Odd-ball amplifier ideas that actually work. All suggestions comments welcome!

[Austin]

After visualizing the power cascode amplifier, putting it together and it actually working the first time I turned it on, I am encouraged enough to try some other off the wall ideas. Have you guys been working on or have any crazy ideas you would like to share? I'm working on one now that shoud be fun, if it works I will post up a schematic but it is very simple. All dc coupled 12ax7 driving a 6sn7 driving a el84. I think it is awesome the 6SN7, 6BL7 the and the 6080 have the same pinout.. Probably alot more tubes too. I also think it's awesome they are all cheap on ebay....

One crazy idea I have for later is using a circlotron as a voltage amplifier by taking the output from the plates instead of the cathodes. Using this to drive the power cascode would make the most backward frankenstein amplifier I can possibly think of and I am pretty sure I could make it work.

[soundguruman]

Thou hast released the Genie from thy bottle...

[J M Fahey]

The upper circuit does not work.
The lower one will, but will also have hellish crackle as soon as you want to set that volume pot.
Thanks for identifying them with your professional name, so people knows they should avoid them.

[soundguruman]

FYI both circuits work, and have been built and tested.
Quite clean, actually.
Abuse reported to moderator.

And for those of you who are interested in the discussion that Austin has started:
"Odd-ball amplifier ideas that actually work."
Good subject, especially for some of you who want to learn something new.

I designed these circuits as a unity gain buffer. This is to compensate for mismatched input impedance.
(Look out folks, there is a secret part to VOX original amps, that is something like this, however it never was drawn on the schematics)
In the top circuit, The first stage was intended to have only a small amount of gain, and I wound up biasing it with a fixed DC voltage of around (-) 1.3 volts.
The second stage in the top drawing is a passive plate follower, yes it's an attenuator. You have never seen one before, I invented it. (hahaha)
And for those who are puzzled, the filament must be ON. That's what starts the electron flow. If the heater is off, there is no signal on the passive plate.

The second one being more conventional is higher current output. Of course cathode follower.

In either one, the output level pot is a trimmer, that is set to one preferred level, permanently. It was never intended to be adjusted while the unit is operating.

The idea behind both of these was to take a high level signal, like a CD player, and saturate a grid of a tube to obtain a "tube warm sound"
Then to attenuate the signal to the point where it could be fed into the next preamp stage without overloading...
It's a hi fi idea.



Now in the third one, I'm going for what I call the "air sound."
This is like an unencumbered delicate kind of input sound.
In this design the DC heaters are especially called for-- because I wanna reduce the noise as much as possible.
Yes again it's an attenuator, but this time the first stage. AND your gonna have to put a tube shield on that one because the plate becomes super sensitive.
And now the first stage is biased with a fixed DC voltage of about (-) 1.5VDC.

[Enzo]

Austin, as long as the needs of the individual tubes are met, many odd circuits will function, some well, some poorly. But you can try most anything. You can invent something right out of your head, and try it. If it works, great, you learn something. If it doesn;t work, great, you learn something from that as well. Then do some research, because you will find that just about anything you can come up with has been done before. Doesn;t mean your idea isn;t original to you, but tube technology was already mature in the 1930s. remember they had radar and short wave radio and even FM back in world war two. Television was invented before that war. They were clever and sophisticated back then. They thought up a lot of stuff. Some we still use, other things faded away because more modern designs work so much better.

SO try it all, and tell us what you find out.

[soundguruman]

I think the Electrovoice cyclotron is pretty cool.

[soundguruman]

Hey Austin for some reason your attachment did not attach...

[J M Fahey]

Dear soundguruman, you deserve 22 Nobel Prizes stacked, if you can have a tube work with both plate and cathode at ground potential.
Electrons are attracted or repelled by potential differences (or "voltage", to dumb it down enough so you can understand it), which your circuit does not provide, simple as that.
So I repeat:
1) your first circuit will not work, because, if any, electrons may jump to the grid (which will act as a plate if more positive than the cathode) but *never ever* to the plate, because it has no voltage difference with the cathode, so audio will not make it to your master volume nor the following circuit.
2) the second is poor engineering at best, and I don't see the caption by it stating that it's a preset volume or that it must be set to a fixed level and be left there.
DC across a volume control is not a good thing.
Clearly you "see" things there that we don't.
Don't understand your reference to a "bottle" . Don't want to jump to conclusions either.
3) your 3rd design does not work either, it suffers from the same problems as the first, no electron will cross the first tube barrier.
*HI FI* ? or ........ "HA HA"?
I don't care that you put your fingers in your ears, and sing "lalalala ! lalalala ! , I can't hear you !!! it works!! it works!!" , because it does not.
Electrons couldn't care less about what you (or me, by the way) "say", they follow Laws of Physics, just like that.
4) Agree that you should shield the first tube in example 3.
Its non-working plate still is a chunk of metal connected to the next grid, it will act as antenna and couple all kinds of junk and noise , even RF into the next tube.
5) in fact, RF is the only thing that will get from the input to the 2nd tube, thanks to the parasitic capacitance from grid to plate.
What? ... about 2 to 5 PICO Farads?
6) what did you call it? ... "air" sound?
Well, maybe some RF in the AIR band , say, 118 MHz, will get through.

Please consider that the *Audio* band considered Hi Fi goes from 20Hz to 20KHz, not exactly what (with a big effort) might pass through your crooked "designs".
Just sayin'

[soundguruman]

Dear soundguruman, you deserve 22 Nobel Prizes stacked, if you can have a tube work with both plate and cathode at ground potential.
Electrons are attracted or repelled by potential differences (or "voltage", to dumb it down enough so you can understand it), which your circuit does not provide, simple as that.
So I repeat:
1) your first circuit will not work, because, if any, electrons may jump to the grid (which will act as a plate if more positive than the cathode) but *never ever* to the plate, because it has no voltage difference with the cathode, so audio will not make it to your master volume nor the following circuit.
2) the second is poor engineering at best, and I don't see the caption by it stating that it's a preset volume or that it must be set to a fixed level and be left there.
DC across a volume control is not a good thing.
Clearly you "see" things there that we don't.
Don't understand your reference to a "bottle" . Don't want to jump to conclusions either.
3) your 3rd design does not work either, it suffers from the same problems as the first, no electron will cross the first tube barrier.
*HI FI* ? or ........ "HA HA"?
I don't care that you put your fingers in your ears, and sing "lalalala ! lalalala ! , I can't hear you !!! it works!! it works!!" , because it does not.
Electrons couldn't care less about what you (or me, by the way) "say", they follow Laws of Physics, just like that.
4) Agree that you should shield the first tube in example 3.
Its non-working plate still is a chunk of metal connected to the next grid, it will act as antenna and couple all kinds of junk and noise , even RF into the next tube.
5) in fact, RF is the only thing that will get from the input to the 2nd tube, thanks to the parasitic capacitance from grid to plate.
What? ... about 2 to 5 PICO Farads?
6) what did you call it? ... "air" sound?
Well, maybe some RF in the AIR band , say, 118 MHz, will get through.

Please consider that the *Audio* band considered Hi Fi goes from 20Hz to 20KHz, not exactly what (with a big effort) might pass through your crooked "designs".
Just sayin'

I can't decide what to do with my Nobel prize money. 22, that's a lot.
When the first atomic bomb was dropped, there was a certain percentage of chance that it would start a chain reaction that would consume all the oxygen and vaporize the entire planet.
And they dropped it anyway. That's comforting.

[Austin]

Listening to this right now, sounds nice. But I want more power so probably will try to connect the screens for pentode mode.... I have low efficiency EPI M100 speakers.

I am thinking about using the extra octal socket for a 6sn7 that I have as a cathode follower. Or maybe cascade for a guitar amp? The chassis had tube recto before so that unused slot bothers me... The 6sn7 is in there now heaters running and still measure 6.3 volts so I guess the heater ccurrent isn't too much for the power tranny.

[J M Fahey]

I can't decide what to do with my Nobel prize money. 22, that's a lot.
When the first atomic bomb was dropped, there was a certain percentage of chance that it would start a chain reaction that would consume all the oxygen and vaporize the entire planet.
And they dropped it anyway. That's comforting.

Don't worry about the Nobel Prize money, because they won't pay until your circuit works anyway

[J M Fahey]

Dear Austin.
Yes, this may work.
What I don't get is that you had to build an (rounding values) 800V supply, to end having a class A pentode which uses only 400V and provides nothing special (DC coupling is sort of wasted because anyway you have an output transformer) .... while you could have built it the conventional way and simply couple them with a $1 capacitor.
And I also fail to see the Cascode here.
Of course, if the idea was just to "build something different", fine with me.

[Austin]

Dear Austin.
Yes, this may work.
What I don't get is that you had to build an (rounding values) 800V supply, to end having a class A pentode which uses only 400V and provides nothing special (DC coupling is sort of wasted because anyway you have an output transformer) .... while you could have built it the conventional way and simply couple them with a $1 capacitor.
And I also fail to see the Cascode here.
Of course, if the idea was just to "build something different", fine with me.

It does work.
The cascode is from the other thread: http://music-electronics-forum.com/t29880/

I am using the same chassis and power supply minus the the 6080. I just wanted to see if I could do the cascode in the power section before. The 6080 required a sepparate heater power tranny though which was just a huge walll wart. I can't use 800 volts with a el84 anyways right? I am hopefully picking up two hammond organ tube chassis with huge power transformers sunday, then I can experiment with the circlotron. Or cyclotron whatever you wanna call it.

DC coupling is one way to reduce or eliminate blocking distortion. It also obviously removes any effect capacitors have on the sound. I could also possibly get closer to class a2 for more power and efficiency with a beefy enough driver tube.

[Enzo]

There are simpler ways to reduce blocking. Direct coupling is not that hard, but look at your circuit. This approach requires a whole extra supply to lift the otherwise conventional power tube stage up 400 volts from the floor.

[exclamationmark]

Actually, I remember reading about tube circuits without a B+ rail that worked off the tiny charge imparted by the electrons being boiled off the cathode. Not exactly sure where I read it though... I'll try to find it, might make for an interesting read!