Mod to FZ1 to work with 9V

[fuzzy645]

Below is a FZ1 schematic.

What would be the best approach to make one that works with a 9V battery.  It seems to me the 2 "general" choices would be to:

a).  Use a technique to bring the voltage of the 9V battery down to 3V so the circuit only sees 3V.   Perhaps by using a voltage regulator, or maybe it can be done with a diode??

b).  Modify the circuit so that it will work with 9V. 

Thoughts?

Thanks

[LucifersTrip]

Isn't the fun of it making it 3V !

but, I'm sure you can do what Small Bear did for the FZ-1A and use a voltage regulator
https://www.smallbearelec.com/Projects/FuzzE-One/FuzzE-One.htm

[fuzzy645]

Thanks.

Just curious, would a simple voltage divider work using the formula Vout = Vin*R2/(R1+R2)

In other words if I put (for example) a 220K and 110K resistor in series off the battery, and tapped off the center the resulting voltage would be 3V.    Maybe even configure with a pot so resulting voltage ranges from 2.5V to 3.5V and see what it does to the tone/drive etc...

Of course I guess as the battery starts to croak, the whole divider forumula goes out the window and a regulator would be more reliable.

[smallbearelec]

...would a simple voltage divider work...

...Of course I guess as the battery starts to croak, the whole divider forumula goes out the window and a regulator would be more reliable.

That is the idea. You can get whatever voltage you want by using combinations of silicon and germanium diodes. I would do this on a breadboard to figure out what works best for you. Note that the biasing will change considerably as you raise the supply voltage. Also, it isn't necessary to do the FZ-1A PNP like the original. There is enough leaky NPN germanium out there, from SBE or E-Bay, that you should be able to build something that is inexpensive, suitably retro and also friendly to a modern pedalboard.

[joegagan]

steve, we built several to your exact recipe, they sound great. someone brought a real 67 germ maestro unit to the shop, in side by side comparison they were amazingly close. this is quite a testament to your schematic and research.

[fuzzy645]

...would a simple voltage divider work...

...Of course I guess as the battery starts to croak, the whole divider forumula goes out the window and a regulator would be more reliable.

That is the idea. You can get whatever voltage you want by using combinations of silicon and germanium diodes. I would do this on a breadboard to figure out what works best for you. Note that the biasing will change considerably as you raise the supply voltage. Also, it isn't necessary to do the FZ-1A PNP like the original. There is enough leaky NPN germanium out there, from SBE or E-Bay, that you should be able to build something that is inexpensive, suitably retro and also friendly to a modern pedalboard.

Thanks Steve.  I have the parts around so I tried wiring up the original 3V version of the schematic that I posted at the top of the page. 

As an experiment, I then attempted to hook up a variable voltage divider up at the battery using a pot and a resistor. When I tested the voltage supply it swept from about 1.5 volts up to 9V (yikes).  At 1.5 it actually sounded pretty sweet, but less fuzzy.  When I ramped it up towards 3V I started getting a white noise/hissing thing going on which went away as I lowered it towards 2V and it quieted up.  Any ideas as to what might be causing this hissing at supply voltages above 2V in this? 

Thanks!

[R.G.]

When I ramped it up towards 3V I started getting a white noise/hissing thing going on which went away as I lowered it towards 2V and it quieted up.  Any ideas as to what might be causing this hissing at supply voltages above 2V in this? 

Either something is breaking over and you're getting zener noise, or  - and more likely - it's beginning to oscillate above the audio range.

[fuzzy645]

When I ramped it up towards 3V I started getting a white noise/hissing thing going on which went away as I lowered it towards 2V and it quieted up.  Any ideas as to what might be causing this hissing at supply voltages above 2V in this? 

Either something is breaking over and you're getting zener noise, or  - and more likely - it's beginning to oscillate above the audio range.

Thanks RG.  Any recommendations on how to rectify the situation, other than to set the voltage divider so that the supply voltage is around 2V, even though the design calls for 3V?

[smallbearelec]

Any recommendations on how to rectify the situation

What I said earlier: The "right" bias resistor values depend greatly on the supply voltage. With the devices I used for Q2 and Q3 (which were fairly high gain), if I raised the supply voltage above about 1.75 volts, I had to change the biasing of the transistors in order to keep the circuit stable. It took a good deal of breadboarding to get the recipe down.

Joe: Thanks for the props! Hope you are well and doing well!
SD

[fuzzy645]

With the devices I used for Q2 and Q3 (which were fairly high gain), if I raised the supply voltage above about 1.75 volts, I had to change the biasing of the transistors in order to keep the circuit stable. It took a good deal of breadboarding to get the recipe down.

OK, I will experiment wtih biasing Q2 & Q3..   One last question (I think).  In going with the Orman diagram at the top of the thread, I would then assume it might be a pretty good idea to replace a couple of the resistors that bias Q2 & Q3 with trimpots.  If that is the case, I'm wondering which 2 or 3 resistors would benefit from this approach the most.  I'm thinking the following:

1). the 470K resistor, maybe replace it with a 500K trimpot
2). either the 2.2K or the 22K by the attack pot (or both) maybe replace the 22K with a 25K trimpot
3) the 10K resistor that is coming off the collector of Q3, maybe replace with a 10K trim pot

Am I barking up the right tree here??

[smallbearelec]

OK, I will experiment wtih biasing Q2 & Q3..   One last question (I think).  In going with the Orman diagram at the top of the thread, I would then assume it might be a pretty good idea to replace a couple of the resistors that bias Q2 & Q3 with trimpots.  If that is the case, I'm wondering which 2 or 3 resistors would benefit from this approach the most.

Am I barking up the right tree here??

Yes. I left the 470K Base resistor for Q2 as is. The resistors that matter are Q2 and Q3 Collector load and Q3 Base bias. Trimpots are not necessary if you have a decent selection of standard fixed resistors. I built my prototype with socket pins where those resistors go so that I could just solder them in place when I was happy. The tweaking procedure is toward the end of this article:

https://www.smallbearelec.com/Projects/FuzzE-One/FuzzE-One.htm