Marsha Valve (inspired by Fetzer Valve)

ragtime8922 · June 09, 2005, 09:30:20 PM

Cool, you have a layout now. One of the forumites is working on a layout for my Bogzer Valve right now. (Bogner front end type boost.) It has a ton of headroom from the 18v power supply. You should try it.

joelap · May 30, 2007, 08:31:55 AM

I breadboarded one up last night, and ran that stage into a JRC4558 tube screamer diode-clipping stage. My intention was to boost the signal with the Marsha valve and use the TS style diode clipping circuit to add grit and distortion. I found that there was no difference in volume between on and off. Used a J201 biased at around 4.7V ... I moved my in and out wires so only the Marsha was connected, and without a volume control (taking output off the .022uf cap), there was only a slight increase in gain. Is this normal? Does this do more coloring of tone than boosting of the signal? The reason why I ask is because in 3 builds using JFETs, I have never gotten a single one to work properly, so this may be the first JFET project (even though it is on breadboard) that is actually functioning as it is supposed to.

sfx1999 · May 30, 2007, 06:46:45 PM

You can get more gain by changing the 2.7k resistor to 1.5k or 820 ohms.

vanhansen · May 30, 2007, 09:37:44 PM

Joe, same rules apply when you've already hit the headroom ceiling, which sounds to be the case with the TS clipping stage. You're just adding more gain/saturation at that point. Try putting the Marsha Valve after that stage and listen for boost. Also, make sure the MV boosts the signal all by itself beforehand. It should give a hell of a boost as long as there is headroom for it afterwards.

joelap · June 02, 2007, 03:42:54 PM

Erik, I must have had it wired wrong or something, cause the next day I went down and the MArsha Valve alone it had a nice amount of grit/boost to it! I dunno what changed overnight, but it was night and day!

WGTP · June 03, 2007, 12:58:03 PM

Has anyone tried a J202. They are supposed to have more gain at around the same price.

Also, checkout the Crunch Pre-amp at AX84. It "blends" a bright and dark channel using 12ax7 valves/tubes. Might give you some more ideas.

vanhansen · June 04, 2007, 12:37:27 AM

Cool, Joe. Sounds like the gremlins just up and left during the night.

It can definitely add some kick. I'd just double-check everything from beginning to end and make sure everything is connected where it needs to be.

WGTP, hadn't tried the J202. Where can one get them? It's like to try a few when I can. I haven't been doing much DIY lately other than a couple pedal mods here and there. Not enough time to tinker on the breadboard and build. I still read up on stuff here though when I can.

petemoore · June 04, 2007, 01:18:07 AM

WGTP, hadn't tried the J202.
Me neither, but I did try the NTE458 Jfet which is more than marginally higher gain than the J201, but also 'harder' sounding in the circuits I tried it in.

MartyMart · June 04, 2007, 04:40:42 AM

Quote from: petemoore on June 04, 2007, 01:18:07 AM
WGTP, hadn't tried the J202.
Me neither, but I did try the NTE458 Jfet which is more than marginally higher gain than the J201, but also 'harder' sounding in the circuits I tried it in.

Agreed - J112 is quite nice though, seems like it's between 2N5457 and J201 gain wise and has a nice soft edge to it
I got some from dpi4parts off evilbay - he's a GREAT supplier for Fet's 'n BJT's etc.
MM

Ben N · June 04, 2007, 01:24:55 PM

Quote from: MartyMart on June 04, 2007, 04:40:42 AMI got some from dpi4parts off evilbay - he's a GREAT supplier for Fet's 'n BJT's etc.

Just wanted to chime in with +1 for Dan.
Ben

RLBJR65 · June 04, 2007, 08:10:05 PM

I've got some J202s. The 201 & 202 sound pretty much the same to me at 9V. However at higher voltages the 202 sounds much better. I built a couple of amp sims / fet distortions (whatever you want to call them

) running at 18V. http://aronnelson.com/gallery/album133/FireFly_Pedal & http://aronnelson.com/gallery/album133/GA5T_Preamp?full=1

In those circuits at 18V the 202s blew away the 201s. 202 seemed smoother and a bit brighter at lower gains and broke up nicely at higher gains. In the FireFly maxed out... oh my...

It scared me, I put the 201's back in!

I know I bread boarded the MarshaValve (never have tried that vero layout I did

) but I can't recall if I tried the 202's in it ?!?

BTW I've got at least 4 new 202's in my bin if anyone would want to trade for 201's or ?

dromilious · June 02, 2011, 01:45:00 PM

Today i tried to built the marsha valve tube version 0.2.Except from the 22n capacitors(i used 10n) i didn't do any other changes.
when i gave it 12 volts from an 500mA adapter i heard only a hummmm and no signal.The tube was lightning a bit !
After that i used a 1 A adapter and before i turn the trimmer i saw smoke...it was from the elect. capacitor.I power it off very fast because it was ready to blow off.
what do you think is the problem?

Renegadrian · June 04, 2011, 07:54:14 AM

Quote from: dromilious on June 02, 2011, 01:45:00 PM
Today i tried to built the marsha valve tube version 0.2.Except from the 22n capacitors(i used 10n) i didn't do any other changes.
when i gave it 12 volts from an 500mA adapter i heard only a hummmm and no signal.The tube was lightning a bit !
After that i used a 1 A adapter and before i turn the trimmer i saw smoke...it was from the elect. capacitor.I power it off very fast because it was ready to blow off.
what do you think is the problem?

Inverted voltage polarity!?

I once built that, actually I didn't like it at all...so it got dismantled soon after...

dromilious · June 04, 2011, 08:13:04 AM

To be honest i didnt check carefully at my adapter with a polymeter.I will see today.What else circuit do you suggest for my 12ax tube? I need a tube sound like the Blackstar HT DISTX.

Renegadrian · June 04, 2011, 09:11:12 AM

go and buy one then!

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Marsha Valve (inspired by Fetzer Valve)