EM Drive: post transistor voltages or hfe from the stock pedal

[thelonious]

Calling all EM Drive owners... would you be willing to measure the voltages on the transistor in your pedal and post them here?

On the tagboardeffects post for the EM Drive (http://tagboardeffects.blogspot.com/2013/01/emerson-custom-guitars-em-drive.html), people have been reporting problems with gated or farty sound. I had similar problems. PRR mentioned that this design is very sensitive to hFE (see http://www.diystompboxes.com/smfforum/index.php?topic=102751.0). In my build, I changed the collector resistor to 3.9k and the base resistor to 2.2M and that improved things, but it doesn't tell me whether I'm anywhere close to where the transistor in the real pedals is biased...

[tca]

...  that improved things, but it doesn't tell me whether I'm anywhere close to where the transistor in the real pedals is biased...

Why do you want that? Does your version sound good? If yes, then it is good!

Experiment: take the EM circuit an 100 BJT's. Try all of them. Take the best sounding one. With one extra component, a resistor, you can get a MUCH better and STABLE booster.

Cheers.

[Gus]

I posted this in response to a seeing the em drive schematic
http://www.diystompboxes.com/smfforum/index.php?topic=103688.0

An EM drive and other simple designs like it will not work correctly without selecting the transistor. And then there is temp stability.

[thelonious]

Why do you want that? Does your version sound good? If yes, then it is good!

Agreed! I'm really only asking to satisfy my curiosity and to figure out what they were trying to accomplish. I can bias mine to get lots of headroom and it sounds fine as a cleanish boost, but I'm curious if that's what they intended the pedal to do or not. In the description on Emerson's website, it says "This pedal does everything from a slight boost/sparkle to a nice, warm light OD sound." I was wondering if they choked down the collector voltage on purpose so that with the gain control up the transistor would clip with just a guitar-level signal. Granted, it's an ugly clip...

I posted this in response to a seeing the em drive schematic
http://www.diystompboxes.com/smfforum/index.php?topic=103688.0

Thanks Gus, I will check that out!

[vandermann]

I just start some experiments with the EM Drive Circuit and to clone the original, I mean, with the same tonal characteristics, would be very nice to have at least the transistor collector voltage or the HFE from the original. So, is possible to some EM Drive pedal owner please post the Transistor Voltages?

Many Thanks!

Cheers, Vanderson

[Gus]

Here is a thread to help show how to sim the simple gain stages like used in an EM drive.  Look at the bottom right of reply #2
http://www.diystompboxes.com/smfforum/index.php?topic=105257.0
Why do you want to clone an EM drive?
I have posting number of screen shots of simple gain stages


Look up the transistor used in the EM drive then download a sim program and make some simulations.

Have you searched for other threads about circuits like the EM drive?

http://www.diystompboxes.com/smfforum/index.php?topic=103683.0
http://www.diystompboxes.com/smfforum/index.php?topic=103688.0

[Grubb]

With one extra component, a resistor, you can get a MUCH better and STABLE booster.

Cheers.

Sorry for reviving this thread, but I would very much like to know where that resistor goes in the circuit and what value it should have. I have looked on this forum but haven't found that information yet. I am playing around with the Em-Drive circuit a bit at the moment and have made one that kinda works, but I'm looking to improve it before I finish the pedal and put it in the sweet enclosure I have for it.