pultec finished

this was a very satisfying build - thanks to purusha for housing&info!


finally found a adequate job for the siemens/wsw isolation amps i had lying around for some time . they do sound huge and go perfectly together with the passive filter network of the eqp1.


i took my time building this. first i breadborded the mid/high boost section section to wind my inductors.
with the inductor finished i started to try various capacitors for the right sound, with the wsw isolation amp already connected. i used signal feedback from output to input for oscillation to find the right values for some stereo-matching.
finally i put the inductors into a brass tube for some shielding and mainly for optics


more/bigger pictures can be found here

that's nice guts! :thumb:

Very nice indeed! :thumb:

Hey Max, that's a serious looking Pultec :thumb:

What inductors and caps did you use?

EDIT: OK, I saw above you did your own inductors :thumb:


Can you give us some sound descriptions ... :grin:

oooooooooo i want one. let me borrow it :wink:
Is that a stereo unit? i'm still learning about this DIY stuff.

Wow man :shock: That looks top notch!! Very neat wireing and all...

i like your innards :thumb:
very sweet build

Oooh! I get happy seeing something like this! :grin:
Great job!

Wow - your cap work is just amazingly well done!

-T

thank you all!

yes, thats a dual mono/stereo unit.
the caps used are ero (roederstein) and the very small values are wima´s.
i was trying styroflex for the high boost section but didnt like it as much as the wima´s in this application.. mind you, thats very subjective, some would say it doesnt matter which brand/kind to use here.

winding the inductor is fun, and if you want a stereo unit its much easier/more precise to match the inductance, since most commercial available inductors have a tolerance of +/- 20% on top of that you will not find the needed values. parts for inductors

to describe the sound, well, look at the output transformers and imagine the sound if you stumble across this isolation amp modules from wsw, watch out!
i am about building the second unit, so this one will be for sale.

Tell us about your power supply. Is that a HexFRED? Do you have a diagram, schematic?

thats a motorola mda2501, a discontinued full wave rectifier. its followed by a lm317 for 24vdc, because the internal psu of the wsw-module wasnt happy with unregulated dc.

-max

I'm not worthy ....... and I have a woody .....

Beautiful.

some information for winding your own inductor
e - core ferrite 25mm with Al=1400nh

tap---------mH---------turns
0------------0------------0
1-----------27----------164
2-----------39----------197
3-----------78----------279
4----------155----------394
5----------312----------558

i did the winding by hand, needs about 10 min excl. lead soldering etc.

WOW! :shock: :shock: :shock:

thanks!

Beautiful work! Inspirational. :shock:

:shock: Very, very nicely built. :thumb:
Excellent wiring - i wish i had the patience to diy my gear this well thought and good looking.
Thanks for the insights of your work. The winding information for your inductor wiring is giving a clear picture of how easy it is actually to do serious ly good sounding diy gear!
'Pultec'-Steffen did this some time ago (inductor-diy for pultec) but it's very nice to show things like this again for everyone who might have missed it.

Thank you and kind regards,

Martin :sam:

with some of my first projects i didnt care so much about layout and wiring. but in case something´s wrong, its so much easier to fix a problem, and since you put more thought into everything, there should be no problems from the beginning.
thanks for your kind words everyone!

-max

Just been asked to modify 4 WSW modules to make usuable with ribbons.
Told that can lower feedback/raise gain by increasing value of R24 on following schematic -
http://www.wsw.cz/11WSW_ISOL_AMP/WSW_SCHEMA_ISOL_AMP.JPG

told to try 10k. Is this a safe starting point - I dont want to change it, power up and the thing go into oscillation burnout!

Any thoughts :?: