Grateful Dead Music Forum

I was just wondering if there are any drawbacks to wiring a twin so it has Reverb on channel 1 as well as channel 2?

Does it negatively effect the amp in any manner? Will it in any way change any of the standard channel 2 properties?

Just really curious about this mod.

also,
I have a friend who has an old twin that has reverb on both channels (which got me thinking about mine), but he swears nothing was done to accomplish that. Is there a state of failure on the amp somewhere that could unintentionally cause reverb to be added to channel 1?

I just did this to my Twin, and it worked great! If you need instructions let me know. Also, a really great place to get deeper info on this matter would be at Hoffman Amps Forum.

Chris

jeffm725 wrote:also,
I have a friend who has an old twin that has reverb on both channels (which got me thinking about mine), but he swears nothing was done to accomplish that. Is there a state of failure on the amp somewhere that could unintentionally cause reverb to be added to channel 1?

it could be a different twin than yours. I just picked up a reverb II twin, and it has reverb on both channels

erock wrote:

jeffm725 wrote:also,
I have a friend who has an old twin that has reverb on both channels (which got me thinking about mine), but he swears nothing was done to accomplish that. Is there a state of failure on the amp somewhere that could unintentionally cause reverb to be added to channel 1?

it could be a different twin than yours. I just picked up a reverb II twin, and it has reverb on both channels

yeah, understood, but in this case, mines is a 68, his is a 70, both are blackfaced....shouldnt be a big difference there.

Imagined Days wrote:I just did this to my Twin, and it worked great! If you need instructions let me know. Also, a really great place to get deeper info on this matter would be at Hoffman Amps Forum.

Chris

Did you notice any difference to channel 2 when you did this, or did channel 2 perform the same as it did pre-mod?

Ch. 2 is the same.

jeffm725 wrote:I was just wondering if there are any drawbacks to wiring a twin so it has Reverb on channel 1 as well as channel 2?

Does it negatively effect the amp in any manner? Will it in any way change any of the standard channel 2 properties?

Just really curious about this mod.

While this is a very popular mod, I don't love it as I do see maybe a minor drawback. The common method is to move the output wire from the Normal channel right to where the signals can meet at the node where it goes to the reverb send and also the 3.3M mix resistor. While this works ok, the design issue I see here is that there are no mix resistors to keep each channel from interacting and loading down the other. They're just hard-wired to eachother. Generally when you mix, you use a matched pair of resistors to help isolate the two channels a bit. So it's not a perfect approach. There could be some mods to improve upon it, but then you're messing with that pure reverb channel (aka Vibrato) preamp signal path.

B

I kinda like having the non-verb channel on mine - when we're low on channels I run my guitar synth into that side since it doesn't need reverb.

It's a TRRI . . . Brad, I know . . .

tcsned wrote:I kinda like having the non-verb channel on mine - when we're low on channels I run my guitar synth into that side since it doesn't need reverb.

It's a TRRI . . . Brad, I know . . .

Couldn't you TRRI just a little bit harder?

fwiw, I've got no operational or tonal problems gigging with Pedal Steel in Ch1 and Guitar in Ch2, with reverb on both channels.
'Maybe not for eveyone but for my needs the advantages outway the drawbacks. I just don't hear a problem. Both channels sound great now!

tigerstrat wrote:

tcsned wrote:I kinda like having the non-verb channel on mine - when we're low on channels I run my guitar synth into that side since it doesn't need reverb.

It's a TRRI . . . Brad, I know . . .

Couldn't you TRRI just a little bit harder?

well played tigerstrat, well played

SarnoMusicSolutions wrote:

jeffm725 wrote:I was just wondering if there are any drawbacks to wiring a twin so it has Reverb on channel 1 as well as channel 2?

Does it negatively effect the amp in any manner? Will it in any way change any of the standard channel 2 properties?

Just really curious about this mod.

While this is a very popular mod, I don't love it as I do see maybe a minor drawback. The common method is to move the output wire from the Normal channel right to where the signals can meet at the node where it goes to the reverb send and also the 3.3M mix resistor. While this works ok, the design issue I see here is that there are no mix resistors to keep each channel from interacting and loading down the other. They're just hard-wired to eachother. Generally when you mix, you use a matched pair of resistors to help isolate the two channels a bit. So it's not a perfect approach. There could be some mods to improve upon it, but then you're messing with that pure reverb channel (aka Vibrato) preamp signal path.

B

Brad,
Thanks!
That is the kind of information that is very helpful. I thought there may be some kind of price to pay with that mod. I need to check my buddies and see if that is how his is done. I wouldnt mind undoing it if he lets me, just as a test to see if it makes his second channel open up a bit, because my second channel sounds so much better than his does and I wondered if it was because of the reverb mod on both channels. From what I gather from your statement, that could be a possibility if the channels are "loading down the other".

jeffm725 wrote: Brad,
Thanks!
That is the kind of information that is very helpful. I thought there may be some kind of price to pay with that mod. I need to check my buddies and see if that is how his is done. I wouldnt mind undoing it if he lets me, just as a test to see if it makes his second channel open up a bit, because my second channel sounds so much better than his does and I wondered if it was because of the reverb mod on both channels. From what I gather from your statement, that could be a possibility if the channels are "loading down the other".

Let us know what you find. The additional loading that comes from the hard-wired combining of the two channels to share the reverb will definitely alter the loading that each channel is used to seeing. This loading may be something you could hear. It's probably not a drastic thing and generally works like a charm for most people, but for those of us wanting the pure and accurate JG reverb channel, I'd be hesitant to add that ch1 to the path via this method.

B