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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

Super Junkbox 6S19P SET

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sorenj07

sorenj07

Member
Joined 2006
I've got a couple 6DJ8's, more than a few 6S19P's, four noval sockets, two 120:12V 20W wall-warts, one 35VA 1:1 isolation transformer, and one 35VA 12V filament transformer.

I thought it would be funny to make the cheapest single-ended amplifier that I possibly can.

My plan (detailed schematic to come):

Use a B+ of a whopping 150V derived from the isolation transformer, preferably solid-state regulated. Use the 120:12V wall-wart transformers in parafeed, as 800:8 output transformers. The choke loads would be Hammond 193C's at 20H 100mA 181R. I'm new to parafeed; would these be all right? I would use smaller cheaper ones but B+ voltage is precious and I need a lower DCR.

The 6S19P's would be biased using a constant current source holding them at 40mA. This would allow +- 40V swing in a pretty linear region, as the plate curves show. I was thinking of using the CCS found here: http://diyparadise.com/yhlmccs.html but the greater bias voltages seem like they might be a problem.

The input stage would be a standard SRPP. The 6DJ8 seems pretty happy with only 150V total B+. With 330 ohm top and bottom resistors, at 5mA total, I get +- 43V, with a bias at -1.63V. I'll want a volume potentiometer! I could also probably use a 12AT7 for a bit more headroom but I don't have any and am poor. I'd probably need to use one if I ever wanted to implement NFB.

So what do you think? Am I crazy, or just very cheap? Does this amp have a chance of working?

An externally hosted image should be here but it was not working when we last tested it.
 
sorenj07

sorenj07

Member
Joined 2006
Oops, bad loadline.

I just realized that I'm burning off 40V or so in the cathode resistor for the 6S19P, so my B+ needs to be about 170V. This is a lot closer to 1.414*my house AC which is usually around 125-127V... Good stuff.

A SRPP using 6DJ8's at 170V should be able to provide the +- 25V pretty easily.

An externally hosted image should be here but it was not working when we last tested it.
 
I

ilimzn

Member
Joined 2005
sorenj07 said:
...Use a B+ of a whopping 150V derived from the isolation transformer, preferably solid-state regulated...
The 6S19P's would be biased using a constant current source holding them at 40mA. This would allow +- 40V swing in a pretty linear region, as the plate curves show.
Click to expand...

You have a crytical error in your reasoning.
The loadline will be that of a current source only if there is no actual useful load to the circuit, which kind of defeats the purpose :)
Secondly, at a whopping cost of one capacitor, you can double the B+ voltage.
 
sorenj07

sorenj07

Member
Joined 2006
Thanks. I'm very tempted to try and put this one together. Unfortunately I have a ton of other stuff on my plate. Once I finish some commission work I should have enough scratch to cover the few parts I need. I want some kind of metal cover to hide the un-belled isolation transformer and the toroidal filament supply :bigeyes:
 
V

Vlauga

Member
Joined 2005
Sounding of a tube 6S19S is very similar on the transistor amplifier. But considerably smaller power))

There is other tube from this series of tubes for application in stabilized sources. It 6S41S.
http://forum.cqham.ru/download.php?id=2702
Its power disseminated by the anode 25 watt.

In this series of lamps there is one more reputable lamp because of the uniqueness. It 12S42S.
http://www.next-tube.com/DataSheets/tubes/12s42s.djvu
Its power on the anode of 120 watt! Its current catode 1.2А!
 
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