Fet version of the JCM800

Original effects with schematics, layouts and instructions, freely contributed by members or found in publications. Cannot be used for commercial purposes without the consent of the owners of the copyright.
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Tube2stomp
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Post by Tube2stomp »

I think I see where the issue (for me) is.
Some things in the jibrish translations of this article and from Viktor Kempf(?) talked about the internal resistance of the fet vs tubes with respect to the loads (where triodes need a higher load then their internal resistance, and fets are... basically kind of like pentodes... which makes some sense now [smilie=a_smartie.gif] ).
Very interesting.

Btw I wanted to know about this design because I understand what the other designs do and how they work, but also because from the sound samples it seems this one does have more circuit<>guitar interaction, which so far in solid state pedals/preamps it seems to be the hard part to mimic.

Wish you guys had these articles translated so the rest of the world could learn something.
Comparing your designs to the rest of the "cream of the crop" out there, is like comparing a Ford Cortina to a Lamborghini Countach :blackeye
Respect.
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yosemitesam144
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Post by yosemitesam144 »

This looks like an incredible project.
has anybody created a single sided pcb version? also what sort of current drain does this have? for finding a transformer.
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KMG
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Post by KMG »

Domain milas.spb.ru temporary unavalable due to moving to new IP address, but all information remains on our server.
You can get info by acsessing server via direct IP address.
http://217.119.30.118/~kmg/index_en.html
Current consuption can be calculated stage by stage from schematic using Ohm law
For example first stage: ((183V - 140V) / 100K = 0.43mA ) + (140V / 220K = 0.64mA) = 1.07mA
By suming cunsumption of all stages you wiil get total current consumption
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yosemitesam144
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Post by yosemitesam144 »

excellent, thanks dude! anybody been working on a single sided layout? i would love to fire this up!
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Post by DrNomis »

Just thought I'd let you all know that the links in the first post of this thread seem to be broken,I tried clicking on the links for the schematics and the demo clips and my web browser can't find the webpages... :)
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Post by briggs »

KMG wrote:Domain milas.spb.ru temporary unavalable due to moving to new IP address, but all information remains on our server.
You can get info by acsessing server via direct IP address.
http://217.119.30.118/~kmg/index_en.html
Current consuption can be calculated stage by stage from schematic using Ohm law
For example first stage: ((183V - 140V) / 100K = 0.43mA ) + (140V / 220K = 0.64mA) = 1.07mA
By suming cunsumption of all stages you wiil get total current consumption
It's all there :)
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I am Klon.
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KMG
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Post by KMG »

New version of fet JCM800 using LND150 with original "plate" voltage.
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For parallel testing I assembled the tube prototype:
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You can compare the sounds of fet and tube preamp boards.
Samples recorded by simply swapping connectors from one board to another (connectors pinouts of boards are the same) via poweramp & cabinet.
Recording path:
E-MU Tracker Pre->preamp->5W Fet PA->4x12 cabinet->Sennheizer E906->E-MU Tracker Pre
Drive
http://milas.spb.ru/~kmg/files/projects ... s_tube.zip
Clean
http://milas.spb.ru/~kmg/files/projects ... s_tube.zip
Clean sounds was recorded from "High" input with low gain setting (CH in file names) & "low" input (CL in file names).

Try to find out who is who on records.
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Post by Cub »

Wow, incredible project and incredible sounds ! All of your clips sound really good and have a very distinguished British accent. I'd be happy to gig or record with either one. Here's who I think is who.


from jcm800_fet_vs_tube.zip :

1. Almost FGT 1 : fet
1. Almost FGT 2 : tube

2. Classic T 1 : tube
2. Classic T 2 : fet

3. Country Esque 1 : fet
3. Country Esque 2 : tube

4. Criminal Def 1 : fet
4. Criminal Def 2 : tube

5. Glassy Paul 1 : fet
5. Glassy Paul 2 : tube

6. Kid Paul 1 : tube
6. Kid Paul 2 : fet

7. LP Delay 1 : tube
7. LP Delay 2 : fet

8. Southern LP 1 : fet
8. Southern LP 2 : tube



from jcm800_cl_fet_vs_tube.zip :

5. Glassy Paul CH1 : tube
5. Glassy Paul CH2 : fet

5. Glassy Paul CL1 : tube
5. Glassy Paul CL2 : fet


6. Kid Paul CH 1 : fet
6. Kid Paul CH 1 : tube

6. Kid Paul CL 1 : tube
6. Kid Paul CL 2 : fet
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Post by KMG »

Note:
Digit 1 represents one preamp, 2 - another.
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Cub
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Post by Cub »

Blimey, I thought you mixed and mashed things up. :D

Let's see, I called no. 1 six times the fet preamp and six times the tube preamp.
I also called no. 2 six times the fet version and six times the tube one. :scratch:

So there you have it, perfectly balanced ! I really can't say which one is which, but both are great. :applause:
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Post by FiveseveN »

Can't say which is which but I kinda like No.1 better. Maybe because it seems a little more saturated.
By the decay I'd wager No.1 is the FET version but that's just for the sake of the "game".
Quite curious on this one.
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Post by Cub »

Come on ! Surely a project this grand deserves more attention than this. 8)
What do you think is the FET and what is the tube and why ? :D
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Post by Ian444 »

I just came across this thread from the contest results. I would guess (yes I can only guess) number 2 is the tube version. I built a JCM800 preamp stompbox running high voltage 2 x 12AX7 and used it for many years, so I should know what it sounds like. If I am wrong, I can only say KMG has done a fantastic job of this, and if I am right, I can only say the same, that KMG has done a fantastic job of this pedal. Its so close, hard to pick which is which :!:
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KMG
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Post by KMG »

About samples, at first time "N1" was recorded SS version (fet), second "N2" - tube version.
About PSU:
For supply I use wall 12VAC adapter (1A max current).
Rectified & stabilized 12VAC gives -12V bias supply (requires about 7mA).
Also 12VAC goes to custom step up trafo 12VAC->250VAC with simple bridge rectifier connected to J5 for HV sipply (requires about 5mA).
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Post by KMG »

I think you can`t use my layout because of use custom step-up trafo.
Schematic of psu
http://milas.spb.ru/~kmg/files/projects ... 150/ps.pdf
R1, C5, C6 is snubber circuit to reduce "ringing" on secondary winding.
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Post by KMG »

I think this multiplier can`t give required HV current.
You can try to use one of these DC-DC (unfortunately in russian language)
http://bsvi.ru/impulsnyj-preobrazovatel ... /#more-397
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Post by Cub »

KMG wrote:You can compare the sounds of fet and tube preamp boards.
Try to find out who is who on records.
I'm still very interested about this. Back when you first posted these clips, I couldn't say which one was the tube amp and which one the FET and I still can't.
Could you please spill the beans about who is who ? :D
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Post by KMG »

by KMG » 15 Nov 2011, 01:46

About samples, at first time "N1" was recorded SS version (fet), second "N2" - tube version.
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Cub
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Post by Cub »

Whoops, must have missed that.
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Post by KMG »

Prototype head (JCM800 preamp + 5W PA):
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Sample
Mix
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