ultra class A superdrive power amp

[oldrocker]

This is the third time I bread boarded this circuit and I can't get anything out of it.  In the Snippets schem it shows a 1K ohm on the primary and 8 ohms on the secondary.  I measured 8 ohms on the secondary but on the primary side it's 63 ohms from blue to green wire and 32 ohms from black to green or black to blue.  Not even close to 1K.  Is the center tap used at all?   This is second transformer too.  I used the other one as an inductor for my Vox Wah.  I feel stupid since this circuit is as simple as it gets.  I'm donig this for fun since I use a Noisy Cricket for my portable amp but I keep coming back to this and I never get it working.

[oldrocker]

OK.  Never mind it's working now.  I wiggled some components around and it fired up sorry for the false alarm.

[didier]

just out of curiosity, may i ask you what you are building?

[KerryF]

He is building the "ultra class A superdrive".  Yes strange name for a pedal.  Ask him for the site with the schematic.  Its in my Favorites, but theres way too many things in there to find it 

[Rafa]

whats the ``ultra class A superdrive poweramp´´??
Is it a poweramp??
Where can I find the schematics

[Harry]

http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html

[didier]

hmmmmm 

[zpyder]

Annnnnnnddddd.... 10 of these in series?  I wonder what kind of volume gain this thing provides...

zpyder

[didier]

Annnnnnnddddd.... 10 of these in series?  I wonder what kind of volume gain this thing provides...

zpyder

i don't think that would have much use... with only 9V distortion will occur rapidly...

right?

[brett]

Hi
The voltage swing on the 8ohm side of the coil is very small (maybe 0.2V, making output only 50mW).
I wonder what it would be like with an emitter-follower after the transistor.  Using something rugged like an MTP3055 MOSFET.  With a little fiddling, the collector of the BJT could go straight into the gate of the MOSFET (the voltage should be about right).  The output can be taken from the output from the mosfet source via a cap.

Would that work? If so, a 2V signal on the collector of the transistor could drive an 8 ohm speaker.  2V/8ohms = 0.25 amps, 0.25A x 2 V = 0.5W.  Not bad.

cheers

[dano12]

Super fun build.

[oldrocker]

Hey dano12,  That enclosure is awesome.  I really like that fake tube.  That is innovative putting the transformer on the outside along with the tube to give that amplifier look.  Nice job.

[bancika]

yeah, looks awesome dano, how does it sound?

[dano12]

Thanks guys! It sounds really quiet. You have to put a booster or overdrive pedal in front of it to get any volume out it.

More of a novelty circuit than anything else.

[Rafa]

Mhhhhhh

Looks interesting easy to build, but does not seem to sound really loud?? Im right??

[MetalUpYerEye]

Rafa

Volume wise i'd venture to say that you're probably better off building a Ruby or Little Gem MkII. (www.runoffgroove.com)

[Rafa]

Yes probably thats the way
Thankssss

[idlechatterbox]

just curious dano, but what was the enclosure originally used for? (I.e., where did you find it)

Pretty cool by the way 

[bancika]

has anyone tried Joe's Micro Class A poweramp with three 2N2089's? It looks similar but with more power. Btw, dano you enspired me to do something similar - to make microp "tubes" out of small bulbs and make very small amp head Cheers

[oldrocker]

Try the Noisy Cricket.  It's a nice sounding 9 volt amp that sounds great out of one or two 12" speakers. That's what I use for a practice amp.