Want to make your guitar active? Build a JFET Booster that 'emulates' a tube triode stage

[@carlgradolph9676]

Brilliant! Thanks for doing this deep dive into the Fetzer Valve circuit. Your PCB design, your insights and tips are most appreciated.

[@electronicsoldandnew]

Pleasure

[@SIXSTRING63]

I will be trying this one out. I’ve been a gigging guitarist for 45 years. I love building and repairing my own gear so this is interesting to me. Thanks for all your research and experimentation. I wish I was closer, I would trade you some guitar lessons for some electronics lessons 🙂🙂

[@electronicsoldandnew]

I certainly need those lessons 😊

[@DavidTipton101]

I was hoping to hear you play guitar Manuel 🎸🙂

[@electronicsoldandnew]

😊 KZbin would probably block it as a service to society 😊

[@mackfisher4487]

Dave, as you no doubt remember when Manuel first started the channel he didn't show his face, then he promised after X number of subscribers he would and did. Perhaps if enough non-subscribers sign up as incentive to play his guitar he will do so..

[@electronicsoldandnew]

😊 I would definitely lose a few thousand immediately if they heard my playing 😊

[@radio-ged4626]

Be great if we could hear a demo! 🎸😁

[@electronicsoldandnew]

You and everybody else would turn off the sound immediately 😊

[@radio-ged4626]

@@electronicsoldandnew I don't believe you. I bet you could knock out a decent tune if you wanted to. 😁

[@t1d100]

Thanks! Tip = I use KiCad to design my boards. Many of the discrete through hole components (caps, resistors, diodes, etc.) can be seated in a (common) 5mm pin spacing. 5mm is common on ceramic cap ("gum drop") through holes. That distance will also accommodate through hole resistors and diodes, if you seat them vertically. A distance of 5mm will also accommodate a 1206 (and smaller) SMD. So, I made a custom footprint that has 5mm pin spacing for through hole components and pads in between to seat SMDs. Now, I have a choice to use TH, or SMD components, without having to buy additional PCB real estate to provide a parallel choice of pad types. I hope that was clear. Cheers!

[@electronicsoldandnew]

👌

[@DustinWatts]

I like to also put my trim pots in a socket. That way I can set the value of the trim pot off board to the value I want and be sure that I only measure the pot value. It makes things a bit more bulky but it makes it so you can accurately set the pot. Or you can use it to easily switch resistors for testing. Now in your case it makes no difference because you go straight from Drain to VCC and from Source to GND. But in other circuits it is not always possible to measure the trimpot accurately because of other components in the circuit.

[@electronicsoldandnew]

👍

[@tubeDude48]

I noticed when you were showing the first schematic of yours, there was C2, but when you were showing the roll-off later, it was labeled C3. Hum! Although characteristics are different, J310 are popular as well. Although their calculator is very nice, to bad they don't allow to switch between the devices.

[@electronicsoldandnew]

I’ve actually got a few J310s so will probably try that as well.

[@tubeDude48]

@@electronicsoldandnew - 👍

[@psionl0]

The capacitor across the input is not a Miller capacitor. Miller capacitance is the capacitance across the grid and plate of the triode. Because of feedback action, part of the capacitance between the grid and the cathode will be the Miller capacitance multiplied by the gain of the triode. But the real problem with Miller capacitance is when use are using tuned circuits. There, Miller capacitance can introduce negative resistance and cause the triode to oscillate. Neutralizing the Miller capacitance was a major problem for wireless receivers in the 1920s. (The introduction of the tetrode and pentode solved this problem).

[@electronicsoldandnew]

👍

[@Byzmax]

Brilliant

[@DAVIDGREGORYKERR]

I suspect that a Philips/Raytheon wire ended vacuum tube might work better and will work of heater voltage of 1.5V and a B+ of 9V.

[@electronicsoldandnew]

👍

[@eddys.3524]

No, you're wrong on C4 .... it passes top-end and lowering the value will cut-off low-end. BTW, in the D-S line you'll want some fixed resistor for in the current circuit you're able to blow up your FET.

[@electronicsoldandnew]

The output load is the scope in this case, but would probably be safer with an on-board resistor.

[@Tekenduis98]

Can I buy one? :)

[@electronicsoldandnew]

Sorry, it’s all DIY. I don’t sell these or any other kits of gear.

[@Tekenduis98]

@@electronicsoldandnew thank you, you did provide the details, i was just being lazy.

[@Tekenduis98]

@@electronicsoldandnew Could you upload the gerber for the pcb please sir, I would like to build one, I check the video description almost daily now LOL.

[@electronicsoldandnew]

I’m just about ready to post another version, so will do both then. Will probably be up next week.

[@Tekenduis98]

@@electronicsoldandnew thank you sir, much appreciated! You are the best

[@mackfisher4487]

Manuel excuse two posts, but I didn't think that this was going to be an interesting episode when it started as it was guitar related. I was wrong, I'm going to play after all with JFETs on my breadboard Without musical accompaniment. I particularly liked how detailed you got into prefaced on the German research papers. Thanks You and it's nice that your sponsor is PCBWay, not some soap company.

[@electronicsoldandnew]

👍 or a manscaping razor 😊

[@mackfisher4487]

Free guitar gadget Suggestion: Manuel, Trade your favorite guitar group your guitar gizmo for a short intro piece of music that you could get past the Google sensors. Perhaps you could even play it, or if worst-case strum the guitar with a mic off and dove in the music. Better yet some cartoon characters seemingly playing the sounds. (Sorry you know I have a warped sense of humor)

[@electronicsoldandnew]

Actually, some of my guitarist friends already look like cartoon characters 😊

[@josealeixes2861]

Muito top seus vídeos

[@electronicsoldandnew]

Obrigado ☺️

[@daveturner5305]

Is it my imagination? I got the impression that the phase difference between input and output was not quite180.

[@electronicsoldandnew]

No, it was not. The capacitors in the signal path will have some effect on phase.

[@daveturner5305]

Of course stray inductance can also have an effect. Thank you for your response.@@electronicsoldandnew

[@electronicsoldandnew]

👍

[@frankc1430]

Jack Daniels

[@electronicsoldandnew]

That’s it 👍