Fuzz FZ1, have I got the wiring correct (image included)

[ericohman]

First time using the DIYLC software and I already love it.

Could some kind soul check to see if this looks correct? I'm a little confused about the ground and the potentiometer wiring (attack pot with jumper through lug 2 to 3, I've read that's a fail-safe method). Also, this would be true bypass right?


NOTE: I do know that the transistor sockets doesn't have the proper symbol, but I couldn't get the P sockets to look like the schematic from http://fuzzcentral.ssguitar.com/

Me and a friend will be building this pedal, we are just waiting on some resistors and perf boards.
Speaking about perf pedal building. I have read the beginner threads on this site but if anyone has got other resources/links please share.

Best regards.

[smnm]

Hi

this is a great pedal that has been almsot forgotten in diy circles because all the online schematics are wrong - there should be a 47OK resistor from the base of Q2 to the power line to make it work properly. The 56k to ground resistor is in the wrong place too, but I don't think that's so crucial to the sound. Layout looks good to me otherwise.

corrected schematic:

[GREEN FUZ]

Yeah. the basic layout looks fine. A couple of the component values differ from those on the schematic but maybe you already knew that.

If you don`t intend to employ an LED, just use a DPDT for the stompswitch instead of a 3PDT and save yourself some money.

[ericohman]

Thanks for pointing out the value difference. I just noticed that I had 100k instead of 10k on one place. 1K5 is the same as 1.5K right?

Concerning the 1K5 resistor, is it a good idea to replace that with a bias control? If yes, any recommendation as what value and type of bias should be used?

Big thanks for the corrected circuit, are you sure it is the correct?
Yes a DPDT would be great but I have some 3PDT's at home so I will go with them.

I've seen a thread (at the gear forum I think) where it says that J Page switched the volume to a 250k log and the attack to a 1k lin pot. In my head that would produce a lot more driven fuzz tone but correct me if I'm wrong and also, if you don't recommend that please say so (and explain why so I can learn from it at the same time)

Puuh, tired of typing from the iPod touch...

[GREEN FUZ]

...I just noticed that I had 100k instead of 10k on one place. 1K5 is the same as 1.5K right?...

Yes, it was the .1uf input cap I was thinking about aswell as the 100k resistor you already mentioned..

[Solidhex]

Thanks for pointing out the value difference. I just noticed that I had 100k instead of 10k on one place. 1K5 is the same as 1.5K right?

Concerning the 1K5 resistor, is it a good idea to replace that with a bias control? If yes, any recommendation as what value and type of bias should be used?

Big thanks for the corrected circuit, are you sure it is the correct?
Yes a DPDT would be great but I have some 3PDT's at home so I will go with them.

I've seen a thread (at the gear forum I think) where it says that J Page switched the volume to a 250k log and the attack to a 1k lin pot. In my head that would produce a lot more driven fuzz tone but correct me if I'm wrong and also, if you don't recommend that please say so (and explain why so I can learn from it at the same time)

Puuh, tired of typing from the iPod touch...

yo

  The 10k from the emitter of q1 is a better candidate for a trim. Changing the volume pot to 250k won't do much since its in parallel with the 56K. Changing the attack to 1K will basically be like having the attack knob turned down all the time resulting in very little fuzz. The person who suggested those mods is either talking about another circuit or just making stuff up.

--Brad

[smnm]

1K5 is the same as 1.5K right?

Concerning the 1K5 resistor, is it a good idea to replace that with a bias control? If yes, any recommendation as what value and type of bias should be used?

Big thanks for the corrected circuit, are you sure it is the correct?

Schematic is definitely correct - based on several photos of original units, and I have built it too. I love it!

[mharris80]

As kind of a side question, where would be a good place to get those 2N270 transistors at?  Does anything Small Bear have substitute well here?

[ericohman]

I was thinking about using germanium AC128. Don't know if that's a good choice though...

Beginner's questions. When you turn a 1k pot to "zero", that's the same as GND, meaning 0V, right?
But what about the difference between a 1k pot and a 100k pot if the pot has been dialed to max (let's say number 10 is painted as max on the pedal).

A more general scenario. What will be the difference in terms of dB to my ears if I switch a 100k volume pot to a 500k volume pot. Quite confused.

Solidhex, which transistors did you dig up for your fz1 clone?

[smnm]

As kind of a side question, where would be a good place to get those 2N270 transistors at?  Does anything Small Bear have substitute well here?

I found some old ones on eaby and was surprised that out of a group of 10 , 8 were good - most are only about 40-50 hfe, but low leakage, and sounding good. I tried a range of other Ge PNPs in there before I got the 2N270s, some were too high gain and a lot of oscillation at max fuzz/acttack, but most sounded good. I made extra effort to find the originals as I like the circuit so much.

Volume pots usually divert the signal to (or from) ground -at zero ohms all the signal goes to ground and as you increase the resistance more and more of the signal goes to the output - when it's fully rotated, all the signal is going to the output, regardless of the value of the pot. So volume pot values are not super crucial for an effect to work - for example there's close clone of this circuit from the '60s that uses 50K instead of 500K for vol and it works fine. What changes is the rate of change in voume as you turn the knob, and the useful portion of the rotation, so getting the right pot makes the circuit easier to use or to adjust to find the (ahem) "sweet spot".  Different tapers and stuff are sometimes specified for maximum usability. There are probably other things (many things!) I don't know about in relation to this, and pot values are more crucial in some circuits than others, but simple fuzz circuits work this way.

[ericohman]

Thanks smnm for explaining that. I meant you and not solidhex when I asked about what transistors you used.

For the attack pot. What are the pros/cons for the lug 2 and 3 connection? The schematic doesn't tell you to solder them but will it work?

pros and cons?...

[smnm]

[quote author=ericohman link=topic=76402.msg624736#msg624736 date=1242219820
For the attack pot. What are the pros/cons for the lug 2 and 3 connection? The schematic doesn't tell you to solder them but will it work?
pros and cons?...
[/quote]

I don't know that - it seems to work the same whether you just use two lugs or three in this kind of situation, it's a convention to join lugs 3+2 together - sometimes I am lazy and just connect 1 and 2 to their respective places, and leave 3 unconnected. I don't know if it makes any difference or not! It works either way.

[ericohman]

me and my friend are going to purchase some pedal related stuff and we want to know if there are anything beside the maestro fuzz schematic we should consider ordering. other resistor values etc to bias transistors...

if anyone has information of approx hfe for Q1, Q2, and Q3 then please share. also, if anyone has measured the voltage from the collector of Q1 Q2 and Q3 it would help a lot.

we will be using pnp germanium AC128 transistors.
in case we would like to bias the transistors with trimpots, which resistors would be the best to replace with trimpots?

thanks in advance

[Solidhex]

Yo

  I find that its more important to find transistors with some leakage than having trimpots all over the circuit. All the transistor positions need leakage to bias in the circuit. If you can find some that have at least 200ua. Stick the lowest gain in Q1. Highest in Q2. Middle one in Q3. You sort of have to strike a balance if you can of leakage vs noise. The leakage will give you more fuzz, too much will get you a bunch of unpleasant sizzle. If you can't find a leaky enough transistor for Q3 you can decrease the 470K to 220K to pull the bias up a bit.

--Brad

[punkin]

Am I reading this right? B+ is 3VDC?

[Barcode80]

Yes. There were two versions of this circuit, and both ran on AA batteries. One was a 1.5v (one battery) and one was a 3v (two batteries).

[Pedal love]

It looks good. This version is nice, but I checked the original schematic from the patent. Who knew that there originally was a small resistor from the collector of Q1 to the battery. I think it was about 400 ohms. I'm going to start checking patents all the time.

[arnqvist]

Nice, I've just read the patent myself, can't seem to find the Q1 Collector resistor though? I'm really quite new to this so maybe I'm mistaken.
But i found that the 470K resistor from the corrected schematic above is stated a 470ohm resistor in the patent.
Is this correct?


http://analogguru.an.ohost.de/001/patents/UsPat_3213181_Fuzztone.pdf

[arnqvist]

Me and a friend (user:ericohman) breadboarded the FZ-1 tonight after the corrected schematic.

We used AC128s with this specs:
Q1: Gain 55, Leakage 190
Q2: Gain 65, Leakage 271
Q3:Gain 60, Leakage 243

The patent document specs the bias voltage for Q1 to -1.5V, Q2 -3V and Q3 -2.5V if i have understood it right.

To get to this value for Q1, I switched the resistor running from the emitter to ground from 10K to about 13K.
For Q2 I lowered the 1k5 collector resistor to 470ohm.
And for Q3 I switched the 10K collector resistor to about 13K.

The pedal sounded great to our ears but...
...now to the questions, the thing is that this is my second build after a rangemaster. And i dont really know yet how to bias properly.

1. Is the resistors i switched to get to the patent values the right way to bias? Or should i fiddle with some other resistors? And if so, why?

2. Should i really be so focused on the patent specs about the bias-voltages? Or does that change due to the switch from the original 2N270 to AC128s with diffs in gain etc.?

3. After I biased them to patent values, played a bit, the bias voltages changed a little and the tone started to oscillate a bit more. I'm thinking this is due to temperature changes of the transistors? Can you make a circuit less temperature stable by changing the wrong resistors for biasing?

Thanks in advance, I really admire you're knowledge guys!

/Petter

[Pedal love]

Nice, I've just read the patent myself, can't seem to find the Q1 Collector resistor though? I'm really quite new to this so maybe I'm mistaken.
But i found that the 470K resistor from the corrected schematic above is stated a 470ohm resistor in the patent.
Is this correct?


http://analogguru.an.ohost.de/001/patents/UsPat_3213181_Fuzztone.pdf

Try it anyway.