SSS Pre Amp LNFB Switch

[Bombacaototal]

Just wondering if anyone figured out an easy way to have the Pre Amp LNFB (rc network) of SSS #001, #002 switchable on/off?

I can only think of doing this in 2 simultaneous legs
1) @V1A cathode: one to move the cathode ground of the V1A to the SSS LNFB network (100r ground, 1M, 0.1uF).
2) @V1B plate: another to make sure the V1B plate signal would not leaking back to the 0.1uF, 1M, 100R

[erwin_ve]

Why do you want that switchable?; it is a different lnfb compared to the ODS lnfb.
I haven't noticed complains on the builds from several members here.
Besides that: maybe it is a controlled positive feedback?

[Bombacaototal]

Why do you want that switchable?; it is a different lnfb compared to the ODS lnfb.
I haven't noticed complains on the builds from several members here.
Besides that: maybe it is a controlled positive feedback?

I want to make the SSS LNFB switchable inspired by Hartman SSS, although he uses two different LNFB approaches for v1a and v1b; but I want to keep the original

As far as the ODS LNFB I would probably put the two 2x10M resistors next to each other in the 2x10m/2x10m/.05 string and switched in a ground point between the 2x10 resistors making sure the cap was on the plate not to have to worry about the 300v rating of the 2x10MM resistor. This set up should also prevent pop noise from switching. I read this approach somewhere in the forum some time ago. Not sure it is the best approach tho

Also thanks for the link to the feedback article on the other post. I spent hours studying it!

[Krinkle]

I used alligator clip jumper wires and switched those in and out while standing next to the head with my guitar plugged in and I couldn't tell the difference. I changed volume settings, etc, still couldn't hear a difference. Just my take on it, if you found that it does make a difference let me know how you had the amp set, etc.

[Krinkle]

Just to add, I was switching both NFB loops in and out, the later (V2) one as well. I was hoping to discover a way to get some easy overdrive and switch it in and out, but no go.

[Bombacaototal]

Just to add, I was switching both NFB loops in and out, the later (V2) one as well. I was hoping to discover a way to get some easy overdrive and switch it in and out, but no go.

Are you using the harman or the #002 LNFB? If the latter I would assume a difference in feel and response although probably subtle

[Bombacaototal]

On the ODS LNFB case would it be fine to have the following string 4x10M/0.5uF with the switch between the plate load and the cap?

[Krinkle]

I used the 002. I'll have to double check MH's layout. I thought they were the same.

[Bombacaototal]

Back on the ODS LNFB, does it make difference sound wise to have 4x10M/.05uf vs 2x10M/.05uF/2x10M

[erwin_ve]

f= 1/(2*pi*r*c) You do the math...