BRETT AND EVERYBODY....MORE FF SPECULATION!

[brian wenz]

Hello Hello--
    Alright......wot about using a germ. tranny in Q1 and a piggyback duo for Q2???   I'm thinking this would allow Q1 to be lower hfe then Q2........but maybe it would depend on what trannys were used for Q2......
Brian.

[b_rogers]

has anyone tried to piggyback a germ yet?  i have some ac188's on the way that are supposed to be pretty high gain..

[Fret Wire]

http://www.geocities.com/SunsetStrip/Studio/2987/britface.html

[javacody]

fretwire, I don't think you've seen RG's reply to adding a diode to a transistor to alter gain. It doesn't work as well as piggybacking, the gain is also pretty hard to control. With piggybacking (especially bretts method with the trim pots) you can basically adjust gain to taste.

[Fret Wire]

I've seen em' both, and tried both methods. Have you tried both yet? You've piggybacked a Ge? There are times, depending on the gain, that the diode method works good in the basic Dallas ckt, with Ge's. Piggybacking works also, especially from the start. Depends on exactly what you're trying to do, the ckt, and what you're trying to accomplish.

[brian wenz]

Hello Hello-
    I've tried piggybacking germs........hfe was too low..didn't sound good.
 There's probably something I'm missing, though!
Brian.

[javacody]

I have tried both. I've even tried the diode mod to decrease temperature sensitivity, and I didn't have much luck. For me (and your experience probably differs) its simply easier to piggyback si trannies.

[brett]

i have some ac188's on the way that are supposed to be pretty high gain..

I've worked with some (20) AC188s and a few are fairly high hFE (150-160).  I figured I'd use them in something besides a fuzzface.  

One of the main reasons I like piggybacking Si is the low noise.  Though I play at home, where noise is a lot more noticeable than live.

It's cool that a number of people have got the diode thing working.  Also, another thread mentioned a PN2369A, which is supposed to have hFE around 50 and sound good in Q1.

[Fret Wire]

The 2369A does work pretty good for Q1. The 2222 works nice for Q2. In my last batch of 50 2222's, 40 were between 115 and 140 hfe. There are other si's also that, between mixing and matching, you can always hit the 70-130 range. This is nice when someone is working with a pcb board of a straight dallas type fuzz ckt.

You're piggybacking method works great. Of course, you're piggybacking right from the start with the circuit.

For Ge's, it's tough when your Q2 is too high. I believe this is what Brian was asking about. The diode "reverse darlington" method sometimes saves Ge's that are over the gain range. You've got nothing to lose by trying. My Ge test board is socketed for the diodes on Q1 and Q2, so I can try them without any changes. With most pcb's, if you are careful, you can drill the addition holes for the diodes. There is usually enough room. Just reverse the diode, and you have the leakage protection.

Many of us have some Ge's just sitting around that have either too much or too little gain. It's nice to find workable, good sounding methods that allow their use. The diode method is just one of those ways.

If you haven't aquired alot of Ge's, don't. With a npn ground board layout that will accomodate both methods, you can use either two si's of the proper range, or piggyback them to dial them in exactly.

[b_rogers]

so the diode mod on plate to plate works ONLY with Ge? why wouldnt it work on Si?

[brett]

As far as my small knowledge of theory tells me, the diode mod on plate-to plate will work for Si.  Except (here's the catch) Si junctions have a smaller, more responsive voltage band for conduction.  The chances of getting a good match between the junction and the diode might be less than for Si.  On the positive side, if you do find a good match, it's likely to be more stable than for Ge (wrt temp etc).  

I'd guess that transistor junctions are going to be more likely to match other transistor junctions than boofy junctions in rectifiers (1N400X) or fancy doped junctions (1N914, 1N4148).  But I might be completely wrong, too.  What have people had practical success with?

[Fret Wire]

I've never tried it with Si trannies. Between piggybacking, and trannies like the 2369A & 2222, there's no need. If you have a bunch of 3904's, piggyback them. With other si's, one that's too high for Q1, becomes Q2. An si that's too high for Q2 becomes a general purpose tranny used for many of the same things you use a 3904 for. For the same cost. Many think they have to use a BC108 or BC109 for a fuzz, and get stuck on that. I don't have one that's even close to low enough. I have some BC108A's that go around 185-210. Most of my BC108's and 109's go 350-475. They go in wah's, where they do some good.

The problem, really, is just to find a way to get Ge's with high gain to be useable in the basic fuzz circuit. We all end up with them, and it's shame to have to use them as diodes or general purpose trannys, especially given their cost. I'd also like a way to use Ge's that are too low. Maybe a 3-transistor ckt like the Tonebender, set up more as a blues type OD.

[brian wenz]

Hello Hello--
  My original question was based on Aron's "Hornet" circuit where he uses a germ for Q1 and a high-gain si for Q2.   I'd like to know if anybody has any experience using a piggybacked pair of si for Q2??
Brian.

[brett]

if anybody has any experience using a piggybacked pair of si for Q2

To me, the "right" gain (100 to 150) in the Q2 position gives some extra dynamics to the fuzz (ie high gain fuzzes like the Blackfire stay fuzzed out until a note is completely decayed, while a good fuzzface seems to change tonally with attack and decay).  When I think of this I am reminded of RG Keen's "technology of the FF" where he describes the high hFE JH-1 and JH-2 fuzzfaces as "sticky".  I think the "stuck to a single, piercing type of fuzz" effect is likely to be due to too high an hFE in Q2.

But does piggybacked Si lack some of the "warmth" of Ge?  Probably.  Would you hear the difference playing live or if you weren't doing a direct A/B comparison? Hard to say.

[RedHouse]

I can answer that Brett.

Your piggy back works Live and Recorded and does a wonderful job eliminating Gemanium's. The "warmth" thing isn't an issue IMHO I did A/B testing and the tone losses from germaniums are high.
(hold the flames please)

I built a few FF's with AC128's and AC125's and ever since your post about piggybacks (after the emitter resistor fix) I've built a few and have been a staunch supporter of your circuit ever since.... I works sooo good.

Your "piggyback" idea is the answer for silicon based FF's. Half the hiss and twice the dynamic range!.

[brett]

Hi.  Glad you like it so much.  By the way - RG Keen had the idea.  I just tried, revised and tested it.  

It seems odd, even to myself, but if I find some cheap AC128s, AC188s or AC125s, I'll still buy some, looking for quiet, fuzzy pairs.  It's a bit like prospecting for gold.  It's addictive. :wink: