One question though: Why do you use the silver mica treble cap in the tone stack and not a ceramic cap? I like them both for different reasons...
Jelle
Geek, I built the the turret boards from G10/FR4 Garolite from McMaster-Carr. After building a few boards with turrets and a few with eyelets, I'm definately leaning more towards eyelet construction. Much cheaper and easier to build!
Jelle, the mica is just tacked in there. I want to hear first hand the difference between the mica and ceramic. I may sacrifice the "Deep" switch location for a "mid-boost" switch and put a .002uF OD on the board.
Looks good, Bob. I used a 6-0-6V 450mA transformer through a D-style voltage doubler. Big mistake! I'm getting over 28VDC unloaded. I guess I can do as you said and just use the 6-0 legs. Question...does that effect the current handling? (Would it become a 225mA tranny?) If I use a voltage regulator, is it pushing things to pump 28VDC through it?
BTW, I injected a boombox signal into the PI today and it sounds pretty good. No squeal so I guess I got the plates wired correctly. The only issue I have is the bias circuit. I have a 220k bias range resistor in there and it just won't work for 6V6s. However, it seems just fine for EL34s. I may throw a switchable 1M over the 220k so I can run either tube.
Looks good, Bob. I used a 6-0-6V 450mA transformer through a D-style voltage doubler. Big mistake! I'm getting over 28VDC unloaded. I guess I can do as you said and just use the 6-0 legs. Question...does that effect the current handling? (Would it become a 225mA tranny?) If I use a voltage regulator, is it pushing things to pump 28VDC through it?
Yes, it affects current handling. Yes that's too much voltage for a regulator. The spec sheet for the 12V 7812 says 14.5 to 27V.
Why not use a bridge and skip the CT, then go into a regulator. That should do the trick.
BTW, I injected a boombox signal into the PI today and it sounds pretty good. No squeal so I guess I got the plates wired correctly. The only issue I have is the bias circuit. I have a 220k bias range resistor in there and it just won't work for 6V6s. However, it seems just fine for EL34s. I may throw a switchable 1M over the 220k so I can run either tube.
Looks good, Bob. I used a 6-0-6V 450mA transformer through a D-style voltage doubler. Big mistake! I'm getting over 28VDC unloaded. I guess I can do as you said and just use the 6-0 legs. Question...does that effect the current handling? (Would it become a 225mA tranny?) If I use a voltage regulator, is it pushing things to pump 28VDC through it?
Hi Normster,
I used your relay layout but changed it slightly.
Couldn't get it working with ground to chassis, so did away with it.
I used a 150mA 6-0-6 tranny and Matsushita(pardon me) DS2Y-S-DC12
relays (draw 16mA I think) and got 18.5VDC unloaded. Used a 270R/1watt
resistor and get 11.5VDC loaded. Didn't use a regulator. Was told by a EE friend who uses and exports alot of his designs that unregulated half wave was fine for this type of relay. Seems to work fine so far. Will let you know if I run into problems.
I have a question about your PAB board, is the 10K resistor to ground needed for it to work?
thank again[/quote]
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The 10k isn't used in the original Dumble circuit so I'll probably eliminate it. I was trying out a dogears suggestion to run the tonestack to ground through a 10k rather than lift it entirely, but I'm not sure I implemented it correctly. I used NEC relays (551-MR62-12USRY) but the same size and type as the Matsushita I think.
I'm with you and Bob, I think I'm going to forget about the voltage doubler and just go with a bridge rectifier. I'll be wiring up the switching this week so I'll let you know how it goes.
I wired the clean channel yesterday and it's nothing like I expected. Nice and clean, but VERY punchy! It's like it hits you in the chest, if you know what I mean. Don't get me wrong, I totally dig it!
Wired up the OD channel today and found that I had my relay wiring about as screwed up as it could possibly be. After straightening that out, I really like this amp. I haven't cranked it up enough to get any sag out of the rectifier, but man, what a ballsy overdrive! All that punch from the clean channel just slams the OD, but no farting. Pretty cool.
I'll probably wire up the reverb and accent switch tomorrow.
BTW, no OD snubbers on this puppy yet. If I crank the Drive and Level too high it WILL oscillate. But it's kinda cool when it's right on the verge of going out of control.