Ultraphonix adventure

[bepone]

Got a few questions on the schematic posted by Bepone vs Aaron's original, mostly on the 4th stage of the drive channel, on Aaron's schematic there is a 45k resistor going into the coupling cap and then into another 45k resistor, when on bepone's schematic, it seems to be closer to the original JCM800 with 0.005uf coupling cap going into the 470k divider resistors. I don't have a simulator to see what frequencies these two setup would affect. can one of you elaborate on this ?

PXL_20231218_211012184.jpg

Bepone have you tried to replace V1 socket ? It seemed you had trouble with it during the build.

47k is not possible , 470k is standard divider in hi gain circuits like marshal soldano/ after mesa and so on..
V1 socket replaced, also nothing changed.. remain only gain potentiometer and after that if the problem persists.. i will go on direct socket build all the components in the air.. to avoid the press board, and if that solve the problem, the the fault is in the board i try to believe that is not because i cleaned and varnish eveything before, we will see..
I have another hi gain build in progress so im concentrated mosty there, on this build i give only 10 minutes per day to not loose much time and motivation

[fred.violleau]

Hey Bepone,Thanks !
I was assuming Aaron's schematic had a potential mistake, but this question remains :

do you have :
V1B plate=> 470k =>.02uf=> V2A and 470k to ground ? looks like a low Pass RC filter into V2A with a grid leak resistor ? (Never seen before, but I don't know much...)
or
V1B plate =>.02uf=>470k => V2A and 470k to ground ? looks like high pass filter + voltage divider right before V2A (JCM 800 schematic and bepone's)

I would choose the second arrangement of components, my understanding is the smaller the coupling cap, the higher the frequencies that get through.
Considering there is two stage of amplification left, I should aim for little to let the distortion add overtones and harmonics.

@bepone, did you use .05uf, .02uf (soldano approved) or .005uf as coupling cap after V1B?

Thanks !

Fred.

[Reeltarded]

Hey Bepone,Thanks !
I was assuming Aaron's schematic had a potential mistake, but this question remains :

do you have :
V1B plate=> 470k =>.02uf=> V2A and 470k to ground ? looks like a low Pass RC filter into V2A with a grid leak resistor ? (Never seen before, but I don't know much...)
or
V1B plate =>.02uf=>470k => V2A and 470k to ground ? looks like high pass filter + voltage divider right before V2A (JCM 800 schematic and bepone's)

I would choose the second arrangement of components, my understanding is the smaller the coupling cap, the higher the frequencies that get through.
Considering there is two stage of amplification left, I should aim for little to let the distortion add overtones and harmonics.

@bepone, did you use .05uf, .02uf (soldano approved) or .005uf as coupling cap after V1B?

Thanks !

Fred.

Me asked too!

here mr V

https://ampgarage.com/forum/viewtopic.p ... 17#p448817

[bepone]

do you have :
V1B plate=> 470k =>.02uf=> V2A and 470k to ground ? looks like a low Pass RC filter into V2A with a grid leak resistor ? (Never seen before, but I don't know much...)
or
V1B plate =>.02uf=>470k => V2A and 470k to ground ? looks like high pass filter + voltage divider right before V2A (JCM 800 schematic and bepone's)

I would choose the second arrangement of components, my understanding is the smaller the coupling cap, the higher the frequencies that get through.
Considering there is two stage of amplification left, I should aim for little to let the distortion add overtones and harmonics.

@bepone, did you use .05uf, .02uf (soldano approved) or .005uf as coupling cap after V1B?

in working amp i have 5nf+470k+470k to the gnd, in oscillating amp i have 20nF+470k+470k to the gnd! should not oscillate because of that
it is ok to test this value and put from 5 -47nF, depending of the output transformer and overall fuzz content in the sound, so leave here option for modificaiton

[bepone]

Me asked too!

here mr V

https://ampgarage.com/forum/viewtopic.p ... 17#p448817

and was replayed

This cap is 5nF, 0.005uF, i dont know what HAD put there but for the bass shape-ing in overdrive i have put 5.. works well in Soldano (SLO) and Marshall circuits, should work also here - following 430k resistors, i wanted to have Dralorics there but i have only box with those values (430k) , not 470k - if i had 470k i will go with them.

Cathode capacitor originally i have put 10uF, but value is critical how i realised from the tests.. Now is 3.3uF but maybe i will increase it to 4.7uF. I have tried 1uF but the sound was too nervous, shrill! Can be fine tuned

[Aaron]

Yes, the schematic has the wrong values. I thought I had updated it. Sorry for the confusion.

Aaron

[Reeltarded]

Yes, the schematic has the wrong values. I thought I had updated it. Sorry for the confusion.

Aaron

Never apologize. WE LIVE FOR THAT! Right?

[caspercody]

Hello

I just saw a video of Amplified Nations amp Ampliphonix and gain, and loved the clean channel sound. Per their website it is based on a Dumble Ultraphonix.

I quickly skimmed through this post looking for a schematic. If I were to make just the pre amp, which schematic would you point me to look at for re-creating the clean channel?

Thanks
Rob

[Reeltarded]

This is Aaron's scheme marked up with my finger.

The shared cathode separated is 2xR/.5C but 10u to 25u over 1k8 works great.

Breaking out the mids to a control is best. Just copy JTM45 47k/250p tone stack but substitute 500kA for bass control.

If only building clean channel make that 470k mixer into a splitter with a second 470k to ground.

IMG_8246.jpeg

[Reeltarded]

:::::::

IMG_4015.png

[caspercody]

Thank You!!!

One other question, about the Dumble overdrive circuit. From what I can find it seems to be the same circuit. Have you found the overdrive circuit to be one design or many different versions? Sorry I cannot attach the schematic I have right now.

Thanks
Rob

[Reeltarded]

OD section from ODS amps?

Plates, cathodes, possible HRM, OD1-2 control values...

[caspercody]

Yes, ODS.

That is what I am trying to figure out, was the overdrive section of the Dumble amps all different? I see that the clean section is different based on the amp style. But I have not found many overdrive sections different in design??

[Reeltarded]

Lots of variation, based maybe first on period and next on person.

[fred.violleau]

If only building clean channel make that 470k mixer into a splitter with a second 470k to ground.

IMG_8246.jpeg

Quick question here, before I solder thing on my eyelet board:
From what I read, 220k mixing resistor are here to tame the signal a bit and avoid channel interaction (these are out of phase).

My build is setup this way :
- channel1 is UP clean
-channel 2 is UP High Gain
- relay ala Dumble to switch from clean to dirt (grounding the unused signal)
- passive FX loop

This is where I experiment :
I have added another relay and switch that allows me to choose different combination of mixer resistor and switch from one to another
ex: switch between 0k or 220k mixing resistor, or 220k and 470k resistor.

good read about the channel mixing resistors here : https://ampgarage.com/forum/viewtopic.php?t=29889

Since I don't have the two channel mixing at the PI entrance Cap, I don't need in theory the mixing resistors.
But in order to have the signal close to the original blackface or Marshall feel, are 220k and 470k still valid values?
If not, what value should I play with ?

EDIT ------
new boards are ready

PXL_20231231_180926594.jpg

and drilling ongoing in the old chassis

PXL_20231230_152244002.jpg

Thanks, and Happy NYE !

Fred.