SE 811 amp schematic...
- Thread starter knockbill
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Why do you want to use tube that requires significant grid current? That is not easiest triode to work with. If you want this kind of power - 211 is much better tube.
If you still want to use 811, google "power drive". Mosfet source follower is the best driver circuit for it.
If you still want to use 811, google "power drive". Mosfet source follower is the best driver circuit for it.
The Eric Barbour schematic is intended for a Svetlana SV811-10 only. Notice the SV811-10 has a mu of 10 while a standard 811A has a mu of 160!
This is an extremely difficult tube to design an amplifier around. It is not the kind of tube that you just follow a schematic and expect it to work. One avenue I have seen that is intriguing is to direct couple the driver cathode follower to the 811A using the grid current of the 811A for the cathode current of the driver. Now that's an interesting idea! All roads seem to lead back to Shishido though when it comes to the 811A and A2 positive grid bias.
This is an extremely difficult tube to design an amplifier around. It is not the kind of tube that you just follow a schematic and expect it to work. One avenue I have seen that is intriguing is to direct couple the driver cathode follower to the 811A using the grid current of the 811A for the cathode current of the driver. Now that's an interesting idea! All roads seem to lead back to Shishido though when it comes to the 811A and A2 positive grid bias.
knockbill
Lunatic Member
Seems on further studying, teh SV811, isn't near the same tube as teh RCA 811s that I have... so teh previously posted schem isn't going to work... Here's one with real 811s, which may do for a test amp... Gotta find a sub for teh 5693, and maybe try this schematic out....
http://tomo.fine.to/V.World/I-811A-J.html
Edit... Looks like 6SJ7 may work as a sub...
Regards,
John
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There seem to be several variations of that schematic. It looks like a it could be fun to build one of these.
knockbill
Lunatic Member
Seems we were typing at the same time, and I figured out I had the wrong tube/schem...Now, the new one looks promising, as do the the ones you sent... I'm not up on the language, tho!!! 6SN7, 6L6 and RCA 811 look like winners to me, and I have em...
I'll try to get them printed out, and head for the breadboard...
Regards,
John
knockbill
Lunatic Member
I think you missed a couple threads!!!! That was the original idea! But, I used the 6BG6s on the 6L6 amp I've been working on (Heathkit A9xx chassis),,, Should have got all the 6BG6s that guy had at Kutztown, wasn't real sure about them, so I only got 3...Live and learn!!
You still get all the credit for using G tubes tho,,, was your idea, last Spring, to use those regulators!!!!
So many tubes, so little time...
Regards,
John
You still get all the credit for using G tubes tho,,, was your idea, last Spring, to use those regulators!!!!
So many tubes, so little time...
Regards,
John
knockbill
Lunatic Member
Did you see the schematics Palustris posted? The 6SN7, 6V6, 811 looks like teh simplest of all, so far,,, and I have most of the parts on hand!!
Regards,
John
knockbill
Lunatic Member
6SN7, 6V6, 811 schematic,,,
Here's the schematic,,, Got couple questions... It appears its only using 1/2 of the 6SN7, wouldn't another tube (6J5) be a better choice? No need for a twin triode here, correct? Looks like B+ is for both channels, but heater supplies are only sized for one, (6.2/4A for the 811,, and 6.3 x2 winding for the 6SN7 & 6V6) if I'm reading it right...
Thanks for the input,,,
Regards,
John
Here's the schematic,,, Got couple questions... It appears its only using 1/2 of the 6SN7, wouldn't another tube (6J5) be a better choice? No need for a twin triode here, correct? Looks like B+ is for both channels, but heater supplies are only sized for one, (6.2/4A for the 811,, and 6.3 x2 winding for the 6SN7 & 6V6) if I'm reading it right...
Thanks for the input,,,
Regards,
John
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I've got one or two of them around here that I can donate to the cause. I know at least one came in a mixed box o stuff. I might have a 6Y6 or 6W6 too. I know I have some random old power pentodes that would probably fit the bill that I will not likely ever use. I'd be happy to put them in your hands just to get them someplace useful.
knockbill
Lunatic Member
Sold!!!
They sound really good in teh "6L6 amp"!!!
What do you think of the 6SN7, 6V6, 811 schematic? I can probably build it with what I have here... I still should have gotten teh rest of them at Kutztown...
Regards,
John
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knockbill
Lunatic Member
You are correct, I fixed it, never could type!
I do have all the tubes and am familiar with them, Never used a triode or 811, which is the reason for this exercise... Most reading I've done recommends interstage transformers, rather than the power tube second stage, but I don't have them, so back to basics...
I usually get the ideas from tubes I have also, but it seems that's bass ackwards, as finding the OPTs is the biggest hangup...
Regards,
John
I do have all the tubes and am familiar with them, Never used a triode or 811, which is the reason for this exercise... Most reading I've done recommends interstage transformers, rather than the power tube second stage, but I don't have them, so back to basics...
I usually get the ideas from tubes I have also, but it seems that's bass ackwards, as finding the OPTs is the biggest hangup...
Regards,
John
knockbill
Lunatic Member
Got a couple more questions,,, Read this on another forum...
" One thing to note however... as the 811A is biased with a positive grid voltage, any fluctuation in line voltage will yield a corresponding fluctuation in both plate voltage "and" positive grid voltage. This will result in a rise in plate and grid currents with an increase in line voltage.
When the output tubes are biased with a negative grid voltage, the opposite happens (negative grid voltage increases as well as positive plate voltage) which helps to self regulate static current flow. This is a slight downside for running transmitting type triodes which require positive grid voltage at lower plate supply voltages.
I used a 5651A voltage reference tube for a regulated positive grid supply to the dynamic driver triode. This results in less drift from line voltage fluctuations and could be a first mod of sorts for the circuit you are showing."
I asked there but didn't get an answer,,, can anyone show this regulated circuit in the provided schematic? Still wondering about the twin triode driver as opposed to, say a 6J5,,,
Thanks in advance...
Regards,
John
which schematic are you looking at ? there are a couple linked here.
A 6J5 is half of a 6SN7. I'd be fine running a single 6SN7 for both channels, using one triode for each vs a pair of 6J5 tubes. That wouldn't even require any change, other than remembering to use the proper set of pins for each channel.
A 6J5 is half of a 6SN7. I'd be fine running a single 6SN7 for both channels, using one triode for each vs a pair of 6J5 tubes. That wouldn't even require any change, other than remembering to use the proper set of pins for each channel.
