Mighty Nut - JFet simulation of a Powerball lead channel

Pruttelherrie · Post by **Pruttelherrie** » 19 May 2011, 19:49

So... On the other forum somebody posted his JFet version of a SLO-100, that made me decide to post my adventures with the Powerball lead stage in pedalform.

But.

In a weird way, I feel much more at home at FSB than at the DIYSB, even with my lowly 7 posts (and counting)... So I decided to post it here, oh well.

Anyway, I did a 1:1 conversion of the Aznaur Mod2 (with Powerball values, of course). I've only made it on perfboard, afterwards I finished the PCB design where I also eliminated the bridges but never got around to etch and test it.
As it is, it fits in a 1590B easily (which I did, see below) and I put a full tonestack in it too, labeled according to the Nut theme. However, I never got the tonestack to sound satisfying. Probably needs scaling down as well? I left it at the high (noisy) pot values and I probably got some log/lin things wrong. So tonight I cut out the tonestack ad fed it directly from the coupling capacitor into a clean channel tubeamp, that worked *much* better. It might need a buffer (extra JFet) at the end and something like SWTC or BMP tonestack.As for the enclosure, haven't had time yet to make a decent etch so it's r^Htape time!

Why Mighty Nut?
A Mighty Nut is a very Powerful Ball

On to the schematic and pics:

1200 dpi PCB: (not mirrored!) http://dl.dropbox.com/u/17081629/mighty_nut/pcb.png
Component placement on the PCB: http://dl.dropbox.com/u/17081629/mighty ... ukking.png

For those interested, the Eagle files:
http://dl.dropbox.com/u/17081629/mighty ... %20Nut.sch
http://dl.dropbox.com/u/17081629/mighty ... %20Nut.sch

What does it sound like? Br00tal. Not really Powerball, a bit 'blander'. No soundfiles yet, until a friend comes by who feels more confident in putting their shitty playing online

jimosity · Post by **jimosity** » 19 May 2011, 19:58

Interesting. The Engl Powerball is one head that I've always kicked myself for parting with.
I'ma have to try this out.

FYI: Wrong link on one of the eagle files. Change one of them to have a .brd extension and it seems to work.

Pruttelherrie · Post by **Pruttelherrie** » 20 May 2011, 07:27

Hmpf you're right. Can't edit it anymore, this is the correct link indeed: http://dl.dropbox.com/u/17081629/mighty ... %20Nut.sch

I get what you're saying. Whatever I do and combine and whatever amp I'm testing, I always come back to my Powerball. This Mighty Nut is part of a try to get it all down to a pedalboard (including a EHX 44 Magnum) so I alway carry my sound with me (preferably by bike) without getting a hernia, but so far I've been unable to replicate it. In process: all-tube-HV-pedal-version of this channel, maybe a SMD version of this JFET simulation.

Pruttelherrie · Post by **Pruttelherrie** » 20 May 2011, 09:38

And I completely forgot tot add: JFETs are J201's, biased a little bit above 1/2 VCC. Kept them at around 5V for a 9V power supply.

jimosity · Post by **jimosity** » 20 May 2011, 19:18

haha.
Still not the right link to the Eagle board.
This should be it.
http://dl.dropbox.com/u/17081629/mighty ... %20Nut.brd

By the way, thanks for posting the Eagle files; I like to move thing around.

Pruttelherrie · Post by **Pruttelherrie** » 12 Nov 2011, 11:50

While I didn't really do much with the JFET stuff above after posting it (still trying to shoehorn the original tube version of the lead channel in a 1590BB), I did discover the AMT Legend series. Product page: http://www.amtelectronics.com/products/ ... eries/e-1/

I bought the E-1 last week, here are some pics of the insides:
https://www.dropbox.com/gallery/1708162 ... 1?h=59d5e6

Post by **audioguy** » 16 Nov 2011, 00:04

Cool... Im a gain freak- o I'll give this a go next time I etch a batch. 1 quick question- how is the 22-23-2041 wired up? I like the concept of using those- but where do they go... I cant make it out?

Pruttelherrie · Post by **Pruttelherrie** » 16 Nov 2011, 16:25

audioguy wrote:Cool... Im a gain freak- o I'll give this a go next time I etch a batch. 1 quick question- how is the 22-23-2041 wired up? I like the concept of using those- but where do they go... I cant make it out?

Oh sorry, it's the tonestack pots, wired like in this one:

I'll have to look up the values when I get home, but you could just as well change them to your favourite FMV tonestack values.
From the treble-wiper you'll probably need a cap as well for getting rid of the DC.

Post by **audioguy** » 17 Nov 2011, 18:45

Yeah I figured they were the tone stack... thanks for the clues!

rocklander · Post by **rocklander** » 17 Nov 2011, 19:11

thanks muchly...so high gain in the dr. boogey/diefet territory, or the bsiab/jcm territory?

elkulon · Post by **elkulon** » 27 Nov 2013, 18:58

Nice work!!!!
I wonder... Did you work with the real amp schematic and put the original values, or you made some mods...???
Which channel would this be???

Pruttelherrie · Post by **Pruttelherrie** » 10 Oct 2018, 15:24

Got a few requests for the 404'd eagle files, here they are!

Pruttelherrie · Post by **Pruttelherrie** » 10 Oct 2018, 15:27

... and the .brd which fell off the post since I can't seem to attach .brd files?!?

temol · Post by **temol** » 15 Oct 2018, 20:26

I've breadboarded this one so here's quick and dirty demo with a DI track. Three gain settings, 9-12-15 o'clock. 4x12 Mesa cab IR. Soundcloud.

T.

J0K3RX · Post by **J0K3RX** » 23 Oct 2018, 00:07

Most of the Engl amps are relatively the same in the preamp section with the exception of the tone stacks. The Power Ball has the Open/Focus mid range voicing and it has a noise gate starting before the tone stack and outputs just before the fx loop. There is no cathode follower/buffer before the tone stack on any of the Engl amps as far as I know.

But, who gives a shit if it sounds good, then it is good!