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Author Topic: MP2 Volume drop  (Read 12911 times)

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Shredzilla

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MP2 Volume drop
« on: Time Format »

Hi!

I've got a volume problem with my ADA MP2. When I start playing everything is fine but after two to three hours there's a sudden volume drop. I tried different poweramps - same result.
Anyone got an idea? Are there any known heat problems? Compared to my other rack gear the MP2 seems to get very hot.

Thanks for your help!
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MarshallJMP

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Re: MP2 Volume drop
« Reply #1 on: Time Format »

I would first try out a fresh pair of tubes.

And yes the mp-2 generates alot of heat,if you rack it,make sure you have enough cooling above and below the mp-2.
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Shredzilla

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Re: MP2 Volume drop
« Reply #2 on: Time Format »

OK. I' ll try some new tubes. Which do you recommend? I guess the current tubes are the original ones from 1994:)


Regarding the heat problems I maybe have to buy a new rack case with more space left to prevent overheating.
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rnolan

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Re: MP2 Volume drop
« Reply #3 on: Time Format »

There are lots of tube possibilities and choice is very subjective.  Basically you need a pair of low noise 12AX7 tubes. My personal preference for the MP2 are the New Sensor Mullard reissues, I've had some for a while now and love them.  MJMP likes Ruby tested JJs. Here's a link to Dougs Tubes with plenty to pick from.  The TUNG-SOL reissues would also be good (I've heard good things about them). (http://www.dougstubes.com/preamp-tubes/12ax7-ecc83-7025.html).
I mount my MP2 at the top of the rack as this gives some space above the unit.  I rack the effects under it as they don't get too hot (or leave a space under it if you can).
The original tubes were Chinese 12AX7s, typically no brand on them, just some red writing saying 12AX7.  And they will be way past their best if the unit has been well used.
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Dante

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Re: MP2 Volume drop
« Reply #4 on: Time Format »

When you take the old tubes out, hang on to them just in case. You never know.

I tried a bunch of variations in my MP-2. I ended up putting some Sovteks in there (12ax7w?). They were the only tubes I could get crunchy enough while still being able to clean up a bit by picking softer. (I think I'm the only guy on the Depot that tries to tone down his gain - ha ha)

rnolan

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Re: MP2 Volume drop
« Reply #5 on: Time Format »

Well you not quite alone Dante, I've toned down my gain quite a bit over the years, my old rhythm sound is now my over the top lead and my (newer) rhythm sound is backed off quite a bit (compared to when I was doing 80s west coast covers eg Mr Big, Skid row etc)  O0
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MarshallJMP

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Re: MP2 Volume drop
« Reply #6 on: Time Format »

I use GE5751 NOS tubes in mine,they give a really nice clean tone,but you will loose gain on the overdrive and distortion voicings.For me this isn't a problem because i use my MP-2 only for cleans.
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Shredzilla

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Re: MP2 Volume drop
« Reply #7 on: Time Format »

I ordered two TAD RT008 Tube ECC83 WA now. My next rehersal will be on friday. The plan is AS follows:
1. Change the tubes and
2. Unrack my mp2
Hope this will help ...
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MarshallJMP

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Re: MP2 Volume drop
« Reply #8 on: Time Format »

Keep us updated!
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Shredzilla

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Re: MP2 Volume drop
« Reply #9 on: Time Format »

Hey!

Here is a quick update.

After I got my mp2 unracked und changed the tubes, the volume was normal during the entire rehearsal.
By the way the old tubes are JJ labeled and they didn't looked very aged. I guess the former owner has changed them.

In the end it's maybe just a heat problem? Then I really have to buy a new rack with more space.

Cheers

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rnolan

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Re: MP2 Volume drop
« Reply #10 on: Time Format »

Do you have your power amp in the rack ?  They also get very hot, an option may be to get a separate rack for the power amp which would reduce heat in the rack and give you more space.  I used to have mu B200s in the rack (and didn't have overheating problems) but when I bought the TS100 (which generates more heat as it's all valve) I gave it its own 2 RU rack, it's also very heavy so makes the racks easier to handle.
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Shredzilla

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Re: MP2 Volume drop
« Reply #11 on: Time Format »

I used to have both power amp and preamp in the same rack. But the day a posted for the first time I got a new power amp (Engl 2x35). So it was just the mp2 alone in the rack.
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Shredzilla

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Re: MP2 Volume drop
« Reply #12 on: Time Format »

Hey!
Me again. Same problem as before. I did everything as you said. Change tubes etc. but i still got output loss from time to time. This seems to be related to preset switching. For example: In the end of a cleanpart i hit the strings hard and then change the preset to an overdrive sound. This sometimes makes the mp2 reduce the output.



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MarshallJMP

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Re: MP2 Volume drop
« Reply #13 on: Time Format »

And you loose volume,not gain?
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Shredzilla

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Re: MP2 Volume drop
« Reply #14 on: Time Format »

yes. i just loose volume.
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