tube regulated screen grid supply

[Andy Le Blanc]

I was going thru some old schematics and I found this....

A 6l6 used in a regulated screen grid supply.

[j-po]

Very interesting! Although not all that useful considering the extra heater current needed. Heater would also have to be elevated a lot as the cathode is at high potential. Similar solid state solution would eliminate the downsides of course.

[Ears]

Here is another old commercial design

[Andy Le Blanc]

fun stuff..... The Grommes has a srpp, the 6.3 fil. ct has a cap. 20uf 500v.

simple tube solutions are great, an old friend of my parents used to work for
a telecom outfit, he said they were always re-examining old tube circuits.

I'd much rather go with a tube, the only real drawback is that they require
a lot of people/labor to make them, and that's not so bad.
Miniaturized solid state makes consumer victims of us all..... anyway.....

I have a few Ideas as to where to use a tube regulated screen supply.
That's a shunt regulator? that resistor divider to the screen sets the Vout?
Any good descriptions of function? Its good to see the srpp in the Grommes.
That's current regulation, CCS.

[KT66]

HiWatt used a 12AX7 configured like this connected to the PI. Can someone explain what is going on in this circuit ?

[Andy Le Blanc]

DC voltage divider, low impedance voltage reference, from mhuss.

But the "why" I don't know, stabilization I think.

[Ears]

Andy, the regulator simply operates like a cathode follower (if that is what you are asking in 2nd post).

[FUCHSAUDIO]

Looks like V3 is acting as a constant current source. No audio applied to it. It supplies bias to the phase inverter (last stage).

[j-po]

Miniaturized solid state makes consumer victims of us all...

A single mosfet might do the job and is not all that miniaturized, pins about as far apart as on a noval tube. Not proven to sound inferior in this application either, so it's just having more tubes for the sake of tubes themself.
Then again, if your selling boutique amps to ignorant mojo-obsessed musicians then tube regulated power supply sounds like its worth at least $1000€.

[Andy Le Blanc]

Right on...... that argument could be carried a long way, where's casey jones?..

Technology for technologies sake? When it begins to be inaccessible, and
dominates your life, its too much, it's very difficult to be self sufficient.

Look at the cellphone apps market, ten years later people might turn around
and realize just what a rip off it really is, Imagine paying for the internet one
web page at a time? And when it breaks, if you haven't shelled out the payment
for the insurance your still stuck with the rest of the contract.

I can use valve based technology without specialized tools. Tubes need a lot
of "PEOPLE" to manufacture, they aren't spit out endlessly by machine.

You are right of course, about the technologically ignorant, but its same
with all tech based products, and consumer markets. Whether its SMD
or tube. The more tube application are used the bigger the market
and the larger the continued need........ for more tubes. I like tubes....

[FUCHSAUDIO]

I believe, if you have a spare tube section, you should use it for sure. Adding solid state if you don't have-to, is silly..

[KT66]

I believe, if you have a spare tube section, you should use it for sure. Adding solid state if you don't have-to, is silly

Ya, but if you wanted to regulate the PS as in the Grommes above too many of the design max parameters are exceeded to use a dual triode. In the example I posted above, Mr. Reeves must have felt it was important to his design, because it actually results in an unused preamp section.

A single mosfet might do the job and is not all that miniaturized, pins about as far apart as on a noval tube. Not proven to sound inferior in this application either, so it's just having more tubes for the sake of tubes themself.

Sure, but tubes are cool. Obviously not practical commercially, but fun to tinker with. Besides, you could use any old/weird/unpopular tube and it wouldn't cost that much.

Could this be used in a different position to knock down the whole PS rail, or maybe in a tube based power scaling application ? - I bet that could add another $1000€ woth of mojo

[skyboltone]

I like the way Leslie did it in their speaker amps. OA2s and OC3s. Actually very reliable and fun to watch.

http://www.captain-foldback.com/Leslie_ ... cs/122.GIF

[KT66]

Interesting. What exactly is the purpose of that Leslie amp ? Must be a clean machine w/ the regulation and local feedback on the power tubes, and what's with the CT on the OT secondary ?

I scoured the web for info on that tube and just found a bunch of dead links. Did find an article that had this to say about the OC3 :

The OC3 regulator tube is optimized for not changing the voltage over a wide range of current. When you go above the specified maximum current, this is even possible, when you do not expect the perfect regulation from it, that you have below 40mA. One of the best voltage regulators ever made - and still available. 50x more stabile than a Zener diode. Gas filled tube, without filaments. Has just two connections, and is used like a Zenerdiode. Can be used as transient suppressor, or stabilizer device. Can be serialized to get the required voltage. Just put four in series and get 420 Volt / 40mA. The American types are lighting pink. The Russian types use Neon gas, and lights up bright orange.

I found this link about an amp VVT has called the Regulator that features it, maybe Tony can chime in and enlighten us : http://www.vvtamps.com/pricing.htm

[ckpop]

The OC3 Modified Fender that Bill Holter from vintage sound owned sounded great. It was a frankenstein and more high gain but bottom line it had a tone qualitiy I have not heard in any other amp.

Maybe there is something to the OC3, Maybe not but worth investigating.