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I picked up one of these dirt cheap at a GC "list" sale. I thought it sounded a little too coarse for my taste in the store but I figured if I just popped in some lower gain 12A_7's, everything would be copacetic.
Only when I got it home and was reading the literature I learned that it did not use regular preamp tubes but the 6021W miniature dual triodes. I need to start reading that sh*t in the store!
I figured that it would come in handy someday- like if I was plugging into a crappy amp at a blues jam- although I hardly ever used it...
A few months ago I saw that SD was coming out with a Twin Tube Blue- voiced for blues with lower gain 6111 tubes (a mu of 20 vs 35 for the 6021's). So I figured- what the heck- why don't I order some 6111's and replace them myself???
The closest I found was a 7327- sold in 20 lots on ebay or as singles from tube_shop.com in England. So I ordered two from England and had them throw in some 6L6 springy tube retainers to spread around the shipping and handling charge a bit (I think it was $8, and the tubes were about $6 each).
I finally got around to changing them out- not too hard if you just take your time. No need to remove the pcb- each tube has 8 leads which were covered with nylon tubing for insulation. Desolder each lead and put the tubing on the new tube and then cut the lead to length. The leads are soldered to connectors which were almost like flea clips (only more solid). I got one of them too hot and the clip came out of the board. It was easy enough to put it back in but when I was all done I thought that I had better pull the pcb out to make sure that nothing was shorting out on the back side of the board. Looked fine so I put it back together, managing to lose one of the chicken head knobs...
So how does it sound??? Well, my initial impression was that the lead channel was a bit more compressed than I prefer. Still, it was a big improvement and I will probably start using this pedal a lot. For those of you not familiar with it, there are two channels, rhythm and lead, each with their own volume and gain controls. And there are bass and treble tone controls which effect both channels. There is a toroid transformer mounted on the board which brings the voltages up to real tube levels (not starved plate voltages as is common with many tube driven stomp boxes).
I could probably get even better sounds (for my own tastes) if I fine-tuned some of the plate and cathode resistors, and/or the coupling caps or Ck caps. It looks like you could replace the resistors from the top, without having to remove out the pcb. It might be trickier to change out some of the caps. But I would want to see the schematic rather than try to reverse engineer this sucker...
Steve Ahola
Only when I got it home and was reading the literature I learned that it did not use regular preamp tubes but the 6021W miniature dual triodes. I need to start reading that sh*t in the store!
I figured that it would come in handy someday- like if I was plugging into a crappy amp at a blues jam- although I hardly ever used it...
A few months ago I saw that SD was coming out with a Twin Tube Blue- voiced for blues with lower gain 6111 tubes (a mu of 20 vs 35 for the 6021's). So I figured- what the heck- why don't I order some 6111's and replace them myself???
The closest I found was a 7327- sold in 20 lots on ebay or as singles from tube_shop.com in England. So I ordered two from England and had them throw in some 6L6 springy tube retainers to spread around the shipping and handling charge a bit (I think it was $8, and the tubes were about $6 each).
I finally got around to changing them out- not too hard if you just take your time. No need to remove the pcb- each tube has 8 leads which were covered with nylon tubing for insulation. Desolder each lead and put the tubing on the new tube and then cut the lead to length. The leads are soldered to connectors which were almost like flea clips (only more solid). I got one of them too hot and the clip came out of the board. It was easy enough to put it back in but when I was all done I thought that I had better pull the pcb out to make sure that nothing was shorting out on the back side of the board. Looked fine so I put it back together, managing to lose one of the chicken head knobs...
So how does it sound??? Well, my initial impression was that the lead channel was a bit more compressed than I prefer. Still, it was a big improvement and I will probably start using this pedal a lot. For those of you not familiar with it, there are two channels, rhythm and lead, each with their own volume and gain controls. And there are bass and treble tone controls which effect both channels. There is a toroid transformer mounted on the board which brings the voltages up to real tube levels (not starved plate voltages as is common with many tube driven stomp boxes).
I could probably get even better sounds (for my own tastes) if I fine-tuned some of the plate and cathode resistors, and/or the coupling caps or Ck caps. It looks like you could replace the resistors from the top, without having to remove out the pcb. It might be trickier to change out some of the caps. But I would want to see the schematic rather than try to reverse engineer this sucker...
Steve Ahola
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