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

ADA Preamps => MP-1 Classic => Topic started by: Scheshevski on February 16, 2017, 08:55:12 AM

Title: Distortion problems w/ ADA MP1 Classic
Post by: Scheshevski on February 16, 2017, 08:55:12 AM
Hi, I was wondering if anyone know of, or have had any problems with the Classic regarding low distortion levels, and have any solutions to those problems? I own or have owned the original MP1, one 3TM and one Voodoo mod and a Marshall JMP-1. I have also tested at least three other MP1s and the distortion on my Classic is nowhere near the levels of any of the other gear, not even close. Without some boost, it is "dead as disco". With a distortion pedal, the thing comes alive. I'm not talking any heavy distortion since I usually use ODs 1 & 2 at 4.0-5.0 on the original, but the Classic doesn't produce even that level of distortion.

Another thing; when using the Clean Tube channel, there is a "hissing sound" until volumes is up at 9.5 and more. It isn't possible to use at levels under 9.5 due to the "hiss".

Any thoughts?
Title: Re: Distortion problems w/ ADA MP1 Classic
Post by: MarshallJMP on February 16, 2017, 09:14:48 AM
Start with replacing R151.
Title: Re: Distortion problems w/ ADA MP1 Classic
Post by: Scheshevski on February 16, 2017, 11:27:08 AM
They said the colors should be Brown, Green, Yellow and Gold for the 150K part buy I don't seem to find such combination. Am I missing something?
Title: Re: Distortion problems w/ ADA MP1 Classic
Post by: MarshallJMP on February 16, 2017, 11:48:07 AM
R151 is a 180k, brown gray yellow gold, you can see it next to the green cap.
Title: Re: Distortion problems w/ ADA MP1 Classic
Post by: Scheshevski on February 17, 2017, 04:26:53 AM
Alright, I changed the part and it didn't help. The hiss is still there and the gain is not much to write home about. :-(
Title: Re: Distortion problems w/ ADA MP1 Classic
Post by: Iperfungus on February 17, 2017, 04:49:45 AM
Did you test different tubes there already?
Title: Re: Distortion problems w/ ADA MP1 Classic
Post by: Scheshevski on February 17, 2017, 05:03:08 AM
Yes, changing the tubes didn't work. :-(
Title: Re: Distortion problems w/ ADA MP1 Classic
Post by: MarshallJMP on February 17, 2017, 12:23:50 PM
What's the voltage on the testpoint next to Q34 ( says 200V)?