DIEFET: Jfet simulation of the Diezel VH4

[ech0es]

Created on the French DIY community http://www.techniguitare.com

http://www.techniguitare.com/projets/Di ... -V1-11.pdf

Sample 1

Sample 2

Sample 3

Schematic with components

PCB

BOM

It was not created with the ROG techniques because the schematic of the VH4 is not known, so we created a preamp with a spectral analysis of an original VH4 to see which frequencies are typical of the VH4 sound (channel 3 & 4 ).
We worked 6 months on it to do the last schematic.

[pz]

And i see you have taken and used the redrawn Varicab schematic from my site...
But that's ok with me.

[ech0es]

I didn't know that it was from your site, i found it on our DIY forum.

Thanks a lot !this schematic permit to do the VH4S version

[analogguru]

I don´t know what is a Diezel VH4 - does it sound like a V8-Diesel-motor ?

.... and the design still uses drain-trimmers - even at the source bypassed stages - which will cause every unit to sound different due to the different drain-currents....

If only the frequency response would be important, someone could use op-amps instead of the FET´s too...

analogguru

[ech0es]

I don´t know what is a Diezel VH4 - does it sound like a V8-Diesel-motor ?

Used by metallica, tool, smashing pumpkins, muse etc...

Matthew Bellamy / Muse
Adam Jones / Tool
Billy Corgan / Smashing Pumpkins
James Hetfiled / Metallica
Kirk Hammeth / Metallica
Mark Tremonti / Creed / Alter Bridge
Wes Borland / Limp Bizikit / Black Light Burns / Marilyn Manson
Mike Mushock/ Staind

.... and the design still uses drain-trimmers - even at the source bypassed stages - which will cause every unit to sound different due to the different drain-currents....

If only the frequency response would be important, someone could use op-amps instead of the FET´s too...

It's the conception of the Jfet simulation: use drain trimmers and adapt them to 6v. (4.5v for 9v sim).

[analogguru]

It's the conception of the Jfet simulation: use drain trimmers and adapt them to 6v. (4.5v for 9v sim).

It is simply a junk-conception, even "stm" from ROG found this out in the meantime:
http://www.diystompboxes.com/smfforum/i ... c=70065.80

analogguru

[ech0es]

Feel free to upgrade but your method is to respect the frequencies of simulated stages BUT , we did'nt start from the schematic of the Diezel. (post 1 of this topic).

You can read the conception here:
http://www.techniguitare.com/forum/viewtopic.php?t=6606

[DSV]

I followed the project on techniguitare. It is not a traditional simulation with the ROG method. In fact it does not stem from the schematic of the Diezel, but from the Dual Rectifier. Then a frequency analysis of a VH4 has been performed, in order to design a post-equalizer capable of mimicking the frequency response of this amp, and has been added to the Rectifet (the techniguitare version of the Dual Recto simulation).

Of course, it could be done with other devices, but that's how the project originated. Maybe in a future version ...

EDIT: echOes, you beat me to it ...

[ech0es]

I followed the project on techniguitare. It is not a traditional simulation with the ROG method. In fact it does not stem from the schematic of the Diezel, but from the Dual Rectifier. Then a frequency analysis of a VH4 has been performed, in order to design a post-equalizer capable of mimicking the frequency response of this amp, and has been added to the Rectifet (the techniguitare version of the Dual Recto simulation).

It was at the beginning, now it's a totally new preamp ! the post eq idea was abandonned for example

[rackham]

Regardless of the trimmers issue, it sounds pretty good to me.

[ech0es]

it's not an issue, it's the same thing for all the ROG sim, and for this sim it's not a problem because we didn't do it from the original schematic.

You just have to adjust them at 6.5v

[audioguy]

The PDF file prints the PCB really poorly, and its nearly impossible to follow the layout. Do you happen to have the Eagle file used?

[ech0es]

see my first post:

PCB

[audioguy]

Yeah when I load that PCB file into photoshop it gives me an error. Standard photoviewers open it fine, but photoshop says something about missing data.

[John Lyons]

Just use the PCB and "Schematic" (which is actually the Layout map).
The PDF is pretty bad! Hard to read and fuzzy.
You could probably just print the schematic and compare it to the BOM and layout.
But why not just make a decent PDF huh?

Sounds ok but the sound clips are overly bassy...

john

[ech0es]

Sounds ok but the sound clips are overly bassy...

You have 3 controls to adjust the bass level: BASS DEEP and the extra control (330k or pot 500k)

[audioguy]

3 bass controls?? yikes

[ech0es]

The bass control is the same as the original on the VH4 (as the teble and middle)because we found the schematic of the tonestack, the deep control is also on the vh4 (see the user manual) it boost around 100Hz, and the extra control will decrease the bass level before the tonestack and the deep control.

[audioguy]

sounds like it could be a very cool box... I might re-work the layout a bit to get it to fit into a standard sized box

[ech0es]

we work on a 1.2 version to add a "dynamic" control

So if you make the extra control as an outside control, it could be a 9-knobs distortion (on test!)

Vol
Gain
Bass
Mid
Treb
Deep
Presence
Dynamic
Cut (the extra control to cut the bass before the tonestack)