I think I found the problem in my Friedman Marshall

[romanianreaper]

As most of you know, I've been trying to figure out why I have a change in tone that comes and goes in my amp. The change is so hard to detect, that sometimes I'll sit there and think "is this sounding right?". The gain is still there but seems like the low end drops slightly and I get a harsh tone, even with the treble, mids, and presence almost at zero.

This amp was previously a Splawn-modded Marshall 1959SLP Reissue. Dave went inside the amp and added the Kitchen Sink Mod as well as reworking the board, etc. Earlier tonight, I was playing the amp and it was very quiet and had great low end, and a nice thick tone. A few hours later I plugged back in and was getting alot of noise and the tone was more harsh. I cleaned the preamp tube sockets (just in case) and tapped on the tubes to see if I could hear strange noises, etc. Everything sounded fine.

I have a footswitch that switches between the two input jacks in the amp. Essentially, this made my one channel amp a two channel amp so I can adjust gain and volume separately. I noticed that the footswitch cord was laying on top of the power strip I use for my equipment. I decided to unplug it and move it and when I did, the harsh tone went away and I had a solid tone again. There was still some noise but to be honest, I think alot of that is due to the wiring in my basement. Also, I don't currently have a headshell so the amp is on top of two 4x12s right near a light in the ceiling.

I'm not an electrical engineer so I can only speculate but seems to me that the footswitch jack might be hooked up in such a way that it is taking away some of the tone somewhere. The footswitch jack is located right next to the FAT, C45, and SAT switches on the back so I wonder if it might be interfering somewhere. I might be totally off base because like I said, I don't know much about how electronics work in an amp.

I do think that an output transformer down the road is still a good idea, especially in a Marshall Reissue amp that is known for a harsh, bright tone. I know Dave is super busy but if he gets an opportunity to jump in here, I'd be curious to see if he thinks that could affect it. Regardless I'm glad I'm not going crazy. By the way, the output transformer and choke in this amp are made by Dagnall. The power transformer is made by Mercury Magnetics.

 

[steve_k]

Is it wired as a two channel amp? Ditch the switch for a bit and check each input individually.

Did you leave the amp on run or standby for the few hours you were away? Tubes get hot, expand, loose some spunk.

Who installed the Mercury iron? That doesn't sound like something Dave would do, given better options for his amps' voicing.

You could also be over-biased.

You should email the big guy. He'll come back to you.


Steve

 

[RACKSYSTEMS]

The answer is no on the foot switch. Frankly I would send it back that way I can check it out. Could be many things.

 

[romanianreaper]

The answer is no on the foot switch. Frankly I would send it back that way I can check it out. Could be many things.

Thanks Dave for the reply. I didn't want to just send you an amp and just say "something is wrong with it". I've been trying to at least pinpoint what I'm hearing with possible locations on the amp, etc.

Thanks again man. - Mike

 

[romanianreaper]

Is it wired as a two channel amp? Ditch the switch for a bit and check each input individually.

Did you leave the amp on run or standby for the few hours you were away? Tubes get hot, expand, loose some spunk.

Who installed the Mercury iron? That doesn't sound like something Dave would do, given better options for his amps' voicing.

You could also be over-biased.

You should email the big guy. He'll come back to you.


Steve

The Mercury was something that Scott installed (I believe). There is a sticker on the transformer that says something along the lines of (Mercury for Splawn Amps) or something like that. I did not have any transformer changes when Dave modded the amp. The Dagnall stuff should be the way it came from the factory.