stupid pedal trick.... sharMall 5xxx preamp in a box

[pinkjimiphoton]

what happens if ya take the preamp from the solid state marshall's of the 80's and run it off a charge pump and stuff it in a 1590b?

this does. not gonna post any build dox, there's already tonnes of info out there. only deviation from stock is a 1500p cap between pin 2 of the 1458 and ground so it doesn't oscillate with the gain pegged.

you can find great build dox for this on tagboardeffects.blogspot.com  look for the marshall 3005 preamp project.

https://www.youtube.com/watch?v=LLJ1E4XmPDo

[GibsonGM]

Took a look (schematic for 12W 3005 is readily available in a search) - couldn't be simpler!  Nice Marshall zing for the era   Doesn't even need clippers ha ha!

[pinkjimiphoton]

hey mike,
nope. they actually kinda make it suck.
no need. that magic 1458 jellybean makes that joyful noise.
since i re-discovered this series of amps, i've aquired quite a few of them
from the 3005 on up to a ...umm...plethora(?) of the 5212's... i have like 6 of them
i use for different things, but the point is, i abandoned pedals live and just plug straight into these suckahs.
and they totally rock.
with this little gizmo, i can plug into pretty much any amp and make it sound like ME. i diggs that, and hard.
next one may have a reverb built into it too. may have to go to a 125

[GibsonGM]

Now I gotta make one, ha ha.  I have a small Marshall like that, with the Contour knob that has always gotten my attention...dial in some fat if you want, or scoop the h3ll out of it for something more modern.  I drive my talkbox with it now. 

Other than Dist+ I never did a lot w/opamp distortion, but those little suckers definitely rock! I've been using a Guvnor too, but of course that uses clippers.
Good find man.

[iainpunk]

yo, pink,

i love the grindy low end without being ''boomy'', is it really the 1458 chip that makes it do the trick?
i might do a 'tonestack delete' build, or something with a rat style filter control.

i can't get over how good that video sounds, ofcourse tone in in the fingers, but its the ''grind'' it produces that makes it just so good

i never actually build an opamp based distortion pedal to completion. i have build a few protoboards, but those never got any enclosures (didn't keep me from gigging with one tho), i

cheers

[pinkjimiphoton]

yo, pink,

i love the grindy low end without being ''boomy'', is it really the 1458 chip that makes it do the trick?

yes

[GibsonGM]

This should 'get one started' with this...

[pinkjimiphoton]

if ya look on tagboard, in the comments someone posted a great layout with the whole package on it, including charge pump. i built it, works great.

[GibsonGM]

I'm more a seat of the pants, throw it on perfboard type, ha ha. 

[ElectricDruid]

PinkJimi builds an op-amp based distortion?!? Without putting even a little bit of germanium in it?! Not even a diode!

My life is complete, I can die happy. Now I've seen everything.

[stonerbox]

PinkJimi builds an op-amp based distortion?!? Without putting even a little bit of germanium in it?! Not even a diode!

My life is complete, I can die happy. Now I've seen everything.

He said what we all are thinking/feeling.

[pinkjimiphoton]

well, technically, its just a preamp, not a distortion.

but i've been using them jellybeans for years and years in all kinds of dirt boxes.... so... lol

[anotherjim]

I was given a Valvestate 8001 to fix up a few weeks back. This has TDA2030 power amp. Very simple.
Had a red LED clipper after the second stage for the lead boost (only one amp channel, just a switch to cause the clipping). Works well.
But the input crackles the guitar vol pot. 0.8v DC leak. Since the 1458 has input bias current maybe some DC is expected? Anyway, it works, I didn't change the chip, just cut a track and added an input cap.
It had other ills like crackly pots. The oddest was the blackening CLR for the panel LED. But it is pretty old now and actually made in GB not China.

[pinkjimiphoton]

i remember them, too. different series, quite a different tone.
with these marshalls, its almost always shitty coupling caps that make the controls scratchy.
i'm kinda surprised it would be scratchy from the guitar control. i've dealt with that too, and its been
in my case a bad ground or a tiny bit of a short in a cord.

but who knows. all i know is, is the earlier pre-valvestate stuff sounds way better. the way the jcm800's SHOULD have been.

[rutabaga bob]

So, did you make/use the accompanying bipolar power-supply board they show?

[pinkjimiphoton]

So, did you make/use the accompanying bipolar power-supply board they show?

""Alltrax7415 October 2018 at 13:59

For those who may be interested, I drew a layout including the bipolar voltage converter using this schematic : https://i.goopics.net/q4WkY.jpg
The input is on a switch to select between high and low.
I went through a few times but better double check before building ;-)
https://i.goopics.net/a9LNp.png""

[GibsonGM]

Looks good Jimi, thanks.  Hey where are people sourcing the 1054?  Just, Mouser etc?  I found a few on fleabay but they seemed expensive and who knows if they're real...

[pinkjimiphoton]

i think i got it at tayda

[anotherjim]

FYI, the 8001 preamp...

[pinkjimiphoton]

i've got the 9004 preamp. i don't see a need for the clean part. or the diodes

the whole series pretty much sounds the same, which is neat cuz there's a bit of change and evolution over the history of marshall producing the circuit.

but the big thing is the 1458. that's the magick sound in these, people use tl0x2's etc, but they sound like total ass.
here's the thing... the bjt front end of the simple 741 (a 1458 is a double 741 pretty much) can't produce as much high end harmonic content so when ya drive it hard you get a real nice warm sound very reminiscent of tubes.

fets may "seem" to act more like tubes... and they do. right up until they clip. and when they DO clip, they clip hard and nasty and have about 2 more octaves of treble response so tend to hiss a lot more.
i rarely ever will use a jfet opamp for distortion, to my ear they all sound hissy and gnarly. they sound great unTIL they clip... but not after.

case in point... a few months ago i hoss traded some stuff with a bud and picked up a really clean 5212 50 watt 2x12 combo. it was CLEAN! looked immaculate. sounded great.. until ya bring it on stage and crank it up. hiss @#$%ing city. like, ANNOYING hiss... and forget using a noise gate to knock it back, nothing i tried worked.

finally said fukkitall, and opened her up, knowing there's pads for snubber caps on the board that usually aren't stuffed, and figuring the judicious application of some small capacitance should help nuke some of the noise at the expense of a bit of presence.
usually i run these amps dimed, other than the tone stack, and turn my guitar up and down. so if its noisy, it will show quick.

so anyways, opened it up, and to my surprise...not really, but for the sake of the story and TRUTH... someone had removed the stock jellybeans and replaced them with sockets.
every socket had a tl072 in it but the first stage, with a tl082.

apparently someone had "upgraded" the amp to "sound better" and made it a hiss machine. the tl082 being a low noise opamp was likely added to try to address it, but it in fact made the noise worse.

so my job was wicked easy. i pulled the fuggin jfet chips and threw them in the junk bin, and replaced with the proper chips as the guv'nor had specc'd.

no more hiss. nice and quiet. can crank it full blast and the "blow" isn't even offensive. no more hiss.

what did we learn? well, WE didn't learn SHIT... but i learned my suspicions were right, and that jfet chips in this kind of application just don't sound as good as a simple '58. 4558's are fine. whatever. get them jfets the hell outta there!

so that's that....

well, WE didn't learn SHIT, but i did learn my gut was right