Valley People TA-103 schematic query

[pvision]

I have a Valley 400 preamp with a mic input. The input amp is a Valley TA-103. I'd like to provide a switch to enable a line-level input via the XLR

The TA-103 application notes (attached) suggest providing a gain switch for mic, instrument & line level inputs and state that Figure 4 shows the schematic. Unfortunately Figure 4 does not appear on any of the PDFs I've found

The switch changes the gain & collector current through the input pair. Any guidance on how to do this, or links to a document that includes Figure 4?

On the Vally 400 schematic there are two 3.32 K resistors to the CMMR pot & ground. Do these set the collector current?

 

[JohnRoberts]

I have a Valley 400 preamp with a mic input. The input amp is a Valley TA-103. I'd like to provide a switch to enable a line-level input via the XLR

maybe add a pad in front of the input.

The TA-103 application notes (attached) suggest providing a gain switch for mic, instrument & line level inputs and state that Figure 4 shows the schematic. Unfortunately Figure 4 does not appear on any of the PDFs I've found

gain is varied by the pot between the emitters.

The switch changes the gain & collector current through the input pair. Any guidance on how to do this, or links to a document that includes Figure 4?

The device currents are established by array transistors configured as current sources (near top of the schematic).

On the Vally 400 schematic there are two 3.32 K resistors to the CMMR pot & ground. Do these set the collector current?

no, it trims the open loop gain between the + and - paths for best CMRR.

JR

 

[pvision]

Many thanks, JR. I was planning to implement a pad but found that comment in the TA-103 docs and thought I'd look into that.

It's above my knowledge level but responses like yours help my transistor general knowledge!