Emerson Custom Guitars E-M Drive.  [traced]

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Emerson Custom Guitars E-M Drive.

Postby The Rotagilla » 11 Jul 2012, 02:15

I count two caps, two resistors and a transistor.

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Re: Emerson Custom Guitars E-M Drive.

Postby soulsonic » 11 Jul 2012, 03:00

I wonder why no battery?
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Re: Emerson Custom Guitars E-M Drive.

Postby The Rotagilla » 11 Jul 2012, 03:35

soulsonic wrote:I wonder why no battery?

Because it would get in the way of those honkin' big caps? :hmmm:

Going green maybe? I've a couple pedals like that, battery snaps would be added upon request.
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Re: Emerson Custom Guitars E-M Drive.

Postby sinner » 11 Jul 2012, 09:28

Or solar powered?

Americans are getting nuts with ecology recently :blackeye

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Re: Emerson Custom Guitars E-M Drive.

Postby IvIark » 08 Oct 2012, 20:09

I see that as the Gain pot being in series with the input.
100n to base
2M from base to collector
4K7 from collector to supply
Emitter to ground
100n from collector to output.

Have I missed anything or does anyone see if differently?
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Re: Emerson Custom Guitars E-M Drive.

Postby Mbas974 » 08 Oct 2012, 20:17

1 of 2 resistor should be the one used for led LED (4K7 most probably)
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Re: Emerson Custom Guitars E-M Drive.

Postby IvIark » 08 Oct 2012, 20:22

I'd assumed the LED resistor was in that heat shrink wrap close to the LED
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Re: Emerson Custom Guitars E-M Drive.

Postby lettuceprey » 09 Oct 2012, 20:24

vero vero vero IvIark! :applause:
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Re: Emerson Custom Guitars E-M Drive.

Postby phibes » 10 Oct 2012, 05:52

sinner wrote:Or solar powered?

Americans are getting nuts with ecology recently :blackeye


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Re: Emerson Custom Guitars E-M Drive.

Postby Bernardduur » 11 Oct 2012, 17:43

Those green caps are those green russian K42Y-2 caps; I have a couple of em. Are being sold on ebay as some fancy PIO caps....... I heard that the lesser voltage ones (150V) are not, only the higher voltages are
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Re: Emerson Custom Guitars E-M Drive.

Postby levispeights » 11 Oct 2012, 20:40

I wonder what transistor they use. J201 maybe?
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Re: Emerson Custom Guitars E-M Drive.

Postby caspercody » 13 Oct 2012, 02:48

I do not think it is a Jfet. I think it is either a PNP, or MOSFET. Because, looking at the number one leg looks to be going to ground. On a PNP transistor this would be the emitter leg, and on a MOSFET this would be the source leg. On the J201 this would be the drain leg, and I am not good with designs but have not seen a J201 with the drain to ground. I found a better picture of the inside, and have attached. Love the sound of this and would love to see a schematic.

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Re: Emerson Custom Guitars E-M Drive.

Postby IvIark » 13 Oct 2012, 13:09

I thought is was a 2N5088 (or similar pin out NPN) and so collector at the bottom with the orientation shown with the 4K7 next to it going from collector to supply. Top cap is the input cap to base, bottom cap is the output cap and so the 2M resistor would then logically be between collector and base. Then the track coming from the top pin to a single wire (emitter?) would be the only connection on the board which needed grounding and so that would make sense. Like this:

[scheme removed]
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Re: Emerson Custom Guitars E-M Drive.

Postby caspercody » 13 Oct 2012, 19:45

Here is what I can make out of the wiring. Not sure about some of the switch connections, but I am sure some of you here can make more sense of what is going on.
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Re: Emerson Custom Guitars E-M Drive.

Postby caspercody » 14 Oct 2012, 04:24

Bread boarded this it it works, but the distortion breaks up??
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Re: Emerson Custom Guitars E-M Drive.

Postby Nocentelli » 14 Oct 2012, 14:52

I tend to use the words "distortion", "break-up", "overdrive", "clipping" etc interchangeably.... Do you mean the overdrive sound is unpleasant, gated, intermittent? A single transistor dirt circuit (with no clipping diodes etc) is rarely sophisticated: This looks vaguely similar to a bazzfuss, or an electra with the clipping diodes removed.
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Re: Emerson Custom Guitars E-M Drive.

Postby caspercody » 14 Oct 2012, 17:21

gated would be a good way to describe it, like a badly biased JFET. On the decay of the notes it sounded bad. And the bass sound was really gated sounded. But the controls worked like in the video. Low gain high volume gave a clean boost, and high gain low volume was distortion.
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Re: Emerson Custom Guitars E-M Drive.

Postby IvIark » 14 Oct 2012, 17:40

There could always be some components on the other side of the board.
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Re: Emerson Custom Guitars E-M Drive.

Postby Nocentelli » 14 Oct 2012, 17:54

Maybe, but I'm inclined to think this is mainly aimed at driving the input of a nice tube amp rather than primarily producing the clipping from within the transistor itself. It's not that disimilar to the Naga Viper: The "Heat" control allows you to drive the transistor itself into clipping by increasing the gain via the emitter - Here, the transistor is already set at maximum gain via the grounded emitter, and the input level pot allows you to reduce the clipping within the transistor for a cleanish boost. The viper doersn't sound great with the heat cranked into a transistor amp, but I imagine the nastier characteristics of tranny clipping would be masked when using a nice tube amp that is in overdrive itself. The same might be the case here.
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Re: Emerson Custom Guitars E-M Drive.

Postby harmaes » 14 Oct 2012, 18:57

I doubt if there's controls underneath. In the video from Mike Hermans I think the pedals sound great in the lower volume regions but I don't like how it breaks up/clips in the higher settings. Indeed an Electra like circuit without clipping diodes. But IMO this can also be done with a SHO or EP booster. I also don't think these mojo caps make loads of difference. But I'd love to hear your opinions about them. :D
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