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

Please login or register.

Login with username, password and session length
Advanced search  

News:

Board added for "ADA Cab Sims" in Other ADA Gear (coz El asked for it LOL)

Pages: [1]   Go Down

Author Topic: MP 2 squeal noise mystery *resolved*  (Read 467 times)

0 Members and 1 Guest are viewing this topic.

jimnastic

  • Newbie
  • *
  • Offline Offline
  • Posts: 14
MP 2 squeal noise mystery *resolved*
« on: Time Format »

Hi - a quick bit of background, I'm a guitarist who like to dabble with circuits (like the DIY pedals and a bit of amp modding) rather than a maintenance type person, so I MIGHT have just got lucky...So I write the below in case anyone has squeal noises with a MP2...

I've been playing guitar for nearly 40 years, and have been trying to collect tones (strat + fender style amp = knoplfer, add DIY Timmy gives Mayer-ish, add a RAT gives Beck, get the idea?) but never got the 80's/90's rawk tones nailed, so I've been on the watch on ebay for a MP1 or MP2. I finally got an MP2 from ebay for £150, and I was really pleased...until I plugged it in... TERRIBLE whining noise, like a high pitched squeal which changed pitch when I moved patches. I had no idea whether the patches were working as designed as it was so bad. Some ebay exchanges with the seller, and we agreed a partial refund and I'd start digging in. So, I opened it up...dear lord...it's a beast inside. Looked at the circuit diagrams on the Vault and started work (BTW anyone who thinks these units are a "bit digital" are soooooo far from reality, analogue paths all over the circuit board!).

I prodded around for a bit, and started to lose faith but spotted TR202 appeared to be "wah level" so tweaked it to the "out" position. THE NOISE WENT AWAY! With some emails with the mighty MJMP I then started swapping the opamps (U205 U207) from the wah circuit around, which made no difference (once I tweaked the TR202 pot back again). I then removed U205 and magically all sounded good! This made sense to a degree because it sounded a LITTLE like a wah on "fully treble" creating the noise. This was odd because the wah was set to "off" in the menu...maybe it had gone high...Nope....

Playing with my now "squeal free" MP2 I realised it was not changing the voicing. Weird...the patches were recalling other things (chorus, eq, distortion) but voicing on the tube was not affected. Now, another email ping pong with MJMP revealed that the voicing changes are done across the valve stages controlled by the TC9164 (U202). Looking across pins 17 to 27 revealed they were (nearly) all locked to 10v which wasn't changing on the program changes and therefore not working the FETS correctly. A quick check that the control from U102 and U103 was making its way to CLK, DAT and STB inputs of the TC9164 chip, and I put an order in for a replacement at Nikko Electronics LTD.

Dropping the new TC9164 chip in made everything work as designed (INCLUDING the Wah circuit, which when I was checking the pins on the original TC9164 were also locked "on").

So if your MP2 sqeals, check if tweaking TR202 changes it...

So, thanks to MJMP for his help, the ebay bargain MP2 works a treat; an AMAZING tool for cleans, auto wah funk, mid gain classic rock and Nuno style shredding! I'm beginning to question whether the whole "boutique pedal" movement is a step back, as these old units provide so much versatility, control, convenience etc, that I think the guitar world may have been moving in the wrong direction for the last few years (although i do love my Timmy pedal!).
But then you guys already know this, and it's our secret!!
 
Hope this helps someone!
Logged

Dante

  • Administrator
  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 1448
  • Nothing more uncommon than common sense
    • The Best Cover Band In Sacramento
Re: MP 2 squeal noise mystery *resolved*
« Reply #1 on: Time Format »

Jimnastic,

Thanks for the tip  :thumb-up:

I certainly agree that the rack gear was the pinnacle of guitar rigs, but hey...who ya askin? Keep the secret, let them tap dance all dang night to shut off the solo boost at the same time as the delay/chorus/octaver - haha. We will continue to push ONE button and run. Oh, and WELCOME TO THE DEPOT!

Logged
ADA Gear: MP-1 Classic | MP-2 | Viper Combo | MicroTube 200 | MicroFet | MXC w/Quad Switch

jimnastic

  • Newbie
  • *
  • Offline Offline
  • Posts: 14
Re: MP 2 squeal noise mystery *resolved*
« Reply #2 on: Time Format »

Thanks Dante!

Now this beast is being used in anger on the Kent (UK) pub rock community, my next job is to write some Arduino midi code to get full use out of it (until a suitable midi controller comes up!)

Logged

rnolan

  • Administrator
  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 4830
Re: MP 2 squeal noise mystery *resolved*
« Reply #3 on: Time Format »

Hey jimnastic, great tips  :thumb-up: many thanks for that and welcome  :whoohoo!: . When you retube your MP2, I highly recommend some Mullard long Plate re-issues, they work really really well in MP2s  >:D
Logged
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
Pages: [1]   Go Up