Attempted Simplification of the Express - Non Traditional

[martin manning]

Looks fantastic rj! Maybe it's time to drop the "attempted" from the thread title? ;^)

[jeff12]

Nice build. Looking at the pictures close, it goes to 11....

[M Fowler]

Today I added a 1M PP switched pot for the bass. It switches in and out the 22uf/25v cap on V1a bias. Even with 6.8m resistor there is a loud pop as the cap discharges to ground. I like what I am hearing without this large bypass cap.

I reduced the preamp tubes V1/V2 to 12AY7. V3 is 12AX7 and JJ EL34L's.

Next will be a PPIMV. I am thinking about going back to presence pot and add a cut control.

Mark

[martin manning]

I added an effects loop by taking the signal into the third gain stage and running it out a jack on the rear panel and then back to V2. It appears to work just fine but I only had one pedal here (80's vintage "real tube" distortion pedal) to play with this afternoon so I'm not entirely sure if it's going to work the way I want it to. I wanted to get away from adding reverb or chorus at the input since I like to use those pedals occasionally. There isn't much good history with effects loops in an Express so consider this an experiment until it proves itself out one way or the other.

rj, you know you have an unused triode right there that could easily become a send buffer stage. That'd keep the FX from loading down the second stage and allow adding a send level control... but now we're recomplicating it aren't we?

[dorrisant]

Martin,
Please continue to complicate!

This is turning out to be an a la carte type thing... pick the mods you like. Throw the mods at it and see what sticks... this is great.

Tony

[fishy]

RJ,
Looks great.
I really like the fact that it still has a nod to the original in the pcb layoutbut simplifies the build.
The effects loop is an interesting topic for sure. The link below has some info which suggests it can be done. Maybe not as good as a wet /dry setup but that is not an option for some and it also depends on how you use the amp.

https://tubeamparchive.com/viewtopic.ph ... ffect+loop

[RJ Guitars]

Looks fantastic rj! Maybe it's time to drop the "attempted" from the thread title? ;^)

Thanks Martin and all you other guys for the encouraging words. It has been successful beyond my expectations in simplifying this amp build and less painful than i originally feared. Since what a Wreck sounds like involves a very limited number of amps and actual witnesses, I think we need more of these out there to see how much they sound like the real deal. The first four have given us a good indication that the concept is legitimate. Once we get the Colossal report we'll know if we want to move on to the next rev... I expect he is sucking solder fumes since I know he got his Mouser parts on Friday... No hurry, just looking forward to your magical touch and the new ideas you bring to the table.

rj

[RJ Guitars]

I like the buffer idea for the effects loop... I've heard this suggestion from two independent sources today and have to agree, it's a good use for that extra triode... I might have to make a little more room on the board to add this in, it seems like a good idea.

I am also curious about this power scaling by regulating the heater voltage. If not a rheostat on the AC, is there any reason not to convert the the heater power to DC and use a solid state voltage controller (VVR) as a controller? It might be worthwhile to get rid of any extra AC hum coming from the heaters.

I am also curious if resistively controlling the heater voltage is a safe and effective power scaling option, what is the down side from using a variac to dial down the whole amp? I'm not necessarily supporting this as a good idea, but rather trying to see why it's not a logical option?

rj

[RJ Guitars]

Today I added a 1M PP switched pot for the bass. It switches in and out the 22uf/25v cap on V1a bias. Even with 6.8m resistor there is a loud pop as the cap discharges to ground. I like what I am hearing without this large bypass cap.

I reduced the preamp tubes V1/V2 to 12AY7. V3 is 12AX7 and JJ EL34L's.

Next will be a PPIMV. I am thinking about going back to presence pot and add a cut control.

Mark

I am thinking that in Merlin's book he suggests that the first gain stage needs to be fully bypassed (22uF is plenty) to reject heater hum in that 1st stage? Do you hear any added hum with that cap out?

I am getting the feeling that you are not a gain loving maniac based on these amp mods. Let us know how pristine the clean sounds remain as you crank this thing up... maybe you will invent the SSS Junior?

rj

[Colossal]

Once we get the Colossal report we'll know if we want to move on to the next rev... I expect he is sucking solder fumes.

I just finished wiring the amp this evening and it is done with the exception of a couple of caps which I am short (but are coming this week) I think it came out pretty good and am looking forward to powering it up! Will post a photo or two tomorrow.

[M Fowler]

I am thinking that in Merlin's book he suggests that the first gain stage needs to be fully bypassed (22uF is plenty) to reject heater hum in that 1st stage? Do you hear any added hum with that cap out?

I am getting the feeling that you are not a gain loving maniac based on these amp mods. Let us know how pristine the clean sounds remain as you crank this thing up... maybe you will invent the SSS Junior? rj

It sounds like a Komet 60 now There is something about a cranked Express that drives me crazy. The way the power section sounds I don't like. I am trying to drift away from that. I figured since I have the opportunity to experiment I might as well keep on. Overall this PCB Express is a great platform for a stable amp. Just because I prefer a Marshall doesn't mean there is anything wrong with the Express or Liverpool. This kit will allow people to build a great PCB based amp and not have to worry about lead dress so much. I don't have any issues just chasing a tone I can live with.

An airbrake doesn't do anything for me either. I'm not sure how the heck anyone could use an Express on a gig, I have never been able to use one and I have three now.

[RJ Guitars]

Hey I am with you on the freedom to make it your own... that is fundamental to making this worthwhile for us. Keep experimenting, we have already broke the mold so now it will be cool to let it breathe and see what kind of life-form comes from it.

I played the Express at church today using an attenuator and having it dialed down to bedroom level and then using an in inline speaker simulator to get a signal we could send to the board. It went well and the amp gave me no trouble but that is not the answer... it was just another dialed down amp with most of it's resources untapped. I have an isolation cab on order so I can turn it up and play. Even if nothing else is accomplished using an "iso" cab, I know my neighbors and the sound man will be pleased.

[M Fowler]

I hear ya brother.

A TAG member owner of Marval Amps was nice to me a few years ago and sent me one of his PCB 18w Atom boards to play with. Working on your PCB Express and my pedal building has driven me to get working on that amp too. I need to order some of those red wire connectors as seen on this picture of a completed board.

Way too many amps I would like to build and not enough time or cash.

[guitarsnguns04]

Mark...pretty cool with the direction your taking it. I like it. I've also found the express is a great platform for mods. Are you planning on making any clips when your finished?

[M Fowler]

Mark...pretty cool with the direction your taking it. I like it. I've also found the express is a great platform for mods. Are you planning on making any clips when your finished?

Yes if I can figure out how to get that done and join a host so I can link the clips. I have never messed with recordings just the thought of having to figure out how it all works drives me nuts! I'm too inpatient for such things; however, I would like to accomplish this. Ran out of room in my cave to set up the equipment so I am slowly moving things around now that my lifting restriction has been raised

Mark