DUNCAN BLUES AMP (What The..........

[TIMBO]

Hi Guys, I find trolling through the Schem Library great for finding info that does not require a Post and shows me that valve amps can have almost unlimited ideas when it comes to the design.This i believe is how we are lured into the quest to find that ultimate TONE and SOUND.

Enter DUNCAN 112 BLUES COMBO.First did not know that it was a connection to Seymour Duncan and the amp was not put into production (could not find much info on the net other that his site) and sound clips sounded good.

The Design  some interesting bits. I think i get drawn to these an other "one off" amps because someone has already done the ground work to try to fine the "TONE/SOUND" ( Many thanks to Tubenit)that no one else has and if this is a blend of a bit of old and new, well this gets the my grey matter stirring.

Start from the Input, I know little about SS electronics but i think this Input is pretty much a no brainer that it injects a little extra gain to the incoming signal (and i believe that the IC may also be interchanged with other ICs to alter that incoming signal but i could be wrong) with the mode switch changing the gain of the first three stages.

The Tone stack, a few different values to the usual.

Active FX Loop, I kept it the same as the original as these IC are easily gotten.

Reverb, Added a one tube Reverb as he did comment that you can't beat a tube Reverb (i agree)

Power Amp and PI, the pi is as the original schem and the power amp is the usual 6L6 set up (some changes might be required)

Master Vol may be deleted as PPIMV may become Master Vol.

PSU,This is the interesting Bit SS rect OK, Lots of FILTERING starting w/ 47uf-Choke-100uf and then what i believe is a SAG resistor (am i correct) "A" "B" "C" & "D" as usual but from here it gets unusual, the dropping resistor is 100k and filter caps are rated @ 63v and a zener of 56v. So are they saying the preamp tubes are only running on around 50-60v  This is very interesting as the Plexi Gain 20 was only getting 70v on the V1 tube and it sounded OK.

I would like some comments on this amp as it got me thinking and i have not been able to find much info. Thanks

[PRR]

http://www.el34world.com/charts/Schematics/files/Misc/duncan_blues112.pdf

[TIMBO]

Thanks PRR, thats about all i can find

[tubenit]

I am genuinely impressed with your schematic and the effort that you put into this!  Great job.  

There is alot about the design that intrigues me in a positive way and some that I don't understand.  

I'll only offer a couple of comments to consider.  I have not had the tone success I want with 12AX7's when they drop much below 140v on the preamps.  Second comment is that the pentode/triode switch works quite well on a 6V6 but I did not find the same positive and dramatic change in volume/tone with 6L6 tubes. Over the yrs, I have removed almost every pentode/triode switch I've installed. s I am not sure it would be that useful IF you use the PPIMV.


With respect, Tubenit

[TIMBO]

Thanks Tubenit,As always you don't know what it will be like till you build it and i have had a lot of those lately  but thats is all part of the fun and learning. I know that if i built it it would not sound any thing like Duncans amp but if the basic amp is there you can always add to it.The original had EL84s the only reason i was going for the 6L6s was i had them and an OT (1650F) that would also be good for the 6V6s (have those).

I would likely build it as is with the low voltage preamp and if need be convert it to Normal Voltages (which i think would not be difficult).
Anyway the Plexi Gain 20 i think will become a work in progress as its problems are above my pay grade and the TOS is calling my name. Thanks 

[FYL]

First did not know that it was a connection to Seymour Duncan and the amp was not put into production (could not find much info on the net other that his site)

AFAICT there's no connection with SD. Duncan Munro is well known for the TDSL as well as useful utilities such as PSU Designer. The Blues Amp is one of the designs on his site.

http://www.duncanamps.com/b112/b112.html

[DummyLoad]

interesting place to inject reverb signal.

--DL