ADM 1540 EQ, adjusting DC offset into output transformer...
Posted: Mon Dec 16, 2013 4:45 am
Hi Joe!
I searched the internet from more info about a pair of 1540 eq's I have, and I stumbled upon a post you made at turtle rock mastering about adding "R82 trimpot and R81" for an DC offset fix. http://www.turtlerockmastering.com/foru ... b&start=30
I just fired up a pair of 1540 eq's and they seems to work just fine, great! After that I recapped them with a definite improvement soundwise.
I then thought I should check the amount of DC offset running into the output transformer and I measured that one gets - 2,1 mV and the other gets 0,7mV. Under 1,0mV seems to be regarded as just fine to send into a output transformer, without using a coupling capacitor blocking dc. So what to do with the one getting - 2,1mV?
Questions;
- Is -2,1mV fine into this transformer (original ADM output trannies) or should I try to modify and adjust the circuit to get below 1,0mV?
- Does anybody know what values to use if I want to implement the "DC offset circuit" in the 1540 schematic to adjust for the unwanted DC offset and get it closer to zero (components R81 to R84 in the schematic, those values are not specified anywhere in the schem as far as I can see...)?
I'd appreciate all the help I can get on this.
Thanx / Mattias
I searched the internet from more info about a pair of 1540 eq's I have, and I stumbled upon a post you made at turtle rock mastering about adding "R82 trimpot and R81" for an DC offset fix. http://www.turtlerockmastering.com/foru ... b&start=30
I just fired up a pair of 1540 eq's and they seems to work just fine, great! After that I recapped them with a definite improvement soundwise.
I then thought I should check the amount of DC offset running into the output transformer and I measured that one gets - 2,1 mV and the other gets 0,7mV. Under 1,0mV seems to be regarded as just fine to send into a output transformer, without using a coupling capacitor blocking dc. So what to do with the one getting - 2,1mV?
Questions;
- Is -2,1mV fine into this transformer (original ADM output trannies) or should I try to modify and adjust the circuit to get below 1,0mV?
- Does anybody know what values to use if I want to implement the "DC offset circuit" in the 1540 schematic to adjust for the unwanted DC offset and get it closer to zero (components R81 to R84 in the schematic, those values are not specified anywhere in the schem as far as I can see...)?
I'd appreciate all the help I can get on this.
Thanx / Mattias