characteristics input trafo

Hello!
I have found pair mic amp modules from any old console.
Here a photo modules:


http://ft.fotoplenka.ru/ft/99/82/48299/111216/800d968a.jpg



http://ft.fotoplenka.ru/ft/99/82/48299/111216/8dda25cf.jpg

Here the provisional scheme:


http://ft.fotoplenka.ru/ft/99/82/48299/111216/65e04e2f.jpg

Prompt characteristics if it is possible, the input trafo?
:guinness:

I think there might be something wrong in the schematic around the input attenuator before the transformer.

And R5, 9K1 seems too low as load for an input transformer.

If you want to know transformer ratio, measure input- and output voltage from it at e.g. 10mV, 1KHz..

Jakob E.

I think there might be something wrong in the schematic around the input attenuator before the transformer.

And R5, 9K1 seems too low as load for an input transformer.

Click to expand...

I copied from the original scheme :?

If you want to know transformer ratio, measure input- and output voltage from it at e.g. 10mV, 1KHz..

Click to expand...

Well I shall try... I.e. the attitude pays off approximately so:
1/6 = 10 mV / X mV
Yes?

[quote author="Xopek"]
I copied from the original scheme :?
[/quote]

You better take a look at the actual pcb then, the schematic is wrong..

1) There is only anything coming into the transformer at "1mV" position.

2) And just adding a resistor in series with the primary of the transformer - without having another resistor across the primary winding - will result in very poor bass response at low gains, i.e. high series resistances - because of the limited primary inductance of the transformer.

The only place where you can control attenuation like this is in zero-field inputs (AKA virtual-ground).

JAkob E.

Tnx Jakob. :guinness: