# Mofeta Pre Amp Mockup Pedal - ARRIVED!



## music6000 (May 13, 2021)

Version 1 :




Version 2:


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## droneshotfpv (May 19, 2021)

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!


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## Robert (May 19, 2021)

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)


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## benny_profane (May 19, 2021)

@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.


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## droneshotfpv (May 19, 2021)

benny_profane said:


> @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?


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## zgrav (May 19, 2021)

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.


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## Quinn301 (May 25, 2021)

Bias to 4.5v?


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## temol (May 25, 2021)

droneshotfpv said:


> 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?



zgrav said:


> 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.


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## Robert (May 25, 2021)

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


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## temol (May 25, 2021)

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?


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## fig (May 25, 2021)

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.


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## Robert (May 27, 2021)

temol said:


> 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.


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## saucy_boss (Jun 10, 2021)

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


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## Robert (Jun 10, 2021)

The standard 6-knob template will work. 

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


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## saucy_boss (Jun 11, 2021)

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?


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