Pro Audio Design Forum

Isnt eaiser to have a switch to select between Cut/boost ? So when the pot is fccw there is 0 gain eihter way, in cut mode fcw this would mean 3dbcut and so on. I might have missed if you discussed this already. That could be done too but it doesn't eliminate the need for a "fixed" gain s...

Paul G wrote: What about having the decode line receiver 1240 feed a switch that is an attenuator with a maximum output of -6dB and have 6dB of makeup gain from an opamp afterward? The output of the opamp would have a low enough impedance to feed the decode circuit. I think it's almost exactly what ...

Looking at Wayne's gain trim circuit above the only downside I see is that the mono sum will be between 3dB and 6dB up already. Having 3dB of gain at the input might have headroom issues. It seems that to "fix" this you would give up the precise level matching by having makeup gain set by...

Thanks Paul and Roger. Here's the variation of the circuit using a pot: https://www.ka-electronics.com/Images/jpg/M-S_Variable_Gain_Trim_Pot.jpg https://www.ka-electronics.com/Images/jpg/M-S_Variable_Gain_Trim_Pot.jpg Not shown of course are the detailed 1243 or follower connections... The layout lo...

OK, so it's not as tall. Cool.

RF; I think a 797 would be fine but we ought to try one for follower unity gain stability issues. I think it will need a 100R Rfb and an optional 100R series resistor with the In+ input pin 3. See http://www.analog.com/static/imported-files/data_sheets/AD797.pdf#page=13 Figures 36 and 37. I used the...

Does it fit the same layout? Is it bigger or smaller than the original one? I'm confused.

Here's a gain trim idea I'm kicking around which only requires a single-pole rotary switch. Something Paul said earlier made me think of this. https://www.ka-electronics.com/Images/jpg/M-S_Variable_Gain_Trim.jpg https://www.ka-electronics.com/Images/jpg/M-S_Variable_Gain_Trim.jpg There may be a more...

OK, back to plan A. I love it. From just quickly looking at it you can see the symmetry. And it's simple with everything clearly labeled. Looking at the layout you have a good low inductance path from the 1646 pin 3 to ground. That whole plane, to the left of the 1646 gets shunted back into Vcc by t...

Roger - Having the relay bypass become pads for optional switches works for me. I don't have a problem using a good switch and since it's only DPDT at that location it's do-able. My thinking was that for a field-recording battery-powered rig, the relays would be off for normal operation using the NC...