# Neurocyton Preamp - Greer Soma



## almondcity (Jan 24, 2022)

I didn't snap a gutshot but wanted to post a successful build on this one. This pedal is absolutely sick, 10x better than the Benson Preamp in my opinion. Biased the trimmers to 4.5v and it sounds beautiful! BUILD THIS


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## Flashheart (Jan 24, 2022)

Looks great. What did you use for the lettering?


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## almondcity (Jan 24, 2022)

I used some rubber stamps I have and StazOn ink


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## Preverb (Jan 24, 2022)

How does it differ from the Broadcast?  I really wanted to build this one but Have a Benson and Broadcast halfway done on the back bench.


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## almondcity (Jan 25, 2022)

This is a jfet overdrive type pedal with full EQ. It's quite different sounding than the Broadcast which to me has kind of a "guitar plugged straight into the console" sound and only the low cut control. All 3 are good pedals but I like this the best, the EQ is more powerful than on the Benson I think


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## bhcarpenter (Jan 25, 2022)

almondcity said:


> 10x better than the Benson Preamp in my opinion.


That’s one hell of an endorsement! What’s your rig like?


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## almondcity (Jan 26, 2022)

Admittedly just a Blues Jr at fairly low volume. Your mileage may vary


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## smithcircuits (Jan 30, 2022)

Building this right now and stupidly soldered in the transformer without checking the orientation. Not sure I can pull it without destroying the pads... I don't suppose it'll work backwards? Anybody got an idea?


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## lrgaraujo (Jan 30, 2022)

I think I've read somewhere (but please don't quote me on that) that the 42tm018 (which is pretty similar to the 141P) can be installed backwards, and that makes sense since it's a 1:1 transformer


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## smithcircuits (Feb 3, 2022)

I got lucky - It works fine with the transformer backwards. Labelled my master & gain backwards too... 😅 Terrible hobby for someone with ADHD. Sounds great though!


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## Svenson007 (May 29, 2022)

smithcircuits said:


> I got lucky - It works fine with the transformer backwards. Labelled my master & gain backwards too... 😅 Terrible hobby for someone with ADHD. Sounds great though!


Cool build! I’ll defiantly be ordering one next. How do you do your labels?


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## innerlight (Aug 13, 2022)

Could someone talk this noob through the calibration process? Right now it’s not actually passing signal, but I’m hoping this is the issue


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## almondcity (Aug 13, 2022)

innerlight said:


> Could someone talk this noob through the calibration process? Right now it’s not actually passing signal, but I’m hoping this is the issue


I biased the jfets to 4.0V on the drain, if I remember correctly.


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## innerlight (Aug 14, 2022)

almondcity said:


> I biased the jfets to 4.0V on the drain, if I remember correctly.


Could you talk me through how to bias? Like where to place DMM probes and what setting to have it on? I'm a beginner!
Also is it possible that a unbiased pedal would not pass signal? My LED is on, it works in bypass, but not when engaged right now. I can hear the pentameters changing the sound also, but no signal is getting through
Thanks!


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## Quirkey (Aug 14, 2022)

innerlight said:


> Could you talk me through how to bias? Like where to place DMM probes and what setting to have it on? I'm a beginner!
> Also is it possible that a unbiased pedal would not pass signal? My LED is on, it works in bypass, but not when engaged right now. I can hear the pentameters changing the sound also, but no signal is getting through
> Thanks!


The simplest way is to clip your ground onto the pedal's ground and then the test (other side) of the DMM to the drain of the JFET. JFET leads are labeled D (Drain) S (Source) G (Gate). Search online for the pinout of the JFET you're biasing. Set the DMM to voltage measurement and then adjust the trimmer until it reads the voltage you're looking for. This is the most quoted article/reference with a lot more detail http://diy.smallbearelec.com/HowTos/BreadboardBareAss/BreadboardBareAss.htm


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## innerlight (Aug 14, 2022)

Many thanks! Ill report back..


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## Roberman (Aug 14, 2022)

almondcity said:


> I biased the jfets to 4.0V on the drain, if I remember correctly.


A while back, Mr PPCB posted that the unit he traced was calibrated to:
Q1 - 4.45v
Q2 - 4.3v
Q3 - 4.46v
Q4 - 4.75v

And to add to the previous advice, i usually just stick the ground probe into one of the screw holes on the chassis. Assuming everything is grounded properly, I find this to be easiest way to go. I've had clips come loose without me realizing it and then I can't figure out what the problem is until I finally notice the black probe flapping in the breeze.

Also, if your pedal works in bypass and you can hear the parameters changing the noise, you're in the ballpark. Might just be a problem w your footswitch wiring or the pcb in/out wires. Post a pic of the guts and somebody in here might be able to help.


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## innerlight (Aug 14, 2022)

Roberman said:


> A while back, Mr PPCB posted that the unit he traced was calibrated to:
> Q1 - 4.45v
> Q2 - 4.3v
> Q3 - 4.46v
> ...


Thanks heaps!
I just made a separate thread to solicit advice, but basically Q2 & Q3 are both up around 8v at lowest adjustment, so I’m wondering if I’ve got a wrong part in there. There’s photos there too! Have a look if you may. 
Thanks again, C


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