input transformer load resistor

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Alexandru marian

Well-known member
Joined
Oct 13, 2014
Messages
127
I am building a handwired G9 with some slight simplification, for example removal of line  input and relay.  Doing so I removed resistors 3, 5, 4 which add to a 10k load across the mic input.  I think I've made a mistake, they are before the input switching...
http://www.gyraf.dk/gy_pd/g9/g9_sch.gif

It is finished but I can't test how it works as tubes are stuck in mail. But looking at the schematic I now have the feeling I need to strap a 10k across the input XLR pins 2-3. 

Measuring now, I only have 21 ohms across 2-3, while measuring a few SS preamps I have here they are all 13k. 

Thanks!
 
Resistors R 3,4 and 5 form line to mic attenutor, if you don't need it take resistors away and don't replace with anything. Just leave those phantom resistors as they are.
Loading resistor should be across secondary of the input transformer, not across primary. Datasheets usually show them as RL (loading resistor) and should have value stated by the manufacturer. It is interesting to see how changing it's value changes frequency response and voltage, i did some interesting experiments with RL.
You better post this things in G9 thread because it is about this preamp, not RL in general.

Good luck with your build.
 
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