BJFE - Emerald Green Distortion Machine [traced]

[roseblood11]

Could be anything rated for 2 ampere, 1200 volt, maybe STTH212



I think the schematic was posted somewhere, but I can't find the link anymore...


Has anybody tried this pedal with a Proco Rat in front of it? A real Vox set to light crunch sounds great if its boosted with a rat. Could be interesting to put both circuits in one enclosure.

[roseblood11]

@ the3secondrule: Could you measure the hfe of all transistors and the leakage of the 2n1309? That would be helpful to understand the biasing...

[modman]

Hi,

Here you go:
http://tagboardeffects.blogspot.se/sear ... l/BJF%2FMP

And no I don't mind and never did if anyone wants to build one for their own use or a friend.

Fun note perhaps is that when doing the Bearfoot version some nice 2N1309 had been scouted for another model and I could not resist to try and liked that.
Original BJF model has same circuit but all were made with silicon metal cans medium gain drivers.

have fun
BJ
BJF Electronics

I drew separately the schematic in accord with the strip board layout.

emraldschematic.jpg

[soulsonic]

@ the3secondrule: Could you measure the hfe of all transistors and the leakage of the 2n1309? That would be helpful to understand the biasing...

The 2N1309 in mine had "329" marked on the side. I assume this is the Hfe.

[modman]

I'm sorry but I made a mistake on the schematic, the FET types are 2N5952.

[Manfred]

I took closer look at the PLC shot,
and found a resistor value of 470kOhms on the gate of the second FET.

By the way, the FET stages are alike in the circutry of the Baby Pink Booster,

[modman]

Better readable now.

Emerald.jpg

[Manfred]

The LED circuitry is the same as with other BJFE pedals.

EmeraldLEDsupply.jpg

[deep_intruder]

In my opinion there are two mistakes, the two caps: 1u and the 4n7 of the last fet, both must be wired to the drain and not to the source!

[smanq]

In my opinion there are two mistakes, the two caps: 1u and the 4n7 of the last fet, both must be wired to the drain and not to the source!

I think the 4n7 cap is right connected to the source (like on other BJF circuits), but the 1uf cap (the circuit output) must be connected to the drain.

[deep_intruder]

In my opinion there are two mistakes, the two caps: 1u and the 4n7 of the last fet, both must be wired to the drain and not to the source!

I think the 4n7 cap is right connected to the source (like on other BJF circuits), but the 1uf cap (the circuit output) must be connected to the drain.

I do not know how is the original, but the layout from tagboardeffects.blogspot.se is as I said.

[Frank_NH]

In my opinion there are two mistakes, the two caps: 1u and the 4n7 of the last fet, both must be wired to the drain and not to the source!

I think the 4n7 cap is right connected to the source (like on other BJF circuits), but the 1uf cap (the circuit output) must be connected to the drain.

I do not know how is the original, but the layout from tagboardeffects.blogspot.se is as I said.

I've been following this thread and deep_intruder is correct. The vero layout has the 4.7 nF cap connected to the drain. There is already a 22 uF source resistor bypass cap at the last JFET, so I don't know if connecting the 4.7 nF cap also to the JFET source would do anything. Hence, it's probably correct going to drain, but perhaps someone could confirm that.

[Manfred]

In my opinion there are two mistakes, the two caps: 1u and the 4n7 of the last fet, both must be wired to the drain and not to the source!

You are right, thanks for pointing out the mistake.
My bad. The stripboard layout is all right.

Here the corrected schematic:

EmeraldCorrected.jpg

[smanq]

OK, the schematics reflect the board layout.
But if the A50K pot controls trebles, I confirm what I said before.
If we connect the 4n7 cap to source, when the wipe is full CW, both first and last stages have a boost on high frequencies (exactly a low cut on first stage); when the pot is full CCW last stage is around linear (4n7 has no effect on circuit) and first stage has a boost on low frequencies. It's same behavior we can see in other BJF circuits, like honey bee. So, in this way: CW=treble boost, CCW=bass boost.
If we connect the 4n7 cap to drain, when the pot is full CW we have a treble cut on last stage and a low frequencies cut on first stage (around a non sense); when the pot is full CCW last stage is around linear, the first stage has a boost on lows. This behavior for me is strange: CW=treble cut, CCW=bass boost.

[Manfred]

OK, the schematics reflect the board layout.
But if the A50K pot controls trebles, I confirm what I said before.
If we connect the 4n7 cap to source, when the wipe is full CW, both first and last stages have a boost on high frequencies (exactly a low cut on first stage); when the pot is full CCW last stage is around linear (4n7 has no effect on circuit) and first stage has a boost on low frequencies. It's same behavior we can see in other BJF circuits, like honey bee. So, in this way: CW=treble boost, CCW=bass boost.
If we connect the 4n7 cap to drain, when the pot is full CW we have a treble cut on last stage and a low frequencies cut on first stage (around a non sense); when the pot is full CCW last stage is around linear, the first stage has a boost on lows. This behavior for me is strange: CW=treble cut, CCW=bass boost.

Your explanation makes sense because there is already a treble control.
It is hard to find out the real circuitry on the pcb shots.
Is there an owner of this device who could check it out which the real circuit is?

EmeraldTwoVersions.jpg

[modman]

Hi guys. The schematic was sent to me a while ago and I think at the time I was asked not to share it, but can't completely remember so here it is. If the author would prefer me not to then please let me know and i'll remove it from here.

It doesn't flow like many of us may be used to seeing schematics for these things and as such the scheme isn't as straight forward to follow at first. Q1 has the source at the top and drain at the bottom

Bearfoot-EGDM-rev2.png

[modman]

Manfred top drawing conforms to this schematic made in 2014...look at the 4nF cap marked as
However, have a look at C14 in the old one: there is written "100k = 10pF", other schematic has this value as 100pF, don't know where that came from.
Maybe the solution the capacitor has 100k written on it, meaning 100,000 (pF) = 100nF?
C15 = 22nF or 22µF? - if you have the unit in front of you, how could you have to guess? Maybe it was traced from pictures, not from a unit.

[asimplesample]

I just ran across this effect today, and found this thread and the 'tagboard' layout. This thread ends with some doubts...has anyone made a final confirmation? Has anyone built one all-silicon?
Thanks!
Larry S.

[BJF]

Hi There,

Oh that schematic doesn't flow well at all.
Really it's a straight forward design and as I wrote several years ago that if you'd take a BJF EGDM apart you would find three transistors

Indeed BJF version is all silicon while when I was making this for Bearfoot and seeing they had 2N1308's in stock I just went for it and really liked the sound and that is precisely what happened.

At your service
BJ

[Seiche]

Manfred, the top one should be correct.

I'm working on it to verify.