Sluckey's November 1

[AlNewman]

Hi,
I'm building a el84 fixed bias amp, and I'd like to figure out the power section before I commit to a preamp.  I would like to have an effects loop installed either way.  So what I'm doing is building the power section with the power amp in as the input to test. I found Sluckey's November schematics, and it looks like it could fit in with what I'm doing.  I'm wondering, is there anything that could or should be done differently with the effects loop, before I start?

https://el34world.com/charts/Schematics/files/Sluckey/November_01.pdf

Thanks

[sluckey]

The November is a proven circuit. What about your effects loop?

[tubeswell]

November 1 is usually a good day for me. :-)

[sluckey]

FYI (and anyone else listening)... Those sluckey schematics in Hoffman's schematic library have NEVER been updated. Many of them have been updated on my website (some with significant changes). I think that November schematic is probably up to date. If you want to be sure you have the most current revision, get it from my website.

[AlNewman]

Awesome, thanks.  And thank you Sluckey for making all that available.

[AlNewman]

The November is a proven circuit. What about your effects loop?

I guess because I'd like to have an input to test my power amp to decide where my voltages are before I decide on a pre amp.   I may want to use a 12at7 vs a 12ax7 for a phase inverter if I can.  I would also prefer the master volume on the back side of the effects loop.  I assume V2a and V2b both work with the tone stack to make the effects loop work?

There aren't any voltages documented in your drawings, I'm curious why you chose 15k plate resistors for your PI? 

[tdvt]

And thank you Sluckey for making all that available.

+1

I constantly refer to SluckeyAmps.com for circuit design & execution guidance.

[sluckey]

I guess because I'd like to have an input to test my power amp to decide where my voltages are before I decide on a pre amp.   I may want to use a 12at7 vs a 12ax7 for a phase inverter if I can.  I would also prefer the master volume on the back side of the effects loop.  I assume V2a and V2b both work with the tone stack to make the effects loop work?

There aren't any voltages documented in your drawings, I'm curious why you chose 15k plate resistors for your PI?

You don't need an input to measure dc volts in the power amp. No problem to move the MV. My pre out and power in jacks were never meant to be used as an effects loop but can be used as such. The jacks are simply inserted between the preamp and the power amp as a convenient way to cross patch other amps. You can send this preamp output to an external power amp or you can patch an external preamp into this power amp. And with no cables connected, this preamp output simply passes through the jacks to the input of this power amp. The TS has no bearing on the use of those jacks.

The power supply voltages are the actual measured voltages of this amp. That is sufficient for a simple straight forward amp such as the November.

This circuit came from ax84.com. I also questioned the 15K PI plate resistors. I was told that there was a lot of group experimenting with the PI in an effort to get it to sound more like a plexi. The consensus was to use 15K. Not everyone agreed.

[dude]

FYI (and anyone else listening)... Those sluckey schematics in Hoffman's schematic library have NEVER been updated. Many of them have been updated on my website (some with significant changes). I think that November schematic is probably up to date. If you want to be sure you have the most current revision, get it from my website.

Hope l’m not hijacking this thread, but building your November with the Hammond AO43 PT and 5Y3, would the EL84s be stressed by the higher voltage and would there be a big difference in the tone..? I know l can build it and see, but just looking for an opinion, guessing about 390 on the plates, thanks.

[sluckey]

I would not use that PT on a fixed bias EL84 because the high B+ would make me nervous. You could use 7189s or 6V6 with no problem. Or you could run the EL84s with cathode bias with no problems.

[dude]

I would not use that PT on a fixed bias EL84

Thanks, l assume the tubes wouldn’t last long. Just that in a “craze”, a few years ago l bought 8 of those Hammond  chassis’s. I did a 6v6 cathode biased, not too bad but lost that tight 1987 Plexi vibe.

[sluckey]

I did a 6v6 cathode biased, not too bad but lost that tight 1987 Plexi vibe.

Easy to convert to fixed bias.

[shooter]

but lost that tight 1987 Plexi vibe.

Ran that pre into a KT88, self biased, got some of the vibe back, most noticed LOUD 1st though 

[AlNewman]

I guess initially, I'd like to test signal voltage rather than dc voltage.  Something I could plug in another amp, and see how mine is working.  At the end of the day, I'd like a useable effects loop for say a reverb or delay pedal plugged in.  I've been doing some homework, and see that Tubinit has used a passive effect loop with good success as well, so I'll carry on.

I was curious about this design because the preamp out is led with a cathode follower, and I thought maybe the effect loop was dependent on this type of circuit.  I figured the tone stack was perhaps a part of the same design to dump voltage and make it play better with the effect loop.  Maybe I think too much.

[sluckey]

The cathode follower drives the tonestack. Same as all the other plexis.