Converting hybrid from ECC88 to 6N1P

[Bravick]

Again, thank you.

I will use your values as a base and start playing around.

Only way to learn.

Regards,
Gideon

 

[still4given]

I have been trying to get the 6N1P circuit to work. I raised the rail voltage to +-75v. I had to lower R6 to 2k2 to be able to get the cathode to 1v. It plays music OK but the offset is not stable. It varies a lot as the music plays. What is normally the lowest rail voltage used with the 6N1P? I could maybe try running a separate psu for the front end.

 

[Koonw]

I have been trying to get the 6N1P circuit to work. I raised the rail voltage to +-75v. I had to lower R6 to 2k2 to be able to get the cathode to 1v. It plays music OK but the offset is not stable. It varies a lot as the music plays. What is normally the lowest rail voltage used with the 6N1P? I could maybe try running a separate psu for the front end.

Please compare this sim with earlier one: plate resistor change to 8.2K as 4.7K is really rolled from ECC88. New 6N1P-EB model, make sure you use the same tube, the earlier model is based on 6N1P-AN there are much differences. Transistors bias maybe higher with 15 zener, you're advise to watch it.

 

[alcroner]

Dont forget it's different sound on al Ecc88 ,E88cc or Russian 6n23 n sound very good
very good are Tungsram E88cc 6922 type lon life,and Philips European E88 cc.
And Sylvania. 6922 heavy bass.

 

[MrCurwen]

I made my suggestions in bimo's thread about a similar circuit.

http://www.diyaudio.com/forums/tubes-valves/281844-ecc88-ltp-2.html#post4506627

Schem2 can be used with 6N1P by doubling values of R1, R9 & R10. Also possibly raising plate voltage a little bit (set by R2 & R3).

 

[still4given]

Please compare this sim with earlier one: plate resistor change to 8.2K as 4.7K is really rolled from ECC88. New 6N1P-EB model, make sure you use the same tube, the earlier model is based on 6N1P-AN there are much differences. Transistors bias maybe higher with 15 zener, you're advise to watch it.

I'm trying to understand what you are saying but I am not yet versed enough in ltspice to make your sim run. You have removed quite a large section of the circuit and I can't see how the nfb feeds. It looks as though you changed R1, R22, R29, R11 from the earlier sim. I have marked up a schematic. Can you please look and see if I have correctly made the changes you suggest. I assume the section you removed was simply for purposes of your sim and not meant to actually remove them.

Thanks, Terry

 

[Koonw]

I'm trying to understand what you are saying but I am not yet versed enough in ltspice to make your sim run. You have removed quite a large section of the circuit and I can't see how the nfb feeds. It looks as though you changed R1, R22, R29, R11 from the earlier sim. I have marked up a schematic. Can you please look and see if I have correctly made the changes you suggest. I assume the section you removed was simply for purposes of your sim and not meant to actually remove them.

Thanks, Terry

Yes, except you have to watch if transistors are over dissipated (too hot?), I am really not looking into it, since the current are more less the same as last change, then it shouldn't run too hot. For your info about the tube model it is closer to the actual operating points in the actual circuit I have so it should be quite accurate, you must be sure to use the same tube and it should measure very closely. To be very precise actual plate voltages are quite a bit higher ( I saw it when I remove coupling to transistors) because the transistors bring down the voltage quite a bit. So change in R1 and R2 is to make 2X ra for 6N1P-EB instead just 1X in the earlier sch. Hope that makes it easier for tube and sonic wise.

The marked circuit is left out as it has no concern. When you make adjustment measurement I believe you should tie NFB to ground and not to amp output yet. You ensure you got reasonable distortion out in open loop from T1 then tie NFB to output. BTW I did not change anything in T1 so that should not affect the rest of circuits.