Introducing the "Cream Pie" !

[Dragonfly]

  Ya never know what's up with these Ge boosters.
  @@Rate, I swapped in an SBxxx [lower gain than the 158, around ~79hfe]

good to know...hfe 79....i'm not a huge fan of the 158's, but sometimes you foind a really good one...ive got one in a hybrid FF that sounds great....the SBxxx trannies seem to be pretty good across the board....

  I'm thinking of using a series fixed resistance on the input

i'm guessing 33k-47k would be more than enough to keep it from slamming the rails...unless youre using active pups...

I was thinking the transistor didn't like not having it's base to ground resistor, but it seems to like it!! I haven't even taken my base voltage, setting collector at 4.2v of 8.2 supply,

see ...thats the "conventional knowledge" that had kept me from trying to set up a germ this way....glad i tried it anyway...see, sometimes being an "idiot" DOES work out !

it 'popped' on low notes [hb's], raising the C voltage via 50k seemed to help, as well as reducing input gain. But none of that is really mattering...the sweetness zone has been found, it's 'competitive...instant hit here...

yep...its the classic case of "sometimes the best way engineering-wise isn't the "best sounding" way....i think that this rudimentary setup just sounds great...are there "better" ways to set up a germ tranny for boosting ? absolutely. do those ways "sound better? not necessarily.

  here's the adjectives...but I think they're applicable...
  there's a smooth presence to the high end, like the highs are compressed, this aspect sets it apart from my RM type, which has near danger high end...I was gathering LP capacitors to mod the RM when I decided to persue this build...nice build too, didn't take long, biases GE's easily, sounds great, A1 booster! 
 

same as my observations...it didnt take me long at all to pull this off the breadboard and box it up !

AC

[Dragonfly]

3) for those who want a bit more control and temperature stability with the germanium trannies, using a fixed collector resistor (probably about 27k or so) and a 20k external pot would allow for easy bias adjustments when gigging in different temperatures....
  And that pot works cool 'offbias w/Fuzz...

my thoughts as well

4) another "stability" thing to do would be, IIRC, put a a germ diode between base and emitter...i'm going from memory on this mod, so feel free to "pipe up" if i'm not remembering correctly....
  My memory is sketchy too, using a diode with threshold same as transistor, reversed/connected to B/E helps prevent thermal runaway by limiting swing on one half of the waveform/hence reducing current?

hopefully one of the "smart guys" among us can help out...was it the "Plate to Plate" website that mentioned this mod ?
 

5) i think i mentioned earlier in the thread that you may be able to use a lower (or higher) value "collector to base" resistor...probably anywhere from 1meg to 6megs or so...i just used a 3meg becuase it was handy...but it works well....
  3m3 is 'big', makes bias EZ, sounds good, and were on hand.

yeah...might be worth trying other values, but really, i'm enjoying the sound "just the way it is"....

6) Pete...a thought that may or may not work here...you could try tacking on a diode onto the input similar to what Joe did with the *antiquity fuzz...might give a cool little bit of compression.
  ...interesting..IIRC the *diode symbol was pointing at the transistor input?

yep...might be a cool mod...then again, might not ...heres a link...
http://www.diystompboxes.com/analogalchemy/sch/antiquity.html

AC

[cab42]

4) another "stability" thing to do would be, IIRC, put a a germ diode between base and emitter...i'm going from memory on this mod, so feel free to "pipe up" if i'm not remembering correctly....
  My memory is sketchy too, using a diode with threshold same as transistor, reversed/connected to B/E helps prevent thermal runaway by limiting swing on one half of the waveform/hence reducing current?

hopefully one of the "smart guys" among us can help out...was it the "Plate to Plate" website that mentioned this mod ?
 

Isn't that what you find in Fuzz centrals Rangeblaster?

Regards

Carsten

[alderbody]

4) another "stability" thing to do would be, IIRC, put a a germ diode between base and emitter...i'm going from memory on this mod, so feel free to "pipe up" if i'm not remembering correctly....
  My memory is sketchy too, using a diode with threshold same as transistor, reversed/connected to B/E helps prevent thermal runaway by limiting swing on one half of the waveform/hence reducing current?

hopefully one of the "smart guys" among us can help out...was it the "Plate to Plate" website that mentioned this mod ?
 

Isn't that what you find in Fuzz centrals Rangeblaster?

Regards

Carsten

I guess that's it!

I tried it in a NPN range i built, and it worked.
But i didn't have the same results in a PNP.

[Dragonfly]

Isn't that what you find in Fuzz centrals Rangeblaster?

Regards

Carsten

yep...looks like it....


but heres where i remember seeing it....  http://www.geocities.com/SunsetStrip/Studio/2987/britface.html#tempcomp

[alderbody]

Since i will use a CV7112 too, i'd like to ask if the hfe is somewhat relevant to the sound.

What hfe was yours?

113

I think i have something in that area...

but i'll definitely try all my CV's, or any Ge i have!

Great job!

THANKS!!! 

[Dragonfly]

[

I guess that's it!

I tried it in a NPN range i built, and it worked.
But i didn't have the same results in a PNP.

for PNP, you have to reverse the diode...see the "above" link for details...

[Dragonfly]

Since i will use a CV7112 too, i'd like to ask if the hfe is somewhat relevant to the sound.

What hfe was yours?

113

I think i have something in that area...

but i'll definitely try all my CV's, or any Ge i have!

Great job!

THANKS!!! 

no problem...please keep me posted as to your results, ok ?

thanks,
  AC

[alderbody]

for PNP, you have to reverse the diode...see the "above" link for details...

yes, i was just reading that article.

The PNP was a very long time ago when i wasn't very much into modding and trying different things.
what i actually did back then, was to lower the gain of the PNP, so that confused me and i dropped it...

...things have changed since that time.... 

[alderbody]

no problem...please keep me posted as to your results, ok ?

thanks,
  AC

will do!

as soon as i get started. (gotta find the time)

thanks again!

[jaydawg]

I have a question.  What roll is the 3M3 resistor between the Base and the Collector playing? Is it a biasing thing?

jaydawg

[petemoore]

  It can pull the base toward...V+...through the Collector resistor...pulls the base up closer to the collector...and is the only bias resistor on the base.
  Being big like that means...it's a big input impedance [high Imp.]...big enough for my purposes, small amounts of HF presevervation may be wrung from even larger resistors [but why..the Ge rolls 'em off anyway if ears tell well of stories such as this], smaller values may rolloff high end, and would tend to start pulling the base up, that would in turn alter the assymetry of the clipping...etc.
  It sets up and sounds real nice with the 3m3, 1m would probably do similar, less than 470k you might hear HF rolloff...and would start pulling harder I guess on the base bias up toward closer to Collector.
  Pre-Fuzz uses are venerable, off-bias use into Fuzz added a nice pronounced 'Khick' to note attacks....that'd be the loud note 'pops' I described as getting [mostly with the 158 biased @~1/2v] which I found undesirable by itself as boost...through Fuzz it becomes cool !

[jaydawg]

Thank you Pete, that makes sense.

[Barcode80]

i'm tempted to build an NPN Si version, what do you guys think? Ge trannies are so expensive, and though i'm planning on doing this stuff commercially eventually, right now my investment needs to stay modest (plus my newbie self cannot figure out why anyone would build any circuit as positive ground, since i don't *yet* know of any benefits besides the added fun of wiring everything differently ps-wose )what do you think about a 2n2222?

also, i was thinking this might make a great component to hardwire into the front of a muff fuzz or a muffmaster. it would likely still fit in a 1590b and would be a great fuzz with added boost. am i right, or do you guys think another fuzz would be better. i want to build it straight onto the same board, i'll call it "fuzz pie" or something.

[jaydawg]

I just replaced the 1K resistor at the emitter with a 5K pot. Worked great. Variable gain. It sounds like unity at 5K and a little louder that stock at 0 ohms. I'm having a great time with this thing.

jaydawg

[8mileshigh]

Hi All,

I perfed the Cream Pie last night after 2 two discouraging builds and a one month break .  First off, I couldn't find  3M resistors at my electronics store so I used a 2M, I used an AC187 and a linear pot instead of an audio taper.   Biased at 4.5v, the Pie only acts as a clean boost, it only starts to sound like the sound clips as I lower the collector voltage to the  1 to 0.5v range.  At the lower point it starts to get compressed and a little odd sounding.   It is ok to have it biased this low ?

Is the 2M resistor the culprit here ?  Sould I add a 1M in parallel with the 2M ?  Any other thoughts  ?  Seems way off compared to you guys.

Still, I can tell that there's some magic in there.
Chris

[coffyrock]

would this circuit work with a silicon transistor, and if so, which number?
I can't get my hands on Germs easily where I am but I can get Si from radioshack.

Looks like a great circuit and I'd love to build it!

[jaydawg]

Chris, I found that mine sounded best when biased at 3.5V.

[Dragonfly]

i'll answer a few questions from different people....

where should i bias it?   well, mine is biased at 5v, i've tried it anywhere from 4.2v-6.5v and had good, but different results, jaydawg has his biased at 3.5v (iirc)...so the answer is........................................<drum roll please>....................................since the circuit works with a wide range of bias voltages, use a pot or a trimpot and bias it where "your ears tell you it sounds best", regardless of what the voltage reading is...the old Joe Meek quote "If it *sounds* right, it *is* right"   apllies here....


the 2 meg resistor should be fine, but would likely make it slightly tougher to bias (though still easy), have slightly less high end, and *may* have slightly less output....just guesses though....


silicon versions are certianly possible...i'd recommend trying 2N2369, 2N3903, 2N2222, etc for a better sound...lower hfe will likely sound better in a silicon transistor version...also, as someone previously mentioned, if youre gonna build a silicon version, try putting a small (47pF-100pF) cap in parallel with the 3meg resistor.


jaydawg...the 5k pot sounds interesting...do you get "use" from the whole range of the pot ?



also...stay tuned for more new Dragonfly creations, including a mosfet overdrive and possible a few other cool "EZ" oddball circuits !

rock.
   AC

[jaydawg]

AC, Yes I'm getting use from the full range of the pot. It goes from around unity to a little hotter then stock.

I think the Cream Pie will make a great building block. It has responded very well to all the tweaks and mods I've tried. I reminds me of the mini-booster with its versatility. I also tried driving it with some other boosters and I sounded great.

Thanks again, this thing has kept me grinning' for the last couple of days.

jaydawg