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Topics - KMG

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Comparision test of 12AX7WS and 12AX7EH, guitar tracks & mix tracks.
Tube preamp JCM800+FET 5W+4x12, gain at 2 hours, tone stack at middle.
WAV 44м
mp3 10м

PS 12AX7WS page.
http://amtelectronicsusa.com/productpage12AX7WS.html

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Tubes and Hybrids / Want SS triode VA curves?
« on: August 05, 2011, 08:11:07 AM »
I think all remember how switched triode/pentode modes in tube PA.
Yes, by connecting second grid to plate.
So we need to find SS tetrode. It is RF dual gate mosfets
http://www.nxp.com/documents/data_sheet/BF998.pdf
So, by connecting Gate2 to Drain (through resistor for safe) we will get SS triode.
Also we must add grid current emulation, it can be done by "Kempf" method.
There are simulation examples
Single common cathode stage

common cathode + cathode follower + tone stack

Today I tested real single stage, it matches exactly with simulation model from NXP

3
Amplifier Discussion / More Interesting Enclosures
« on: March 07, 2011, 08:30:44 AM »
2x400W monitor in old (dead) ocilloscope case.
10 band EQ, active crossover, 8x bridge/paralleled LM3886`s in each channel



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Schematics (pdf)

Stage by stage frequency response in comparison with the original tube version


Ready to transfer PCB (pdf)

Upper side assembly (pdf)

Bottom side assembly (pdf)



Sample (gain control only by volume knob on gutar)

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Preamps and Effects / V30 speaker simulator
« on: January 28, 2011, 06:53:18 AM »
For use with single or dual supply & additional possibility to use "-" or "+" of power supply as reference ground with single polarity supplying.
Construction allows you to add it to existing design simply by drilling hole for the output jack.

Frequency response

Dark blue - original С6 = 100 nF, red С6 = 47 nF, light blue С6 = 33 nF
Schematics

PCB (ready to tranfer)

Upper side assembly

Bottom side assembly



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Amplifier Discussion / Fet version of Marshall Superlead Plexi
« on: January 21, 2011, 05:04:47 PM »





Preamp section:



Volume controls & tonestack has standard values like in original tube prototype MARSHALL 1959SLP.

For PA is used "Fet power amplifier with transformer output" 40W version.

7
Preamps and Effects / Fet version of ENGL530 MOD2
« on: January 16, 2011, 02:47:31 PM »




Project files





Controls

Reamping samples.
Tone controls at preamp in middle position, "Presence" and "Depth" at PA also in middle position.
Digits after channel name represents "Gain" setting.
http://milas.spb.ru/~kmg/files/projects/Engl530/fet/reamp/5W4x12/
Recording path: E-MU Tracker Pre->Fet Engl->Fet PA 5W->Bull 412V+L(4x12)->Sennheiser e906->E-MU Tracker Pre
Reamping samples through Speaker simulator V30 preamp output.
Tone controls at preamp in middle position.
Digits after channel name represents "Gain" setting.
http://milas.spb.ru/~kmg/files/projects/Engl530/fet/reamp/SIM_V30/
Recording path:
For files without "R" in name:
E-MU Tracker Pre->Fet Engl->Speaker simulator V30->E-MU Tracker Pre
For files with "R" in name additionally through Digital reverb engine AL3201 with dry/wet mix 50/50:
E-MU Tracker Pre->Fet Engl->Speaker simulator V30->Digital reverb engine AL3201->E-MU Tracker Pre

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Preamps and Effects / Fet version of the JCM800
« on: January 16, 2011, 01:42:05 PM »
Schematics (pdf)

Stage by stage frequency response in comparison with the original tube version (stage2 with different gain positions)

Ready to transfer PCB (pdf)

Upper side assembly (pdf)

Bottom side assembly (pdf)

Assembled board

Controls and input jacks (pdf)

Project page (with some samples)
http://milas.spb.ru/~kmg/jcm800fet_en.html

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