Planning an Express build - questions ...

[Tonegeek]

I have a few questions before I start a wreck build. These are in order of importance:

It appears there is an unused triode in the Express schemo. I would like to put in an FX loop and use this as the recovery amp. Anyone done this and what is the downside?

How important to the tone/stability is the ground scheme? No disrespect intended, but I much prefer the Dumble ground scheme over the wreck one as it looks like there could be ground loops doing it the wreck way. I can see some advantages though in that shorter wires are used which may outweigh the issues that loose connections, potential ground loops could cause. If I decide to stick with the TW scheme can Alpha pots tolerate solder on their backsides?

I might want to use an aluminum chassis that is 20X6.5X2.5 (standard Marshall I think). Is this advisable and again will it affect the tone and/or stability of the amp since the layout will have me using longer wires in some spots and routing a bit differently?

Also, could I use filter cap cans mounting externally instead of the internal bundled caps?

I have a feeling there are stability issues that dictate the wreck layout but it never hurts to ask. I definitely don't want to lose the TW magic by going too far off the reservation.

thanks

[jjman]

I'm currently trying to install a parallel effects loop for reverb/delay. In front those affects get "blocked" by the 3rd stage's clipping (in my theory.) I've confirmed it's not the output stage for sure. So I'm trying to install the loop after the 3rd stage to jump over the "blockage." Parallel type so I can send only a small portion of the signal to the effects unit, thereby avoiding overdriving it. I'm working with no point of reference since I can't find a schematic. I can't use the extra triode on mine since it's running trem. So far it looks like I can implement it and avoid overdriving the effect unit. Problem is will the return signal be strong enough to be heard adequately? I don't want to attenuate the dry side of the parallel paths since I finally got all the stages clipping when I want them to. I may just need to do that when the loop is in use. Work in progress....

With your spare triode you can bring it back up after the return. Where are you looking to put the loop? Parallel or serial? Line level or low level? Many say the send and the return should be buffered. I'm still ignorant on the impedance thing, regarding loops, which is why I'm willing to proceed with my attempt using no buffers.

[Tonegeek]

I'm currently trying to install a parallel effects loop for reverb/delay. In front those affects get "blocked" by the 3rd stage's clipping (in my theory.) I've confirmed it's not the output stage for sure. So I'm trying to install the loop after the 3rd stage to jump over the "blockage." Parallel type so I can send only a small portion of the signal to the effects unit, thereby avoiding overdriving it. I'm working with no point of reference since I can't find a schematic. I can't use the extra triode on mine since it's running trem. So far it looks like I can implement it and avoid overdriving the effect unit. Problem is will the return signal be strong enough to be heard adequately? I don't want to attenuate the dry side of the parallel paths since I finally got all the stages clipping when I want them to. I may just need to do that when the loop is in use. Work in progress....

With your spare triode you can bring it back up after the return. Where are you looking to put the loop? Parallel or serial? Line level or low level? Many say the send and the return should be buffered. I'm still ignorant on the impedance thing, regarding loops, which is why I'm willing to proceed with my attempt using no buffers.

I can almost guarantee a serial loop won't work without at least a common cathode triode stage to bring the level back up. Most FX don't have enough gain to drive a PI which seems to be the best place to do a loop. With a parallel loop there will be some losses to deal with as well but I know less about them. As you mentioned above, I used a single triode once to implement a serial loop on a Twin and it worked very well. I took the signal out right after the volume control, on to the effects and back into the triode which fed a master volume and then to the PI. The best loop I have ever used is on my Dumble clone. It has level controls going out and coming back and uses 2 triodes (search Dumbleator in the Dumble forum).