that's not it at all... that is a cascode differential stage with buffers. it's a mic pre i designed for electro harmonix. there is a way to do a 211 amp similarly, if that is what you are after: the cathode coupled amplifier. you need more swing to drive it than you ordinarily would, but it works very nicely... 211's have a medium mu, so you still don't need much swing.
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i think you should consider doing something much simpler first... you don't need to get so tricked out to start. pimping stuff up IS fun, but it is a lot more work to get it right. a chinese 845 run with fixed bias and a low plate voltage is easy... one power supply for the B+ and a couple of heater supplies for the driver and output stages. easy to drive. A2 is very interesting and you can get more power from lower B+, than you can from class A operation, but you need more stuff, more circuit, more soldering and yanking stuff apart when it isn't working like you want it too.
you have to remember the 211 has a very low plate voltage in the example, and not running at full dissipation. the 211 can be run in class C and the grid is designed for it. pulses up to 180 mA at the plate are typical, at 1200 volts too. probably that means 20 or 30 mA into the grid for short duty cycles. A2 at the 450 volt operating point is no problem. the cathode, on the other hand, is only capable of so much emission before stripping. that IS an issue. but, from experience, i can tell you can exceed the average max current rating at lower plate volts, and even run up to peak current, provided there is limiting built in. this circuit is a good candidate for accomplishing those things. there are other ways to do it, too.
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well, the 211D has a 50 watt max rating for class C, but that is not for a whole duty cycle. i would guess the average dissipation would run between 5 and 15 watts, depending on the plate voltage. higher plate voltage means less grid dissipation. always. this is stuff you test for, not calculate. but the 211 grid is very tough. it has to be.
most of the transmitting tubes from the 30s to 40's, such as the 203, 805, 810, etc. have very tough grids... old school plate modulated class C pounds on the grid. all of these tubes are good candidates for A2 operation.
most of the transmitting tubes from the 30s to 40's, such as the 203, 805, 810, etc. have very tough grids... old school plate modulated class C pounds on the grid. all of these tubes are good candidates for A2 operation.
What kind of power out are we talking from this circuit using 211?
Looking at 450V
It would be interesting to increase the B+ so we can generate 10W..
The EL34 is shown triode connected or are we in pentode ?
Regards
M. Gregg
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a conservative ball park guess is 8 watts or so... but the distortion and headroom could be quite optimal for all that. tubes are absurd in this regard. i don't think the power thing is an argument for a 211 here. again, you could get the same thing driving a 300B or a triode connected 6550 with a low enough impedance driver stage. there are very affordable reissue versions of all these tubes. in this case, it was just about using a 211 at a non-optimal B+ and getting away with it. that is a fun concept to explore! but you are starting out with some severe limitations. there are limits on what you wind up with.
LOl..
I have EL34 running SE...Some people might just want to run 211 because they can..
Its like the otl build auto bias 6C33C...just for fun.."Built"..This tube is a pig to get drive for so Cathode drive is very interesting..
Its also interesting to look at cathode drive with OP tubes..I have never thought about it..
I know some guys have built the Dinosaur with 845...
I think the thing is the sound of the 211..perhaps the fact that they have built a 211 amp..Also its triode..
Also interesting looking at different and unusual ways to drive the OP tubes..
I think as you say the 300B might be interesting in this circuit or the dinosaur..
Regards
M. Gregg
I have EL34 running SE...Some people might just want to run 211 because they can..
Its like the otl build auto bias 6C33C...just for fun.."Built"..This tube is a pig to get drive for so Cathode drive is very interesting..
Its also interesting to look at cathode drive with OP tubes..I have never thought about it..
I know some guys have built the Dinosaur with 845...
I think the thing is the sound of the 211..perhaps the fact that they have built a 211 amp..Also its triode..
Also interesting looking at different and unusual ways to drive the OP tubes..
I think as you say the 300B might be interesting in this circuit or the dinosaur..
Regards
M. Gregg
Just a thought,
After reading your blog..I'm with you all the way regards an amp to listen to music and people singing...measurement Ok it has its place...but if a bird singing dosen't sound like a bird singing then whats the point
I guess thats the autobias point..switch it on and listen to it...if the equipment is a bigger distaction than the music something is wrong..
Perhaps thats your vocation "make it real"...LOL
Regards
M. Gregg
After reading your blog..I'm with you all the way regards an amp to listen to music and people singing...measurement Ok it has its place...but if a bird singing dosen't sound like a bird singing then whats the point
I guess thats the autobias point..switch it on and listen to it...if the equipment is a bigger distaction than the music something is wrong..
Perhaps thats your vocation "make it real"...LOL
Regards
M. Gregg
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