My original schematic - Cup of Joe

[Joecool85]

Here is what I've been working on.  I haven't tried building it yet...but here is what I have.



What do you think?

If anyone wants to try building it and tell me results, that'd be cool.  I have way too much going on so I won't get a chance to build it for a while.

[R.G.]

It will be a very quiet pedal.

It will have zero output. The tone and volume controls are supplied with DC through the connection to the battery, but they get no signal voltage.

[Joecool85]

Wouldn't they recieve signal through the trannies?  If not, care to explain how I might solve this dilema?

**edit**
I see...would it be a good idea to run a wire from the collector of Q2 (top tranny, I know I didn't label them) over to the tone?  Also, if I do that, do I need the DC running there also?

Thanks for the help btw.

[MartyMart]

Move you're whole tone/vol section to the top of Q2, junction with 100k from 9v
Then you'll have some output 
Tone control may "steal" some level though !

MM.

[Joecool85]

How is this?

[Joecool85]

Move you're whole tone/vol section to the top of Q2, junction with 100k from 9v
Then you'll have some output 
Tone control may "steal" some level though !

MM.

Is my revision above just as good?

[MartyMart]

Yes, I think that will work .....
you may need a volume recovery tranny before the output, depends how much
level is left after the tone pot ?

MM.

[Joecool85]

Cool!  Any other ideas?  Better yet, someone want to build it?   

If not, be looking forward to me building it sometime within the next month or so hopefully.

[MartyMart]

You could try a feedback resistor from Q1's base to Q2's emitter, say 47k
"Fuzz Face" style

MM.

[Joecool85]

You could try a feedback resistor from Q1's base to Q2's emitter, say 47k
"Fuzz Face" style

MM.

I thought about that, but I like how mine is different from a fuzzface.  I might experiment with that though when I do build it.  I was thinking more of a 120k though.

[Joecool85]

Yes, I think that will work .....
you may need a volume recovery tranny before the output, depends how much
level is left after the tone pot ?

MM.

Just noticed what you said here....what exactly do you mean by volume recovery tranny and what would it do?  Boost the volume?

[MartyMart]

OK, another 3904 with 10k from 9v to Collector, 390k from 9v to Base and 100k from Base to ground.
Ground the emitter and take output from collector.
This should make up for the tone control volume loss.
( from memory, so I hope it's right !! )

MM

[Joecool85]

Huh.  I guess what I'll need to do is build the pedal and if I get a lot of volume loss then I will consider doing something like that.  Or I might move the tone to the front of the circuit.  I dunno.  I think it should be pretty loud, but we'll see I guess.

[johngreene]

I think you will have a biasing problem. the 1n914 will see to it that the base of Q2 sits at 2 diode drops above ground meaning about .6V across the 1K emitter resistor. .6V/1K = 600uA of bias current through Q2. 100K to Vbatt with 600uA yields 600uA*100K = 60Volts. You would have to drop the collector resistor to something like 7.5K to get 4.5 volts at the collector. What's the reasoning behind the 100K to Vbatt and the 330k resistor both connected to Q1's base?

--john

[Joecool85]

The reasoning behind the 100k resistor going to V, was to get power to the tranny...and the reason behind the 330k resistor was to throw a little resistance between the collector and the base of Q2.  I tried it in a bazz fuzz circuit and liked the results.

Any help is appreciated if you think my schematic is flawed.  Maybe take out the 100k that leads to the junction of the 330k resistor and collector of Q1?

**edit**
Also, are you saying that the trannies aren't getting enough juice?  The bazzfuzz circuit uses a 100k resistor with a 2n3904 with good results.

[johngreene]

Ok, maybe this will help. As you can see by the bias voltages, the trannies are full on. With an input signal of sufficient amplitude, you get a slamming output signal with octave tossed in. But as the input decays, it gates out to nothing.



--john

[Joecool85]

WOW!  Cool program!  So...how do I fix that problem btw? 

And also, is that program free/where can I get it?

[johngreene]

There are free versions of spice available. What I am using is Cadence PSD 15.1 which is a little pricey for the average 'joe'.

Change the collector resistor (R1 in my schematic) to 10K and you should have some fun with it.


--john

[Joecool85]

Now...if I change R1 to 10k, wouldn't that be too much power for a 2n3904?  Or is it ok because it is using 2 - 2n3904s?

Also, is it possible you could give the schematic you did but with 10k so I can see what voltages should be on it?

I appreciate all the help with your awesome program.

[johngreene]

There is only 600uA of current flowing through the 2N3904 so no, it's not too much power.

Here's the schematic:



--john