Is it safe?

[titus]

Hi,

Is it safe to jumper the channels on a silverface Fender
amp (Deluxe Reverb specifically). I just read about
it and always thought it was not good for the amp.
I just read that the controls between the channels
become interactive and you can dial in the distortion
you want. Why haven't I seen this more?
Sorry for the stupid questions.
I just don't know.....and curious now.

Thanks,
-Titus

[eryque]

It is safe, but won't do anything particularly good. Because of the extra gain stage in the vibrato channel, the two channels are out of phase. Jumpering them will make your sound thinner, not beefier.

I could swear that one of Gerald Weber's books describes how to add reverb to the normal channel, which migh put the two channels in phase with each other and allow jumpering. I met a guy at a jam once who jumpered his channels, and when I asked him how he got the two channels in phase he said it was jumpered internally. I took this to mean that he had no idea what he was talking about :)

[Dacious]

No. You can do this to a Tweed Deluxe which has four inputs and two channels, or a Silverface Bassman where the two channels are in phase. You will do no harm, but the sound will as Eryque says, be thinner. You could put the input through a device with stereo outs, like a delay or chorus and put the outputs through both channels.

[5965]

The sound is not necessarily thinner.

Which frequencies are cancelled depend entirely upon what circuit is used as the primary and how you balance the channel volumes. When the volumes and tones are near equal (not necessarily by the numbers, but by the sound) there will be noticeable cancellation.

However, if you have the volumes offset (one channel on 2 and the other on 4, or whatever) there are some interesting sounds to be gotten that are not at all thin. It's also a way to clone reverb/tremolo to the Normal channel, and it gives a form of tonal control over those two functions that is otherwise absent.

Some people find it useful. Try it for yourself and see what you think. It won't hurt the amp.

[zook]

Originally Posted by Dacious

No. You can do this to a Tweed Deluxe which has four inputs and two channels, or a Silverface Bassman where the two channels are in phase. You will do no harm, but the sound will as Eryque says, be thinner. You could put the input through a device with stereo outs, like a delay or chorus and put the outputs through both channels.

I have jumpered the channels on Bassman heads and they sound great. They do not have the same number of gain stages on each channel, however. The bass channel has three stages, the normal channel only two. There is an unused 1/2 a 12AX7 in the amps.

Winnie

[gls500]

Originally Posted by eryque

I took this to mean that he had no idea what he was talking about :)

That nearly made me spit out my drink :D

[Bluesbob]

I played a place Friday night where last time I used my '73 DR. Everybody said my playing had more muscle, but I knew it was because I was using my '69 Bassman 2X10 combo with the channels jumpered. Winnie, are you saying that the bass and normal channels are out of phase in my bassman? If so, that shoots down that theory.