Quote1. 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.

Quote2. 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.

Quote3. 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.

Quote4. 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".

In progress design of final version of micro PA + speaker simulator +  mini mixer +  headphone amp

Additional sample (mix) of micro PA (250mW) on cabinet
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/s/AR.mp3
Guitar - LP
Preamp - UENGO-1 (http://kdyworks.com/index.php?option=com_content&view=article&id=68&Itemid=63)
Cabinet - 1x12 CELESTION G12M

Under the anisotropy I meant that the tube stage input impedance is different for positive and negative half-wave.
And the ratio of the impedances is different for different input signal amplitudes.
This changes the DC voltage at the interstage capacitor.
This looks like applying to grid virtual DC bias depending on input signal amplitude & varying in time.
Static oscillograms
K1 - Plate
K2 - Input (before input decoupling capacitor)
K3 - Grid
K4 - Cathode









Dynamic response to "burst" input signal




...

& finally

Rest of oscillograms there:
http://milas.spb.ru/~kmg/files/projects/dualrectifier/test/compl/dyn/

2 Loudthud.
You left aside one important aspect of tube stage emulating - grid detecting.
This lead to anisotropy of the stage input impedance.
Due to it dynamically changes the operating point of the stage.

Hi Phil.
Convertation from schematic to board is simple.
1. Annotate whole schematic (reference designators) manually or automatically if need.
2. Export netlist.
3. Start "cvpcb" to assign shapes to components & save result.
4. Read netlist in board editor.
All components will be placed into board.
So you can start to move them to proper places & route traces.
There are good enough PDF help files in different languages:
...\KiCad\doc\help\

I purchased LND150 & trafos for micro PA from mouser:
http://au.mouser.com/ProductDetail/Supertex/LND150N3-G/?qs=sGAEpiMZZMvECErq9cesgJdUgk/FlBvJcYi5pvrBL5Q=
http://au.mouser.com/ProductDetail/Xicon/42TU400-RC/?qs=sGAEpiMZZMv0IfuNuy2LUQ0m87amfyq2VwqQkCtNXxk=
Shipping costs for Australia:
http://au.mouser.com/EstimateShipping/EstimateShipping.aspx

Regards, Michael.

QuoteI will look into the *Kicad*

http://kicad.sourceforge.net/wiki/Main_Page
The main advantage of kicad is "free of charge" - you don`t need to pay for it.
But it has most features of "big" CAD.
Also it multiplatform - "Linux, Windows and experimental on Mac OS X."

QuoteIf you want this to take off You need to present it as a Normal single sided board layout.

I use components that I can simply obtain.
So rerouting to non smd components will make problem for me - hard to assemble & test, to present fully checked project.

QuoteI have no doubt your ideas are worth building but surface mount is not for the average home builder.

There You can download kicad files for this project (if You use kicad):
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/full/kicad/
There You can download archive of my kicad libraries (with 3D models):
http://milas.spb.ru/~kmg/share.zip
Overwrite existing kicad files in "share" folder.
Try to change shapes of smd components by yourself & reroute board.

QuoteWait till some of you chaps hit 50 years plus and your eyesight starts to let you down and you will see the sense in SANE layouts.

Check my date of birth in profile. About a half of month later I will have jubilee.

PS Clock repairing visor can solve problem


Mike.

Link to full project (microPA, eqivalent, cabsim)
http://milas.spb.ru/~kmg/index_en.html
Micro power amplifier for line recordimg ver. 2

Preliminary (test) single board version of "recording box" (Micro PA, load equivalent & speakersim).

QuoteI figure I will use two 4 ohm speakers wired in series, then wire that set in parallel with an 8 ohm speaker making the total load 4 ohms... or would it split the watts between the two 8ohm loads, IE - one speaker gets 50% and the other two get 25%?

Exactly: 50%-25%-25%

Full (Micro PA, load equivalent & speakersim) schematic:
http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/sim/micro_eq_sim.pdf

Micro PA, load equivalent & speakersim assembled in box.

Full micro PA project

Quote from: joecool85 on October 21, 2011, 03:46:52 PM
KMG, I haven't had a chance to listen to your latest samples, but seriously, is this what you do for a living?  It seems you're working the hell out of this circuit.  Are you planning on selling PCB kits?  Full built amps?  Anything?

No, it's my hobby to change my thoughts from main work.
Only one item now in production - 5W fet PA kits (assembled & tested board).

In plans home recording box - micro PA+load equivalent+cabsim.
You can use micro PA output on cab for night playing with recording from sim output.
Or you can pass singal to sim input form big amplifier output (in parallel with cabinet) for recording without mic.