• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

EH SCOTT 510 Console tube amps to be modded as mono blocks.

You have a stage in there with a gain of 1 - the cathode follower. It made sense to have a low impedance source to drive the power amp at at the end of a long cable - but not really needed when its in the same chassis. Connect the existing gain stage to the phase inverter, take the cathode follower stage and change it to a gain stage at the input.

Right now, the feedback gives an overall gain of about 10. Assuming an 8 Ohm speaker, that's 1.2V in for 12V out (18W). Adding half a 6SN7 will make that less than 0.1V - you WILL need an input pot.
 
So, Tom Bavis, that sounds like a good plan, but I'm lacking the experience to be confident in my implementation of this adding of half a 6SN7 to the front.

This is my thinking- 1. Eliminate the cathode follower stage: Connect C48, (0.05uF) from Pin 2 of V9 to pin 1 of V10. Delete R44(470KΩ), R45(1800Ω), R46(10KΩ) and C50(0.05uF). Ground Pins 4,5 and 6 of V9 and see if it works properly.

2. Build a 1st AF Amp stage out of the cathode follower stage: Install a 100K potentiometer at the input signal before R40 (100KΩ) and 0.01uF cap going to Pin 4 of V9. Add a 0.05uF cap from Pin to Pin 1 of V9. Still need to calculate an Anode resistor and Cathode Resistor. Research indicates a 750Ω Cathode resistor and maybe 47KΩ anode resistor @ 1W each.

Am I missing something?

Anyone have better resistor values?

Side note, I thought about just turning the cathode follower into a gain stage after the first half of V9 but figure it would invert the phase and cause issues with NFB. Is that correct?
 
You must log in or register to reply here.
Back
Top Bottom