Mofeta Pre Amp Mockup Pedal - ARRIVED!

[music6000]

Version 1 :


Version 2:

 

[droneshotfpv]

As soon as the PCB being in stock sent me an alert, I ordered WITHOUT hesitation! Can't wait to get this together. These mock ups look awesome!

@PedalPCB I didn't see the build docs yet, but wanted to know what POTS I needed for this build. I have pretty much every DIODE, transistor, and resistor / caps I could dream of, but I am running low on POTS. Was going to order those today if I needed to due to my stock being low.

Thanks in advance!

 

[Robert]

This has a charge pump (18V) so electrolytic caps should be rated accordingly.

R1 1M
R2 68K
R3 68K
R4 680R
R5 680R
R6 470K
R7 470K
R8 820R
R9 680R
R10 3K3
R11 56K
R12 100K
R13 47K
R14 562K
R15 100K
R16 1K
R17 22K
R18 1K
R19 100K
R20 47K
R21 562K
R22 47K
R23 100K
R24 100K
R25 100K
R26 100K
R27 22K
R28 10K
R29 10K
R30 100K
R31 1K
R100 4K7

C1 100p
C2 100p
C3 22n
C4 47u
C5 22n
C6 47u
C7 470p
C8 680p
C9 4u7
C10 47u
C11 2n2
C12 270p
C13 22n
C14 22n
C15 100n
C16 1u Film
C17 1u Film
C18 100n
C19 100n
C20 470p
C21 1n
C22 1n
C23 2u2
C24 47u
C100 100u
C101 10u
C102 10u
C103 10u

D100 1N5817
D101 1N5817
D102 1N5817

Q1 2N5457
Q2 2N5457
Q3 2N5457
Q4 2N5457
Q5 2N5088
Q6 2N5088

IC1 TL072
IC100 TC1044SCPA

NORMAL A1M
BRITE A1M
MASTER A50K
BASS A1M
MID B25K
TREBLE B250K

BIAS1 20K Trim (3362P)
BIAS2 20K Trim (3362P)
BIAS3 20K Trim (3362P)

 

[benny_profane]

@PedalPCB The JFETs are a bit of a surprise there. It's 2n5457 and not J201? I remember seeing some preliminary traces of the EAE circuit that did have 2n5457, but the emulation circuits usually go the ROG route.

 

[droneshotfpv]

@PedalPCB The JFETs are a bit of a surprise there. It's 2n5457 and not J201? I remember seeing some preliminary traces of the EAE circuit that did have 2n5457, but the emulation circuits usually go the ROG route.

Correct me if I am wrong, the 5457's are tighter, and brighter sounding than the J201's, right? But otherwise a perfect replacement for J201's?

 

[zgrav]

I suspect there is as much variation in behavior among J201s and among 2N5457s than there is between the two different types of transistors. Either one, or both, would likely work in the build.

 

[Quinn301]

Bias to 4.5v?

 

[temol]

Correct me if I am wrong, the 5457's are tighter, and brighter sounding than the J201's, right? But otherwise a perfect replacement for J201's?

2N5457 is not perfect replacement for J201. Unless it's a source follower (buffer). For a gain stage - no. Expect less gain from 2N5457 in the same curcuit. Where did you get this info that 2N5457 sounds brighter than J201?

I suspect there is as much variation in behavior among J201s and among 2N5457s than there is between the two different types of transistors. Either one, or both, would likely work in the build.

It all depends. There's a reason for a specific type of transistor in the circuit. There's a dfference between J201 and 2N5457 and there's also difference between individual J201s, even from the same reel. But still.. for J201 you can expect Vp range between 0.6-0.9V and for 2N5457 between 1.6-2.2V. So even J201 with highest Vp is quite far from 2N5457 with the lowest Vp.

Of course, both models of the transistors will "work", but the final effect will be different, depending on the model.

 

[Robert]

Coincidentally I built the prototype with J201's first, it did work but had significantly less gain.

 

[temol]

One comment to my previous post - J201 vs 2N5457, in terms of gain, biasing, etc. Above (lower gain of the 2N5457) is true if only drain resistor value is adjusted and source resistor value does not change. And that's probably very frequent scenario when replacing transistor (for example J201) with different model. But.. if we increase value of the source resistor, than it's a different story.

PedalPCB - I'll wait for the schematic. Is it based on/similar to the Black Hole?

 

[fig]

I don't crank up the LTSpice Weasel or soldering iron when swapping JFETs, so that makes sense from a practical application perspective-type thingy.

 

[Robert]

PedalPCB - I'll wait for the schematic. Is it based on/similar to the Black Hole?

It's similar up to the phase inverter section.

 

[saucy_boss]

Is there an existing drilling template I can use for this build?

 

[Robert]

The standard 6-knob template will work.

https://docs.pedalpcb.com/project/6BandEQ-Potentiometer.pdf

 

[saucy_boss]

Thank you!

also wondering if the trim pots are equivalent in function to the coda effects blackout? Do I adjust in the same way as their docs?