freestompboxes.org

Yeah, I agree. These grounded emitter amplifiers never sound right to me. I'm just guessing people wouldn't be losing their minds over this thing if the real units sound like the one I boarded So I must be missing something...I couldn't imagine I made a mistake with this simple circuit. I did add a buffer on the input, and some switchable diodes on the output, and a simple presence tone stack, sounds pretty cool that way...but not at all like the EM drive, more like lets say an Electra, or Woodrow, or COT50.

ok, finally listened to some demos, and it does get kinda fuzzy with the gain maxed...not bad, just not what I'd expected.

IMPROVEMENT: resistor R2 connected over collector-base and Q1=MPSA18: sounds very good!

That's what my first guess at the circuit was which caspercody breadboarded and said didn't sound right.

I used a 2N5088 when I breadboarded it, and it sounded unbiased. I also tried it with R2 to +9volts, and it still sounded unbiased. Maybe the 2N5088 transistor does not work in this circuit. I was also using a 100k pot for the volume (do not remember what value I used for gain, but I know it was not 250k), maybe the size of the pots affected the sound I was getting?

I think the circuit need a high gain transistor (MPSA18: Hfe=900)

Very important the pots value!!

eBay pots: https://www.ebay.com/itm/Guitar-potenti ... 5ae2725f39

I tried IvI's latest vero-layout with a MPSA18 and it sounded extremely gated. I couldn't get a sound out of this thing without hitting the strings really hard and it just died almost instantly.

I tried it with 5088s which were ok. 2n222s were ok but not really any better.

It's not a bad unit but IMHO, it sounded better with single-coils and pretty much exclusively with smooth picking or finger-picking.
Even at the lowest gain values, there was always a slight fizz-fuzz-buzz whathaveyou when the low E was hit hard. The higher the gain the more of it the circuit had. That's why I investigated it and tried different values of different transistors but nothing made it sound very good to me.
My conclusion was just that it was a circuit that didn't suit me well....

let's face it, there is a ton of better sounding circuit around, this one is not the holy grail as supposed

nooneknows wrote:let's face it, there is a ton of better sounding circuit around, this one is not the holy grail as supposed

To me it's always a question of who you ask... me? no. However, I can hear it being really really good for other players out there.

yes, of course, what's good for me could be someone's nightmare, I forgot to put the "IMHO" word in my sentence.
Anyway I think there is a misconception about this type of circuits, the assumption 'less is better' is not always true and often people tend to bend their ears to psychoacoustic ghosts, especially when golden words like "oil and paper capacitor" are said (common in esoteric hi fi world) and prices rise up to stellar levels.

nooneknows wrote:Anyway I think there is a misconception about this type of circuits, the assumption 'less is better' is not always true and often people tend to bend their ears to psychoacoustic ghosts, especially when golden words like "oil and paper capacitor" are said (common in esoteric hi fi world) and prices rise up to stellar levels.

Couldn't agree more.

Schematic with TONE CONTROL: sounds good! a very important improved.
·

I've tried with BS170 (MOSFET) has worked well, sounds good too: RECOMMENDED!
·

I still have the circuit mounted in the box, may as well try that... thanks!

I've tried connecting 2M resistor like in Rugeb's schematic and tried BS170 and MPSA18 like he suggested. To me, the circuit became much more clean and it doesn't distort much at the maxed gain settings. I guess this can be an improvement if you are looking for super clean boost. But I'm looking for exact replica of the original. So I'm reverting back 2M resistor to 9V which distorts but not in a pleasant way.

By the way, I've tried both mojo and compact version of lvlark's layout and IMHO, I like the compact version better. The gain is much nicer with mylar film caps. I think my PIO caps need to be break-in but those mylar film caps are doing much better job bringing nicer gain tone on this circuit than the PIOs at the moment. But it still doesn't get pleasant gain tones like on youtube videos. It's a mystery

crazyabe wrote:I've tried connecting 2M resistor like in Rugeb's schematic and tried BS170 and MPSA18 like he suggested. To me, the circuit became much more clean and it doesn't distort much at the maxed gain settings. I guess this can be an improvement if you are looking for super clean boost. But I'm looking for exact replica of the original. So I'm reverting back 2M resistor to 9V which distorts but not in a pleasant way.

NOTES:
1 - The circuit is a DRIVE (not FUZZ or DISTORTION).
2 - Tested with single coil or humbuckers = more or less distortion.
3 - Tested with transistor amp or tube amp = more or less distortion.

Hey, i have built this one following rugeb tips. Tone cap is a Bianchi 47n, black beauty caps i had lying around the shop, bs170, 250K log pots... I think it sounds good. It isn't any holy grial at all, imho, but i will give it some weeks at my pedalboard to see how it behaves in next rehearsals...

I've personally classified this circuit in the WOT section (where WOT means Waste Of Time).

I've got the original unit. Mitch at Emerson let me have one for almost nothing I bought 400x stereo jacks from him + White EM drive with shipping to Iceland for $550. The pedal is blemished according to him but it's not even visible hah!

Anyways, I would only classify this as a booster, not a drive or fuzz. When you turn up the drive, it sounds nice until you go about 2 o'clock and further. Then it just sounds farty and not good at all. It's got plenty of output before that so I like it as a booster / tone enhancer.

geiristudio wrote:I've got the original unit......

In the original unit: what transistor is used?