hoodun

Re: Langevin AM16 input and output pads...
« Reply #20 on: January 30, 2015, 08:55:50 PM »
A fixed, switchable 20db 'U' pad is your best bet.

'Usually you see a switch which adds a 620 ohm in series to each
balanced input wire and a 169 ohm that shorts between the two.
This will give a 20 db pad. '

It's the best match and is recommended as the most transparent option.

There's a discussion here

http://groupdiy.com/index.php?topic=139.0

Mark

So this along with an Output pot? I've read that a 10k  pot on the output with a 620 resistor is best. How about wiring a pot up to R1? currently I am reading 580 ohms here (schematics say 680ohms). So I was thinking of wiring a 250ohm pot that will bring me to 680 and allow adjustment down to 430ohms. Or will a switch make more sense? ...I'd hate to wait for a pot to arrive in the mail for nothing.


Biasrocks

Re: Langevin AM16 input and output pads...
« Reply #21 on: January 31, 2015, 03:23:55 PM »
Rob posted the answer a few posts up.

http://groupdiy.com/index.php?topic=50215.msg743678#msg743678

So this along with an Output pot? I've read that a 10k  pot on the output with a 620 resistor is best. How about wiring a pot up to R1? currently I am reading 580 ohms here (schematics say 680ohms). So I was thinking of wiring a 250ohm pot that will bring me to 680 and allow adjustment down to 430ohms. Or will a switch make more sense? ...I'd hate to wait for a pot to arrive in the mail for nothing.
http://SharktankPro.com

"I'd rather use an SPX90 than a UA plugin....." Joe Barresi

Rob Flinn

Re: Langevin AM16 input and output pads...
« Reply #22 on: January 31, 2015, 04:45:21 PM »
If you study the diagram I posted that Winston drew, you will see that even with the 1k pot turned right down (i.e shorted), so you get no output level at all you still have the 2 x 301ohm (602 ohms) resistors across the output transformer, so it sees a load it is comfortable with as a minimum.
regards Rob


 

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