DMP-11 Mixer Configuration

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UrbanCyborg
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DMP-11 Mixer Configuration

Unread post by UrbanCyborg »

I've had a DMP-11 Mixer in my keyboard setup for years, but just recently got into a feedback situation that's blown something out. It never happened before mainly because, lacking the unit's manual, I suspect I didn't have the external effect send enabled. The instant I did, WOW! Took me about three seconds of severe ear pain before I cut power. Unfortunately, after that the left channel on at least some inputs was missing, both at the stereo outs, and on the headphone jack. I'm still localizing the exact circuit affected, but would appreciate any suggestions on how to proceed.

The setup is pretty messy, but the key parts in the feedback problem are the DMP-11's external effect send and the SPX-900 on that send. All impedance level switches were set to handle +4dB levels, and the left and right returns from the SPX were routed back to the DMP as inputs 7 and 8.

The SPX wasn't blown, and apparently still works fine, and the DMP's internal Effect Send 2, which I have set to stereo reverb, inputs equally to both left and right busses internally, as shown by the DMP's meter.

Other than repairing the DMP-11, I'm concerned that this may not be the correct way to use the external effect send. Just trotting through the SPX-900's factory presets, I came across several that started to feedback at a low level even at the severely reduced settings I have things at now. This almost makes the arrangement unusable, unless I don't much change things at the SPX-900. It just doesn't seem safe to have the unit configured in a topology containing a feedback loop. Thoughts, anyone?

Thanks for any response.


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parametric
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Re: DMP-11 Mixer Configuration

Unread post by parametric »

Sorry to hear that . . . .

Sends and returns can be a minefield setup-wise . . . .

I think you need to have a very clear idea of the signal path in your mind . . .

I've not had extensive experience with this but seem to remember that, when channels are used for send/receive

They need certain settings disabled to avoid this feedback problem (unpress the send to mix button for instance?)

My (now distant) experience is with SoundCraft mixers, so these things things may be done differently on a Yamaha Mixer . . .

Anyhow - here's the user Manual for the DMP-11

DMP11E.pdf
(5.44 MiB) Downloaded 19 times
perhaps it will throw some light on the matter?

parametric


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UrbanCyborg
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Re: DMP-11 Mixer Configuration

Unread post by UrbanCyborg »

Thanks, Para. I did find a manual, and have been reading it. Seems the topology I'm running is exactly how the day to do it.
Working with the unit a bit more, it now seems that the sliders are non-functional. The status display correctly updates, but there's no audio effect. I'll have to go through the schematics and see if I can get a handle on what's happening.


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Re: DMP-11 Mixer Configuration

Unread post by parametric »

I'd like to think that the mixer should NOT be damaged by a feedback event - just your ears or blown tweeters?

Is there a system reset somewhere that you could try that might restore normality?

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Re: DMP-11 Mixer Configuration

Unread post by Jared Sager »

Hi there. Sorry to hear about the trouble you're having with your DMP11. I also own and use one on a daily basis in my home studio. When I bought my unit it was non functional. I had to replace every electrolytic capacitor in the unit starting with the power supply as well as the battery. I actually own both the user manual and service manual for this unit so just let me know if you'd like a copy of the schematics. I had a problem appear on mine recently that I haven't been able to repair or diagnose as of yet. Anytime that I engage the first effects bank on the unit it starts some uncontrollable oscillation. Effects bank 2 works just fine. This is especially irritating since the main reason I had been using the unit was for the Symphonic effect on bank 1. My advice would be to go through and replace all of the electrolytic caps starting with the power supply. In the least you'll need to inspect them and make sure that none have ruptured. I found numerous caps leaking on my unit upon disassembly. I know it's a pain in the ass but it definitely needs to be done. As always be very careful working inside the unit as some capacitors could be deadly if not discharged properly. Good luck.


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