Mosfet Driver 2.0 with LND150 depeltion mosfet

[claudiologic]

Hello diysb community, it's the first time I've made a post here, and well, even though I don't know much about electronics, I've been forced to want to enter this world for obvious reasons. I am a guitarist and I would love to make an effects pedal that is based on the work of madbean pedals, it is the tube driver with the modification of removing the tube and using a mosfet, especially LND150, since I have read very good references on this fet.
I have designed the schematic please don't be so severe with criticism I don't know much about electronics haha
 
Here I leave the schematic to see if you can help me build it. If you want the schematic to make some modifications, leave your emails here.
PS: I would like to keep the design as close to the design of the tube driver with the only modification of the output buffer thanks.

[antonis]

Hi & Welcome..

In case of J1 Sleeve makes conduct with metal enclosure, it will short power supply..

[claudiologic]

Hi antonis, could you explain to me how to do that in a small scheme plz 

[antonis]

Simply by changing +12V and GND J1 wiring..
+12V -> TIP and GND -> SLEEVE..

[niektb]

Simply by changing +12V and GND J1 wiring..
+12V -> TIP and GND -> SLEEVE..

But that's not really pedal convention right? and considering the fact that there is no reverse polarity protection...?

[antonis]

What convention we're talking about..??

[claudiologic]

Simply by changing +12V and GND J1 wiring..
+12V -> TIP and GND -> SLEEVE..

Ok now I understand, thanks for the note, I'm going to make the change and I'll start buying the components and I'll assemble the breadboard and I'll be publishing the progress

[Clint Eastwood]

Hi there,

Replacing the tubes with LND150's will work electrically, but they will sound very different overdriven. There has been a very serious attempt to make them sound like tubes by adding circuitry, here is a link to a schematic: http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfSch.pdf

[claudiologic]

Hi there,

Replacing the tubes with LND150's will work electrically, but they will sound very different overdriven. There has been a very serious attempt to make them sound like tubes by adding circuitry, here is a link to a schematic: http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfSch.pdf

hello clint my schematic is based on tube driver, although I really don't understand much of the schematic you gave me, I would like you to explain more or less, another thing in this effect pedal the lnd150 works with smaller voltages

[niektb]

What convention we're talking about..??

The fact that all guitar pedal supplies are center negative?

[Ben N]

I think what Antonis was suggesting was an expedient for when the power jack is not insulated from the enclosure. The use of a standard plastic bodied power jack would take care of the problem without reversing anything. Maybe the confusion arises from the use of the TRS symbol in the schematic, and indeed, anyone using a non-isolated TRS jack should follow Antonis's advice.
As for the lack of polarity protection--just add some. You can easily mount a rectifier diode on the power jack at the cost of the voltage drop, or else wire a Schottky in series to the board.

The whole project is interesting to me, since the Tube Driver famously runs the tube at low voltage for a tube. Claudio, you are substituting the LND150, a MOSFET that can run at real tube-level voltages, in this circuit, which I guess makes sense, although I wonder if results might be better bumping the voltages up a bit higher. Anyway, carry on, curious to see how it goes.

[claudiologic]

I think what Antonis was suggesting was an expedient for when the power jack is not insulated from the enclosure. The use of a standard plastic bodied power jack would take care of the problem without reversing anything. Maybe the confusion arises from the use of the TRS symbol in the schematic, and indeed, anyone using a non-isolated TRS jack should follow Antonis's advice.
As for the lack of polarity protection--just add some. You can easily mount a rectifier diode on the power jack at the cost of the voltage drop, or else wire a Schottky in series to the board.

ok I will make the changes in the schematic so that it works in this way and I will put the polarity protection diode as niektb says and I will also make a better adaptation of the schematic so that there is no confusion also taking into account what Antonis says.

On the other hand, what client eatswood mentions is interesting because he suggests the adaptation of an additional circuit so that the lnd150 behaves like a vacuum tube, specifically a triode, I got this image that perhaps cannot help but if some modifications have to be made I would ask the electronics gurus for help, it would be very helpful.





I suppose that what is marked with blue would be the singular adaptation of a triode state. If you want to see the entire post of where everything came from, this page. https://www.ssguitar.com/index.php?topic=2039.0

The whole project is interesting to me, since the Tube Driver famously runs the tube at low voltage for a tube. Claudio, you are substituting the LND150, a MOSFET that can run at real tube-level voltages, in this circuit, which I guess makes sense, although I wonder if results might be better bumping the voltages up a bit higher. Anyway, carry on, curious to see how it goes.

on the other hand what ben n suggests seems super interesting to me but we would have to modify the entire schematic and the circuit to make it work that way which gives me an idea of ​​being able to apply it to some known and simple preamp stage I got a bottle preamp rocket amp adapted in pedal format but that does not use tubes but the MOSFET lnd150 here is the site https://www.thegearpage.net/board/index.php?threads/henning-bottle-rocket-preamp-pedal-video-and-audio-clips.2156695/ . On the other hand we can also adapt that tube driver with real voltages as suggested by dan n the idea is welcome.

[claudiologic]

sorry the image was not uploaded I upload this post so you can appreciate the image

[Ben N]

Just be careful with high voltage. You don't want to mess with that if you aren't sure you know what you're doing (unlike the usual 9v+ we generally fool with, that can only kill transistors & caps). The Tube Driver is a legit design, and your experiments with the LND150 are valid. I was just thinking aloud in my previous post. But there are LND150 preamp designs out there. I think Johnny Reckless has one posted on the forum. Do a search if you're interested.

[Clint Eastwood]

sorry the image was not uploaded I upload this post so you can appreciate the image

Yes, this is the basic 'trioderized' LND150 circuit. Note that it needs a negative bias voltage at the negative side, about -3 volts if I remember well. The Bat54 schottky diodes soften the corners of the clipped positive halve of the waveform. The diodes between the gate and source provide an artificial grid current,  this is responsible for the soft clipping of the negative part of the wave.
Without all this, the LND150 will clip more sharply than a  triode, especially on the negative side.
Although this may all look a bit complicated, don't be intimidated, this stuff is really worth looking into.

[iainpunk]

welcome to the forum

i see that you are dropping a lot of volume in between gain stages, is this to tame the gain? then why not one gainstage less

also, why is the output buffer by-passable?

cheers

[bean]

also, why is the output buffer by-passable?

cheers

It looks like this schematic was adapted from my "Archibald" project and re-worked for the mosfets. For the Archibald, the output buffer is an add-on which the BK Butler did not have. So, it was made bypass-able via a DIP switch.

[claudiologic]

sorry the image was not uploaded I upload this post so you can appreciate the image

Yes, this is the basic 'trioderized' LND150 circuit. Note that it needs a negative bias voltage at the negative side, about -3 volts if I remember well. The Bat54 schottky diodes soften the corners of the clipped positive halve of the waveform. The diodes between the gate and source provide an artificial grid current,  this is responsible for the soft clipping of the negative part of the wave.
Without all this, the LND150 will clip more sharply than a  triode, especially on the negative side.
Although this may all look a bit complicated, don't be intimidated, this stuff is really worth looking into.

     Ok now everything makes more sense, I made some adjustments to the schematic I would like them to correct me if there is any mistake, I made two models because the truth is I'm not sure haha the first one.
In the first one, add the components exactly as it trioderized the lnd150. I still don't have the values of the resistances that simulate the tube. I suppose that many tests have to be done to see how it is. So the first one is:



In this schematic it is the same as the original schematic in the first post with the difference of the circuitry improvement of the lnd150.
In the following add 2 bjt transistors to simulate the bias that appears in the schematic published by clint eastwood:



I accept suggestions and criticism to improve the design

[claudiologic]

also, why is the output buffer by-passable?

cheers

It looks like this schematic was adapted from my "Archibald" project and re-worked for the mosfets. For the Archibald, the output buffer is an add-on which the BK Butler did not have. So, it was made bypass-able via a DIP switch.

Yup I just took off the tone control and the  vacuum tube, but im thinking if I have to make some modification in the drain voltage of the mosfet but I dont know, btw great pedal archibald i see some videos and sound good very chewy.