"Piggybacking" trannies for lower gain

[Ed Rembold]

To reply to R.G.'s question about why I used an Si and Ge diode
in series-
Simple,  It gave me the closest match to the diode drop of the piggy-back transistors I was "removing".
By the way the transistors I used in Miss Piggy were all 2N5088's
this could be why I didn't like the tone.
Who knows?
I gotta set this aside,  but I'm curious to hear what the rest
have to say about this deal.
Thanks, Ed R.

[idlefaction]

also of interest, i liked the sound of my piggybacked fuzz face when i cranked the gains of the transistors up to 90 and 110, and they also became far easier to bias.  

with low gains the bias on Q2 goes from 1V up to 2V and then jumps to 7V with increasing resistance on the collector of Q2, whereas with the higher gains the bias went up steadily and let me dial in 4.5V a lot easier.

is there a reason for specifying 1.2V on Q1?

[brett]

1.2V is simply what I've measured on Q1's collector when I've trimmed for a good sound in various Si fuzzfaces and an Si Hornet.  So it's just a guide.  Other values probably sound as good or better...

[Kleber AG]

Hello Ed, I've tried 2N5088s and 2N5089s and could not have a really good sound with them  :?
The bad thing is that when I was trying this things I was doing it like crazy at the breadboard and have not put the right attention or enougth care, OK that was just a crazy mess  :shock:  After had the 2n3906s sounding good, I thought the 2N5088s would be even better, but we may still have some weird factor somewhere the keep given us unpredictable results, at least for me...

How are you measuring HFEs of the piggy backed combos so easy?

Kleber AG
PS: I must say that with the easy face and 2N3906s I really had a GREAT sounding fuzz with a little dirty from my JCM800 amp.

[RDV]

I know I'm chiming in a bit late here, but I have a comment. I have a "Well Tuned Ge Fuzzface" and I don't like it much. I also have one that I built(not as well tuned ) that to me sounds much better. Maybe I just don't have the right rig, or maybe I just don't like the basic sound of the fuzzface, but lately the only sound I've been comfortable with is my double mosfet booster or my modded peppermill OD into an already cranked tube amp(JCM900 50watt).
I like a tight sort of OD or distortion and a FF just won't do it for me. Believe me though, I've tried.

Regards

RDV

[javacody]

How are you measuring HFEs of the piggy backed combos so easy?

I used my DMM. It has an hfe tester for transistors. I just slipped em both in at the same time.

[brett]

RDV said

I like a tight sort of OD or distortion and a FF just won't do it for me. Believe me though, I've tried.

I can strongly relate to your problem.  Neither my Ge FF nor my Si-Ge Easyface were ever as tight and mud-free as I wanted (certainly not as tight as my tubescreamer or my Vox 1901).  And Si in a  FF seemed to make it "congested".  Hence, to find a better fuzzface I tried RG's suggestion of piggybacking transistors.

I think that RDV (and others) can make an important contribution here.  Who better to test the new circuit than people who never really liked the old circuit?  

You may like to try the Miss Piggy circuit (above).  Instead of the 2x 1k resistors shown, I suggest using up to 10k emitter resistors in each gain stage.  It seems that PN100 or 2N3904 transistors are best (of those tested so far).  Good luck.

[bwanasonic]

I know I'm chiming in a bit late here, but I have a comment. I have a "Well Tuned Ge Fuzzface" and I don't like it much. I also have one that I built(not as well tuned ) that to me sounds much better. Maybe I just don't have the right rig, or maybe I just don't like the basic sound of the fuzzface, but lately the only sound I've been comfortable with is my double mosfet booster or my modded peppermill OD into an already cranked tube amp(JCM900 50watt).
I like a tight sort of OD or distortion and a FF just won't do it for me. Believe me though, I've tried.

This is a good example of how tough it is to discuss various distortion/OD/ Fuzz circuits and what sounds *good*. If you are using an already cranked JCM900, your idea of what sounds *good* is going to differ from someone using say a 15 watt SS practice amp or maybe a Fender Twin.  Are you trying to sound like Slayer, Blink 182, Mudhoney,  SRV, Jimi, the Allman Bros. , Carlos Sanatana or early Iggy and the Stooges? Personally, I found the DIY Ge FF I made to be a revelation, but lately I haven't been bringing it to gigs, as I prefer the sound of the *Marshall* channel of my Rivera nailed with a mosfet boost. I used a vintage TS9 for over a decade, but now the sound of it just makes me cringe. Some people even like the sound of a Boogie Triple Rectumfryer. To me it sounds the way burnt plastic smells, but some people like that smell.

Kerry M

[Boofhead]

Here's the one of the older threads on this topic from the archives. You will probably have to log-in to read it.  The thread was titled "altering transistor gain"

http://diystompboxes.com/sboxforum/viewtopic.php?p=39549&highlight=resistor+series+diode#39549

Putting that aside, you can add a simple control which lets you vary the tone between the modded and unmodded.  Wire Q2 as usual then on the base put a 10k pot in series with a 1k then put that in series with a diode, transistor BE (B = anode E =cathode), or a transistor with the B and C connected together (B+C = anode E =cathode).  Wire-up as:  "anode" goes to the base of Q2, "cathode" goes to the 1k resistor then through the 10k pot then that goes to the emitter of Q2.   Choose the collector resistor of Q2 so the collector voltage of Q2 is roughly centred around 4.8V over the extreme pot positions.

[Paul Perry (Frostwave)]

a 'HexFET'  is six piggybacked FETs in the same three-leg package.  

errr, I don't think so, it's the hexagonal grid structure. As seen here:
http://www.irf.com/technical-info/an937/an-937p2.htm

[RDV]

Are you trying to sound like Slayer, Blink 182, Mudhoney,  SRV, Jimi, the Allman Bros. , Carlos Sanatana or early Iggy and the Stooges?
Kerry M

My favorite sound is the big, massive "Live @ Leeds" tone, but alas, I have no Hiwatt CP103. I'm getting pretty close with my P-90 equipped Les Paul & the boosted Marshall.

Shakin' all over

RDV

[WGTP]

To clarify my previous post, I meant to use 1 pot of a dual gang pot for each of the resistors at the transistor junctions, but wired in reverse.  Sounds like a 5K or 10K would work and by varying the nob, the hFE between the Q's would change and you could go from having the Q1 low and Q2 high, to having the Q2 low and Q1 high,  I'm thinking this would change the character somewhat.

Another option would be to wire them the same and vary the hFE up or down with both Q's at the same time.

Not sure which would be the most useful.  

[javacody]

What would be really cool is to put a couple of meters on the pedal to display hfe of Q1 and Q2. How would you do that? Also, a switch to switch out the second tranny for each pair.

[idlefaction]

javacody - if there's some way to use an opamp to mathematically 'divide' voltages, you could measure the voltage between each side of a resistor in series with the base and collector of each Q and do a divide-by operation on the two voltage drops, and scale the result,  to find the Hfe.

that would sure be a good use for a VU meter    have you seen joe gagan's nitroburner, with the VU meter for bias?  hahahaha

don't forget that bias moves when you disconnect the extra Q's though.  

[petemoore]

What are you having great success with as far as transistors and 'cross emitter' resistors in you're Miss Piggy or Piggiebacked FF's?
  Im having real good time with a 2k2 between the 104 hfe Ge and 3906 in Q1 and a Ge hfe 148 only in Q2.
  It is actually quite low gain, about 2/3's Fuzzy and Rocks most of the  stages I put after or before it, as well as being just the Blues Face by itself !!!

[javacody]

Darren,
   You would need several 3 displays then, maybe those little led level displays?

[idlefaction]

haha, yeah you could do that!!!  *grin*

but they'd look cooler if you ran your signal into a three-way crossover and then had three led displays giving you a spectrum analyser  

woah, a spectrum analyser pedal!  that would rule.  absolutely no functionality at all, all it does is load your signal down *giggle*

[Carlos Best]

Guys, im trying to make a Fuzz factory and was wondering if I could Piggyback the PNP transistors the same you do with NPN


The resistor goes from emiter to emiter?

[brett]

Hi
It's just the same.  Add a transistor, leave the collector unattached and put a resistor between the emitters.  I generally like low resistances (say 2.2 k to 4.7k) and low gain, but other people like higher resistance and more gain (say 10k).
cheers
PS was piggybacking done 5 years ago?  I haven't had time to go back and really sort it out.  I guess the subsequent popularity of low hFE 2N2369A made piggybacking kinda redundant.

[Carlos Best]

Thanks Brett!!

Its like I got a bit late on the topic

Anyway I gonna give this a chance. Don't know if were I live (Argentina) I could find the

2N2369A
so it seems it's time for second chance on piggybacking

regards!