Need help to identify this preamp board

[ilfungo]

Hi
I'm searching info about this mic preamp board
schematic, pin connections...
Ifound some picture on the Net and they seem CHILTON?
Thanks!

 

[mjrippe]

Looks like nice Sowter input transformers! Could possibly be from a Chilton console, see if they match the attached schematic.

 

[ilfungo]

Thanks!!!
On monday when I go to my studio I will check,

 

[ilfungo]

The schematic seems correct!
I've added wiring connections, could someone tell me if them are correct?
Where connect the 10k GAIN pot?
Thanks!!!

 

[mjrippe]

My wild guess would be R1.

 

[dmp]

From that schematic it looks like the card can either be configured as a line amp or a mic amp, and the mic amp can be modified to reduce from 40 to 25 dB by changing the listed resistors.
I don't see anything about a 10k gain pot
I would try it as a fixed gain mic amp with an attenuator (fader) on the outputs.

 

[ilfungo]

ok thanks!!!
this circuit can drive directly an output transformer or I need another stage to drive it?

 

[mjrippe]

ok thanks!!!
this circuit can drive directly an output transformer or I need another stage to drive it?

Two transistors per input, no way is it going to have +4dBm into a load. Another stage for sure.

 

[ilfungo]

could something like this work to drive 600 ohm transformer?
Thanks!

 

[bananamoon]

I have that mixer. I have hand drawn schematics somewhere, I can check them out if you need more info. Gain pot is 22k on mine and there is a line amp card to drive the transformers.

 

[MidnightArrakis]

I have that mixer. I have hand drawn schematics somewhere, I can check them out if you need more info. Gain pot is 22k on mine and there is a line amp card to drive the transformers.

[I have hand drawn schematics somewhere] -- Should you believe that your hand-drawn schematics are truly accurate in their representation and are clear enough to be easily read and interpreted when viewed, then send me a clear copy of what you have and any other associated and/or related material and I will go ahead and create a set of CAD-generated schematic copies of your schematic information so others can use them as needed. Sound like a plan???

PLUS!!!.....if anyone like -- mjrippe -- is able to provide me with any updated and/or improved circuit changes to the original set of schematics, then by all means "chime-in" and let me know what could make this circuit better and/or more operational. Team effort.

I'm....."Standing By".....

/

 

[bananamoon]

Apparently I stopped drawing the schematics at the mix module... But I can draw it out sometime next week. There is a unknown component (black with twirly leads... a thermistor?), if someone can point out what it is. I found a PDF manual for the M10 with almost all the schematics... except the line amp... (there is some kind of universal amplifier module at the end). I sent it to be posted in the document forum. I had 3 of these M series mixer a one point and they all had different revisions and mods. This one is LA2c.

 

[mjrippe]

Twirly leads could be an inductor? The universal amp with output transformer would be a good output stage choice.

 

[analogguru]

...... There is a unknown component (black with twirly leads... a thermistor?), ....

No, it is a (germanium) diode and the twirly leads are made that the diode doesn't get damaged during soldering.

 

[mjrippe]

@analogguru Oh, that makes sense with the shape of the body having a ring around one end. Thank you!

 

[bananamoon]

Schematic for the line amp. I've tripled checked to make sure it's right, but I've got a teething toddler... I forget things...