sam:

> how can i figure out the approx pwr output?

Put it under your pillow and dream the answer.

Asking me isn't going to get you real far. Dukane introduced new models every year or two, and "1B45A" isn't one I know or apparently written-up on any websites.

Short of me breaking into your pad and seeing this beast myself, you have to tell us everything you can observe. Tell us all the tube types. Very preferably the type shown on the chassis, not the types that are in it now. (They may have been replaced with "equivalents", but we need to know what it was designed for.) How many knobs? Rectifiers? Is there a 2-pin jack marked "500"? Date codes anywhere?

I did find a 1A45-A. If the B is similar, you got yourself a killer 45 watt amp. That would be a reasonable rating for a quad of non-GC 6L6 in PA duty. (BTW: this schematic is so old they use "M" for "Kilo".)

And if it is 45 watt output with 70V and 25VCT outputs.... You could hang 16 ohms across the 25V terminals, or 4 ohms from one 25V screw to CT, and get 36+ watts, essentially full power. Or hang 8 ohms from 25V to CT and get 20 watts. You can make a heck of a racket with 20-30 watts. But it isn't any SVT and never will be. It may not be a "crowd punisher", unless you can get the crowd to carry it for you.

If it has vacuum rectifiers, and you are not a purist, I betcha you could convert to silicon, upgrade all the power caps (they are shot anyway), run 6L6GC (or 6550) and gain 50% of power. Maybe 70 watts with a quad of 6550 in fixed-bias (without the 5U4s you can probably heat a quad of 6550 on the original 6V winding). That's not a lot of increase to the ear (couple or three dB). I did it to a lot of PA amps for cooler running and solid peaks. But in guitar duty many players prefer the softer peaking of hollow-state rectifiers. The "lower output power" seems to be compensated by the more dynamic overdrive.

Here is an essay on hacking PA amps into MI amps.

Those mike transformers sound OK, but a modern transformerless mike input is noticably (even to my ears) more transparent.

> oil caps and filter chokes. screw that electrolytic crap

Do you know how big 100uFd of oil-cap is??? You can't do it all with chokes (anyway, they are heavy).

What is wrong with electro-caps in a power supply? Yes, the stuff from 1940 is dead already, but caps I installed in the 1970s are still going fine. And modern caps are better. Get the Panasonics from Digikey, get the highest temperature rating they got, and they will probably out-live you. (And they are so much small than the old caps that you can probably hollow-out the old cans and hide the Psonics inside.)

my apologies, my impatience is showing!
a guitar tech freind that lives down the street has some old bass output transformer that ill probably switch too, or a hammond - something that can give me 4 ohms @ 100w. that schematic is right on the money from phase inverter to output transformer. so thats the info i needed, again thankyou. the unit i have has the same pentode mic pre that ampex 600's do, 5879 or something.
thanks for the link! im going to take a day or so and get through it, hopefully that will give me a better concept of what i want to do, and how exactly i should be doing this.

if you dont mind PRR i might still run some stuff by you.
thanks again
-bryan sours