• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

6P45S PPP Monoblocks.

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kodabmx

kodabmx

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Joined 2011
#1
See 6P45S PPP Monoblocks. for the latest schematics.
So I've decided to cannibalise some of my other amps that collect dust to build 2 6P45S monoblocks.

Triode connection. B+=290V-320V. Idle 120mA/tube. Load=650R or 1300R EDIT: 2600R

Basically, I'm thinking of building the amp I have with both channels in parallel. In PPCalc:
With a 1300RLa-a, I get 22.5W class A, 119W total.

What do you think? This entire project will only cost me the price of the chassis.

R1-R4 = 10R. R5-R8 1k = R9-R12 = 220k
The OPT will be made of two Triad VPT18-13800 in parallel. (500VA)


170W from "triodes" for less than the price of 30W from a pair of 300B


Hot tip: Heater cord works well for top caps. 300V rated (so good to much higher than that in practice) and 105c rated, too.
 

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#3
Nice, but in this design there is no reason to. B+ is only 320V, and heater cord is 70 cents per foot for 16/2. Voltage rating is mostly a liability thing. This wire insulation is probably good to 2kV, but if it isn't, you can't sue them.
 
#5
Voila.

This is as it's built now, but I've used one of these for it, too. 500W 12VDC transfer 18VAC & 0-220v-380v inverter module | eBay

Well I finished them. Here's a pic of one of the second one.

So right now, I'm using 6A10 diodes for the heater supply. I get only 11.4V loaded which is -10% of the rated voltage. I found the SM74611 diode with a forward drop of only 26mV @ 8A, but there are surface mount.

Any reason I can't just dead bug them?
 

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#6
Did you try them in pentode mode with local feedback?
You would be surprised. 🙂
One way is, to use secondaries for 4 and 16 Ohm to cathodes.

I am attaching the schematic of my 30W amp with 12BQ6 output tubes. Sweet!
 

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#15

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#17
I got them surplus for $6 CAD each... They are used pulls from Uninterruptible Power Supplies.

Here's a better picture... It looks like it's stereo, but it's parallel mono.
 

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#19
#20
Those resistors are duplicated in both drawings, and should connect to the -V bias lines instead of ground. As shown, the phase splitter can be used with a cathode biased output stage, and they can be omitted if using the output stage shown in the schematic.

Diabolical Artificer said:
"I got them surplus for $6 CAD each." That's a good price, is there a good place near you for surplus? All the old surplus places here in the UK have long since closed down, there may be on or two left but nothing like there used to be.


A.
Click to expand...

Yes there are a couple of pretty good fishing holes for surplus in Toronto.
 
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