Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Preamps and Effects => Topic started by: KMG on January 16, 2011, 01:42:05 PM

Title: Fet version of the JCM800
Post by: KMG on January 16, 2011, 01:42:05 PM
Schematics (pdf)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/jcm800mvfSchS.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/jcm800mvfSch.pdf)
Stage by stage frequency response in comparison with the original tube version (stage2 with different gain positions)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/st1S.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/st1.jpg)(http://milas.spb.ru/~kmg/files/projects/jcm800mv/st2S.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/st2.jpg)(http://milas.spb.ru/~kmg/files/projects/jcm800mv/st3S.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/st3.jpg)
Ready to transfer PCB (pdf)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/jcm800mvfLutS.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/jcm800mvfLut.pdf)
Upper side assembly (pdf)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/jcm800mvfCompS.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/jcm800mvfComp.pdf)
Bottom side assembly (pdf)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/jcm800mvfSoldS.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/jcm800mvfSold.pdf)
Assembled board
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/brdtopS.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/brdtop.jpg)
Controls and input jacks (pdf)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/RegS.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/Reg.pdf)
Project page (with some samples)
http://milas.spb.ru/~kmg/jcm800fet_en.html
Title: Re: Fet version of the JCM800
Post by: DJPhil on January 16, 2011, 02:12:56 PM
Excellent work!
That's a very well thought out and documented project. I bet you'd be able to sell boards or kits for it. I don't think I've seen such a well made DIY high voltage FET tube sim circuit before.
I'll bet that you'll have folks who are trying to make their own asking about the power supply board soon. It might get tricky for those of us working from 115VAC. I bet I could sort something out from older tube circuitry, after all, it makes sense. :)

You've got a really good article on your site about FET simulation (http://translate.google.com/translate?u=http%3A%2F%2Fmilas.spb.ru%2F~kmg%2F&sl=ru&tl=en&hl=&ie=UTF-8) as well! (Google translate link to english)

Thanks for all this, I've got some reading to do.  :tu:
Title: Re: Fet version of the JCM800
Post by: KMG on January 16, 2011, 02:24:36 PM
Examples of two power supplies. Both has 12VAC input from wall adapter.
Simple transformer
http://milas.spb.ru/~kmg/files/projects/sharp/fet/Ps.pdf
DC/DC
http://milas.spb.ru/~kmg/files/projects/200vdcdc/200dcdcSch.pdf
Title: Re: Fet version of the JCM800
Post by: KMG on September 06, 2011, 06:15:01 AM
JCM800 preamp using LND150
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/brdtop_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/brdtop.jpg)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfSch_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfSch.pdf)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfLut_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfLut.pdf) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfComp_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfComp.pdf)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfSold_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfSold.pdf) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfSold1_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfSold1.pdf)
Comparative samples with tube prototype
Drive
http://milas.spb.ru/~kmg/files/projects/jcm800mv/jcm800_fet_vs_tube.zip (http://milas.spb.ru/~kmg/files/projects/jcm800mv/jcm800_fet_vs_tube.zip)
Clean
http://milas.spb.ru/~kmg/files/projects/jcm800mv/jcm800_cl_fet_vs_tube.zip (http://milas.spb.ru/~kmg/files/projects/jcm800mv/jcm800_cl_fet_vs_tube.zip)
Title: Re: Fet version of the JCM800
Post by: J M Fahey on September 06, 2011, 01:48:08 PM
IM_PRESS_SIVE !!!!!!!!!!!!!!!!!!!!!!!! :tu: :tu: :tu: :tu:
You have nailed it *exactly*.
Congratulations !!
Thanks for sharing your awesome work.
Can you explain how did you record this?
Did it go through Cab+mike or is it all emulation too?
Thanks.
Title: Re: Fet version of the JCM800
Post by: KMG on September 06, 2011, 03:17:12 PM
Photo of tube prototype:
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/tube/brdtop_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/tube/brdtop.jpg)
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

PS Any thoughts who is who on samples?
Title: Re: Fet version of the JCM800
Post by: Tubis on March 14, 2012, 03:31:10 AM
Some questions to an old post:

1. The 2SK215 circuit has the gate diod feed by the drain. The LMD150 circuit by the source. Why the difference?

2. Why do the circuits need a negative supply on the source and why do that supply need to be buffered?

3. How crucial is the type of diods? You use different types for the two circuits?

4. Does the circuit need to be high voltage or can you get good results with 10times lower voltage?
Title: Re: Fet version of the JCM800
Post by: KMG on March 14, 2012, 08:01:46 AM
Quote
1. The 2SK215 circuit has the gate diod feed by the drain. The LMD150 circuit by the source. Why the difference?
Different VA curves.
I used 2SK216, 2SK215 has max 180V drain voltage.
Quote
2. Why do the circuits need a negative supply on the source and why do that supply need to be buffered?
Because with autobias with source network tied to GND I can`t get stage gain, frequency response & top/botton clipping points same as for tube prototype.
Quote
3. How crucial is the type of diods? You use different types for the two circuits?
In source network you can use germanium/shottky diodes, they has similar knee curve.
Quote
4. Does the circuit need to be high voltage or can you get good results with 10times lower voltage?
I started with low voltages but understood that this can`t give "true tube sound".
Title: Re: Fet version of the JCM800
Post by: phatt on March 14, 2012, 09:19:33 AM
Quote from KMG;
"I started with low voltages but understood that this can`t give "true tube sound"

Yes I'm quite convinced that high voltage plays a big part even though I've never found a good explanation of that point it makes perfect sense that even a banana would benefit if you run it from big voltage. :cheesy:
Phil.
Title: Re: Fet version of the JCM800
Post by: Tubis on March 14, 2012, 11:32:26 AM
Whats your take on this circuit?

http://gtlab.net/gtlab4/wp-content/uploads/2009/03/soldano1.jpg
 
How close to tube can that sound?

And why the neagtive supply on that? Dosent that get eaten upp by the drainfeed anyway?
Title: Re: Fet version of the JCM800
Post by: KMG on March 15, 2012, 04:11:56 AM
I started low voltage fet experiments with Victor Kampf idea.
http://www.sugardas.lt/~igoramps/article68/article.htm
But sound was not close enough to tube one & I moved to high voltage experiments.
First was Bogner Ecstazy preamp. Even without grid current emulation it gives results close to tube sound.
Fet version:
http://milas.spb.ru/~kmg/files/projects/xtcfet/pedal/samples/denn/kmg_xtc_mix.mp3
Tube version:
http://milas.spb.ru/~kmg/files/projects/xtcfet/pedal/samples/denn/denn_xtc_crunch_bluesmix.mp3
I tried to use Kampf`s idea with 2SK216, but in this case stage fall to FET saturation or has very fast beginning of grid limiting depending on diode biasing.
After discussing with author of this article http://gtlab.net/gtlab4/archives/216 (where this schematic http://gtlab.net/gtlab4/wp-content/uploads/2009/03/soldano1.jpg was published), I used his idea with 2SK216 & it works fine.
But I don`t tried his schematics in original.
When I start experiments with LND150 I tried to use Kampf`s idea again & it works fine with this type of FETs.
If you want to try JFET soldano you must use JFETs with cutoff voltage 0.6-0.8 Volts.
Stage tuning procedure (translated from article).
1. Set voltage at drain 6-7 Volts by adjusting source resistors (1k*).
2. Connect left pin (by schematic) of gate resistor to VSupply. Check drain voltage, it must be 2.5-3 Volts. If it high decrease resistance of R(22k*) from -bias supply, othervise increase it.
Title: Re: Fet version of the JCM800
Post by: Tubis on March 15, 2012, 01:34:21 PM
So many questions :-[

In the source network...there is a diod called ES1J.
Google says its a silicon fast recovery. Is it crucial or would any old silicon diod do?

What ratings does all the diods in the source demand when it comes to voltage and current?
Im now talking about the lnd150 circuit.

And finaly,  wouldn't it be nice to model the power amp with lnd150 high voltage as well? I can se on your home page that you done a 12V poweramp model. But wouldn it be nice to be able to run that with the preamp at the same voltages?

I like your work by the way....got me all exited. And i happen to have a 100 lnd150 collecting dust at home.
Title: Re: Fet version of the JCM800
Post by: KMG on March 16, 2012, 07:25:34 AM
Quote
In the source network...there is a diode called ES1J.
Google says its a silicon fast recovery. Is it crucial or would any old silicon diod do?
Germanium/shottky diodes added to source network to round sharp edges then stage enters/exits from cutoff state by summing VA curves of diodes & fets.
Then previous stage outputs full clipped voltage span, peaks on gate may be up to -160 volts.
Because LND150 has gate protection zener, fet source follows gate with voltage less than gate voltage by amount of protection zener breakdown voltage.
Diodes in source network become reverse biased. But maximum reverse voltage for BAT54 is 30 Volts. So I added high voltage fast diode to source network.
Title: Re: Fet version of the JCM800
Post by: Ilya-v on March 20, 2012, 07:35:50 AM
KMG,

According to this final gain stage schematic:
(http://milas.spb.ru/~kmg/files/projects/dualrectifier/test/lnd150/St1_th.jpg)

R2 & D1 control how (softly/round/when) the grid is clipping when the input is reaching the bias point (-1.5)?

C1 is miller capacitane emulation.
What exactly D2, D3 and D4 are doing in terms of 12ax7 biasing equivalence?
R? and C2 are the same as Cathode resistor and Capacitor as in the 12ax7?
Title: Re: Fet version of the JCM800
Post by: KMG on March 20, 2012, 07:54:53 AM
Quote
R2 & D1 control how (softly/round/when) the grid is clipping when the input is reaching the bias point (-1.5)?
R2 defines "softness" of grid clipping. Voltage drop on D1 & R3 defines point of clipping.
Quote
C1 is miller capacitane emulation.
Yes.
Quote
What exactly D2, D3 and D4 are doing in terms of 12ax7 biasing equivalence?
As I wrote above:
Quote
shottky diodes added to source network to round sharp edges then stage enters/exits from cutoff state by summing VA curves of diodes & fets.
D4 added to protect shottky diodes from destructive breardown
Quote
R? and C2 are the same as Cathode resistor and Capacitor as in the 12ax7?
No, left resistor defines stage gain below cutoff frequency, right R defines gain above cutoff, RC defines cutoff frequency.
Title: Re: Fet version of the JCM800
Post by: Ilya-v on March 20, 2012, 12:52:55 PM
Thank you KMG.

So.. R2 (1K), D1, D2, D3 and D4 are "SET" values to emulate the 12ax7 response right? There is no need to play with them?

What do you mean by "Point of Clipping"? the negative grid bias voltage like -1.5v in a 12ax7?

With what Resistor the Capacitor forms the RC filter? R?1 or R?2 or together?
Do they effect only the frequency or the grid (gate) auto-bias point also?


Can you please elaborate more about replacing a 12ax7 gain stage with an lnd150.
For example:
* How to calculate the Cathode Resistor & Bypass Capacitor in the lnd150 gain stage to be equivalent to the 12ax7.
* How to actually bias the Gate of the lnd150 to be equal to the auto-biased grid of the 12ax7.
* How important are the values of all the diodes in the circuit and what they actually for.
* Why we need a Negative voltage at the Soure.

A document like this: http://www.freewebs.com/valvewizard1/Common_Gain_Stage.pdf
Will be SUPER effective in terms of explaining the "How To"s.

And most important:
Can we actually place 2 gain stages like these (with access to some pots) into a 12ax7 shape clear plastic enclosure and stick it in any 12ax7 place?
Patent it maybe?   8|


I greatly appreciate the info here.
Thanks.

P.S.
к стати, Я так плохо читаю по руский что не надо даже пробовать.
Some Translit.ru help here took me about 10 minutes.  :)
Title: Re: Fet version of the JCM800
Post by: KMG on March 21, 2012, 04:56:43 AM
Quote
So.. R2 (1K), D1, D2, D3 and D4 are "SET" values to emulate the 12ax7 response right? There is no need to play with them?

What do you mean by "Point of Clipping"? the negative grid bias voltage like -1.5v in a 12ax7?
"Grid clipping point" (starting of "grid" current) defined by voltage drop on R3, forward voltage drop on D1 & fet cutoff voltage.
It`s very hard to calculate it mathematically because there is no detailed description of diode VA curve at currents about tens of microamperes.
Quote
With what Resistor the Capacitor forms the RC filter? R?1 or R?2 or together?
Do they effect only the frequency or the grid (gate) auto-bias point also?
frequency cutoff defined by:
f = 1 / (2 * π * C * (R?1 +  R?2))
Auto-bias point defined by negative source bias voltage & DC voltage drop on R?1, R3, D2-D4.
Separete source biasing allows to independently adjust gain/frequency response & DC operating point of stage.

I don`t see the way to calculate exact stage "on paper". You can try to use simulation programs to estimate values.
I use testing board to adjust values for each kind of stage using signal generator, oscilloscope & RMAA for frequency response check.
(http://milas.spb.ru/~kmg/files/misc/StendS.jpg) (http://milas.spb.ru/~kmg/files/misc/Stend.jpg)
This is old photo witn 2SK216, now I replaced them by LND150.

Only way to eliminate negative voltage at the source, is to use positive biasing of "grid" network.
But it`s not suitable for input (from guitar) stage.
Title: Re: Fet version of the JCM800
Post by: Ilya-v on March 21, 2012, 02:31:35 PM
Thank you. I greatly appreciate this.
Title: Re: Fet version of the JCM800
Post by: bassetrox on June 06, 2012, 06:47:16 AM
Hi KMG and everyone,

The sound clips sound great, excellent project!!

How much current does the LND150 circuit draw? Without sitting down and working it out, I presume the valve pre would draw maybe 20-30mA max from the HT rails, how much does the SS version draw? I've got a couple of HT tiny torroids I could run in parallel, but they're only 25mA each.
Title: Re: Fet version of the JCM800
Post by: KMG on June 06, 2012, 07:42:50 AM
Current consumption can be simply calculated from schematic using voltage drop on R30.
(340V - 290V) / 10K = 5mA.
Title: Re: Fet version of the JCM800
Post by: joecool85 on June 08, 2012, 09:48:59 AM
JCM800 preamp using LND150
...
Comparative samples with tube prototype
Drive
http://milas.spb.ru/~kmg/files/projects/jcm800mv/jcm800_fet_vs_tube.zip (http://milas.spb.ru/~kmg/files/projects/jcm800mv/jcm800_fet_vs_tube.zip)
Clean
http://milas.spb.ru/~kmg/files/projects/jcm800mv/jcm800_cl_fet_vs_tube.zip (http://milas.spb.ru/~kmg/files/projects/jcm800mv/jcm800_cl_fet_vs_tube.zip)

Are the first clips the LND150 and the second clips are the tube or the other way around?  I like the sound of the second clips, although the biggest reason is it sounds just a little more trebley and I like that.
Title: Re: Fet version of the JCM800
Post by: KMG on June 08, 2012, 10:06:02 AM
First time "N1" was recorded SS version (fet), second "N2" - tube version.
Title: Re: Fet version of the JCM800
Post by: bassetrox on June 11, 2012, 11:03:39 AM
Course it can.

I had a browse around your website. The FET poweramps with op tx sound great too. Do you think you could get similar results using vertical mosfets? The 2SK216s seem to be obsolete and from what I can tell there aren't that many lateral power mosfets around.


Current consumption can be simply calculated from schematic using voltage drop on R30.
(340V - 290V) / 10K = 5mA.
Title: Re: Fet version of the JCM800
Post by: joecool85 on June 11, 2012, 11:08:08 AM
First time "N1" was recorded SS version (fet), second "N2" - tube version.

Interesting, so I did prefer the tube version.  From what I can tell though, it was primarily due to a treble boost in that circuit.  Maybe something to consider for future circuits?
Title: Re: Fet version of the JCM800
Post by: KMG on June 13, 2012, 05:06:50 AM
bassetrox, it`s very bad news
I don`t find any replacement for them.
Quote
Do you think you could get similar results using vertical mosfets?
Vertical mosfets has several disadvantages - positive temperature coefficient (needs temperature compensation) & high transfer ratio.
Title: Re: Fet version of the JCM800
Post by: bassetrox on June 18, 2012, 10:41:44 AM
Yeah, that's what my research turned up.

The only lateral mosfets I can track down the are the exicon models from profusion. If anyone has any other suggestions I'd be interested!

bassetrox, it`s very bad news
I don`t find any replacement for them.
Quote
Do you think you could get similar results using vertical mosfets?
Vertical mosfets has several disadvantages - positive temperature coefficient (needs temperature compensation) & high transfer ratio.
Title: Re: Fet version of the JCM800
Post by: KMG on October 26, 2012, 07:10:40 AM
I got ordered PCB's for JCM800 based on LND150
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/Jcm800Boards_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/Jcm800Boards.jpg)
Title: Re: Fet version of the JCM800
Post by: joecool85 on October 26, 2012, 11:45:52 AM
So...are you going to start selling these things or are these just for your own use?
Title: Re: Fet version of the JCM800
Post by: KMG on November 04, 2012, 01:02:40 PM
Quote
So...are you going to start selling these things or are these just for your own use?
Bare boards are not planned for sale. Primarily I plan to use these boards in this design
http://www.ssguitar.com/index.php?topic=1981.msg19551#msg19551
Maybe I'll sell small amount of assembled boards as a kits (but not just now).
Title: Re: Fet version of the JCM800
Post by: KMG on November 19, 2012, 04:00:22 PM
Prototype head (JCM800 preamp + 5W PA):
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Prototype_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Prototype.jpg)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Prototype1_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Prototype1.jpg)

Sample
Mini Head Medium Power (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/samples/reamp/S1.mp3)
Same controls setting except master volume turned to MAX position
Mini Head Full Power (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/samples/reamp/S2.mp3)
Title: Re: Fet version of the JCM800
Post by: 2308to on December 01, 2012, 07:41:38 AM
Prototype head (JCM800 preamp + 5W PA):
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Prototype_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Prototype.jpg)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Prototype1_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Prototype1.jpg)


Sample
Mini Head Medium Power (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/samples/reamp/S1.mp3)
Same controls setting except master volume turned to MAX position
Mini Head Full Power (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/samples/reamp/S2.mp3)

Sounds Killer !!
Title: Re: Fet version of the JCM800
Post by: KMG on December 04, 2012, 07:01:45 AM
Additional samples
Mini head, gain at 2 hours, presence 2 hours, Depth & TS at middle positions (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/samples/reamp/S3.mp3)
Mini head, gain at full position, Depth, presence & TS at middle positions (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/samples/reamp/S4.mp3)
Title: Re: Fet version of the JCM800
Post by: KMG on December 24, 2012, 02:08:34 AM
The planned mini-head design
Budget version
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Head20_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Head20.jpg)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Head21_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Head21.jpg)
Custom version
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Head22_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Head22.jpg)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Head23_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Head23.jpg)
Title: Re: Fet version of the JCM800
Post by: J M Fahey on December 26, 2012, 12:34:46 PM
*Very* cool and good sounding.
Doubly so now you packed it inside a Tolex covered cabinet  8)
Title: Re: Fet version of the JCM800
Post by: KMG on December 27, 2012, 06:05:56 AM
Another several samples
High input, gain at 3.5, TS, presence & depth at middle
High input, crunch (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/samples/reamp/S6.mp3)
Low input, gain at 8, TS, presence & depth at middle
Low input (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/samples/reamp/S5.mp3)
Low input + reverb in loop (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/samples/reamp/S5R.mp3)
Title: Re: Fet version of the JCM800
Post by: KMG on January 10, 2013, 04:42:26 AM
Test of Prototype.
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/Prototype1_th.jpg)
With SS
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/brdtop_th.jpg)
 & Tube preamps.
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/tube/brdtop_th.jpg)
Because they have the same board connectors pinouts, swapping was very easy.
Controls settings are the same for different preamps while recording.
Fet_vs_Tube (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/samples/reamp/Fet_vs_Tube.zip)
Archive contains mix & only guitar tracks.
Legend:
SX_Y
X - track number
Y - preamp number
SX_YG - only guitar without mix.
Try to estimate who is who.
Title: Re: Fet version of the JCM800
Post by: jubal81 on March 05, 2013, 04:48:53 PM
Amazing stuff! My guess is preamp1 are the fets and preamp2 are the tubes.
Title: Re: Fet version of the JCM800
Post by: KMG on March 08, 2013, 10:56:11 AM
Sх_1 - Tube
Sх_2 - Fet
Title: Re: Fet version of the JCM800
Post by: KMG on March 14, 2013, 07:41:07 AM
First "production" item of SS JCM800+5W
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/front_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/front.jpg)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/rear_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/rear.jpg)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/top_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/top.jpg)
Title: Re: Fet version of the JCM800
Post by: joecool85 on March 15, 2013, 04:21:47 PM
First "production" item of SS JCM800+5W

That is awesome!  Are you going to be selling these online?  If so, how much?
Title: Re: Fet version of the JCM800
Post by: KMG on April 03, 2013, 12:11:02 PM
Video test by Konstantin Dolotov (camera mic)
http://www.youtube.com/watch?v=cB5XaE_vEJk
Title: Re: Fet version of the JCM800
Post by: THChrist on April 03, 2013, 09:38:56 PM
Sounds amazing, i really want one.
Title: Re: Fet version of the JCM800
Post by: KMG on May 20, 2013, 07:57:44 AM
FET JCM800+5W (Clean, input Low) video test by Konstantin Dolotov, MD421 mic.
http://www.youtube.com/watch?v=1PUBfrtLzK0
Title: Re: Fet version of the JCM800
Post by: J M Fahey on May 20, 2013, 11:19:31 AM
Incredibly good sound. Congratulations. :dbtu:
By the way, your friend plays very well.  :dbtu:
Title: Re: Fet version of the JCM800
Post by: KMG on May 21, 2013, 05:44:11 AM
FET JCM800+5W (Clean, input Low) video test by Konstantin Dolotov, camera mic
http://www.youtube.com/watch?v=VTPZJFrwnPQ
Title: Re: Fet version of the JCM800
Post by: mhelin on September 03, 2013, 02:00:11 PM
Quote
Quote
2. Why do the circuits need a negative supply on the source and why do that supply need to be buffered?
Because with autobias with source network tied to GND I can`t get stage gain, frequency response & top/botton clipping points same as for tube prototype.

I take it that you don't have to use negative supply if you are NOT trying to emulate some known amp. In fact in this JCM800 emulator only three first gain stages actually use additional negative biasing.

How about using a lower supply voltage in range of 48-100V?
Title: Re: Fet version of the JCM800
Post by: blackcorvo on September 08, 2014, 11:58:21 AM
I take it that you don't have to use negative supply if you are NOT trying to emulate some known amp. In fact in this JCM800 emulator only three first gain stages actually use additional negative biasing.

I believe the last two stages are just buffers (source followers), so they don't really affect the distortion sound, right?

How about using a lower supply voltage in range of 48-100V?

I tried this at 120v and seems to work OK with about -2v bias, but I don't have a scope to check curves:

Rg 1M+47k, Rp 100k, R2/D1 1k/I.R. LED, R3 330R (but I'll probably change to 220R later), D2-D4 1x 1N4007, LeftR 1k5, RightR/C2 1k/220nF.

Wonder if an I.R. LED for D2-D4 would work OK as well? I'm not really looking for an authentic replication of a certain amp's sound, I just want decent overdrive/good voltage swing. Most of the distortion I want will come from the power tubes anyways (6AS5, 8K P-P, fixed-bias -13v).

I also would like to point out that I used a "sourcedyne" (split-load) inverter in my prototype, with 47k for both upper and lower loads, 1k source resistor, 10k stopper and 470k Rg. B+ at 125v.

Maybe there's a way to get a more plesant distortion curve in that inverter as well?
Title: Re: Fet version of the JCM800
Post by: tomfiggy on March 25, 2015, 12:39:23 PM
How many people have built one of these on here? I think I'm going to give it a shot. Does the PCB work OK? I was going to make a one off with the artwork in this thread. Any updates to that or the schematic?
Thanks You
Title: Re: Fet version of the JCM800
Post by: juanMotta on January 21, 2017, 02:06:14 PM
Hi, any one knows who have build this?

Juan Motta
Title: Re: Fet version of the JCM800
Post by: phatt on January 22, 2017, 02:20:45 AM
Just PM KMG as I'm sure he can point you to people who have built this unit.
Be aware it is not a simple build,, Also It will likely require the exact parts if you want to use his PCB layouts.
Depending where you live you may not be able to access the same parts and too late if you already printed the PCB. 8|

I strongly recommend you breadboard the circuit before you commit to a build. Not because I doubt KMG but it's complex and better to find any issues before you build stuff like this.
Phil.
Title: Re: Fet version of the JCM800
Post by: juanMotta on January 23, 2017, 05:37:42 PM
Just PM KMG as I'm sure he can point you to people who have built this unit.
Be aware it is not a simple build,, Also It will likely require the exact parts if you want to use his PCB layouts.
Depending where you live you may not be able to access the same parts and too late if you already printed the PCB. 8|

I strongly recommend you breadboard the circuit before you commit to a build. Not because I doubt KMG but it's complex and better to find any issues before you build stuff like this.
Phil.

Thanks for your answer!! yes, i already pm Kmg but i don´t have any answer i also sent an email to the 2 email address of his web page.
Title: Re: Fet version of the JCM800
Post by: juanMotta on January 28, 2017, 07:11:17 PM
Sorry for the question... but can i build the 15 watt version of the kmg fet amp with 1 amp transformer? is not specifed in the layout and schematic Just said the 80 v +-.

Title: Re: Fet version of the JCM800
Post by: rankot on March 01, 2017, 01:22:59 PM
I started low voltage fet experiments with Victor Kampf idea.
http://www.sugardas.lt/~igoramps/article68/article.htm
But sound was not close enough to tube one & I moved to high voltage experiments.

I tried to read Victor's article, but I am not sure what is Rc value on this page. Could you please explain it?
Title: Re: Fet version of the JCM800
Post by: phatt on March 03, 2017, 12:51:30 AM
I tried to read it also but it's in Ruski or some thing so I'm stumped. :'(
Phil.
Title: Re: Fet version of the JCM800
Post by: J M Fahey on March 04, 2017, 02:54:16 AM
https://translate.google.com/translate?sl=ru&tl=en&js=y&prev=_t&hl=es-419&ie=UTF-8&u=http%3A%2F%2Fwww.sugardas.lt%2F~igoramps%2Farticle68%2Farticle.htm&edit-text=

Mind you: D1, D2 and D3 are not "diodes" per se but Russian Germanium transistors "connected as"  diodes, they add Germanium roundness and smoothness to what would otherwise very harsh FET clipping.

They also tried Schottky diodes, which clip at a level similar to germanium, but although the clipping level was close, edges were sharp.
Of course, Russians can still easily buy Germanium transistors at their Electronics shops.
Title: Re: Fet version of the JCM800
Post by: KMG on April 13, 2017, 12:04:16 PM
Hi guys.
Unfortunately my IP was erroneously banned for a long time.
Now I returned back.
About
Quote
Hi, any one knows who have build this?
Many people build this preamp by youself, but unfortunately not in in English speaking countries (Russia, Ukraine, Israel). Many peoples purchased full version (F-800) with 5W poweramp.
I strongly recommend you to build LND150 (http://milas.spb.ru/~kmg/jcm800fetLnd150_en.html) version of preamp by the two reasons:
1. 2SK216 is very difficult to buy (they end of production, there are many fake ones at ebay)
2. LND150 more close by sound to the tube one.
Also this version does not require any trimming after assembling.
Some responces about sound of the F-800 you can read in this thread http://forum.guitarplayer.ru/index.php?topic=273237
Unfortunately in Russian, but you can use Google translate.
Title: Re: Fet version of the JCM800
Post by: joecool85 on April 13, 2017, 01:03:41 PM
Hi guys.
Unfortunately my IP was erroneously banned for a long time.
Now I returned back.
About
Quote
Hi, any one knows who have build this?
Many people build this preamp by youself, but unfortunately not in in English speaking countries (Russia, Ukraine, Israel). Many peoples purchased full version (F-800) with 5W poweramp.
I strongly recommend you to build LND150 (http://milas.spb.ru/~kmg/jcm800fetLnd150_en.html) version of preamp by the two reasons:
1. 2SK216 is very difficult to buy (they end of production, there are many fake ones at ebay)
2. LND150 more close by sound to the tube one.
Also this version does not require any trimming after assembling.
Some responces about sound of the F-800 you can read in this thread http://forum.guitarplayer.ru/index.php?topic=273237
Unfortunately in Russian, but you can use Google translate.

Sorry about the block, KMG, and welcome back!

Also, is there a kit for this available?  Parts and PCB?
Title: Re: Fet version of the JCM800
Post by: KMG on April 14, 2017, 09:19:09 AM
Now I have only "full version" boards (preamp+5WPA+PS)
(http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/MainBrd_th.jpg) (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/head/MainBrd.jpg)
For separate preamp I can offer gerber/drill files:
jcm800mvfGerber.zip (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfGerber.zip)
Title: Re: Fet version of the JCM800
Post by: joecool85 on April 14, 2017, 11:34:19 AM
Now I have only "full version" boards (preamp+5WPA+PS)
For separate preamp I can offer gerber/drill files:
jcm800mvfGerber.zip (http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/jcm800mvfGerber.zip)

That's perfect!  How expensive is it to get the boards?  Do you sell a kit with the components as well?
Title: Re: Fet version of the JCM800
Post by: rankot on May 08, 2017, 09:38:18 AM
Is it possible to use any other combination of diodes? ES1J is not available in my country. Also, can I use two BAT85 instead of BAT54, they seem to be almost identical?
Title: Re: Fet version of the JCM800
Post by: KMG on May 17, 2017, 08:28:29 AM
Instead ES1J you can use any Superfast(Ultrafast) Rectifier Diodes with the same specs.
Quote
can I use two BAT85 instead of BAT54
Yes.
Title: Re: Fet version of the JCM800
Post by: ASTN on June 29, 2017, 10:50:57 AM
Hi, KMG
I can't get to you site (( Everytime I click the link I get a page with  'The requested URL could not be retrieved' message.
Title: Re: Fet version of the JCM800
Post by: Stephenl on January 08, 2018, 09:42:45 PM
Sorry for resurrecting such an old thread as my first post. I've been looking at KMG's LND150 circuit for a while and I'm interested in breadboarding it to try it out.

Are there through-hole versions of the BAT54S, BAV70, and ESIJ? I've never tried soldering SMD parts...but it looks like a pain, especially if not using a pcb with SMD pads. If there isn't a direct equivalent, what specs are important to crossover?
Title: Re: Fet version of the JCM800
Post by: Katoda on January 09, 2018, 01:33:18 PM
Well, I don't think soldering smd components is that difficult, I soldered 5150 circuit with the same topology and components on a protoboard. That being said, I think you can substitute ES1J for any ultra fast high voltage rectifier diode, two paralleled bav70 for a single 1N4148 and the two bat54s for 4 1N4148, but wiser members than me should confirm or deny that.