Baldwin Organ amp schematic needed

Rex Everything

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Hey All,

I am in need of a schematic for a Baldwin organ amp I'm working on updating for audio use. The info I have is: Baldwin Amplifier Model PC, Tone Chamber System "S"

Your help will be appreciated

T.I.A.

Rex

ba5.jpg
 
Are you sure you want to use the original circuit on these? What is the tube compliment? You could probably find a better Hi-Fi circuit.
 
Are you sure you want to use the original circuit on these? What is the tube compliment? You could probably find a better Hi-Fi circuit.

I'm not sure at all. Do you have any suggestions?

Tube compliment is 4-6l6's, 2-5U4's and a 6SL7 driver.

Let me know what you have in mind.
 
I have the schematic for this (and other Baldwin amps) somewhere... I will dig around.

I have a pair of them, and I strongly advise using a different circuit for the front-end. It won't be expensive or difficult to get it working "stock", however, so perhaps give it a whirl before proceeding. The power supply is excellent, as you might guess just from looking at the power transformer and choke!

The existing circuit is a 6SL7 or 12AX7 paraphase inverter, which does not offer especially good. Also, the output stage tubes share a single cathode resistor, so well-matched tubes are necessary for good performance. There are a number of ways in which these amps can be improved. Unfortunately, I've been too lazy to try any of them on my own pair.

edit-uploaded attachments, but keep in mind that none of these are actually for the identical amplifiers! The first is "closest" but has an additional stage in front. The 12AX7 driver stage listed in other schematics is similar to that used in the later PC amps. Hopefully some of these can be pieced together so the actual schematics can be guesstimated!
 

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I'm not sure at all. Do you have any suggestions?

Tube compliment is 4-6l6's, 2-5U4's and a 6SL7 driver.

Let me know what you have in mind.

So it runs the 6L6s in parallel push pull? I doubt if you'll find anything ready made online, but I could sketch you up something. First thing we need to know is the primary impedance of the output TX. Take your variac and tickle the outer tails of the primary (just tape the center tap off so it doesn't short to you or anything) with 50v. Make sure it's exactly 50v, then measure the voltage on the 8 ohm speaker tap to speaker neg. Divide the 50 by what you read at the secondary. This gives you the turns ratio (N). Now take N and square it. Take that number times the sec. Z which was 8, and you have your primary Z. You can use different voltages or different speaker taps, just adjust the equasion accordingly. If you could also get the secondary voltage of the power TX (AC), that would also be useful. Are you planning a mono rig, or what?
 
Jay, if the schematic is correct, it is 3k8 - pretty useful, fortunately :)
 
So it runs the 6L6s in parallel push pull? I doubt if you'll find anything ready made online, but I could sketch you up something. First thing we need to know is the primary impedance of the output TX. Take your variac and tickle the outer tails of the primary (just tape the center tap off so it doesn't short to you or anything) with 50v. Make sure it's exactly 50v, then measure the voltage on the 8 ohm speaker tap to speaker neg. Divide the 50 by what you read at the secondary. This gives you the turns ratio (N). Now take N and square it. Take that number times the sec. Z which was 8, and you have your primary Z. You can use different voltages or different speaker taps, just adjust the equasion accordingly. If you could also get the secondary voltage of the power TX (AC), that would also be useful. Are you planning a mono rig, or what?


Well this should take me a while to figure out. Hopefully the schematic JonS posted is correct :)(Thanks JonS:yes:)

Mono rig nothing, I have a second one of these to make a sweet set of mono blocks(also have a third on with the 12ax7 driver and a line on a second one of those :yes:) Now I need to come up w/ 8 6l6's & 4 5U4's somewhere :D

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jon s that first one looks exactlly like another I have that is to small for me to read. I think that may be the correct one as it says PC amps on it also.
 
My pair is the 12AX7 version, and everything else looks the same as the 6SL7 version, 'cept for the driver tube. I don't know why that schematic includes another stage in front (I've never seen one with the extra tube) - but it does say "PC" on it.

I don't have well-matched quads of 6L6s (the nice GCs shown are not usable due to poor matching), unfortunately, but in my testing I thought they sounded acceptable. No shortage of power. I was using quads of KT66s in each for a bit.

To save money on 6L6s, it would also be possible to convert these to use pairs of 6550s or KT88s each.
 

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And I typed all that out with one finger.:no: It's hand written in there, but I don't have any reason to doubt it (sounds about right).
 
So does each amp have two output TXs? I'm cornfuzed.

Never mind, I was looking at the wrong schematic.
 
So does each amp have two output TXs? I'm cornfuzed.

Never mind, I was looking at the wrong schematic.

Some are designed for biamping, and have a second OPT underneath the chassis ... these models are just big beefy mono amps. :thmbsp:

One finger? What happened??
 
Post up your ideas for a circuit Jay. I wouldn't be opposed to going to 6550 or keeping with the 6l6 design.

I'll trust what the experts here at the tube forum come up with.

Warm that bench up Jay :thmbsp:
 
That schematic of Jon's is very close but not exact - as Jon says, I don't think you have the front end 6SQ7 stage on your amps, the signal goes straight into a pot at the 6SL7 input. Also, the PS has an extra cap section with that 4-section can on top - but now that I look closely at my fuzzy version of the schematic, (which doesn't have the 6SQ7 stage) it seems that two of the 20uFs are just in parallel. Jon's schematic's makes the reading a lot easier though.:thmbsp:

Good idea to also look at 2x KT88/6550 in PP vs. 4x 6L6 in PPP.
 
Wow, I completely missed this thread until pointed here by Rex from the new thread. Where was I?

You could certainly use a bogen-esque type schematic. Things will need to be a bit different on account of a different opt, but it'd work :thmbsp: Also would need to make CCS, not hard but new to most tube-heads :D
 
There are a million different circuits out there you could use.

Maybe tell us what driver tubes you have/would want to run in there.
And what output tubes do you have/want to run in there as well then.

Running paralell 6L6 in original form, lends you to those, or more traditional
pairs of EL34/KT88 and could be changed in and out.

May be able to make it so you could run the quad of 6L6, or pull them and
run just a pair of EL34/KT88 with a little creativity.

What will you be using for speakers, and what will you be using for a preamp?

Also which circuit that's posted resembles these amps best in there original form?
 
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