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Author Topic: Gain drop off  (Read 6903 times)

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DannyjoeCarter

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Gain drop off
« on: Time Format »

Well my main Holy Grail MP-1 is having issues now  >:(
After about 45 minutes of playing the gain seems to drop off from a very high gain Bogner Uberschal type of drive to a stock JCM 800 and it's driving me nuts! >:D Anyone ever have this happen and what could be some suggestions as t why this could be happening before I box this up and ship it off to MJMP?

 It doesn't make any noise nor does the volume drop but it just gradually gets less and less gain and does this in about 5 minutes once it starts around 45 minutes into playing.  :dunno:
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Kim

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Re: Gain drop off
« Reply #1 on: Time Format »

The first things to always check (because it might be the easiest as well) is to try another pair of tubes in there and see if that does the trick.  Then good clean jack contacts, front volume pot, etc.
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rnolan

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Re: Gain drop off
« Reply #2 on: Time Format »

Hey DjC, gain drop but not volume smells like the tube circuit, and as Kim said it may be the tubes (what have you got in that one ?).  Now 45 mins in seems heat related (to me, my guess).  I've had some issues with MP-2 (which get very hot) being close to other MP-2 or MB-1 in my studio rack, not necessarily quite the same symptoms but also similar. We had/did a few post(s) before regarding heat (have a dig/search around here). Various members use a fan to keep their rig cooler.  Now, you have a tube poweramp = lots of heat (which rises) and can affect the tubes in the MP-1 (though you have that 2RU Mesa face plate (maybe take that out for better heat dissipation ?).  My TS100 is in a separate 2 RU rack (mostly because it's heavy  :facepalm: ) but also to keep the heat out.  Easy test though, take it all out of the rack (at least the poweramp!), set it up with plenty of distance and ventilation etc on a bench or somesuch and see how that goes.

But may be as simple as tubes  :dunno: .
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MarshallJMP

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Re: Gain drop off
« Reply #3 on: Time Format »

Tubes would be my first idea too.
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Samuraipanda

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Re: Gain drop off
« Reply #4 on: Time Format »

Has this happened more than once?

The reason I ask is I experienced gain drop once but it was just the battery in my wah sputtering out. Do you have anything battery operated in front of the MP1?
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DannyjoeCarter

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Re: Gain drop off
« Reply #5 on: Time Format »

Thanks for the responses guys!
 It does seem like it may be the original ECC83s that it came with, which I LOVE the tone of those tubes!!!!
 I have popped in a new set of JJs and I am still waiting to see if the gain drop will happen.

Now as several of you have mentioned about heat issues - I don't think that is a problem ( see attached photo ) but I will report back after a little more time.

 I will say I'm not sure I like the tone and attack of the JJs and much more prefer the stock tubes that came in that unit.
I did see on this forum awhile ago about a good Chinese replica of they originally put into the MP-1s - anyone have any suggestions?  :)
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rnolan

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Re: Gain drop off
« Reply #6 on: Time Format »

Hey DjC, SC says that TADs are the closest to the original bottles, and IIRC that's been confirmed by others (not that I don't trust SCs opinion, he started me on the Mullard LP road way back LoL which is what I would put in it).  Now you don't have much clearance on top of the MP-1 and the 4 output tubes in the boogie are generating allot of heat (which rises) and the Mesa face plate restricts airflow (it looks cool but isn't helping).  Does it get cold where you are ? Bloody hot here right now (41 C today ~106 F). All that said, my MP-1 rack (when I had it) never gave any problem with the B200s down the bottom (and they get hot).
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Studio Rig: MP2/MB1 > Eurorack UB2442FX-Pro > TC M-One XL > Behringer Truths (with Truth Sub) / QUAD ESL 63s
Live Rig: MP2/MB1 > Alesis Quadverb > Alesis Midiverb 4 > Yamaha AM802 > B200s/Carvin TS100/DCM200L > ADA Split Stacks/Mesa P112s

DannyjoeCarter

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Re: Gain drop off
« Reply #7 on: Time Format »

Hey DjC, SC says that TADs are the closest to the original bottles, and IIRC that's been confirmed by others (not that I don't trust SCs opinion, he started me on the Mullard LP road way back LoL which is what I would put in it).  Now you don't have much clearance on top of the MP-1 and the 4 output tubes in the boogie are generating allot of heat (which rises) and the Mesa face plate restricts airflow (it looks cool but isn't helping).  Does it get cold where you are ? Bloody hot here right now (41 C today ~106 F). All that said, my MP-1 rack (when I had it) never gave any problem with the B200s down the bottom (and they get hot).

 Well the Mesa has a fan that blows like a turbine and even after an hour of playing the very top of the unit is warm to the touch but never hot Richard.
Also that's great info on the TADS!!! Also from all the MP-1 we have purchased we have a cache of original MP-1 red stamped ECC83s and from the look and construction appear to be Chinese tubes so tomorrow I'm going to test a few of those because currently with the JJs I'm still losing gain now after about 15 minutes   >:D
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rnolan

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Re: Gain drop off
« Reply #8 on: Time Format »

Mmm, well good news re boogie fan  :thumb-up: (you can fry an egg on top of a B200s after an hour LoL), 15 mins till JJ drop in gain = something else is getting warm/hot and fading  :dunno: . You could try removing the MP-1 from the rack and sit it on top (just to rule it out heat wise ? and if you are swapping tubes....).
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Iperfungus

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Re: Gain drop off
« Reply #9 on: Time Format »

Hey Danny...I've TADs on my MP-1 right now (7025s V1 and 7025 V2, both Highgrade selection) and they sound great!
Very, very close to original "red stamp" chinese 12AX7-A the unit arrived with (great tubes, indeed).

I'm going to test Ruby selected JJs there... ^^

By the way...about the gain drop issue...did you already attempted to connect regular outputs to power amp instead of send?
Could it be the the issue arises from something going wrong on send jack connector and/or level pot?
Have a try...
« Last Edit: Time Format by Iperfungus »
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Rack stuff from Hell:

ADA MP-1 (modified by MJMP)->TC Electronic G Major->Marshall Valvestate 8008 power amp

Marshall JMP1->Alesis Quadraverb GT->Advance Tube Technologies TA '70 tube power amp

Zoom 9150->Marshall Valvestate 8004 power amp
Zoom 8050 MIDI Controller
Zoom FP01 Expression pedal

Behringer FCB1010 MIDI controller

Blackstar HTV 212 stereo cabinet with 70/80 Celestion speakers

Amps:

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Stomps, stomps, stomps...and stomps (Bogner rules!):

TC Helix phaser, Xotic RC Booster, TC Sentry noise gate, Bogner Ecstasy Blue, Bogner Ecstasy Red, Mad Professor Royal Blue Overdrive, Sonic Research Turbo Tuner, TC Flashback delay

Guitars:

2018 Arrogantia Pandora Vendetta 24 HH Trem-1987 PRS Custom-1988 Fender Strat Plus-2016 Custom assembled Fender Strat-2013 Gibson SG Standard-1995 Gibson Les Paul Studio-1991 MIJ Ibanez RG570FM TB-2016 MIJ Ibanez RG655M SPM-2002 Bruno Traverso Custom "Tommy" Silky-2017 Kramer Baretta Special-2010 Simon & Patrick Woodland CW acoustic

rnolan

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Re: Gain drop off
« Reply #10 on: Time Format »

Hey Max, interesting point you make re using send as main out and definitely worth a try (as you suggested), DjC is the first (as far as I know) to use the Fx send exclusively as the main out (except for trouble shooting).
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Studio Rig: MP2/MB1 > Eurorack UB2442FX-Pro > TC M-One XL > Behringer Truths (with Truth Sub) / QUAD ESL 63s
Live Rig: MP2/MB1 > Alesis Quadverb > Alesis Midiverb 4 > Yamaha AM802 > B200s/Carvin TS100/DCM200L > ADA Split Stacks/Mesa P112s

DannyjoeCarter

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Re: Gain drop off
« Reply #11 on: Time Format »

Hey guys thanks as always for all the suggestions on this!
I spoke with MJMP and he made a great point regarding this so I thought I would share -
Neither the outputs or fx send affect the gain structure and all come after so it had to be on the preamp tube board or the tubes!

 So now as of today this is getting fun again!!!!  :banana: I have replaced the preamp tubes and the gain drop off has stopped!!!!!  :banana-trip:
Wicked tone again from my Holy Grail  :headbanger:

 But here is what is interesting - Of the 5 somewhat working MP-1s and the one on it's way to MJMP, I have collected the tubes from them and done various swaps. To my ears the original red stamped ECC83M sound incredible and I am going to build a collection of those! Yes I have several sets of JJs but to me they real REAL solid and rigid but almost too stiff for my playing taste. So those old red ones are the magic for me and MJMP suggested I contact Doug's tubes for a similar replacement.

 Anyone else still using their original red stamped ECC83Ms?
If not - please PM me seriously, I want to buy them from you!!!  :headbanger:
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Systematic Chaos

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Re: Gain drop off
« Reply #12 on: Time Format »

Hey DJC,

the ECC83M is a rebranded Chinese 12AX7A (info from Marshall R&D who used the ECC83M around that time as well). The closest (and I mean real close) new tube you can get is the TAD 12AX7A-C (RT001)

The Chinese 12AX7A (Shuguang plant) was widely used in a gazillion of guitar amps/manufacturers in the 80s and went through some revisions (rev A - rev C).
TAD has their tubes built by the Shuguang plant as well but to TAD specs...and for the RT001 they took all the best bits and pieces of the Chinese 12AX7 and "designed" them into one tube which is their best-seller 12AX7A-C. You´ll get the sound of your beloved ECC83M on tiny spoonful of steroids.


SC
« Last Edit: Time Format by Systematic Chaos »
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Iperfungus

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Re: Gain drop off
« Reply #13 on: Time Format »

Original tubes on my MP-1 were red stamped 12AX7A...100% chinese tubes, no brand on them.
Very good tubes...and I will keep them!

The same tube (but with nothing stamped on it) was in the Zoom 9150 (I will keep it as well).

I agree about TADs...I put there a couple of 7025, as I already wrote...and they sound very, very close to originals.

But I'll try JJs soon...
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Rack stuff from Hell:

ADA MP-1 (modified by MJMP)->TC Electronic G Major->Marshall Valvestate 8008 power amp

Marshall JMP1->Alesis Quadraverb GT->Advance Tube Technologies TA '70 tube power amp

Zoom 9150->Marshall Valvestate 8004 power amp
Zoom 8050 MIDI Controller
Zoom FP01 Expression pedal

Behringer FCB1010 MIDI controller

Blackstar HTV 212 stereo cabinet with 70/80 Celestion speakers

Amps:

Rivera Pubster 25
Blackstar Fly 3 amp + external speaker

Stomps, stomps, stomps...and stomps (Bogner rules!):

TC Helix phaser, Xotic RC Booster, TC Sentry noise gate, Bogner Ecstasy Blue, Bogner Ecstasy Red, Mad Professor Royal Blue Overdrive, Sonic Research Turbo Tuner, TC Flashback delay

Guitars:

2018 Arrogantia Pandora Vendetta 24 HH Trem-1987 PRS Custom-1988 Fender Strat Plus-2016 Custom assembled Fender Strat-2013 Gibson SG Standard-1995 Gibson Les Paul Studio-1991 MIJ Ibanez RG570FM TB-2016 MIJ Ibanez RG655M SPM-2002 Bruno Traverso Custom "Tommy" Silky-2017 Kramer Baretta Special-2010 Simon & Patrick Woodland CW acoustic

Iperfungus

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Re: Gain drop off
« Reply #14 on: Time Format »

I have replaced the preamp tubes and the gain drop off has stopped!!!!!  :banana-trip:
Wicked tone again from my Holy Grail  :headbanger:



 :thumb-up:
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On the run again!

Rack stuff from Hell:

ADA MP-1 (modified by MJMP)->TC Electronic G Major->Marshall Valvestate 8008 power amp

Marshall JMP1->Alesis Quadraverb GT->Advance Tube Technologies TA '70 tube power amp

Zoom 9150->Marshall Valvestate 8004 power amp
Zoom 8050 MIDI Controller
Zoom FP01 Expression pedal

Behringer FCB1010 MIDI controller

Blackstar HTV 212 stereo cabinet with 70/80 Celestion speakers

Amps:

Rivera Pubster 25
Blackstar Fly 3 amp + external speaker

Stomps, stomps, stomps...and stomps (Bogner rules!):

TC Helix phaser, Xotic RC Booster, TC Sentry noise gate, Bogner Ecstasy Blue, Bogner Ecstasy Red, Mad Professor Royal Blue Overdrive, Sonic Research Turbo Tuner, TC Flashback delay

Guitars:

2018 Arrogantia Pandora Vendetta 24 HH Trem-1987 PRS Custom-1988 Fender Strat Plus-2016 Custom assembled Fender Strat-2013 Gibson SG Standard-1995 Gibson Les Paul Studio-1991 MIJ Ibanez RG570FM TB-2016 MIJ Ibanez RG655M SPM-2002 Bruno Traverso Custom "Tommy" Silky-2017 Kramer Baretta Special-2010 Simon & Patrick Woodland CW acoustic
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