ADA Depot - A Forum To Support Users of ADA Amplification Gear

ADA Preamps => MP-2 => Topic started by: jnelson on April 08, 2018, 06:17:37 PM

Title: mp2 comp on no sound
Post by: jnelson on April 08, 2018, 06:17:37 PM
I talked to jmp about this issue years ago, but ended up moving around a lot and never got back
to following up on it
you turn compressor on and it mutes the unit, turn it off and you get sound but cannot use comp
any idea's 
really would love to get it back up n running ,
also I have a pair of mp1's I'm looking to get in touch with jmp but it seems his old site isn't working
the e mail address is incorrect, not exactly sure on that one, starts with phillipe if anyone knows about
it.
thanks for any help.
John
Title: Re: mp2 comp on no sound
Post by: rnolan on April 09, 2018, 06:27:38 AM
Hey John, MJMPs email is in his profile (click on his name in any post he's posted to).  His web site is working for me (http://www.marshalljmpmodshop.net/index.htm)

Cheers R
Title: Re: mp2 comp on no sound
Post by: MarshallJMP on April 09, 2018, 10:08:45 AM
I'm still alive  ;D

Just send you a PM with my email address.

The compressor thing is a known problem with the mp-2, usually if you wait some time it will start to work. Sometimes it takes a minute, sometimes 30 minutes.
Title: Re: mp2 comp on no sound
Post by: rnolan on April 10, 2018, 03:08:53 AM
There's also a related (maybe) issue where you get no output at all unless you start the unit with a patch that includes the compressor, ie when you power down make sure the current patch has compressor on so when you power on again, that patch is loaded.  One of my units did this, though seems ok now after the noise mod.
Title: Re: mp2 comp on no sound
Post by: jnelson on April 18, 2018, 06:12:29 PM
so still no fix for the problem?  ok I plan on getting my old rack out soon and trying it again to see if it works, will update as soon as I check it out.
planning on doing at least 1 of the mods JMP has for sale to one of my mp1's as soon as I get a chance, I have not played guitar since my dad
passed away several years ago, not exactly sure why.. just happened, but am trying to get back into it and man it sure is different after taking such
a long break !
thanks for the help guys, cannot thank you enough !
John
Title: Re: mp2 comp on no sound
Post by: rnolan on April 19, 2018, 03:51:30 AM
Let us know how you go, condolences BTW  :facepalm: :wave: , I know the feeling.
Title: Re: mp2 comp on no sound
Post by: MarshallJMP on April 19, 2018, 05:03:14 AM
Well it seems to be a thermal problem, with mine if I heat up the area where the switching fet's are it works. At least with one of my MP-2's.
Title: Re: mp2 comp on no sound
Post by: rnolan on April 19, 2018, 06:07:53 AM
Hey MJMP, This is an interesting area...  seems to be age related (in one sense) but I have 4 MP2s and they are all fine (2 with noise mod, 2 stock), as Julius Sumner Miller said (if anyone remembers him) "why is it so  :dunno: "
Title: Re: mp2 comp on no sound
Post by: MarshallJMP on April 19, 2018, 09:03:34 AM
Well 2 of my mp-2's have this problem, the others don't.
Title: Re: mp2 comp on no sound
Post by: rnolan on April 20, 2018, 02:00:26 AM
Do you think it may be component related ? as in a batch of whatever bit(s) have gone off over time and they were only in a run of units  :dunno:
Title: Re: mp2 comp on no sound
Post by: vansinn on April 20, 2018, 02:45:45 AM
Never had that issue myself, but given how damn hot both the Analog Devises dual compandor and associated opamp runs due to +/- 24 volt rails, I'd start looking at those two chips.
Title: Re: mp2 comp on no sound
Post by: MarshallJMP on April 20, 2018, 08:41:44 AM
No it's a problem with the switching. It's the FET/ diode.
Title: Re: mp2 comp on no sound
Post by: vansinn on April 20, 2018, 01:15:55 PM
The engineer has know-how; the university-educated has know-why
Careful, when arguing against superior knowledge..
;)
Title: Re: mp2 comp on no sound
Post by: MarshallJMP on April 20, 2018, 01:23:55 PM
The engineer has know-how; the university-educated has know-why
Careful, when arguing against superior knowledge..
;)

 ;D  Well did some work on this problem before, so I know where it is, don't have a solution yet.
Title: Re: mp2 comp on no sound
Post by: jnelson on April 23, 2018, 06:41:37 PM
you don't happen to have one laying around that has the issue to replace parts on to see what works do you ?  just curious.
still haven't gotten around to digging the rack out, yea I'm slow, getting back into this is going to be harder than I anticipated grrrr
that and I have plenty of amps laying around etc....
but would like to get the ada stuff running again....
i do have a q on the 3tm for the mp1 though, does one do like the brown sound and
another do like a triple rectifier soundish?
since i have 2 mp1's i have been thinking about doing both of them with different mods
instead of using an axe fx...
John
Title: Re: mp2 comp on no sound
Post by: MarshallJMP on April 24, 2018, 03:29:46 AM
Well I already replaced all the parts surrounding the switching and nothing helped. My guess it's pcb thing, maybe it's conducting or something. Not sure.
Does the comp work after a while?
Title: Re: mp2 comp on no sound
Post by: vansinn on April 24, 2018, 07:58:48 AM
I guess this already has been tried, but anyways:
Has anyone tried following the logic/control signals with a scope to determine whether or not the compressor can actually be controlled?
And likewise follow the audio signals and the precision rectifier part of the compandor chip?
Title: Re: mp2 comp on no sound
Post by: rnolan on April 25, 2018, 01:43:11 AM
Hey John, plenty to read on 3TM and other MP1 mods in the MP1 threads.  MDRT makes a huge difference, really opens up the dynamics.  3TM (from what others say) is great if you want more gain but you loose the cleans. Eg MJMP uses 3TM for distorted stuff and a MP2 just for cleans.
What do you need/want them to do ?  what style etc.
Title: Re: mp2 comp on no sound
Post by: jnelson on June 23, 2018, 08:49:52 PM
sorry it took so long to reply, really busy at work lately, I work in hvac... I play a lot of maiden, dream theater style stuff and occaisionally some satch and vai
I have a simulclass 290 and a triple rectifier sitting around , but was hoping on going back to my ada stuff so I can use them with a switcher to go through a couple pre amps and have them routed through an effects unit or two..I've got a lot of stuff sitting around, some old digitech 2112 and a 2120 , valve fx and a few more , but only one art effects unit, a nitro I think its called, just want to use it for delays, reverbs and pitch shifting etc... actually I have 2 mp1's and 1 mp2
so I sure would like to use all 3 in a switching set up if I can figure out how to do it with no noise....im looking for someone locally that can do the mods for me, I have a guy that does a lot of 80's type stereo repair that I am sure can do the work, I just have to get in touch with him to see if he has time, if not I may have to send them out to someone , I live in Illinois close to Chicago, if you happen to know anyone that would help a lot
thanks for any and all help
John
Title: Re: mp2 comp on no sound
Post by: rnolan on June 24, 2018, 04:39:05 AM
Hey John, if you want to switch between a few preamps I'd suggest you use a small/medium mixer (eg a Eurorack UB2442 or later equivalent).  So all your units come into channel pairs 1/2, 3/4 etc keeps them all stereo.  Then use 2 FX sends to feed you Fx unit (L/R) and bring it back into a channel pair or 2 returns. So this will mix all your outputs together and let you use the same Fx across them all. Obviously Mixer out to amp > cabs.So the trick will be switching to each preamp input. You could use a small custom switch, I modified an old Peavy channel/reverb switch to be  an A, B, A+B by adding another jack and re-wiring the foot switches.  Also there are A/B switches available.  A simple solution would be mount 5 jacks and 4 foot switch buttons, so 1 jack is guitar in, the other 4 feed 4 different preamp inputs and the buttons just turn that feed on/off (so you can feed them all individually or in any combination)
However, if you do a parallel split of the signal to each preamp, you could do your switching by creating a bunch of patches on each preamp and mix and match which preamp(s) you want at any given time.Or you could do it switching preamp output pairs, easiest way to do this would probably be use a digital mixer you can control via midi  :dunno: to mute/un-mute channels