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Author Topic: MP-2 Help!! Pics included...  (Read 5086 times)

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Offline drewloo

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Re: MP-2 Help!! Pics included...
« Reply #15 on: November 18, 2005, 09:09:28 PM »
Not to bum you out even more, but I was looking at the SD website re: the mp-2 and saw this: 

http://www.sounddevices.com/tech/oscillation.htm

Quote
Oscillation with Transformer-Balanced Inputs
Sound Devices Support Oscillation with Transformer-Balanced Inputs

Problem
Depending on several conditions, chiefly the microphone, the transformer-balanced inputs, such as those on the 302, 442, MixPre, MM-1, MP-1, and MP2, can get into an oscillating condition with a microphone that renders the audio unusable. This oscillation is often described as a "motorboating" condition since this low frequency oscillation sounds like a motor boat.

Cause
Microphones with low rejection to common-mode phantom voltages fluctuate their output level based on the phantom voltage supplied. This variation "wiggles" the bipolar +/-15 volt audio rails -- which subsequently fluctuates the phantom voltage rails, which fluctuates the output level and sets up the oscillation.

Sound Devices field mixers and preamps are very portable products and have compact, efficient power supplies. The AA batteries in the product supply several voltages including, ±15 volts for audio, 48 or 15 V for phantom power, and 5 V for LED's. The power supply is suitable for most microphones, but is susceptible to oscillation with microphones prone to drawing current based on output level.
Remedy

With microphones prone to this condition, several things can be done to minimize and/or prevent the condition.

    * Engage the high-pass filter.
    * Use 48 V phantom even if not required.
    * Power the microphone(s) from an external phantom supply.
    * Power the mixer from an external, DC power supply.

Additional capacitance in the mixer would also help the condition, however, these units have the most capacitance that will fit into their chassis.

The same microphone that exhibits this condition with the MixPre or MP-2 may not exhibit the problem with another preamp with a larger phantom supply with more capacitance.
Microphones Know to Exhibit this Problem

    * AKG Blue Line Series
    * AT 4073
    * Sanken CUB-01, CS-1

I highly doubt your blue wires relate to this but I see that you're running Blue Lines so I'd thought I'd mention it in case you experience this problem in the future.  Good luck, bro.

You can't be a real country unless you have a beer and an airline - it helps if you have some kind of a football team, or some nuclear weapons, but at the very least you need a beer.  -FZ

Offline L Ron Hoover

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Re: MP-2 Help!! Pics included...
« Reply #16 on: November 18, 2005, 09:18:13 PM »
I sold said MP2 to the person who sold it to you. It worked perfectly fine when I sold it to him. (I taped Les Claypool the Saturday night before it was shipped on Monday) It was sent in to Sound Devices two years ago because it wasn't powering off of the external jack (I had to use AA batteries for one show and it worked fine) I sent it in the following week, and they fixed that problem, and tightened, or replaced the gain pots. (Obviously that jumper cable had something to do with the fix) I always used the external power jack, so I didn't think to have it modified for rechargeables at the time. Have you read the PDF on how to operate it? There is a switch off/bright/blinding for the level lights. Is phantom on? Have you eliminated all other possibilities. This thing worked great when it left my hands. It was packaged very well when I shipped it, and I assume the person who sold it to you did so as well.

I ran MG300s into it.


It sounds like the above post may be the problem. I don't mean to sound like I'm busting your chops. Sorry if it comes off that way.  I just know that the thing worked great for me.

Lee
« Last Edit: November 18, 2005, 09:23:38 PM by L Ron Hoover »

Offline aberg

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Re: MP-2 Help!! Pics included...
« Reply #17 on: November 18, 2005, 09:21:46 PM »
I sold said MP2 to the person who sold it to you. It worked perfectly fine when I sold it to him. (I taped Les Claypool the Saturday night before it was shipped on Monday) It was sent in to Sound Devices two years ago because it wasn't powering off of the external jack (I had to use AA batteries for one show and it worked fine) I sent it in the following week, and they fixed that problem, and tightened, or replaced the gain pots. (Obviously that jumper cable had something to do with the fix) I always used the external power jack, so I didn't think to have it modified for rechargeables at the time. Have you read the PDF on how to operate it? There is a switch off/bright/blinding for the level lights. Is phantom on? Have you eliminated all other possibilities. This thing worked great when it left my hands. It was packaged very well when I shipped it, and I assume the person who sold it to you did so as well.

I have tried every possible setting. I'm not really a newbie anymore and have a general good understanding of how this type of gear works. As far as I can tell, it's not working properly.

After the external power jack problem was fixed, did you ever try running it off AA internals? Maybe their fix caused it to stop working on internals. The person who sold it to me, however, says that it tested ok using energizer lithium AAs. I've been testing it using regular duracells.

This is a frustrating problem because I don't really know what could have happened here.

Thanks for your input though. It's good to find out that those blue jumpers are supposed to be there.

Offline Chris K

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Re: MP-2 Help!! Pics included...
« Reply #18 on: November 18, 2005, 09:24:47 PM »
re oscillation...i ran 391's with the mp-2 for a long time and never had a problem





My gear: JK Labs AKG DVC > M10
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Offline aberg

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Re: MP-2 Help!! Pics included...
« Reply #19 on: November 18, 2005, 09:26:37 PM »
Yeah, I don't hear any sort of oscillation with it, rather I don't hear anything at all  >:(

Offline L Ron Hoover

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Re: MP-2 Help!! Pics included...
« Reply #20 on: November 18, 2005, 09:26:59 PM »
Did you connect everything before powering it? I'm pretty sure I had used alkalines in it for opening bands to conserve power in my SLA as well. Not to sound like an ass again, but you do realize that the power switch goes one way for external power, and one way for internal.

Offline aberg

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Re: MP-2 Help!! Pics included...
« Reply #21 on: November 18, 2005, 09:30:59 PM »
Yeah, I'm aware of all the features on the mp-2.

Don't worry, you won't offend me. I know sometimes people overlook really obvious mistakes.

I'm fairly convinced I have everything set up properly. Perhaps it is an issue with oscillation and this "unusable audio" is just fairly inaudible.

I suppose I should wait for the external cable to arrive so I can test it with an external power source. That is one of the listed remedies. It is likely Sound Devices would find nothing wrong with the unit, I imagine.

Offline aberg

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Re: MP-2 Help!! Pics included...
« Reply #22 on: November 18, 2005, 09:31:26 PM »
re oscillation...i ran 391's with the mp-2 for a long time and never had a problem

Did you ever use AA internals with it successfully?

Offline Chris K

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Re: MP-2 Help!! Pics included...
« Reply #23 on: November 18, 2005, 09:33:18 PM »
make sure the tape return switch on the front is not in the locked position. it should be in the middle. if it is engaged and nothing is plugged into the tape return input (which is actually on the output side of the mp2) then you will hear nothing

with mics plugged in and phantom on do you hear sound with a headphones from the headphone jack
My gear: JK Labs AKG DVC > M10
              AKG 460 ck61/ck62/ck63 > DR-70D
             
A live concert to me is exciting because of all the electricity that is generated in the crowd and on stage. It's my favorite part of the business, live concerts.
-Elvis Presley

Offline Chris K

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Re: MP-2 Help!! Pics included...
« Reply #24 on: November 18, 2005, 09:34:45 PM »
re oscillation...i ran 391's with the mp-2 for a long time and never had a problem

Did you ever use AA internals with it successfully?

yep. positive end goes in first. if you are getting the power light than the thing is getting power.
My gear: JK Labs AKG DVC > M10
              AKG 460 ck61/ck62/ck63 > DR-70D
             
A live concert to me is exciting because of all the electricity that is generated in the crowd and on stage. It's my favorite part of the business, live concerts.
-Elvis Presley

Offline L Ron Hoover

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Re: MP-2 Help!! Pics included...
« Reply #25 on: November 18, 2005, 09:38:00 PM »
make sure the tape return switch on the front is not in the locked position. it should be in the middle. if it is engaged and nothing is plugged into the tape return input (which is actually on the output side of the mp2) then you will hear nothing

with mics plugged in and phantom on do you hear sound with a headphones from the headphone jack


I'm willing to bet that's it.

Offline aberg

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Re: MP-2 Help!! Pics included...
« Reply #26 on: November 18, 2005, 09:38:28 PM »
make sure the tape return switch on the front is not in the locked position. it should be in the middle. if it is engaged and nothing is plugged into the tape return input (which is actually on the output side of the mp2) then you will hear nothing

with mics plugged in and phantom on do you hear sound with a headphones from the headphone jack

Ok, the tape return swith only has two positions, to the left, and then centre. I have it in the centre, and headphones on, phantom on.. mics plugged in... gain up, headphone level up, and nothing... no oscillation sound, no sound of any kind.

Offline aberg

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Re: MP-2 Help!! Pics included...
« Reply #27 on: November 18, 2005, 09:42:00 PM »
Ok, reading the manual, it says the tape return has 3 setting, locking left, centre, and then momentary right. I can see how that works now. In any case, the switch on mine has always been in the middle position, and still no sound, no level meters, etc.

Offline aberg

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Re: MP-2 Help!! Pics included...
« Reply #28 on: November 18, 2005, 10:08:37 PM »
I think I will try two things before sending it in, powering from external source, and running it with a different set of mics. Hopefully it's fine.

Offline larrysellers

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Re: MP-2 Help!! Pics included...
« Reply #29 on: November 18, 2005, 10:20:29 PM »
That mp2 has really been a p.i.t.a. for you. A new gear purchase is something you should be able to feel happy...and maybe a little guilty ::) for spending the cash. +T for your troubles.

 

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