TL Audio C2001 calibration

[scott2000]

I picked up a TL Audio Indigo C2001 4 way hybrid tube microphone preamp. I have had to source various parts for it including some of the 2k2 trim resistors that are for output trim and output balance. There are no test specs for this unit and I was wondering since new tubes, some resistors, caps and these trim resistors were installed, is there any way to make sure these resistors

http://www.mouser.com/Search/ProductDetail.aspx?R=CB10LV222Mvirtualkey20420000virtualkey279-CB10LV222M

are set correctly using the schematic (Page 2 of I/O PCB schem)?? RV1,2,3 and 4 are output balance trims. Does that mean I need a scope to see if pins one and two of the xlr outputs are equal for each of the four output xlrs? If so, is there a method I can use?I don't have a scope but do have software I can generate tones with and use the spectrum analyzer in the software as well. I'm not really experienced beyond testing components and don't know how to interpret what affects what in a circuit that would help me with this. I just wasn't sure if these resistors ( RV5,6,7 and 8)affect the opamps or anything else in a negative way if they aren't set correctly. Is this a THD/distortion type adjustment? I'd appreciate any direction. I know it's asking a lot for a method I can use. There has to be some type of calibration I would imagine. II have a tech I can bring it to but, without a schematic, it may be easier to tell him what I need him to check for???Thanks in advance!

 

[PRR]

Me, myself, I would set the pots to center and rock on.

The input trims give +/-1dB gain change to match the channels. But there is a tube in there so gain will vary between channels at least 1dB. Moreover, there is a gain pot in the front end. The ONLY places you "know" what the gain is will be full-up and full-down. (And full-down is subject to absolute tolerance of that knob-pot.) I say center 'em all. If any channel is obviously lower gain, something else is wrong.

The output trims really should not be needed. There are many dodgy "electronic balanced outputs" where loading is critical. Center "should" be an excellent trim. Some rainy day you could run a 400Hz tone through at some convenient level and put a voltmeter to the outputs.  The ACV pin 1 to pin 2, and pin 1 to pin 3, should be very similar. Within 10%. Don't see how it could need 1% trim.

 

[ln76d]

Some TL audio boxes have really similaar topologies, i would look for similar schemtics (or parts of it) from other models and look for test specs for it.  Also various test specs documents from TL could give you some clues.
http://www.tlaudio.co.uk/docs/partner_area%20HIDE%20AWAY/