This is a work in progress, but I thought I'd throw it out and see if any of you older, wiser builders see any glaring errors. It's a 6V6 ODS with 5AR4 rectifier. Transformers are Trainwreck style from Moose. (300-0-300, 300mA PT; 35W 6.0k primary OPT) It's going into a "standard" Dumble chassis similar to the ones Funkalicious is having built.
The values on the board are sure to change, but I would like some eagle eyes on the power supply layout and relay/tonestack wiring. The power supply is using a 50/50uF cap can for plates and screens, then back to the usual axial caps. Note that the 56k isolation resistor for the reverb tranny is hanging off of the terminal strip on V5.
Anyway, let me know if you see any potential smoke leakage.
I don't see any mistakes off hand. Looks like a decent layout to me.
My only question is the 50/50uF filter. With a tube rectifier this is a bit high. I can't remember off hand, but I think it should be 33uF on the first stage.
Bob-I wrote:I don't see any mistakes off hand. Looks like a decent layout to me.
My only question is the 50/50uF filter. With a tube rectifier this is a bit high. I can't remember off hand, but I think it should be 33uF on the first stage.
Thanks for checking it over, Bob. Yeah, I'm not too sure about the 50/50 either. I've got a 32/32 and a spare 5AR4 as a backup but thought I'd try pushing the limits first. I've seen tube charts ranging from 50 to 60uF depending on the tube brand. (This one's a Ruby.)
BTW, Scott mentioned having 10k to ground in boost mode. Could you look at the boost relay circuit and tell me where the 10k goes? (Sorry, switches and relays confuse the hell out of me.)
Bob-I wrote:
BTW, Scott mentioned having 10k to ground in boost mode. Could you look at the boost relay circuit and tell me where the 10k goes? (Sorry, switches and relays confuse the hell out of me.)
Hmmm.... send me the visio file and I'll add it in. I think I know where it goes.
glasman wrote:It looks like the two have of the 50/50 are in parallel (yes / no).
If in parallel this is to much. A 5AR4 is rated for 60uf max. You could not only take out the tube, but maybe the tranny as well.
FWIW, on the 20 watt combo I built a while back I used a total of 50uf and it seems to do pretty good. He was taking my head off last night
My 2 cents....
Nice layout.
Gary
Thanks, Gary! (I may build this one with blue Garolite as a tribute. )
I'm using the first half of the 50/50 to filter the plates, then it goes through the choke, then to the screens. At least that's what I think it's doing. Hopefully I didn't screw this up.
Bob-I wrote:BTW, Scott mentioned having 10k to ground in boost mode. Could you look at the boost relay circuit and tell me where the 10k goes? (Sorry, switches and relays confuse the hell out of me.)
Normster wrote:BTW, Scott mentioned having 10k to ground in boost mode. Could you look at the boost relay circuit and tell me where the 10k goes? (Sorry, switches and relays confuse the hell out of me.)
I think you mentioned that rather than lift the tonestack completely from ground, to instead keep a 10k reference to ground so that the volume increase is less dramatic. I know you explained it to me once before, but since I don't use a boost circuit in my other clone, I've pretty much forgotten the details.
Hi Normster:
What I want to know is about the heaters. You've got two wires coming out of the PT and going to ground. Presumably these are center taps. If one of them is for the 6.3VAC filament windings, better put a 100 ohm resistor between it and the ground. On the other hand, I think the pin-outs on the 5AR4 heaters are two and eight. They are not hooked up in your layout. How will you get them? Does the Moose tranny include a 5 volt rectifier winding?
Edit, I don't know why I don't just check these things first. The Moose tranny has a 5 volt winding. Never mind.
Dan
Last edited by skyboltone on Mon Jul 03, 2006 5:03 pm, edited 2 times in total.
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
The only boost mod I have done is to use a .003uf and 100k series network where the bass cap breaks from the treble pot. I have since removed it.... It does work nice though. A little more gain and a cool low end.
Normster wrote:
dogears wrote:Whatchoo guys talkin' bout??
Normster wrote:BTW, Scott mentioned having 10k to ground in boost mode. Could you look at the boost relay circuit and tell me where the 10k goes? (Sorry, switches and relays confuse the hell out of me.)
I think you mentioned that rather than lift the tonestack completely from ground, to instead keep a 10k reference to ground so that the volume increase is less dramatic. I know you explained it to me once before, but since I don't use a boost circuit in my other clone, I've pretty much forgotten the details.
Normster wrote:This is a work in progress, but I thought I'd throw it out and see if any of you older, wiser builders see any glaring errors. It's a 6V6 ODS with 5AR4 rectifier. Transformers are Trainwreck style from Moose. (300-0-300, 300mA PT; 35W 6.0k primary OPT) It's going into a "standard" Dumble chassis similar to the ones Funkalicious is having built.
I'm curious to learn why the 35W OT? Are you contemplating being able to substitute EL34s ala T'wreck practice? If so, does that throw the usual balance of pre vs power stage distortion out of whack (due to running the EL34 at low voltages)?
Thanks for bring up this topic. It's one that has been on my back burner for a while.
Zippy wrote:I'm curious to learn why the 35W OT? Are you contemplating being able to substitute EL34s ala T'wreck practice? If so, does that throw the usual balance of pre vs power stage distortion out of whack (due to running the EL34 at low voltages)?
Thanks for bring up this topic. It's one that has been on my back burner for a while.
I bought a set of Moose's trannys to replace the Hammonds in my Express but decided to use them for this build instead. I'm building it primarily as a 6V6 powered amp but I may throw in some EL34s just to hear what they sound like.
BTW, last week I played an original '80s Fender Esprit through my Dumble clone. The pickups were hot enough to drive the clean channel into overdrive with the master at 11 o'clock. IMHO, the Dumble is capable of some killer power amp distortion! (We just don't like to think of it like that. )
Normster wrote:BTW, last week I played an original '80s Fender Esprit through my Dumble clone. The pickups were hot enough to drive the clean channel into overdrive with the master at 11 o'clock. IMHO, the Dumble is capable of some killer power amp distortion! (We just don't like to think of it like that. )
Interesting comment regarding the Esprit. I have a spruce-topped Esprit with original everything (except the rack rash on the back - that came later in its life). When a Les Paul-wielding friend tried it, he commented that the pickups seemed weak.
Regardless, I don't play that loud anymore and am looking for "low power" alternatives (compared to the Traynor twin I used to play when I had hair atop my head and a much stronger back). A 20W Dumble clone seems a great way to go (for me).
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