Alright, I've got a 6922 tube that has to run off 150V (I already have the psu for it since I used it before in another configuration). Since it has a mu of 33 I'd like to get the highest gain possible, which I gather will be 33. I can't find a datasheet on the 6922 so I don't know it's plate resistance or any other specs and I forget what they are. I gather I'd have to bypass the cathode resistor with a cap to attain my desired voltage gain. I just don't know what values of the cathode resistor and plate load resistor would be optimal for a 150V operating voltage. Any help would be apreciated. By the way the load it will be hocked up to will be a cathode-follower if that makes a difference. Thanks alot again for any help I get. I'd be using a single half of a tube, no balanced operation here. Or would I need a ccs to attain the gain I want?
Frank is correct about the CCS, but I do wonder why you want to get ALL the gain you can? Any of those configurations to maximize gain will compromise distortion and bandwidth. If you need more gain, why not use a higher gain tube and run it in a lower distortion, higher bandwidth mode? Or use a cascode topology?
Re: 6922
Looking at it on the CAD, the only place I can actually find a mu of 33 is when the grid is zero, and the current is up around 15mA with Vak of about 50V. In most of the places where you will actually operate it, it's more like 27 - 29, and the Rp is about 3 - 4k. So even with a CCS, you're not going to get a gain of 33 from it.
datasheets galore
fdegrove said:
Looking at it on the CAD, the only place I can actually find a mu of 33 is when the grid is zero, and the current is up around 15mA with Vak of about 50V. In most of the places where you will actually operate it, it's more like 27 - 29, and the Rp is about 3 - 4k. So even with a CCS, you're not going to get a gain of 33 from it.
datasheets galore
Others have said that this tube is unreliable at full disipation but since you will be using only one section this will help.
In my experiance using a 6DJ8 at some 80% disipation (both sections working) did cause a degradation on the tube, what went wrong I can't say.
I have been using 6922 at around 1/2 disipation with no problems.
In my experiance using a 6DJ8 at some 80% disipation (both sections working) did cause a degradation on the tube, what went wrong I can't say.
I have been using 6922 at around 1/2 disipation with no problems.
IME, a cascode can easily be made to have no particular sound, i.e., output indistinguishable by ear from the input. Joe Curcio has done some excellent cascode-based designs; his power amp driver design, a cascode diff-amp, is particularly good. My own phono preamp uses a FET-tube cascode; quite linear and very low noise.
My experience with cascodes has been less than positive. Output indistinguishable by ear from input? I wish. Anything that uses caps, resistors, active components is immediately distinguishable. Or wire 
To my ears the cascode has much inferior sound compared to resistor, choke or transformer loading. The entire bias arrangement around the upper tube is also very difficult to get to sound well. Exaggerated dynamics, unnatural timbre. Seems quite successful in commercial gear so tastes obviously differ.
peter
To my ears the cascode has much inferior sound compared to resistor, choke or transformer loading. The entire bias arrangement around the upper tube is also very difficult to get to sound well. Exaggerated dynamics, unnatural timbre. Seems quite successful in commercial gear so tastes obviously differ.peter
The reason I'd like that much gain is because I've been using a 6922 as the voltage gain stage in my poweramp with a gain of about 8 and I'd like to up that gain so that I can remove the preamp (but keep the same tube in the circuit). I'd rather avoid chokes since they take up alot of room and I've got space problems already with this amp so I guess a CCS would be the best bet?
JB, use a different kind of tube. There are higher mu triodes with the same pinout. No need to go through contortions to make a specific tube work (and suboptimally, at that) if what you want is something it's reluctant to give.
Funny, that's exactly the opposite of what Nelson Pass said about why he stopped using cascodes.
Funny, that's exactly the opposite of what Nelson Pass said about why he stopped using cascodes.
CASCODE.
Hi,
Hmmm...how can a circuit exaggerate dynamics?
I can see a few circuits that could compress dynamics, but...exaggerate them?
That a cascode circuit could alter timbre...yes, pretty much the same way penthode circuits could alter timbre, I suppose.
I feel this is a matter of taste and tonal balance, some people may like a bit of odd order distortion...
Some circuits to discuss: the totem pole and the grounded grid circuit. ( As a reminder for my own reference)
Cheers,
Hi,
Hmmm...how can a circuit exaggerate dynamics?
I can see a few circuits that could compress dynamics, but...exaggerate them?
That a cascode circuit could alter timbre...yes, pretty much the same way penthode circuits could alter timbre, I suppose.
I feel this is a matter of taste and tonal balance, some people may like a bit of odd order distortion...
Some circuits to discuss: the totem pole and the grounded grid circuit. ( As a reminder for my own reference)
Cheers,
If you've only got 150V to play with, but want Av = mu, you need a CCS anode load. MPSA92 is a good transistor for this sort of thing. Additionally, you need a full data sheet:
http://frank.pocnet.net/sheets61.html
The 6922/E88CC is a very nice little valve at Va = 90V or so...
http://frank.pocnet.net/sheets61.html
The 6922/E88CC is a very nice little valve at Va = 90V or so...
UHF oscillation
E88CC/6922 was designed for use as a UHF front end in televisions. Given half a chance, the little perisher will oscillate at UHF, and you won't see that on any (affordable) oscilloscope. Don't even think of using it without grid-stoppers. Surface mount resistors on the socket pins are ideal, and allow you to minimise their value.
E88CC/6922 was designed for use as a UHF front end in televisions. Given half a chance, the little perisher will oscillate at UHF, and you won't see that on any (affordable) oscilloscope. Don't even think of using it without grid-stoppers. Surface mount resistors on the socket pins are ideal, and allow you to minimise their value.
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