I have a nice pair of SE 3.5K OPTs, but no 4 ohm tap so I'm stuck with 3.5K. I want to use a higher gain tube in triode so I can use a lower gain driver. So not 2a3 or 300b.
I usually use trioded EL6 and EL12 types into 5K but they're 1.1K Rp and not so good into 3.5K. I was wondering about KT88 or 6550 but I read that they make poor triodes - no idea how true this is. Data suggests they're around 900ohms Rp in triode.
PSE is possible with EL84 or 6V6, which would come out at around 1K, but I'd prefer a single tube in triode. Looking for a dissipation of around 18W.
I usually use trioded EL6 and EL12 types into 5K but they're 1.1K Rp and not so good into 3.5K. I was wondering about KT88 or 6550 but I read that they make poor triodes - no idea how true this is. Data suggests they're around 900ohms Rp in triode.
PSE is possible with EL84 or 6V6, which would come out at around 1K, but I'd prefer a single tube in triode. Looking for a dissipation of around 18W.
Well, you might possibly look at a 3C24... higher mu triode, albeit would require Class A2 for lower voltages. I did a 3C24 SET amp a decade ago... 3.5K load and 4-watts output.
Hello.
I recommend GU29/GI30 in triode, I built an amplifier on this tube and obtained 15W of output power with distortion of 0.2%.
Peter
I recommend GU29/GI30 in triode, I built an amplifier on this tube and obtained 15W of output power with distortion of 0.2%.
Peter
Low Rp and high Mu means high transconductance, am I right?
E130L comes to mind, 27mA/V and with triode curves available in one of the old data sheets. Quite expensive though.
E130L comes to mind, 27mA/V and with triode curves available in one of the old data sheets. Quite expensive though.
6S33S or maybe half of the tube 6S41S ( from this one You can build good SE amp, but don't know amplification factors off-hand ).
Andy,
If you settle for less power (about 3-3.5W if you drive it to A2), trioded E55L has only 600R impedance.
If you settle for less power (about 3-3.5W if you drive it to A2), trioded E55L has only 600R impedance.
If you want to try these transformers with the tube you already have (EL6 and EL12) you could try adding CFB by connecting the secondaries between the cathodes and ground. By doing so the transformer impedance will increase to 3850 ohms from 3500 (as the transformers effectively becomes autoformers with a slightly higher turns ratio) and the local feedback will lower the tubes Rp a bit.
I mocked up a version of Michael Koster's Schadeode and tried it with several different tubes. My power supply maxed out at 550 volts and the output transformers were rated for 80 ma.
The following post has links to the schematics. A mosfet is used for the front end so I know this is not a design you prefer. But, it should be some indication of what you can do with a trioded KT88. I don't know what the ra was in Michael's design but according to the datasheet it is 650 ohms for a trioded KT88.
https://www.diyaudio.com/community/threads/set-build-recommendation.370350/#post-6599691 see post 18
After the post above I tried a KT88 at 80% plate dissipation and got < 0.1% distortion at 1 watt, 1% distortion at 10 watts and 3% distortion at 16 watts. I used a 5k impedance transformer for all tests. With a higher B+ voltage or a transformer rated for 100ma I expect I could have got 18 watts but the difference would be negligible.
These results were achieved with a Bud Purvine 5k transformer at 80ma and 470 volts Plate to cathode. Bias was 30 volts. I did not try this experiment with a 3.5k impedance transformer which might be more ideal for the KT88.
I liked the sound as much as all of my other all tube SE amps with the exception of my Mingda 300B amps.
Steve
The following post has links to the schematics. A mosfet is used for the front end so I know this is not a design you prefer. But, it should be some indication of what you can do with a trioded KT88. I don't know what the ra was in Michael's design but according to the datasheet it is 650 ohms for a trioded KT88.
https://www.diyaudio.com/community/threads/set-build-recommendation.370350/#post-6599691 see post 18
After the post above I tried a KT88 at 80% plate dissipation and got < 0.1% distortion at 1 watt, 1% distortion at 10 watts and 3% distortion at 16 watts. I used a 5k impedance transformer for all tests. With a higher B+ voltage or a transformer rated for 100ma I expect I could have got 18 watts but the difference would be negligible.
These results were achieved with a Bud Purvine 5k transformer at 80ma and 470 volts Plate to cathode. Bias was 30 volts. I did not try this experiment with a 3.5k impedance transformer which might be more ideal for the KT88.
I liked the sound as much as all of my other all tube SE amps with the exception of my Mingda 300B amps.
Steve
What about this one?
http://www.r-type.org/pdfs/s11e12.pdf
Apply 10-20% plate to grid feedback to lower the internal resistance. a pentode with unbypassed cathode resistor as driver (e282F,12gn7a...many high gm pentodes to choose from)
http://www.r-type.org/pdfs/s11e12.pdf
Apply 10-20% plate to grid feedback to lower the internal resistance. a pentode with unbypassed cathode resistor as driver (e282F,12gn7a...many high gm pentodes to choose from)
Attachments
When You see written E282F or 12GN7 as drivers - that are high gain & high current requirments me thinks.
Why not try a 10Y into a F2a. That’s what I’m building at the moment.