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[Chamai]

Need some help guys
When i mix some chorus with distortion, i get this weird swelling compressed sound on random notes. it almost sounds like a tremolo. this only happens when i use output B to my power amp. anyone had similar experiences with this issue?

right now im using output A, everything works great. but using output B sounds weird with chorus in the mix.

[rnolan]

See other posts  from both me and MJMP, seems if you want to run mono with chorus (assuming what you are doing ??) go with A out of MP1 ?

[Chamai]

will do~ thanks for the reply. i am a complete noob with this pre amp. i just picked it up a few days ago. still a lot to learn. i will be picking up a 2nd one as a spare in the near future as well.

[rnolan]

Hey Chamai, run it in stereo, it will blow you away, these (MP1/2) are the best guitar preamps on the planet IMHO 

[Chamai]

ah damn, what a hassle. started my ada up today and i got this weird hollow sound and gain is gone. need tubes is all i need hopefully

[rnolan]

Bummer  , hope it's just tubes but while they do sometimes just die, they usually just go off a bit over a long period of time and you don't really notice until you put in new ones.  Plenty of chat on here about tube choice, very subjective area.  Based on some other posts we (MikeB and I) are going to try a Mullard short plate in V1 position and a boogie STR (probably a JJ) in V2 in his MP1.
Anyway let us know how you go fingers crossed it's just tubes but if not there are some very good people here who can help work out whats wrong and how to fix it.
Cheers R

[Chamai]

swapped out the old tubes and put in some new groove tubes. my ada is good as new. i think the previous owner never changed the tubes. there is no brand or anything written on the tubes.

[rnolan]

Fantastic  very glad to hear 
That sounds right, the original Chinese tubes just had red writing 12AX7A IIRC and no brand, so they would be very old. Also worth doing is EPROM upgrade v2.01 is latest available (http://www.marshalljmpmodshop.net/miscellaneous_parts_and_replacement_tubes.htm).  It will display version on start up (or sticker on top of eprom). It's an easy replacement.
Check the tube discussions for other tube alternatives (for you 2nd MP1), although GT do a good job testing and re-branding various tubes (there's a few good articles posted as well about the different tube manufacturers and tester resellers).  Do the GTs say where they are made ?
Cheers R