Various Output Transformers

[Toxophilite]

I have here 3 different organ OPTS
All were used originally with a pair of 6BQ5
However they're different in size and turns
The smallest is from a Hammond organ same as found in the AO-43  30-1 turns ratio  -8ohms
The middle one without bell caps is from a 'stereo' Baldwin organ amp, it powered the leslie, Is about 3/8" bigger than the hammond on 2 dimensions 24- 1 turns ration into an 8 ohm speaker
The black one is from the same Baldwin amp . It is roughly the same dimensions as the one with no bell caps(just on end) and is 37.5-1  turns ratio..I can't remember what the speakers were(oops)


Out of curiousity does the larger size of the Baldwin ones indicate more power handling capability,, maybe more bottom end capability. Or does it need to be a more significant size difference?


Interestingly I had another Baldwin amp I sold   that ran 2 6L6 into an OPT the exact same size as the non bell cap one pictured, though it did have a different model number on top.

[sluckey]

You may want to tag those transformers with all the info you have while it's fresh on your mind.

[DummyLoad]

the baldwin (larger black one) is a 30W part. it was drive with 2 pair of 6BQ5. guestimate is that it's reflected Z is around 4K. build a hot-rod princeton reverb or deluxe reverb with either 2 5881, EL34 or 4 6BQ5


--pete

[Toxophilite]

Good idea! Some labelling is in order.


Dummyload, From examining the inside of the amp (which powered the black transformer and the one without bell caps) one can see that each is powered by 2 6BQ5/El84 in pushpull .
-The black transformer powered a pair of small ceramic magnet 12" speakers
-and the one without bellcaps powered a big ceramic magnet 10" speaker that was part of a leslie setup in one side of the organ. Interestingly that OPT was mounted off the amp on the side of the internal leslie cab!


There are 2 separate volume controls on the amp each attached to the different 'channels' .
One for the Main amp and one for the Rotary amp


I've had one of these a couple years back and it was the exact same setup


I really wish it was a 30 watt OPT though!! but it's currently just being driven by a pair of 6BQ5s
it's also the same dimensions as the non bellcap one , it's just standing on end (kind of tall and narrow) Still a fair bit bigger than the hammond AO-43 unit

[HotBluePlates]

The common setup for amps like you're describing is to have 2 pairs of EL84's (assuming the big OT was not on a chassis by itself). Each pair has its own OT, and generally bass is stripped away. Then there is a 3rd OT to which only bass is sent, which is fed by both pairs of EL84's.

This allows for stereo operation, and smaller core size for the treble-only OT's. FWIW, deep bass is essentially omnidirectional, which is why most stereo recordings have the bass panned to the middle (because deep bass without significant overtones will seem to come from everywhere even if it is panned to only one speaker, which is why subwoofers work the way they do).

You may want to tag those transformers with all the info you have while it's fresh on your mind.

All of the above is why Sluckey's advice is spot-on.

Better yet, keep an OT, output tubes and the associated power supply all together. They're generally sized to work together and already have the needed trade-offs built-in.

[Toxophilite]

On this Baldwin organ(and I've had two of this specific model pass through my hands, complete organs, that just use tubes for the amplifier not the tone generators)
It's just the two channels, no crossovers, or extra bass channel, One OPT is on the chassis (black)and the other sits on the side of the Leslie cab(non bell cap) No other OPTs, Not even a choke.
Just the PT and the two OPTS


The hammond transformer was from an E-100 organ amp that I picked up for my friend to make a bassman out of .
I scrounged the OPT that was on the same chassis for a reverb channel and it happens to be the exact same unit as the AO-43 uses


The other two are together from the same amp


I will be labelling them for sure
Thanks!

[Toxophilite]

Judging by the tryout I had tonight in a larger rehearsal room with my loudish drummer
2 AB763 deluxes in stereo aren't quite enough to achieve clean headroom
So I'm hoping to convert Amp1(the main amp) to a vibrolux with 6L6GCs as the circuit is almost identical
But I need a bigger/better OPT!!


As stated in my first post of this thread I have two bigger ones both of which were originally powered 2 EL84s both from the same Baldwin 2 channel stereo amp
they both measure about 3 1/8" by 2.5" by 2.5" (the black one is standing on end so it looks bigger)
one is 24 to 1  and the other is 37 to 1 turns ration
By the formula found on this cool page http://www.radioremembered.org/outimp.htm

I've determined that with a primary voltage of 415
the 24-1 will see 4611 ohms at the primaries with a 8 ohm speaker load
and the 37-1 will see 5460 at the primaries with a 4 ohm load
Both these numbers are pretty close to the 500O ELR that a 6L6 wants to see at the primaries


Considering the size of them (a fair bit bigger than the OPT of the hammond AO-43)
Do you think these units would do the job for an AB763 vibrolux?? or am I grasping at straws?


I figure they used more substantial OPTs for a pair of El84 on these baldwins to handle the bottom end of the bass pedals. that of course is just my guess.

[Toxophilite]

Since no-one's chiming in I decided to do a little experimenting!


I needed to dig back in to Amp 1 anyway to install the JJ can cap and clean up the mess of the homemade job I made, It's working but I have the extra JJ unit and it does make for a much tidier chassis




Anywho
i took the black 37-1 pushpull OPT off the baldwin chassis and after disconnecting the one on the Hammond A0-43 AB763 deluxe build(AMP 1) I wired it in (sitting beside the amp but connected to the chassis with a ground "strap"
It worked fine and surprisingly quite considering the makeshift attachment
I popped in some Sylvania 6L6Gcs I had (they had broken guide pins , thanks for the tip Sluckey, I made some prosthetic ones from old octal sockets, worked a charm) and put the bias at -45 like a AB763 vibrolux and played through it


It sounds good and starts to break up in basically the same place as the deluxe (just past 5 on the volume)
I'm having a hard time telling if it's a lot louder..it seems like it probably is but it's pretty hard to tell, sounds really nice though through the 2 10s


Maybe I'll record it, then swap in some 6V6's re-bias and compare wave files and report back

[DummyLoad]

i have p/n 0512-028812A that was salvaged off of a baldwin type 46x organ amp and it was driven by 4 6BQ5. if you have the same p/n it should work with a pair of 6L6 in configured to operate at about 30-35W.

my partner in crime and self have/had 3 sets of them; partner kept one set, i kept one set, and we used the third set to build the EF86 channel of a matchless DC30. pic below.

--pete

[Toxophilite]

Tried it out
It was interesting test
i have a 2 x 10 cab at 4ohms (2  8ohms in parallel)
volume at about 6


Put a mike on one speaker
tried it with 6L6s biased like a vibrolux
re biased like a deluxe and then 6V6s


Only about 1 db average RMS difference with the 6L6 coming out on top


then though heeey the 6V6 is wanting to see 8 ohms but is seeing 4 ohms


So I did the same test but unhooked the un-miked speaker and of course the 6V6 was now about 2 db louder!!


but of course I thought it's putting all it's power into the one speaker the 6L6s are splitting it between both


So I moved the mike back about a yard, pointed it at the center and tried again


This time the 6L6s were on average about 2-3 db louder


My recording engineer friend says that 6dbs louder is about double volume so 2 db is about 30% more
So it seems like I'm getting more juice out of the amp
To the ears it's not a huge difference but maybe enough


interestingly I tried the same experiment with the SF line out this amp has and the results were almost exactly opposite

[Toxophilite]

this one is baldwin part number 512-031278


the other OPT from the same amp is 512 -023628