new here..have you seen this?

[tedmich]

this was hard (for me) to find

its supposedly what an EMG 81 has inside...a pretty crappy op amp:



terrible slew rate (~1V/us) and could in theory run at 36VDC (!)... anyone run 4 x 9v batteries?

[salvarsan]

Slew rate is much worse, around 0.2 V/uS.
The op amp was chosen for battery life and
draws only 100uA.

There are better inexpensive opamps that will work just as well.

For comparison, the OPA2604 is a recording-grade audio opamp
that draws ~11ma and would drain your average 9V battery
in less than a day.

-drh

[David King]

That schematic has been kicking around the web for years with no way to know if in fact that's the op-amp EMG chose to use. EMG lists their max supply voltage as 27V not 36V. In their active bass electronics they like to use LM442s I see no reason why they would drop to this when batt savings really isn't an issue for most folks.

"Aktive", "Shema"? Only scandinavians spell like that...

[David Schwab]

That schematic has been kicking around the web for years with no way to know if in fact that's the op-amp EMG chose to use. EMG lists their max supply voltage as 27V not 36V. In their active bass electronics they like to use LM442s I see no reason why they would drop to this when batt savings really isn't an issue for most folks.

"Aktive", "Shema"? Only scandinavians spell like that...

I think it's Polska. I actually know where this came from. I posted some photos of the innards of the 81 some time ago sent to me by a pickup maker in Poland. The same fellow and a friend reverse engineered the circuit from the PCB extracted from the 81. It took quite some time... a couple of years actually (not saying they were working on it the whole time). But that's when he sent me that schematic.

If I remember they didn't know what op-amp is was because it was marked with a private label number.

[tedmich]

I think it's Polska. I actually know where this came from. I posted some photos of the innards of the 81 some time ago sent to me by a pickup maker in Poland. The same fellow and a friend reverse engineered the circuit from the PCB extracted from the 81. It took quite some time... a couple of years actually (not saying they were working on it the whole time). But that's when he sent me that schematic.

If I remember they didn't know what op-amp is was because it was marked with a private label number.

wow a cloak and dagger pickup maker!...I guess it shouldn't just be the amp heads digging through Dumble epoxy potting compound.

To paraphrase the Head of Coke when asked by a writer if he could publish their secret recipe: we don't rely on secrets to keep market share...we've got marketing for that...

EMG is worshiped by (too) many

[David Schwab]

wow a cloak and dagger pickup maker!...I guess it shouldn't just be the amp heads digging through Dumble epoxy potting compound.

To paraphrase the Head of Coke when asked by a writer if he could publish their secret recipe: we don't rely on secrets to keep market share...we've got marketing for that...

EMG is worshiped by (too) many

Sometimes it's just curiosity. Though I can't speak for the motives of the guys that ripped the 81 apart. He did say it was dead though.

I ripped apart a working SA once, just because I like taking things apart.

I have no desire to copy it, but I did learn a couple of things in the process.

Boy they wind a lot of wire on them bobbins!