• 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.

Super Junkbox 6S19P SET

sorenj07

Member
2006-05-04 9:15 pm
Berlin
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?

[IMGDEAD]http://img232.imageshack.us/img232/8693/6s19pccsxx4.th.jpg[/IMGDEAD]
 

sorenj07

Member
2006-05-04 9:15 pm
Berlin

ilimzn

Member
2005-02-11 1:25 pm
Zagreb
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.

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

Member
2006-05-04 9:15 pm
Berlin
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:
 

Vlauga

Member
2005-05-24 12:38 am
Msk
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!