Different Take on Dumbleator

[gktamps]

I had all of the parts ready to make another Dumbleator and then got inspired by Martin's miniaturized version. Using a chassis box I had on hand for building power supplies for some of my audio gear, I thought it would be interesting to use a prefabricated tube effects loop using a subminiature tube and pack everything into a 5-3/4" x 8" x 2-3/4" box.

The power supply filter nodes are reduced (could have dropped one more but decided to use a choke between the 47uF and 22uF caps. Adjusted the B+ dropping resistor and added dropping resistors to the heater supply to drop the voltage from 7V to 6.2V, since the tube effects board draws so little current. Also removed the trimmers from the board and substituted with pots.

It sounds excellent. More neutral than my more standard Dumbleator, very clean and clear, despite some obvious but minor frequency distortion as shown in the o-scope picture. All in all, very satisfactory, despite the higher cost due to using a pre-fabbed buffer board, but nice to have in a small package. The labels are rather cheesy, but serve for now.

MiniDumbleator1.jpg

MiniDumbleator2.jpg

MiniDumbleator3.jpg

MiniDumbleatorSqWave.jpg

[martin manning]

Nicely done! I find the independent gain and buffer stages can be used in other ways too.

[dbharris]

Looks great!

-Dan

[gktamps]

Nicely done!

Thank you!

I find the independent gain and buffer stages can be used in other ways too.

Please say more, Martin.

[martin manning]

I find the independent gain and buffer stages can be used in other ways too.

Please say more, Martin.

You have a gain stage and a CF stage with 1/4" inputs and outputs, so you can have a booster and/or buffer out front to overdrive the amp's input stage, or use them for experimenting with other circuits on your bench.

[gktamps]

Looks great!
-Dan

Thank you, Dan!

Greg

[gktamps]

Good points, Martin. Hadn't really considered using it in the input of the amp, but could also be a great way to drive non-buffered pedals. And I didn't think of using it for other circuits on the bench. Thanks!
Cheers,
Greg