RH84 SE, pentode driver... advice please

[revintage]

Yeah, 6N1P can be worth a try.

 

[e_fortier]

Yeah, 6N1P can be worth a try.

Well, I did some work with the 6N1P (instead of 12AT7) and I really feel that the 807 should only be used in PP amp. 2 days ago I completed a 12AV5GA SET and it is an absolute amazing sounding amp, for the ones interested I have attached the final schematic as built. It's only unfortunate that it is only about 2.5W but it is a real sweet sound.

I have a nice quad of RCA 807 I believe I will keep them for a decent PP amp, I sure hope I like the sound once completed. I received my voltage reg but haven't try them yet for the screen voltage regulation.

So, since no matter what I do I do not like the sound of the 807 (I simply like it but the 12AV5GA..I really got hooked and I will make a second one eventually !) Is there an output tube that would work well in my set-up...B+ of 350V, Ia max of about 75mA with the 5K, 15W OPT ? Looking for about 8-10W.

The 6N1P really sound good with the 12AV5GA so my issue with the sound is really the 807...that's the fun or risky part of DIY you never know the end result...

Any recommendation are welcome..I think a KT88 SE would fit the bill or maybe a 6V6 SEP.

Thanks,
Eric

 

[revintage]

Adjust 6N1P Ua ca 175V. If you have a E88CC/6N23P, try that instead as it havemuch better linearity and a lot higher Gm.

 

[e_fortier]

Adjust 6N1P Ua ca 175V. If you have a E88CC/6N23P, try that instead as it havemuch better linearity and a lot higher Gm.

Well, I decided that I had enough of the RH807, after many, many attempt with all your help I'm still not very excited when I sit to listen to this amp, I much prefer my new 12AV5GA trioded strapped but the power is not much. I'm not giving up on the 807 so I will now simply try a 807 amp in UL mode (thanks Edcor...) and the 6N1P as driver with the same bias on the driver as on the 12AV5GA amp which is 9mA.

To lower Va to 175Vdc I had to reduced Ia to 7.5mA...OMG this current sucks the life of the amp, pretty scary !!! Like mentioned by someone else on this forum the 6N1P really shines at 9-10mA, below this value all the magic goes away. The actual liveliness simply goes away with a bias of 7.5mA, even my kids noticed...For the ones interested I have attached my 12AV5GA SET schematic with a bias of 9mA on the driver and lowered Va driver from 200Vdc to 180Vdc. Works like a charm If Tubelab is reading this, Thanks a lot, what a great sounding tube when trioded strapped.

I have also attached my new proposed schematic for the 807, feel free to attack !! Maybe a new thread would be more appropriate since it won't be a Schade amp anymore.

Thanks to all.

Regards,
Eric

 

[e_fortier]

Please take a look at the overall 807 design, make holes in it, recommend any changes you think would improve the design, etc. This is just the first cut at a workable design so comments, suggestions, changes, etc. are more then welcome.

Let me know what you think.

Rgds,
Eric

 

[e_fortier]

Please take a look at the overall 807 design, make holes in it, recommend any changes you think would improve the design, etc. This is just the first cut at a workable design so comments, suggestions, changes, etc. are more then welcome.

Let me know what you think.

Rgds,
Eric

Hi,

Sorry to reactivate an old thread but I received a few private message regarding the 807 and 12AV5GA amps, after some tweaking and 120Hz hum reduction (I did not have any inductor in the power supply) here are the final 2 amps.

I recently brought these 2 amps to a very friendly DIY gathering and I came back home without my 2 amps, some DIY friends borrowed them for a 3-4 weeks period to auditioned them with all sorts of music before going ahead and building their first tube amp. I got to listen to 24 bit recording, you can actually hear the difference vs 16 bits

Rgds,
Eric

 

[smoking-amp]

Since the 12AV5 is a low g2/g1 Mu (4.3) Sweep tube (and 807 is a high g2/g1 Mu tube), you might want to try something bigger in the Sweeps for similar sound but more Watts. The 6HJ5 (Mu 4.2) and 6CB5 (Mu 3.8 and octal base) are relatively cheap for 24, 26 Watt tubes. The 6CB5 has been compared to the 300B in triode mode. You will want some higher B+ to get more Watts with them (well, if the screen grid will tolerate that in triode mode, maybe not). The 21HB5, 21GY5, 21JZ6, 21KA6, 22JF6 are also low Mu medium size (18 Watt) Sweeps, and available for $1 each at VacuumTubes.net or ESRCvacuumtubes.com.

 

[xenofonn]

GU50!!

Hi,

Sorry to reactivate an old thread but I received a few private message regarding the 807 and 12AV5GA amps, after some tweaking and 120Hz hum reduction (I did not have any inductor in the power supply) here are the final 2 amps.

I recently brought these 2 amps to a very friendly DIY gathering and I came back home without my 2 amps, some DIY friends borrowed them for a 3-4 weeks period to auditioned them with all sorts of music before going ahead and building their first tube amp. I got to listen to 24 bit recording, you can actually hear the difference vs 16 bits

Rgds,
Eric

Excellent schematics!! Anyone tested GU50 tube in this circuit? Excellent tube and cheap!!

 

[yoaudio]

Please take a look at the overall 807 design, make holes in it, recommend any changes you think would improve the design, etc. This is just the first cut at a workable design so comments, suggestions, changes, etc. are more then welcome.

Let me know what you think.

Rgds,
Eric

Check this schematic out, I'm planning on building this one someday. I bought a stash of tubes with a few nice 807's.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.