Topic: Aerco MP-2 preamp - Part 2

[goodcooker]

I bought one from Hypnocracy here at TS back in 2017. It had been converted to internal LiPo batteries and they were end of life/swollen. I bought some new ones and after installing them I couldn't get it to work on the batteries at all but it worked fine on the external DC input. Sent it back to Jerry and he fixed it. A few years later it developed the same issue. I guess the connection to the power circuit from the batteries is pretty fragile - which is weird since the rest of the thing is built like a tank.

Last year my friend Darby had one that had the same issues so I gave it a once over to see if I could bring it back. It has the same issue - nothing on batts but works on the DC input. We did a trade for it IIRC.

I tried using the #2 for a show last year for a Lachy Doley recording with my ADK A51s. It was completely blown. I chalked it up to a mismatch with the sensitivity of the mics although I'd never had an issue running them with any other preamps.

I'm sending them both to Nick to reference while working on Myco's. At least one of them is working 90%.

[Myco]

I bought one from Hypnocracy here at TS back in 2017. It had been converted to internal LiPo batteries and they were end of life/swollen. I bought some new ones and after installing them I couldn't get it to work on the batteries at all but it worked fine on the external DC input. Sent it back to Jerry and he fixed it. A few years later it developed the same issue. I guess the connection to the power circuit from the batteries is pretty fragile - which is weird since the rest of the thing is built like a tank.

Last year my friend Darby had one that had the same issues so I gave it a once over to see if I could bring it back. It has the same issue - nothing on batts but works on the DC input. We did a trade for it IIRC.

I tried using the #2 for a show last year for a Lachy Doley recording with my ADK A51s. It was completely blown. I chalked it up to a mismatch with the sensitivity of the mics although I'd never had an issue running them with any other preamps.

I'm sending them both to Nick to reference while working on Myco's. At least one of them is working 90%.

Thanks so much!

[coop]

I bought mine in 1990 and it made great tapes and even better digital recordings.  I wish I hadn't sold it.

[Gutbucket]

I tried using the #2 for a show last year for a Lachy Doley recording with my ADK A51s. It was completely blown. I chalked it up to a mismatch with the sensitivity of the mics although I'd never had an issue running them with any other preamps.

Possible anecdotal confirmation-
I only ran a borrowed Aerco a couple times about 15 years back to give it a try with some on-stage recordings.  Both times the resulting recording was "completely blown / distorted".  I think I was running ADK TLs thru it (goodcooker's post sparked my memory of this), but might have been Gefells. I also never had that problem with those mics through other preamps.  At the time I chalked it up to something wrong in the Areco.  The owner (Spyder9) sent it back to Jerry to check out, but I'm unsure if he determined that anything needed to be done to  it or not.

[goodcooker]

I tried using the #2 for a show last year for a Lachy Doley recording with my ADK A51s. It was completely blown. I chalked it up to a mismatch with the sensitivity of the mics although I'd never had an issue running them with any other preamps.

Possible anecdotal confirmation-
I only ran a borrowed Aerco a couple times about 15 years back to give it a try with some on-stage recordings.  Both times the resulting recording was "completely blown / distorted".  I think I was running ADK TLs thru it (goodcooker's post sparked my memory of this), but might have been Gefells. I also never had that problem with those mics through other preamps.  At the time I chalked it up to something wrong in the Areco.  The owner (Spyder9) sent it back to Jerry to check out, but I'm unsure if he determined that anything needed to be done to  it or not.

The one I've had for years and ran many times with mics of similar sensitivity to the ADK a51s (15mV/Pa - I often ran mk41s with it 14mV/Pa and MBHO KA300s 12mV/PA) never had any issues beyond the odd slightly distorted transient peak now and then at a really loud show.

The one I had the problem with last outing was the one I got from Darby. I have a suspicion that this one is made with the higher gain structure for nature recording. It was a loud show that came out distorted but not crazy loud. It was a smallish club with a hanging line array and I was 40 feet from stage in my usual FOH cage spot.

I initially thought they had different transformer models in them but I was confusing manufacturing lot numbers with model numbers - they both have model JT - MB - CPCA. The older lot number has the printing directly on the top of the can. The newer lot number has the printing on a white sticker on top of the can. They should be the same.

[coop]

FWIW,  I never ran the gain higher than 20db - the lowest setting available.  I used it with AKG 460's, Schoeps cmc5/mk4, Neumann km184, Neumann km84.  That preamp really went through the 9 volt batteries.

[Myco]

FWIW,  I never ran the gain higher than 20db - the lowest setting available.  I used it with AKG 460's, Schoeps cmc5/mk4, Neumann km184, Neumann km84.  That preamp really went through the 9 volt batteries.

Just a user, not in repairs, but Nick is finding that most of these units have power issues. The fact that you are burning through 9v would lead me to believe that you have one as well. When mine worked correctly the 3 9v's would be enough to power me through an entire weekend festival of shows.

[coop]

FWIW,  I never ran the gain higher than 20db - the lowest setting available.  I used it with AKG 460's, Schoeps cmc5/mk4, Neumann km184, Neumann km84.  That preamp really went through the 9 volt batteries.

Just a user, not in repairs, but Nick is finding that most of these units have power issues. The fact that you are burning through 9v would lead me to believe that you have one as well. When mine worked correctly the 3 9v's would be enough to power me through an entire weekend festival of shows.

A set of 9v would last for three GD shows.  I never pushed it after having a power failure during a 2nd set. 

[spyder9]

[ The owner (Spyder9) sent it back to Jerry to check out, but I'm unsure if he determined that anything needed to be done to it or not.

I had Jerry remove the internal bats from the circuitry.  He then installed an external coaxial power connector.  Never had a problem since.

[gormenghast]

FWIW,  I never ran the gain higher than 20db - the lowest setting available.  I used it with AKG 460's, Schoeps cmc5/mk4, Neumann km184, Neumann km84.  That preamp really went through the 9 volt batteries.

Mine was fixed 20db with a red case.  I’d like to buy it back if whoever has it is reading this.  One piece of gear I really regret selling. 

[auxren]

Anyone have one that isn’t working or with issues that they are willing to sell or lend me to repair and study the circuit?

[weroflu]

I have a probably wrong, hazy memory that these were close to the op amp mic pre schematic on the jensen site. lots of point to point and a diy pcb. would be curious to see the schematic if anyone has one.
if someone comes up with the schematic i'll whip up a layout - can't guarantee best low noise.