EF86 MODERN CLASSIC--CHANNELS MIXABLE?

18watt-specific Tech Talk - Building, Fixing, Parts, Mods...

Moderators: CurtissRobin, colossal, zaphod_phil, Daviedawg, Graydon

User avatar
colossal
Moderator
Moderator
Posts: 434
Joined: Thu 05/10/07 2:00 am
Location: Moving through Kashmir

Re: EF86 MODERN CLASSIC--CHANNELS MIXABLE?

Post by colossal »

ViperDoc wrote:
Tue 10/26/21 8:15 pm
I see a filter capacitor as the last device in the circuit before injecting into the phase inverter on most schematics. Would it be any different to resistor-mix both channels before heading into such a filter cap and THEN into the PI, or keep it as in the current schematic as above? Would each filter cap BEFORE the resistor mix protect each channel?
You mean coupling capacitor in that context. That cap is coupling one stage to another, not filtering the ripple on the DC supply. It is blocking DC from the plate from the next section and is critical for the correct operation of the LTPI.

The design choice of one channel per side of the phase inverter allows the user to A/B and so gives two distinct tonal voicings. This makes for a killer sounding and versatile amp. Dial one side for your cleans and one for your overdrive. Set up effect chains on each. Simple and easy. Each stage is capacitively coupled to the phase inverter.

You can also resistively mix the channels which allows jumpering to run them in parallel, much like a Plexi. The resistors are not one-way check valves, however. That is, when you turn channel B down, it affects A, or if you turn A up, it affects B; they are interactive. You can also cascade the channels with a relay or switch. This might be useful for some wanting to get their clean from say a 12AX7 channel and then cascade that into a pentode channel for their lead tone. You have coupling capacitors "upstream" of your Volume/Gain controls, otherwise you would have DC on your pots which would be both noisy and unsafe.
3 x

ViperDoc
Occasional poster
Occasional poster
Posts: 187
Joined: Mon 05/18/20 8:09 pm

Re: EF86 MODERN CLASSIC--CHANNELS MIXABLE?

Post by ViperDoc »

Many thanks as always, Colossal.
1 x

Post Reply