Real frequency response of microamp with 42TU400 (voltage on load).

http://www2.mouser.com/ProductDetail/Xicon/42TU400-RC/?qs=LQJGOuQCHKRtcvI3oCfSfuwbaFhDLjEAJ9ZlMC7IssI%3d Or http://www2.mouser.com/ProductDetail/Xicon/42TU008-RC/?qs=h3Xc2LqAealmGyWU7eTMoQ%3d%3d 42TU400-RC gives higher power output ~250mW. 42TU008-RC gives ~200mW but better bass representation. Samp...

Now it planned for production with stereo mixer (to mix with -1 tracks) & phone amplifier. http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/full/Drawing_th.jpg http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/full/Drawing7_th.jpg http://milas.spb.ru/~kmg/files/projects/fetpa/mi...

Full project with speaker equivalent & speaker simulator http://milas.spb.ru/~kmg/microfetpaV2_en.html Only PA (first item on page) http://milas.spb.ru/~kmg/fetpa_en.html Comparision with Randall RG75 (live) https://www.youtube.com/watch?v=dm67Lv4KGBI Comparision with Randall RG75 (mix) https://...

JR=2SK208 (Toshiba)
Gate-source diodes - small signal shottky BAT54
Be careful when selecting replacements, Victor Kampf selected for this design types of fet/shottky that matched by their curves.

Five cents from me, sound of micro PA (250mW) loaded on 1x12 cabinet
LP guitar->preamp UENGO-1->micro PA->cabinet 1x12 CELESTION G12M->Sennheiser E906 microphone.

Mix sample

DrNomis if you please, can you measure transformation ratio for both transformers (active resistance also).
I want try to find replacements.

lolbou wrote:There's one component missing between the transformers (ceramic cap?) though holes are there. Single or factory mod?

It's presented on Schematic 2&3

For transformers for this project we can try to use these
http://ru.mouser.com/catalog/644/2427.pdf
I used 42TU400-RC in my fet micro PA
http://milas.spb.ru/~kmg/microfetpaV2_en.html

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

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.

Full project
http://milas.spb.ru/~kmg/index_en.html
Micro power amplifier for line recordimg ver. 2

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 12VA...

Schematic

V(sim) - micro PA+equivalent(cab)+sim.
V(sim1) - only sim with additional stage simulating speaker impedance frequency response addition.

KMG! interesting! I just ordered parts to build your V30 sim, is this better? Can you give us more details? /Taz Start reading there: https://www.freestompboxes.org/viewtopic.php?f=1&t=14521&start=40#p167166 Final schrmatic: http://milas.spb.ru/~kmg/files/projects/fetpa/micro/xicon/full/PaE...

Final board

Boxed

Micro PA, load equivalent & speakersim assembled in box.

J1 input
1- signal input.
2- signal gnd.
3- 12V (output to possible fet preamp).

J2 feedback (possible Presence/Depth controls)
1- feedback output from OT.
2- feedback input.
3- gnd.

J3 output/PSU
1- PA output (load).
2- gnd (load/PSU).
3- 12V input from PSU.