Additional samples, cab_s - microPA+4x12+mic, cs_s  - microPA+speaker equivalent+cabinet simulator
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/s/2-Classic%20T_cab_s.mp3
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/s/2-Classic%20T_cs_s1.mp3
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/s/4-Criminal%20Def_cab_s.mp3
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/s/4-Criminal%20Def_cs_s1.mp3
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/s/6-Kid%20Paul_cab_s.mp3
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/s/6-Kid%20Paul_cs_s1.mp3
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/s/8-Southern%20LP_cab_s.mp3
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/s/8-Southern%20LP_cs_s1.mp3
Frequency response

Results of testing Xicon transformers in micro PA (instead of russian trafos, that hard to find).
Schematic

Voltage frequency response on resisitive load with Presence & Depth action (real device).

Comparative voltage frequency response on resisitive load & cabinet with Presence & Depth = min.

Sim (LtSpice) project with measured parameters of TM008
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/sim/
It gives about 100mW of power, really audible at 4x12 cab & suitable for "night" playing.
For line recording I plan to use this kind of load to simulate speaker impedance for adequate interaction of PA with load.

And frequency correction after load to simulate cabinet/mic response.

PS Sample:
Fet JCM800->Micro PA->4x12 cabinet
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/s/8-Southern%20LP.wav

Photo of tube prototype:

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?

JCM800 preamp using LND150




Comparative samples with tube prototype
Drive
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

While testing I found that there is no need in additional gate protection, only high voltage diode in source chain.
So, the basic stage for lnd150 is the following

Comparative samples of "glass" JCM8000

And SS (last version) JCM8000

http://milas.spb.ru/~kmg/files/projects/jcm800mv/jcm800_fet_vs_tube.zip

Actually the basic stage.


RG (with interstage circuits) and RP are original (from tube schematic).
Q1, Q2, ZD1 and R1 is Q3 gate protection, in the first stage is not used, just put in 20V zener at gate.
R2 determines the smoothness of "grid" limitation, R3 voltage at which it occurs.
R4 determines the gain at low frequencies, R5 - gain above the cutoff frequency, C2 - the cutoff frequency.
C1 simulates the Miller effect  (0-100pF, depending on the gain of the original stage and presence of capacitor in the cathode).
VBIAS for JCM800 got the same for all stages "-2.75V"
JCM800 using LND150

Reamp sample
http://milas.spb.ru/~kmg/files/projects/jcm800mv/fet/lnd150/s/8-Southern%20LP.mp3

QuoteCan you please add the driving voltage on each step?

I don`t remember values, but they was the same for both stages (tube & fet).

QuoteI would love to see what comes out of a 2nd stage, when the first is overdriving and providing all it can (200Vpp or thereabouts?)

Will be, wait some time.

QuoteCould one of your trick fet triode circuits replace the AX7 that is used in my circuit?

Yes, but HV versions requires negative bias voltage, or biasing grid potential (VR100, R103, R107 in your schematic).
Look there for new info.
http://www.ssguitar.com/index.php?topic=2039.msg15437#msg15437

Continue the story
1-st stage of JCM 800 (2k7/0.68u, 100k)
Left - 12AX7, right - LND150 (with different component values of course)







"See the cat? See the cradle?"


Schematic of test equipment.

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

Quote
But I was actually reffering to *line driver transformers* as used in buildings where very long wires are used to link many speakers.
If anyone is interested I'll try to find more info.
Phil.

Found at least one type
http://www.rcf.it/en_US/products/commercial-audio/attenuators-transformers/td-105
Primary 100V with center tap

Samples recorded by my friend DKS from GtLab
Tube preamp UENGO-1 + 5W Fet PA
Midgain
http://milas.spb.ru/~kmg/files/projects/fetpa/mp/samples/JTR_FET_MIDGAIN.mp3 (1,89МB)
Highgain
http://milas.spb.ru/~kmg/files/projects/fetpa/mp/samples/Uengo_Hg8_M.MP3 (1,8МB)

Quote from: villll on July 08, 2011, 07:38:42 AM
Thanks for your post!
Alright I'll see if I can find some schematics. I might try building my one idk. Was thinking i'd make the two parallel stages dissimilar, one cleaner than the other, and use a pot to blend them together.

Examples of paralleling different stages
Legendary amps
Hiwatt DR103
http://milas.spb.ru/~kmg/files/schematics/hiwatt/DR103/DR103_preamplifier.pdf
Marshall SLP
http://milas.spb.ru/~kmg/files/schematics/marshall/1959SLP/1959SLP1.gif

Sound comparision - 5W fet PA against 2x6L6 PP, 1хV30 1/3 open cabinet
http://milas.spb.ru/~kmg/files/projects/fetpa/mp/samples/1.wav
http://milas.spb.ru/~kmg/files/projects/fetpa/mp/samples/2.wav

QuoteWhat type of guitar and pickups were used in this recording?

It`s reamp of these DI samples
http://milas.spb.ru/~kmg/files/distr/DI%20Samles/Metaltastic%20HD%20DI%27s/
As know someone post on forum part of DI`s by this group
http://www.youtube.com/watch?v=NR7dG_m3MsI