Fender M-80 Chorus

[nash56]

Hi everybody !! I'm a new user in this forum and I'm from Italy.

I've just bougth 2 days ago a fender amplifier M80 chorus 2x12" (black knobs ) and I'm really impressed from the power of this transistor ampli as well as from the great tunes.

Now I would like to have a simple information from other owners regarding the power, as putting the volume level less than position "1" I have an high volume, very difficult to use at home (too high). I don't know if this is problem of the volume pot that don't work well, or is normal for this little beast !!

I've used many time a Fender 75, valve ampl., but I play usually at 3-4 volume level.

Thanks a lot for your help !
Nash56

[techineer]

Does the volume suddenly jump from nothing to very loud before '1'? If you keep turning it up, does it continue to get louder?

If the volume jumps to maximum and remains the same for the remainder of the control rotation, it suggests a broken volume potentiometer.

[Gtr_tech]

It could be they used a linear taper pot. Thats a common complaint with the "hot rod" series amps....they go from nothing to balls out in a small turn of the master knob. IF thats the case replacing it with an audio taper pot will tame the beast.

[Steve L]

M-80 Volume Issue

That volume issue is very common on the Fender solid-state amps of that era.
The volume and gain pots in many of those amps are audio taper, however they are usually double pots, both connected as active gain controls on two stages, rather than the typical passive volume you commonly see in most Fender tube amps.

The easiest way I have found to tame the volume issue is to modify the circuit, usually by placing an appropriate resistor in parallel with the pot or the whole feedback circuit in the first gain stage. Sometimes you can do this in both stages.

The value of the resistor and where you put it depends on the circuit. I don't have an M-80 chorus schematic so I can't offer any suggestions right now.
There are other ways to modify the circuit as well and most of these will not affect the tone very much.

All that being said..........One thing to keep in mind before you modify anything is that if you are playing the amp alone in a quiet room, the high gain can be an issue.
However, if you gig with the amp in a live band situation, you will probably find that the way Fender did the gain is actually pretty good and you may want to leave it alone.

Steve