Fetzer Valve

[StratDudeDan]

my current project is just a general volume boost inside a Squire SuperSonic, i'll post the link to the schematics soon.

problem: i don't know much about booster circuits. if i did, i would probably be trying to add one to my strat or SG sometime soon.

question: i found this fetzer valve and was wondering if this is what i'm looking for as an onboard switchable circuit for this thing.

i know a 9V pack would be needed, and the wiring for both that and the supersonic are very simple (two humbuckers, each w/ their own volume straight to a pup switch, no tone, no taps, no phase, nothing).

what i don't want: distorted or overdriven sound. i'm looking for a general volume boost. if some of the tone changes, i'm fine with that as long as it doesn't suck. i was gonna breadboard that before i actually installed it.

i also don't want to go into this project if i know in advance that it's not what i'm looking for. other than tone circuits or coil taps, this would probably end up being my most advanced electronics project for a while.

thanks in advance!

EDIT- the Supersonic's schem is found here.

Edited September 13, 2004 by StratDudeDan

[lovekraft]

If you want your boost to sound like the clean channel on a Fender amp, use the Fetzer Valve - that's what it's designed to do. If you're looking for something that doesn't color the sound much, try Don Tillman's FET preamp, or run a search for the Alembic Stratoblaster. And if you don't want an overdriven sound, make sure that your volume boost doesn't overdrive your amplifier's input.

[Kevan]

...and for all the "Fletch" fans, sorry to burst your bubbles, but there is no such thing as a Fetzer valve on any aircraft.

[StratDudeDan]

k, how/where would i wire in either of those? is the fetzer supposed to replace the current volume/tone controls? is the FET booster nothing but an in-line booster? is there any way to make either of these switchable (i.e. an on/on that would cross between boost/non-boost?)?

thanks for the help so far, the guy liked the idea of having a "fender preamp" onboard, and i liked the simplicity of the FET circuit, so we're still hashing out what it's gonna be.

[Dugz Ink]

I sent the link for that web page to a friend of mine; he's a circuit geek, and I have a lot of respect for his knowledge. (He built his own version of a Neve mic-pre... plus copies of various other high-end gear.) Here's what he had to say about this Fetzer valve schematic.

It acts more like a DI circuit.... a JFET having a high input impedance and low impedance output. So the JFET acts like a variable resistor, varying the amount of 9V power corresponding to the input signal coming from the guitar. So in effect, having an output voltage that is bigger than the input, but varies proportionally to the input signal.

I wouldn't go as far as calling it a "emulation of the classic Fender 12AX7 or 7025 tube input stage". That's pushing it in the hype department.

This is as inexpensive as you can get, minimal parts count, cheap parts, so it wouldn't hurt to try it.

I hope that helps.

D~s

[StratDudeDan]

k, after speaking with the guy and doing a wee bit of research, the Fetzer wins over the FET.

new question, below are two differnt wiring options. which one would work out best.

main query is, in option A, would the "pickup volume" change anything about the sound or overall volume of the mod? is it worth my time?

main problem, i only have 2 pot spaces to work with without heavily altering the shape the guitar is in currently (i'm already finding room for the 9V, not interested in more), so i was gonna try and at least use the existing mounts and whatnot that i have.

[lovekraft]

So in effect, having an output voltage that is bigger than the input, but varies proportionally to the input signal.

Your associate has a firm grasp of the obvious - that's as good a definition of a voltage amplifier as I've heard recently. Both triodes and JFETs act as voltage controlled high impedance current sources, hence the similarities in their circuit designs.

I wouldn't go as far as calling it a "emulation of the classic Fender 12AX7 or 7025 tube input stage". That's pushing it in the hype department.

Here - compare the two, and judge for yourself -that circuit architecture looks identical to me.

<EDIT> The 100K trimpot is a set-and-forget adjustment - you won't ever need access to it after the initial adjustment unless you replace the transistor. You can use a DPDT switch to change between active and passive modes by simply bypassing both the input and output of the Fetzer. Simply use your volume pot in place of the 100K pot shown in the Fetzer schematic.

Edited September 14, 2004 by lovekraft

[StratDudeDan]

k, one last question and then i should be set:

1k5?

i haven't seen this before. is this a 1.5k or 5w resistor or, well, i don't know?

EDIT- and where can i get one?

Edited September 14, 2004 by StratDudeDan

[lovekraft]

Sorry, my bad - 1K5 is 1.5K, it's used on schematics because it's easier to read. You can get everything you need build a Fetzer at Radio Shack - use the MPF102 transistor they stock and 1/4 watt resistors.

[javacody]

Dugz Ink, you might want to ask your friend if he has ever used a JFET for classic amp simulations. They get you in the ballpark. Brian and Gary over at RunoffGroove have been providing do it yourself effects to the DIY Effects community for years. How many projects has your friend provided? Perhaps he's jealous he didn't think of it first?

They've gone through some classic amp circuits recently and converted them into distortion pedals using JFET's. Listen to the clips on their site, the pedals retain the character of the amp they were duplicating and sound damn good. All this for free. I see no hype in that.

For boosts, I would try and dissuade anyone from putting a boost in their guitar. Build yourself a free standing boost. You can use it for all of your guitars then. Also, you have to buy fewer batteries (as you have one boost for all guitars instead of a boost in all your guitars) and its easier to change batteries. You can also tweak the values of the boost, or even build a whole new boost (and keep building different boosts to suit your moods or to find the best one).

Go here for some good booster projects:

http://www.generalguitargadgets.com/

Also, check out the beginner project section here for a great boost (it walks you through every step!):

http://www.diystompboxes.com/forums/stompboxforum/

Finally, check out Jack Orman's site, I highly recommend his mini-booster. I've built two of them myself, each with different JFETs and different tweaks:

http://www.muzique.com/

He has a couple other boosters and some cool fuzzes as well.

[lovekraft]

Nice to see another Runoff Groove fan here! I highly recommend them! All their stuff is simple, straight-forward, and very musical sounding.

[Dugz Ink]

How many projects has your friend provided? Perhaps he's jealous he didn't think of it first?

You could be right... he hasn't built any Fetzer Valves... just a home-grown Neve mic-pre and stuff like that. As a matter of fact, we put together a DIY area on another forum and made him the moderator.

Your associate has a firm grasp of the obvious - that's as good a definition of a voltage amplifier as I've heard recently.

Because he's the moderator for that forum, and because he gets a a lot questions from people who don't know a capacitor from a diode, he always explains things as simply as possible.

Sorry if you guys got your feathers in a ruffle. Maybe I shouldn't try to help anymore.

D~s

[javacody]

He'pin' is awesome an' yer t'be commended fo' it, but slammin' other varmints's wawk ain't right fine, an' thass whut yo' did by way of yer friend's comment. No offense, but yo' made yer friend soun' like he's on a bit of an ego trip. ah's sho'nuff he's a mighty smart guy but guess whut? Thar's lotsa other smart varmints in this hyar wo'ld an' us backwards hicks might even knows one o' two, o' gosh, we might even be smart varmints.

ah's a moderato' at a fo'um too. Kin ah join his exclusive club?

Edited September 20, 2004 by javacody

[lovekraft]

Sorry if you guys got your feathers in a ruffle. Maybe I shouldn't try to help anymore.

Lighten up, we were just taking your friend to task for being a little on the pompous side, not to mention condescending and dismissive. His overly-technical description of a common-source JFET amplifier without ever calling it by name makes me wonder about the depth of his education, and that "hype" comment was at least a little inflammatory. Surely he didn't think we were all so inexperienced that he could get away with it, did he?

Nobody wants to run you off, your help is appreciated, and I don't think anybody has gotten the idea that you were trying to do anything other than help. Your friend is obviously fairly informed, but assembling a Neve preamp, with the circuit boards and the schematic already done for you, really isn't much of an accomplishment for an experienced tech - it's slightly more complicated than painting by numbers. He does nice work, and I congratulate him for having the patience to put together a complex, fiddly circuit like the Neve, but that doesn't exactly qualify him as a designer.

His quote was what was objected to, and that shouldn't reflect on you - sorry if we hurt your feelings in the process. Any personal disrespect you felt was totally unintentional, at least on my part, but your friend just needs to get over himself.