API style eq (MAP3100) how fine tune output level
« on: August 13, 2018, 10:41:59 PM »
Hi. Got one of these rare gems. Sounds absolutely fantastic. I would like to tweak the output signal level. The opamp inside has a pin named "trim" as the 2520 does. I suppose that it is intended to well, trim the signal. How to use it? What signal is it expecting? A resistor to ground? A trimpot maybe?

I was hoping somebody that knows an API style EQ (550?) may help.


3nity

Re: API style eq (MAP3100) how fine tune output level
« Reply #1 on: August 19, 2018, 06:20:04 PM »
It should be a 325 style line amp..there's a gain set resistor..you find a schematic or trace the schematic
Life is a path, death the destination.

squarewave

Re: API style eq (MAP3100) how fine tune output level
« Reply #2 on: August 19, 2018, 07:26:42 PM »
Hi. Got one of these rare gems. Sounds absolutely fantastic. I would like to tweak the output signal level. The opamp inside has a pin named "trim" as the 2520 does. I suppose that it is intended to well, trim the signal. How to use it? What signal is it expecting? A resistor to ground? A trimpot maybe?
No, "trim" on the op amp itself is definitely not trimming the signal level. It's probably output offset trim. Don't mess with that. You could end up putting DC through the transformer which would cause distortion or worse.

There is probably a resistor on the - input of the op amp that will set the gain. But without a schematic it's difficult to say.

Re: API style eq (MAP3100) how fine tune output level
« Reply #3 on: August 19, 2018, 09:07:08 PM »
I would like to tweak the output signal level. The opamp inside has a pin named "trim" as the 2520 does.
I was hoping somebody that knows an API style EQ (550?) may help.
the "trim" pin is output offset, as in a 2520.
the pin connections of the MAP 3100 are the same as an original API 550a equaliser (unbalanced input),
with the possible exception of pin 11.
pin 11 on the 3100 is labeled "input hi, 12 dB gain"
pin 11 on a 550a is gain adjust, per resistor table in the documentation.

r2d2

Re: API style eq (MAP3100) how fine tune output level
« Reply #4 on: September 05, 2018, 05:14:05 AM »
Hi. Got one of these rare gems. Sounds absolutely fantastic. I would like to tweak the output signal level. The opamp inside has a pin named "trim" as the 2520 does. I suppose that it is intended to well, trim the signal. How to use it? What signal is it expecting? A resistor to ground? A trimpot maybe?

I was hoping somebody that knows an API style EQ (550?) may help.
any image of the back side of pcb ?
..... Cracking D.Vader Firewall ...  II-)


 

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