Topic: Aerco MP-2 Information > $750 new & 1 Month Lead Time

[thegreatgumbino]

Christian (musicsherlock) and I were PMing about the Aerco, and I called Jerry yesterday with some questions.  Here's some things that we found out...

• As it says on the site, you can select either stepped gains or pots.  The former is a switched network with 6 positions, and the 6 gain levels can be selected by the buyer.
  
• I asked if it would be possible to have a single 'stereo' gain dial (either stepped or not), and a second 'balance' dial with a center detent.  Jerry liked the idea and said he'd like to offer that option to others as well, but has to check into the availability of a small enough pot with a detent.  His latest followup seemed to indicate that such a piece may not longer readily exist, but he has an idea about how to fashion one nonetheless, though it may cost a little extra to the buyer.
• The RCA outputs can be replaced or supplemented with XLR outputs on a pair of short (or long) cables, since there isn't really room inside the box for a pair of output XLR
  jacks.  However, these would not be balanced, so there's no advantage except for those that find an XLR connector either more convenient or reliable.  The default RCAs aren't quite audiophile quality, though we're looking to see if a better part might exist that will also fit.
• If you really wanted XLR output jacks, you could put them on the back of the unit and skip the internal powering capability, or have Jerry install a pair of 5-pin XLRs on the front - one for intput, one for output.  Again - no advantage except if you prefer the connector.
• External powering is 9-20v.  The box is designed to give priority to the external power connector when sufficient power is plugged in there.  If it falls too low, the box automatically and seamlessly switches to available internal power (3 9 volt batteries).  There is no battery meter or indicator, but Jerry indicated that he could install a momentary switch and LED with a small amplifier circuit which would show if power was being drawn externally or not.  For an extra few bucks it might be worth it for those long festival taping situations.
  

That's about it!  I'm pretty sure I'll be ordering one shortly with gain settings: 0, +12, +18, +24, +30, +42 which gives reasonable 6dB steps in my most used gain range, as well a 0dB setting and what I'd consider a higher than normal gain (+42dB).  Fortunately, going into the 744t, if I really need more gain, it's easily applied.  These numbers seemed like a nice compromise.  And if Jerry can make a workable balance knob, I'll be thrilled.

- Jason

Thanks for the info, Jason.  +T

I hope more people start giving Jerry feedback & helping him tweak the MP2.  I think it's awesome that he's open to this as well.  If enough feedback is given, and he's remains open to helping develop/progress the box, it could turn into THE pre for our purposes.

[JasonR]

Great details, Jason.  Thanks for posting them.

I'm a huge fan of the single volume + balance config. Though I have to say that it isn't such an advantage with stepped pots becuase they're easy to move in sync and the jumps are so big that it doesn't matter.

No prob.  I think the seperate balance knob would have a lot of value in either gain setup.  With a stepped gain, you really have no way to bias toward one side or the other to compensate for an off-center placement or other side-related gain difference.  So adding the balance knob gives you that.  If you also go with the continuously variable gain pot, then you have a true single 'volume' knob for levels as well.  Either way, I think it adds some real value.

I just suggested in an email to Jerry that if the custom center detent pot was problematic, I wouldn't be adverse to a bypass/lockout switch that would bypass the setting of the balance knob and just lock the gain at center.  At least then it also becomes a knob I don't have to worry about hitting by accident in situations where an equal balanced L/R is fine.  I also inquired about other types of locking pots, so we'll see what comes of that.

- Jason

[musicsherlock]

Great details, Jason.  Thanks for posting them.

I'm a huge fan of the single volume + balance config. Though I have to say that it isn't such an advantage with stepped pots becuase they're easy to move in sync and the jumps are so big that it doesn't matter.

Thanks to Jason as well for asking all the right questions!

Freelunch...the single-dial stepped gain is customized based upon your needs...assuming you have a known pair of mics that you will keep for a long time, you will know what gain is needed for most taping environments.  You can then customize your steps at any six choices. I run AKG 480's which have pre-attenuation pads on the mic bodies of: -10, 0, & +6 dB...if I chose a gain scheme such as 0, 12, 24, 30, 36, 42, this would give me the following gain choices: -10, 0, 2, 6, 12, 14, 18, 20, 24, 26, 30, 32, 36, 38, 42  Advantages for me would be less "jump" from selection to selection, fine tuning adjusted through A/D, less likely to erroneously change the duel variable gains (my biggest complaint from running the SD MP-2). The biggest dB jump I will encounter within that range is going from +6 to +12.

Jerry has been gracious enough to communicate through numerous emails with me and Jason...and has been obviously open to numerous suggestions.

[shruggy1987]

does anybody know how the external power interfaces with this preamp?

[musicsherlock]

from PM's with Jason Reiser who asked Jerry similar question...

- External power takes precedence and the internal 9v connectors are a backup.  So if you put some 9v batteries inside and plug into external power, you'll be running off the external power.  If the jack becomes disconnected, you'll seamlessly switch to internal power.  I like how he thought that out.  More manufacturers should do this.

- 9 Volts is sufficient for external power, but it's the minimum suggested.  Some of his documentation listed 10V so I wanted to check.  I think I'd plan on running from an RC car battery (9.6V NiMH)

- No battery indicators - only experience.  Fortunately the seamless switching to internal power makes this just a missing luxury.  I hadn't thought to ask if an LED indicator could show where power was being drawn from (external or internal) as this would be a useful way to know if your external battery dropped below some threshold and now it's using the internals, so you should swap power soon.  I'll ask in a followup email.

[shruggy1987]

that makes sense, but what is "the jack"?  what is the actual physical interface between the external power supply and the mp2?

[Thom Joad]

Ben, you can check mine out anytime you want.

There is a male barrel plug type post (I think it's size "B") on the side of the unit.  Then I have the female barrel plug on one end of a cable and the other end is terminated in a standard 4 pin XLR, that goes to my 12V SLA.  Runs the thing for days.

[shruggy1987]

sounds good.  by the end of the summer i will be fully ready to make a decision on a preamp.  this one is definitely a top candidate.

[hammerhorror]

that makes sense, but what is "the jack"?  what is the actual physical interface between the external power supply and the mp2?

My MP2 DC power jack is the same size as the UA-5, Marantz PMD671, etc... I believe the radio shack plug is identified as size "M".

The external power jack is floating so you can use a positive or negative type plug.

[hammerhorror]

Performed an external battery test on the Aerco MP2 today.

I took out the internal 9 volt batteries and hooked up my 9v 5400mah lithium-ion DVD battery to the MP2 to find out how long it would power it for.

Test source info: Home Stereo > JW Mod AKG 463's > Aerco MP2 > RME ADI-2 > Marantz PMD671. I am running phantom power on the Aerco.

So far it has been going for 5 hours and 20 minutes.

Unfortunately I have to leave for work now and don't know how much longer it will go for. But that is a good start.

Also wanted to mention that most of the literature states that the MP2 should be run on 10v-30v of DC power, but mine states that it is rated for 7v-30v DC power. I am not sure if this has been changed on the newer units or not (bought mine new this month).

I will try to do a longer test with the DVD battery in the future, just wanted to let people know that it will at least go for 5 hours and 20 minutes. Should even go for alot longer because the meter on the battery has not even moved.

-John

[musicsherlock]

would under supplying voltage cause damage?

[thegreatgumbino]

• I asked if it would be possible to have a single 'stereo' gain dial (either stepped or not), and a second 'balance' dial with a center detent.  Jerry liked the idea and said he'd like to offer that option to others as well, but has to check into the availability of a small enough pot with a detent.  His latest followup seemed to indicate that such a piece may not longer readily exist, but he has an idea about how to fashion one nonetheless, though it may cost a little extra to the buyer.
• The RCA outputs can be replaced or supplemented with XLR outputs on a pair of short (or long) cables, since there isn't really room inside the box for a pair of output XLR jacks.  However, these would not be balanced, so there's no advantage except for those that find an XLR connector either more convenient or reliable.  The default RCAs aren't quite audiophile quality, though we're looking to see if a better part might exist that will also fit.
• If you really wanted XLR output jacks, you could put them on the back of the unit and skip the internal powering capability, or have Jerry install a pair of 5-pin XLRs on the front - one for intput, one for output.  Again - no advantage except if you prefer the connector.
• External powering is 9-20v.  The box is designed to give priority to the external power connector when sufficient power is plugged in there.  If it falls too low, the box automatically and seamlessly switches to available internal power (3 9 volt batteries).  There is no battery meter or indicator, but Jerry indicated that he could install a momentary switch and LED with a small amplifier circuit which would show if power was being drawn externally or not.  For an extra few bucks it might be worth it for those long festival taping situations.
  

That's about it!  I'm pretty sure I'll be ordering one shortly with gain settings: 0, +12, +18, +24, +30, +42 which gives reasonable 6dB steps in my most used gain range, as well a 0dB setting and what I'd consider a higher than normal gain (+42dB).  Fortunately, going into the 744t, if I really need more gain, it's easily applied.  These numbers seemed like a nice compromise.  And if Jerry can make a workable balance knob, I'll be thrilled.

- Jason

Great details, Jason.  Thanks for posting them.

I'm a huge fan of the single volume + balance config. Though I have to say that it isn't such an advantage with stepped pots becuase they're easy to move in sync and the jumps are so big that it doesn't matter.

No prob.  I think the seperate balance knob would have a lot of value in either gain setup.  With a stepped gain, you really have no way to bias toward one side or the other to compensate for an off-center placement or other side-related gain difference.  So adding the balance knob gives you that.  If you also go with the continuously variable gain pot, then you have a true single 'volume' knob for levels as well.  Either way, I think it adds some real value.

I just suggested in an email to Jerry that if the custom center detent pot was problematic, I wouldn't be adverse to a bypass/lockout switch that would bypass the setting of the balance knob and just lock the gain at center.  At least then it also becomes a knob I don't have to worry about hitting by accident in situations where an equal balanced L/R is fine.  I also inquired about other types of locking pots, so we'll see what comes of that.

- Jason

Anyone have any more conversations with Jerry regarding these upgrades to the unit?

I know the unit switches from external to internal power seamlessly, but I wonder if he'd consider upgrading the connection to a locking one similar to the V3?

[thegreatgumbino]

Could the rca outs be replaced with bnc connectors?  I've never worked with them before, and know nothing about them, so this may be a dumb question.  But, it seems that would be pretty stable, and all you'd need is a bnc > ? interconnect to run to your A/D or recorder.

[Rick]

Could the rca outs be replaced with bnc connectors?  I've never worked with them before, and know nothing about them, so this may be a dumb question.  But, it seems that would be pretty stable, and all you'd need is a bnc > ? interconnect to run to your A/D or recorder.

what about miniXLR?

[thegreatgumbino]

Could the rca outs be replaced with bnc connectors?  I've never worked with them before, and know nothing about them, so this may be a dumb question.  But, it seems that would be pretty stable, and all you'd need is a bnc > ? interconnect to run to your A/D or recorder.

what about miniXLR?

That could work pretty well too.  I think the big thing is trying to find a connection that isn't very obtrusive on the inside of the box & provides a solid / reliable connection on the outside.