Darlington booster and some other (edit)

[tca]

Hi,
 I've tried this schematic, on the simulator and on the breadboard:



but in only works on the simulator and I'm getting mad trying to figure out why it does not work on the breadboard.

I guess I'm doing something wrong? But what?

Thanks.

[Bill Mountain]

Are you positive that your transistors are good?  Orientation?  Have you tried it with just one?  Maybe a single Darlington tranny?

I'm just spit balling here.

[tca]

Bad transistor! Grrrr!

[tca]

I should also explain why the Darlington configuration.
I need a, at least 70dB, booster. I could use a opamp... but my first idea was to use amz Muff boost, two in series, each of them has 30dB gain so doubling that value would be ok for my needs. But the first stage overdrives the next and I don't like the sound of it. What I really needed was a clean 70dB boost. That explains the first entry.

Probably the Darlington booster can not give the 70dB that I want, in its current setting it as 20dB

Probaly I'll try theconfiguration of two BJT in series with direct coupling?

Sugestions/comments?

References on a clean BJT boost?

Thanks.

[Earthscum]

A single bc109 transistor can easily take a signal to pure clipping. You just need to change how much gain the configuration has. If you feel you need multiple stages then you may image google for Tim Escebedo Bootstrapping for Gain.

[tca]

Thanks for mentioning Escobedo's circuits, I always forget to check them (no need to google, have all of them here!)

P.S. (edit) Bootstrapping is indeed a good idea!

This is the simulation of Jack Orman's Muffer



and this is my interpretation of Escobedo's idea:



Have to breadboard this tomorrow. Looks promising!

Thanks again.

[Earthscum]

I might have to give that a shot, too... I've only bootstrapped Fets, that BC109 sim looks like it could have some killer sound!

[tca]

Hi,
just assembled the circuit here is the sound sample is great for blues but not enough gain (not as much as the simulation shows); it is overdriven by a BOSS OD-3 with null distortion. The bootstrap does not work on the breadboard, at least one can not notice that (connecting and disconnecting the capacitor).

Edit: Just  correct a few errors works fine!

I'll be opening a new thread with the result... it is no longer a booster is distortion box, a triode emulator, or something like that!!

Cheers.