My amp has a subtile distortion even clean!?

[arnek85]

Hey everybody,

I have got a Mark III blue stripe and since last week it adds a slightly subtile distortion to the signal. Even at super clean settings.

Anyone an idea? I guess it's a problem in the preamp section.

Cheers!

 

[Promethean]

Could just be a bad tube... tried swapping one at a time?

There was a known reverb glitch which caused a slight distortion in the background of my Purple Stripe at any clean setting if reverb was used. Mesa sent me a note with a fix - an extra earth connection. Dont know if the Blue Stripes had same problem but might be worth checking re. ‘Mkiii reverb glitch’

 

[GJgo]

Could also be time for new caps.

 

[darkbluemurder]

My understanding was that the reverb glitch was fixed in the Blue and Green Stripes.

I also believe that we discussed the power supply caps in another thread.

Other potential causes for what you describe could be a faulty optocoupler. The lead circuit has one at the input and one at the output. If either of them does not break the circuit clearly when in clean mode you could have spill over. Try the following: put the amp in clean mode, play a guitar and turn the lead drive and master. Does the distortion you hear increase? If no, the optocouplers should be fine.

Good luck,
Stephan

 

[GJgo]

When Mike B. serviced my blue stripe he performed the reverb mod to it.

 

[darkbluemurder]

In that case I stand corrected.