built-in dumbleator pwr question

Overdrive Special, Steel String Singer, Dumbleland, Odyssey, Winterland, etc. -
Members Only

Moderators: pompeiisneaks, Colossal

User avatar
Bob-I
Posts: 3791
Joined: Thu Feb 02, 2006 10:06 pm
Location: Hillsborough NJ

Re: built-in dumbleator pwr question

Post by Bob-I »

groovtubin wrote:Bob, how in the world did you dream that one up! lol! AWESOME!

jim
I pretty much used Aiken's article on feedback amps and went from there. I'm really happy with it. The Dlator in the 4x6V6 amp is ok, but the parallel loop is more transparent in that the dry side of the effect (SS Effect of course) is not used at all.
User avatar
heisthl
Posts: 1800
Joined: Fri Sep 29, 2006 5:35 am
Location: Phoenix

Re: built-in dumbleator pwr question

Post by heisthl »

Bob-I wrote:
Yes, that's critical. You can get phase problems if you mix both in the device and on the loop.
You should be able to. Here's the schematic I used. Notice there's NO grid load on the mixer/gain stage. The feedback loop creates a virtual ground. Very strange at first when you measure the cathode and get 0 volts there, you have to measure against the virtual ground. :?

Bob- Assuming a 12ax7 for this schematic does the feedthrough for the dry signal seem to be close to unity? Does it give the amp that little extra "something" that a regular D'lator does when effects are not used?

I noticed your still using the 10K and 1k5 values, the tube might be better served with the 27K and 1k8 values.
Former owner of Music Mechanix
www.RedPlateAmps.com
User avatar
Bob-I
Posts: 3791
Joined: Thu Feb 02, 2006 10:06 pm
Location: Hillsborough NJ

Re: built-in dumbleator pwr question

Post by Bob-I »

heisthl wrote:Bob- Assuming a 12ax7 for this schematic does the feedthrough for the dry signal seem to be close to unity? Does it give the amp that little extra "something" that a regular D'lator does when effects are not used?

I noticed your still using the 10K and 1k5 values, the tube might be better served with the 27K and 1k8 values.
It's a 12AT7. I have a switch to shut off the loop and yes, it's just a slight increase in volume when switched in.

I'm not a guru but I think with the AT the 10k/1.5k are about right, correct me if I'm wrong.
Post Reply