DIEFET: Jfet simulation of the Diezel VH4

[audioguy]

PLease post a report on that layout... it looks like the one I used and had no luck with, but I could be wrong.

[rrhoads33]

I haven't tried it yet, but I've read, that some already used it, but there were no complaints at all. So it might be doing well. The only thing I'm worrying about is that the layout might hum or oscillate, because there could be too narrow spaces between lines that lead through unamplified and those which lead through the amplified signal.

I haven't checked the layout for this, but on the first sight it seems, like the primary aim was to create a layout as small as possible.

[rrhoads33]

... Am I missing something or did you two just sign up to say, that I posted something interesting?

[Scruffie]

Due to the flood of topics labelled Off Topic, someone knows there forum lingo and I think that is just some misleading spam... The purpose of... I don't even know what that achieves, no advertising and hardly cluttering the site... then again perhaps these two can prove us wrong??

[DimebuGG]

Found! There was one @ diystompboxes

Ground loop is obvious. At least ground trace should be cut once at any point. Need some verified layout on this?

[Ripthorn]

I haven't tried it yet, but I've read, that some already used it, but there were no complaints at all. So it might be doing well. The only thing I'm worrying about is that the layout might hum or oscillate, because there could be too narrow spaces between lines that lead through unamplified and those which lead through the amplified signal.

I haven't checked the layout for this, but on the first sight it seems, like the primary aim was to create a layout as small as possible.

I used that layout and it works well. I actually used it and put in the v1.2 mods and those required no additional space.

[audioguy]

Im sitting down to build this right now... which schem was used to number the parts? looks like the 1.21 scheme, as the 1.1 I have the part numbers are not lining up correctly.

[kupervaser]

Hello everyone,

I assambled the pcb yesterday and tested it. However all I get is oscillations.
I measured the voltages and it seems to be all good. I also checked the whole pcb with the schematic and the values are correct and it seems i haven;t made any mistakes during soldering.

This layout has been used


This schematic has been used:


I checked with hte audioprobe and the oscillations start just after C11, the side which goes to the treble potmeter. I can hear good aplified and high gain sound on the source of the Q5.
The controlls don't do much. Volume works well, gain is very low. When i put the deep potmeter on 0 I have low gain sound, when I turn the Deep up I get oscillations almost immidiately. The sound I hear is similar to the Fuzz Factory.

I don't know where to look any more, I checked the pcb very thoroughly.

I used a voltage doubler, which gives me around 17,66 volts on the output. I adjusted the trimpots so the transistor recieves the half of the voltage. But the trimpots don;t really do much in my case at the moment.

Has anyone had this kind of a problem?

All the help is appriciated.

[kupervaser]

I still haven\t solved the problem, if anyone can help me would be very cool.

[rrhoads33]

Do you get guitar signal and oscillations or just oscillations.

Right after C11; Hmm... Is it a very deep humm (approx. 40Hz) or very high?

If there's no guitar signal at all at the output you should trace that signal first and find the position, where it's gone the first time;

Cheers

[kantul]

I still haven\t solved the problem, if anyone can help me would be very cool.

What fet combination are you using?
Try different combination like mpf102 .
I using mpf102 on Q1,3, & 5.
hope it helps.

[kupervaser]

Hello kantul,

I used 5 j201 fets. I have removed the C26 from the pcb during debugging. If you look on the layout I posted it is the first capacitor after the treble pot. So basicall now there is a cut in the circuit. When I use the audioprobe now, I hear a good aplified sound on the treble pot (I assume the fets are working properly). But after the cut, strating from the 220K resistor I hear oscillation only. The problem is there i guess. That part of circuit oscillates on its own because there is no guitar input since i removed C26.

[shinichikudo]

simulation credit auto
I must be the stupidest person in the world. I cannot get this to work.

[rrhoads33]

Test if the 33k in the feedback loop of U1a is connected properly. If this resistor would be missing, the whole thing would oscillate. Also check the area around this resistor a bit.

Cheers

[kupervaser]

Do you mean the 33K resistor between the 1 22nF capasitors above the U1a? Ok i will.

Can you explain this oscillation a bit? Why would the circuit oscillate if the resistor wasn't good?

Kind regards,

[rrhoads33]

See it like this: Higher Frequencies can better pass a capacitor than lower ones.

Ground is 0V in your circuit. Every guitar sound, that is lead to ground "disappears".

If the high frequencies are lead to ground over the resistor, they disappear, if they go back into the circuit, they'll be amplified.

I've just noticed, that the feedback loop of the Opamp goes back into the inverting input, which means, that the 33k is not the problem. In this case the problem would be, if one off the 22n caps would have bad contact.

I see, that the 470pF capacitor to ground before the + input of U1a filters high frequencies at the input. It should be checked as well.

You'll get a lot of information about this, when you google for "RC oscillator"

http://www.electronics-tutorials.ws/osc ... lator.html This page is quite interesting; And don't mind the phase shift things; They aren't really important for you now.

Cheers

[kupervaser]

Thanx for your help, i will read the website very carefully and will try all the things you advised me tonight. Tomorrow I will post the results.

[rrhoads33]

Seems like the nights are longer in your country than in mine

Any results yet?

Cheers

[kupervaser]

Hey, i got it to work.

THe schematic and the partslist differ in 1 component. The capasitor just after the DEEP pot, the on that connects to the sweeper must be 1,1uF like the schematic sais. This capasitor (C27) in the partslist is beeing marked as 1nF. So i changed that but nothing improved. Then i swapped the capasitor in the feedback loop, from the sweaper of the DEEP pot to 120k and 39k resistors (on the schematic it is the one that has no value). That capasitor is the C31. According the partslist C31 is 100nF. I swapped it for 1nF and it worked.

THanx for your help

[kupervaser]

Hey, i got it to work.

THe schematic and the partslist differ in 1 component. The capasitor just after the DEEP pot, the on that connects to the sweeper must be 1,1uF like the schematic sais. This capasitor (C27) in the partslist is beeing marked as 1nF. So i changed that but nothing improved. Then i swapped the capasitor in the feedback loop, from the sweaper of the DEEP pot to 120k and 39k resistors (on the schematic it is the one that has no value). That capasitor is the C31. According the partslist C31 is 100nF. I swapped it for 1nF and it worked.

THanx for your help