Hybrid Si/Ge orpheum or fuzzrite?

[superferrite]

Anyone try do do a hybrid with this kind of circuit?  Which half would be more stable as Ge?

I've built a few hybrid fuzz faces, but they're quite different from these beasts.
I was thinking of having the first stage Si and the blended second Ge.

Opinions?

[John Lyons]

The second stage is where the big fuzz comes into play so I'd go Germy there.
I don't think there is any stability difference between stages as they are
cascaded and about the same as far as operation.

I loves me some OrPheum/fy2/fuzzrite. 

[superferrite]

Cool, that is what I was thinking, too.
Why is there a capacitor to ground after Q2 in the Si version and not in the Ge version?  Would it matter if I omitted that?
http://www.diystompboxes.com/smfforum/index.php?topic=89396.0 for the schematics I have...

[John Lyons]

It's a hi frequency/oscillation prevention thing.
Since silicons are generally higher gain that cap keeps things under control better
as far as possible oscillations due to the gain being higher overall.
The Cap and the resistor work together...the 100k and the 47k are a voltage divider
and the cap filters out high end at the division of those resistances.

[superferrite]

So is this necessary if the second stage is Ge?   I was thinking of just having the 100k resistor to the emitter of Q2 like in the Ge version.
I guess I could put in a socket to swap out a cap to taste if it is too fizzy.

My Ge fuzzrite is too tame, and the silicon versions I have built of the fuzzrite and orpheum are too nuts.  I was hoping this hybrid would be a sweet compromise.

[John Lyons]

Use lower hfe silicon transistors. 150 or even lower
Emitter resistors will work as well.
Just breadboard the circuit and try the cap thingie...

[LucifersTrip]

Cool, that is what I was thinking, too.
Why is there a capacitor to ground after Q2 in the Si version and not in the Ge version?  Would it matter if I omitted that?
http://www.diystompboxes.com/smfforum/index.php?topic=89396.0 for the schematics I have...

I was actually told by another member here in an old post that the omission was a mistake. I've made a bunch of ge Orpheums (my favorite fuzz so far) and all have the cap. They are all loud, brutal and nasty and have more than enough high end, so I don't think I'd make it without  the cap. If you need to tame it a little, like the FF across Q1 BC, a very small cap across BC of Q2 will do it.  

Believe it or not, I've found the best sound to have 120-150 hfe for Q1 and 30-50 hfe for Q2.  When I started raising Q2 higher, I was just getting a sharper, cleaner sound with more treble and I starting losing the dirty fuzz.  Unlike the FF, which is sensitive to leaky transistors, this is not, so don't worry about picking super low leak ones. Tho, if you pick very high leak ones, you will get hiss.

Also, unlike the FF where a pot on Q2's collector is mainly used for a trim to get Q2C's voltage to 4.5v, on the Orpheum you get a full sweep of great tones from 0 - 50k if you sub a 50k pot for the 47K on  Q2's C. If you turn the 50K pot to 0K and still get a really cool buzzy fuzz with no gating on the high strings, you know you've chosen the right transistors.

I usually get unity at about 30-40% volume (and as I said, it's nasty), so I never even considered a silicon version.

good luck

[John Lyons]

was actually told by another member here in an old post that the omission was a mistake.
Heh, just looked at my orpheum schematics and yeah, they both have the.1 to ground. 

Believe it or not, I've found the best sound to have 120-150 hfe for Q1 and 30-50 hfe for Q2.
True...I have a silicon variant that likes 50hfe in Q2. (silicon)

you get a full sweep of great tones from 0 - 50k if you sub a 50k pot for the 47K on  Q2's C.
uh-huh, I use only 47k on one I made (took out the 100k).

Fun fun fun

[mac]

As long as you use low leaky germs and/or play indoor temperature stability is not a problem. On stage under direct sunlight... mmhh...

Most of the sound of this family of pedals comes from the two capacitors connected to the blending pot. You are mixing the negative signal of the first transistor with the positive signal of the second one at different levels. Experiment, just for fun! If the collectors bias at 4.5v or 2v have noticeable but little impact on the overall tone.

I'd say germs will make a difference. You can add a emiter resistor of 10% - 20% of the collector value bypassed with a big cap, and tweak the feedback resistor to get a collector voltage that sound good to you, and that will keep stable under temperature changes.

mac

[superferrite]

Well Arizona is pretty damn hot much of the time, so it may be an issue.
Thanks for the information.  I will experiment!

[LucifersTrip]

Well Arizona is pretty damn hot much of the time, so it may be an issue.
Thanks for the information.  I will experiment!

The Orpheum is not affected much by temperature. Remember, it sounds good with the full sweep of the 50K pot, so it does not have to be set at a specific point to sound good....it ain't no Fuzz Face.

[Gus]

http://fuzzcentral.ssguitar.com/schematics/foxeylady2k.gif

I simmed it and the stages are sensitive to hfe.

What the collector voltages sim at with the LT spice stock transistor models
2n2222 first stage about 4.0 VDC and the 2nd about .24VDC
2n5089 first stage about 3.47VDC and the second about .25VDC
2n4401 first stage about 4.67VDC and second about .30VDC



You need to keep in mind that if you change the collector resistors you change the output resistance and how it interacts with the blend pot and high pass cap values and 22k and output volume control.  

Because R5 and R6 are cap bypassed, adjusting the emitter resistor value for the  collector voltage desired should be the best way, keep in mind the RC time constant of the 2nd stage Emitter RC

[LucifersTrip]

...and for my actual ge Orpheum Q2 collector voltages

50k pot      Q2C
-------------------
50K          -3.08
37K          -3.34
25k          -3.71
12K          -4.11
0K            -4.52

The closer you get to 0K, the more you get a buzzy wasp fuzz with smaller sustain.  For this ge Orpheum, I get a full on saturated nasty fuzz from approx 50K - 20K and the more buzzy wasp fuzz from there on down to 0k

[Gus]

Just adjusted some values in the sim.  Making R4 in the schematic I posted a 680 and a 1K external trim pot in series looks to be a nice adjustment.

I posted the screen shot to help people understand the circuit, note the change in collector voltage with transistor number( hfe).