Could somebody suggest a lower gain alternative to a EF184 in a long tailed pair same pinout. Still would like Va max of around 350v.
EF80? Not sure about how good the quality is for audio, but the EF184 is meant to be the descendant of it.
EF80?
Va max. for the EF184 is 250V. Va max. for the EF80 is 300V.
Whether the EF80 will have less gain than the EF184 will depend ofcourse on the circuit.
Va max. for the EF184 is 250V. Va max. for the EF80 is 300V.
Whether the EF80 will have less gain than the EF184 will depend ofcourse on the circuit.
I have used this valve in many radio/communications situations .
Due to its high gain =GM 15mA/V you sometimes had to add compensation but I take it you are talking of an audio situation --yes ?
Its designed as an IF amplifier not as an audio tube that's why its WORKING voltage is around =200V/200V I have never run it at its limit .
If you are looking for a plugin replacement at a lower gain another IF amplifier in that rage earlier was the ubiquitous =EF80 used by the 1000,s in many old valve UK TV,s gain=7.4mA/V.
A thought is E80L although the main cathode pin is on pin 3 and pin 1 is the screen its SQ .
Please do not fall into the trap of Head-Fi posters in the tube rolling section with whom I had --well a BIG row ! before I left many years ago who advocated VARIABLE MU valves/tubes for audio --great in communications radio but audio ! but if anybody disagrees with me here I do not intend to get back into that argument although I presented documented manufacturers data /respected communications engineers with a string of university degrees I was "laughed out of court " , I realised I was wasting my time .
Due to its high gain =GM 15mA/V you sometimes had to add compensation but I take it you are talking of an audio situation --yes ?
Its designed as an IF amplifier not as an audio tube that's why its WORKING voltage is around =200V/200V I have never run it at its limit .
If you are looking for a plugin replacement at a lower gain another IF amplifier in that rage earlier was the ubiquitous =EF80 used by the 1000,s in many old valve UK TV,s gain=7.4mA/V.
A thought is E80L although the main cathode pin is on pin 3 and pin 1 is the screen its SQ .
Please do not fall into the trap of Head-Fi posters in the tube rolling section with whom I had --well a BIG row ! before I left many years ago who advocated VARIABLE MU valves/tubes for audio --great in communications radio but audio ! but if anybody disagrees with me here I do not intend to get back into that argument although I presented documented manufacturers data /respected communications engineers with a string of university degrees I was "laughed out of court " , I realised I was wasting my time .
As noted above, EF80 has ca. 7.5mA/V (vs. ca. 15 for EF184).
The less well-known Mazda 6F23 has the same pin assignment, and 9.5mA/V.
The less well-known Mazda 6F23 has the same pin assignment, and 9.5mA/V.
Can you post the actual circuit where it will be used?
I can imagine lots of ways to lower excessive gain, from NFB (if used) to attenuation to, well, designing it with lower gain.
Tube rolling looks like a blunt instrument to me.
And it´s neither easy nor foolproof, changing tube will certainly alter other parameters, starting with bias or working point.
Its a long tailed pair/phase splitter on an audio amp. It has a CCS in the tail. So the plate voltage won't change if I change type. I just found a 6CB6 again 250v. I build an amp with the EF184 and this worked fine (although I had to find two tubes which were roughly matched).
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6BR7 is more a modified pinout EF86 ... EF184 does the job very well in audio, as 12BY7A do 😉
A designed for audio tube/valve is the SQ ( military ) E80F -- gold pins -1.85 mA/V ,will stand up to transformer vibration -- CV 2729--(UK forces designation) long life =80000 hours .
in a driver position, it's a preamp tube, as 6BR7 and EF86 , EF804, 5879... 12BY7 is much more better and linear as did HK in the Citation IIThe 12BY7 is a power pentode used at outputs the OP is not using it for that but more for driving as he quotes= EF184 which is certainly not an audio output pentode , so yes the E80F is used in driver positions of audio amplifiers and is well recommended in that position.
I went for high voltage gain in the LTP as the original design takes the GFB to the LTP stage - this is unconventional. If taken to the cathode of the first stage then the gain of the LTP does not need to be so large. In that case I would DC couple the first stage to the LPT and do away with the CCS to the negative rail. Its for a new design.
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Your right I did and my mistake when I realized that the OP wanted to use them in the driver section I should have posted earlier on it .
I was drawn to the fact that its nearly pin compatible with an EF184 so its easy to move a couple of connections but if all the OP wants is a tube that will act as a driver not at the output then a low noise audio tube is more satisfactory.
I was drawn to the fact that its nearly pin compatible with an EF184 so its easy to move a couple of connections but if all the OP wants is a tube that will act as a driver not at the output then a low noise audio tube is more satisfactory.
A lot of thought must have gone into the Citation II there's quite a few FB paths and a lot of low impedance drive. I need about 1-2W anode power dissipation sorry should have said this earlier. There's also compacton 6J11.
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Looks good on simulation about 40% of the voltage gain and obtainable too - cheers.
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6AU6 is a 7 pin mini, though.
EF184 is a 9 pin mini.
So definitely a different pin-out. A different socket, actually.
But I think there is a 6AU6 equivalent in 9 pin mini. ?
You mention that you need less gain. Is that the only problem? Look at the first two stages of the amp. It has a 'shunt feedback stage' or 'anode follower' happening, with R31 and R36 defining the negative feedback. Perhaps reduce the value of R36 to get the gain you desire? That would be a lot easier than redesigning the LTP driver stage around a different type pentode.
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EF184 is a 9 pin mini.
So definitely a different pin-out. A different socket, actually.
But I think there is a 6AU6 equivalent in 9 pin mini. ?
You mention that you need less gain. Is that the only problem? Look at the first two stages of the amp. It has a 'shunt feedback stage' or 'anode follower' happening, with R31 and R36 defining the negative feedback. Perhaps reduce the value of R36 to get the gain you desire? That would be a lot easier than redesigning the LTP driver stage around a different type pentode.
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