ADA Depot - A Forum To Support Users of ADA Amplification Gear
Let's Get Technical => Troubleshooting Problems => Topic started by: Shredzilla on January 26, 2014, 12:36:22 PM
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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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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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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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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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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)
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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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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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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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Keep us updated!
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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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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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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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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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And you loose volume,not gain?
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yes. i just loose volume.
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What presets do you go to and loose vol ? (pls list all settings from patch x to patch y). Also what firm wear (EPROM) version in your MP2 (will show on start up)
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I'll post my settings on friday. My rack is a three our ride away:(
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EPROM is 1.41
Here are my Presets:
Clean
Crystal Clean
Drive 40
Master 74
Lo +6
Mid +6
Hi +6
Pres +6
100+6
170+6
280+8
470+6
800+0
1,3+0
2,2+2
3,8+4
6,3+4
Crunch
Warm Vintage
Drive 83
Master 59
Lo +4
Mid +6
Hi +8
Pres +6
100+6
170+8
280+6
470-2
800+0
1,3+0
2,2+0
3,8+4
6,3+2
"Metal"Preset
Ultimate High Gain
Drive 70
OD 62
Master 53
Lo+6
Mid+4
Hi+6
Pres+8
100+2
170+6
280+4
470+0
800+4
1,3+2
2,2+4
3,8+4
6,3+2
Lead
Warm High Gain
Drive 80
OD 72
Master 62
Lo+4
Mid+6
Hi+6
Pres+6
100+0
170+4
280+2
470+4
800+2
1,3+0
2,2+0
3,8+0
6,3+2
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Hey Shred, just to confirm, when things are normal you don't loose volume with your patch changes/settings ?, but sometimes suddenly you do ?
Are you using the compressor ? or any other MP2 effect/circuit ? e.g. wah in any of the patches.
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Yes. Everything is pretty normal and then suddenly I loose volume.
I don't use the compressor or any of the effects of the MP2.
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Is it possible that high input levels - some level LEDs glow red but not the clipping LED - can cause my problems? The manual says a red glowing LED means that the level is 3db below clipping... :???:
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Hey Shred, mmm I'm not sure that the red is causing the volume drop, it may be part of the issue ?? It's not good gain structure though, I've never seen a red led on my MP1/2s ever (well maybe with the clean sound with lots of compressor flick here and there), I'm guessing, but it sounds like something is getting too hot ? and running to red leds will exaserbate that to some extent i.e. things are working harder/more heat (but if you have 3db to spare at red... should be ok ?, depends on the sound a bit though). Your patches have quite a bit of eq boost so will add (lots of) gain/vol, may be worth trying the same "curve" but based around 0 (e.g. turn them all down the same amount (lost of us run mids -4, -6) and then turn master vol up).
Thing is, when I look at your patch settings, yeah they're high and eq (very) up... but the unit should take it. Another thing to consider is, has anything else in you chain of things from guit to cabs got the ability to shut/quieten down when driven to hard ? (is it the MP2 ??). One check, when the problem starts, does power cycle restore normal ?
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Hey rnolan, thanks for help. I forgot to mention that the red LEDs only flash when I'm on my cleanpreset. rest of my presets show no red LED flashing.
I'm not sure if heat is causing my problems because I have good air circulation under and above the mp2. I'll try out the "same curve at different base" thing.
I noticed that lot of you run your mids down to -4 and lots of the factorypresets have mids turned down. for me this sounds too bassy:)
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Can you hookup the amp to the effect send so we can rule out some part of the circuit?Set the button on line level.Let me know how this goes.
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Hey rnolan, thanks for help. I forgot to mention that the red LEDs only flash when I'm on my cleanpreset. rest of my presets show no red LED flashing.
I'm not sure if heat is causing my problems because I have good air circulation under and above the mp2. I'll try out the "same curve at different base" thing.
I noticed that lot of you run your mids down to -4 and lots of the factorypresets have mids turned down. for me this sounds too bassy:)
If it sounds too bassy (apart from turn down the bass lo or graphic eq), turning the room eq knob up gets much less bass (for carpeted /deader rooms) and down adds quite a bit of bass (wooden floors, shiny reflective rooms). Probably best to run up sounds with it at 12 o'clock. Also if your cabs are on the floor the bass tends to couple with the floor and increase, I put mine up on milk creates.
If you check the MP2 signal flow (page 2 of user manual) you'll see where MJMP wants you to take the signal (loop send) straight to your amp inputs, if you don't get the power drop like this then the issue is in the last part of the signal flow/circuit after the loop (so play for same time etc to when problem happens and beyond i.e try to reproduce it).
And again, if when the problem happens you turn in off/wait 10 secs and back on does this correct it ?
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When volume drops and I switch off the MP2 and wait for about 20 secs everything is normal again.
Using the effectloop makes no difference. I reduced my clean channel gain to 20 and normalized the graphic eq settings in all of my presets. After this I had no problems untill now.