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dkbuilder: simulate a Poweramp

Posted: Tue Mar 26, 2019 9:07 am
by tramp
As follow-up to this thread: viewtopic.php?f=44&t=19586
I'll show how I simulate a Poweramp within the dkbuilder.
I give the Hoffman Plexi a whirl, taken from her: https://el34world.com/Hoffman/files/Hof ... 6V6-V2.pdf

I start with the poweramp part and create the following schematic with gschem:
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after starting the dkbuilder virtual env I run the following command:

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./build-plug.py -i PlexiPowerAmp.sch --table_neg 1 -x 3.0  --build

to build a nonlinear guitarix plugin from the schematic. It produced the response tables for positive and negative waves.
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This shows us that the response is equal on both sides.
After doing some sound tests with this I'm satisfied with the result.
As next I create a circuit for the master/tonestack part:
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and run finally after some tries the following command:

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./build-plug.py -i PlexiPowerAmptone.sch --table_neg 1 -x 3.0 -o 0.8  --build

were the -o parameter reduce the table steeper to reduce the gain a bit, which otherwise is really huge.
which result in this response curves:
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It shows us that here we've a phase inversion and a slightly different in the response on positive/negative input.

In case anyone wonder, I've put a lowpass filter in front of this part, as this one tends to be a bit noisy when cranked up, the lowpass filter out at 11kHz and reduce the noise slightly.
Now I come to the preamp section, I only use the normal channel
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Again I put a lowpass at 11kHz on the input, as this part has the same problem then the previous.
Then after fiddling with some settings I run:

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./build-plug.py -i PlexiPowerAmp_pre.sch --table_neg 1 -x 3.0 --build

and get the following response tables:
Image
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Again we see a phase inversion, and this time a markable difference in the response on the positive/negative side.
Sound test in guitarix gives me nice results, so I stick all together to a single LV2 plug:

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./build-plug.py -i PlexiPowerAmp_pre.sch PlexiPowerAmptone.sch PlexiPowerAmp.sch JTM_p1.sch JTM_p2.sch --table_neg 1 2 3 -x 3.0 3.0 3.0 3.0 -o 1.0 0.8 1.0 --oversample 2 --buildlv2 -n Plexi


Additional I set it to 2x oversampling and I add a JTM cabinet simulation.
Result is this one:

Image

in case you want to try it out, you'll find it here:
https://github.com/brummer10/GxPlexi.lv2

Re: dkbuilder: simulate a Poweramp

Posted: Tue Apr 02, 2019 6:39 am
by asbak
Another beer I owe you Mr Tramp, awesome

Re: dkbuilder: simulate a Poweramp

Posted: Wed Apr 03, 2019 3:43 am
by funkmuscle
dude this sounds 'a-freakin'-mazing'!!!!
only tried with single coil neck pickups, added your fuzzface..... got Jimi's tone!!

Re: dkbuilder: simulate a Poweramp

Posted: Thu Apr 04, 2019 8:07 am
by Rodney
Holy shit, this is amazing :shock: . You are awesome, thanks for that, I will compare it to the cream machine. Is it possible to release the JCM 800 power amp as well? That would be great.

Thanks a bunch :mrgreen:

Re: dkbuilder: simulate a Poweramp

Posted: Thu Apr 04, 2019 9:35 am
by Rodney
Just to say that I tried it with the GxJCM800pre -> GxPlexi -> GxUltraCab and I am really impressed. Wow man, this rocks so hard! I find the UltraCab to be even better than loading Impulse response files in a Convolver loader (probably because they lack the nonlinear part). Big thanks again and keep on rockin :twisted: