PCL82 PCF802 low wattage amplifier

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Thomas_H
Posts: 42
Joined: Wed May 07, 2014 2:48 am
Location: Brasil

PCL82 PCF802 low wattage amplifier

Post by Thomas_H »

Hi,
just finished a new small amplifier with some TV tubes I had laying around.
Both the PCL82 and the PCF802 have odd filament voltages, 16v and 9v respectively, but as they require the same current I'm using them in series from a 24-0-24v transformer.
This way I could also use the 48v in a simple voltage multiplier scheme to bust the voltage to around 230v.

The idea was based on the croaker presented on the Wattkins forum, but using the extra triode of the PCL82 as another gain stage to bring this amp in the distortion territory.
The build was a little complicated since I wanted to use an old tube radio tuner chassis, that was almost too small for it. The PTP wiring also didn't helped in this case...

PT still not on the chassis since I was testing the best position and orientation. It ended up behind the preamp tube, 90 degres to the OT. I first thought I could put it over the remaining tube socket hole, but when align with the OT the hum increases considerably.

Here the schematic and some pictures:

Image
Image
Image

and a short testing video:

https://www.tumblr.com/video/thomaseh/159273578478/250/
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RJ Guitars
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Joined: Tue Nov 14, 2006 3:49 am
Location: Los Alamos, New Mexico
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Re: PCL82 PCF802 low wattage amplifier

Post by RJ Guitars »

Cool idea and nice use of the hardware you had available. At a glance it looks similar to a build I did a couple months back: http://diyguitaramps.prophpbb.com/topic128.html I have grown to like the pentode/triode tubes as well as using a pentode as the first gain stage.

Do you have any plans or thoughts about how to build a cabinet for it? I really like the way my little amp sounds but haven't found a cabinet idea that I like yet.

Thanks for posting this.
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Thomas_H
Posts: 42
Joined: Wed May 07, 2014 2:48 am
Location: Brasil

Re: PCL82 PCF802 low wattage amplifier

Post by Thomas_H »

Very Nice RJ, haven't seen it, but I had a similar problem, but it was due to blocking distortion.
That's why I added the last 100k leak resistor before the PCL82.
This small amps are too sensitive for gainy preamps. With the extra triode of the PCF802 there is even more gain on tap.
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