PNP FF Schem: Pull Down & Power Filter? Q1 & Q2 Voltage Readings?

[Ben Lyman]

If I want to put this from my breadboard into a box should I use the standard add-ons that I have used for my others?
1M pull down and where? input to +9v?
Electro Decoupling cap, what and where? 47uF, 100uF, +/- legs to which 9v?
1k power filter from battery - or + lead?
Is LED status light an option?

Is there anything special I should know about properly wiring this thing to the I/O jacks, switch and pots inside the box?

Sorry about all the questions, I've never made a PNP pedal and I am finding it to be a bit confusing.
Thanks!

EDIT: I think I have it mostly dialed in now thanks to Russ and Lawrence, but...
What kind of readings should I get from the transistors & how to adjust?

[Groovenut]

If I want to put this from my breadboard into a box should I use the standard add-ons that I have used for my others?
1M pull down and where? input to +9v?
Electro Decoupling cap, what and where? 47uF, 100uF, +/- legs to which 9v?
1k power filter from battery - or + lead?
Is LED status light an option?

Is there anything special I should know about properly wiring this thing to the I/O jacks, switch and pots inside the box?

Sorry about all the questions, I've never made a PNP pedal and I am finding it to be a bit confusing.
Thanks!

Ben,

You can treat + ground circuits almost the same as - ground. The biggest dfference is the polarity of devices( and the way the power supply is wired).

Your pull down 1M will go from input to 9V+ like you said.
Your power filter decoupling cap will go in the same location it would in a - ground circuit but the polarity will be + on the electro to ground (9V+) 47u or 100u is fine
Your 1k filter resistor will go from the 9V-on the battery and feed the - terminal on the electro. Though 1k might be a bit too high. Try 220R with the 100uF filter cap. That should filter down to 7Hz and only cost you about a half a volt in supply.
The LED orientation will change to anode to ground (9V+) cathode to power (9V-)

No unusual i/o wiring because the input/ouput caps block the dc and its orientation from the i/o. Wire them like normal.

[Cozybuilder]

If you are using only a battery for power, then there really is no reason to put in the power filtering. I would recommend polarity protection in case someone touches the battery to the connector backwards (1n5817 is simple, effective, and only drops about 0.2V). Another popular way is to use an inverter circuit- there is a lot written about this. The main thing is do not hook up a 9V wall wart powered supply jack like you would a negative ground circuit, theres lots written on that too. There are also ways to keep a positive ground fuzz face circuit and use isolation caps on the input and output.

However my suggestion is to go simple and use a battery-only supply and as your knowledge & skills increase, you can expand your power supply repertoire. Batteries last a long time in a fuzz face.

[Ben Lyman]

Thanks so much. I forgot about the polarity protection, all I have on hand are 1n4001 (thru 007) or 1n4148 and these mystery things:

Would any of those work?
I'm still a little confused about how the electro decoupler cap attaches... I guess if I were to ask, I would ask, "as normal or backwards?"

[Cozybuilder]

The rule on electrolytics is the side marked + goes to the more positive potential, the other leg goes to the more negative potential. (Likewise, if the cap only has the negative side marked [like most Aluminum electrolytics], then that leg goes to the more negative potential). If unsure which is more positive, use your DVM and measure.

I can't read the diodes in your posting (maybe Zener?). The 1n4001-4007 series will drop about 0.7V, same with the 1N4148- typical small signal silicon diodes. They will work fine, there is just less voltage available to the circuit. The 1N5817 is a Schottky diode, its cheap, and has a much lower forward voltage drop (typically 0.2 to 0.3V), thats why I suggested it.

BTW- I love fuzz faces and the whole family of FF derivatives! Back in the day my 2 effects were a Dallas Arbiter fuzz face (gray hammertone) and a Thomas Cry Baby.

[Ben Lyman]

The rule on electrolytics is the side marked + goes to the more positive potential, the other leg goes to the more negative potential. (Likewise, if the cap only has the negative side marked [like most Aluminum electrolytics], then that leg goes to the more negative potential). If unsure which is more positive, use your DVM and measure.

I can't read the diodes in your posting (maybe Zener?). The 1n4001-4007 series will drop about 0.7V, same with the 1N4148- typical small signal silicon diodes. They will work fine, there is just less voltage available to the circuit. The 1N5817 is a Schottky diode, its cheap, and has a much lower forward voltage drop (typically 0.2 to 0.3V), thats why I suggested it.

BTW- I love fuzz faces and the whole family of FF derivatives! Back in the day my 2 effects were a Dallas Arbiter fuzz face (gray hammertone) and a Thomas Cry Baby.

Thanks again, I think I'm starting to get it now. If I just go ahead and suffer the .7v drop from the 1n4001, what kind of drawbacks can I expect? Shorter battery life? A need to rebias the trannys?
And the LED, if I understand this, will actually light up fine when reversed?
And the battery + will go to the ring/sleeve of (stereo) input jack to be switching on/off when guitar is plugged in? Pots, board, and jacks all grounded to the ring/sleeve of said input jack?
I'm really sorry to be so thick on this! It's driving me crazy, I am terrible with words but seem to understand schematics and most pictures better.

BTW, back in the 80's my only two pedals were a Big Muff Pi and a Thomas Cry Baby! But I have always loved just about all fuzzes!

[Cozybuilder]

Does this help?



With battery power, I suggest using a superbright LED and relatively large resistance to minimize the current draw.
eg: 3mm blue, 47K- its still very bright!

[Ben Lyman]

Does this help?

Yes! Thanks

[Ben Lyman]

It sounds great now but (of course) I wonder if I can perfect it. I am having a hard time finding out what the transistor readings should be... ugh, searching! 
Before I breadboarded it, I measured Q1 at 72 and Q2 at 97 using the method described by Keen and Steve Daniels at the Small Bear FAQ link.
anyway here's what I get. what, if anything, would you change?

Q1
C 0.64
B 0.12
E 0

Q2
C 4.73
B 0.64
E 0.56

From a google search and on a totally random page somewhere out there, some guy said the ideal readings were a bit higher than mine, but the Q2c would be 4.5 which I think I can do but it doesn't seem to affect the other readings.
Thanks again!

[duck_arse]

about your mystery things - they have no polarity band on the glass, so they may be a bi-directional .... something. I don't know what, a transorb (in glass?) or a diac (wrong number) or something else. have you put it to your meter on diode setting?

and about your voltages - put your black meter probe on ground/sleeve, and poke around with the red probe. all your voltages will/should then be minus (including your supply volts). (and search here for the gus method of biasing a FF.)

[Cozybuilder]

If it sounds good, then you are very close (or there). If you want to fine tune the sound, stick a 10K pot in place of the 8K2 and tweak until it sounds perfect- you might already be there with the 8K2. Anyhow, once you're satisfied, remove the pot and measure the resistance, call that R1. Measure the 470R and call that R2. So R1 + R2 will give your ideal bias resistance. Select two fixed resistors whose sum equals R1 + R2-  just make sure R2 is at least in the hundreds of ohms. These two form a voltage divider, so relatively speaking a higher value for R2 and lower value for R1 will result in a volume gain. You will get a crazy loud pedal if R2 is a high percentage of the total bias resistance.

[Ben Lyman]

Thanks again cozy, I'm still curious about whether or not I should be concerned with the readings on Q1 col & base. I wonder if selecting a different transistor would change everything or can I adjust some other resistor somewhere.

Thanks duck, sorry I guess I should have put "-" next to those readings, but that's what they are

Thanks

[Electric Warrior]

Your voltages look alright. Q1C is high-ish for a germanium fuzz face, but much lower than in a silicon one. Nothing to worry about.
You can get the voltage on Q1C down (and Q2C up) by selecting transistors with more leakage. You can also try higher and lower hfes, matched hfes or one higher than the other. Everything has an effect on the sound, so let your ears be your guide.

[Ben Lyman]

Thanks EL! I have a pile of mid 1960's Ge here from some broken short wave radios, I'll experiment a bit.
On a side note: check your mailbox as I have a question re:TB's.
Thanks again

[Ben Lyman]

about your mystery things - they have no polarity band on the glass, so they may be a bi-directional .... something. I don't know what, a transorb (in glass?) or a diac (wrong number) or something else. have you put it to your meter on diode setting?

I have not put it them my DMM yet, thanks I didn't even think of that... but I don't even know how 
It's hard to see even with a magnifying glass but I think they say 102 Z 50v and have a symbol of some kind, maybe a U with a line under it?
Anyone else, see my pic ^up above in reply #3^ if you just know what those are already

[duck_arse]

more mystery - maybe a thermistor? can we have a real, real close close-up, to see what's inside the envelope?

I dunno what a transorb or a diac would measure on the dmm, diode or ohms. a thermistor on ohms would change it's value with temp, that's about all they do.