preamp info

[flatart]

Hi, can you please confirm that this attached schematic is correct:
it's the 124 ODS preamp schema without FET input and without rock-jazz switch.
Moreover can you confirm that, when the PAB boost is ON, 2 x 22M resistors are NOT bypassed. Viceversa when the boost is OFF 2x22M resistors are bypassed. right?

[martin manning]

There are a lot of you's here but it looks right to me.

I just redrew that part of icracer's schematic myself in order to get a better look at the topology of the tone stack and the effect of the R/J switch.

The 22M resistors are wired across the relay contacts so there is no "pop" when the relay is switched.

MPM

[flatart]

thanks martin, but I didnt undertsand what you mean wwhen you say "The 22M resistors are wired across the relay contacts so there is no "pop" when the relay is switched".

[martin manning]

Let's say the relay contacts are open and there is no resistor across them. There will almost certainly be a voltage difference across the contacts, and when they are closed a pulse will be fed into the signal path, causing a pop in the speaker. The resistor is there to reduce the voltage differential. Since there is almost zero current through the grid the voltage drop across it will be very small. In a DC circuit you will often see a cap placed across switch contacts to suppress noise, like on a standby switch, for example. In this case that won't work since the intent is to disconnect the lower part of the tone stack, and the (AC) signal would pass through a cap.

MPM

[roadkingbluzs]

Slightly off topic. Are eyelets or turrets used on Funks relay boards? Size?