success on the FZ1A build

[joegagan]

a few weeks ago, a customer called up wanting a satisfaction fuzz.

using the excellent tutorial at small bear, zac laid out a new pcb so we could build one for the guy. after we got it finished, he purchased a brontoboost instead from us, and ordered a real 1968 maestro original fz1. he brought it into the shop today, and left it with us so we could compare it to our clone. the maestro was amazingly clean and original , except for a female jack grafted into the original input cord. 68 was still germ, it had 3- 2n2614s.

after much AB testing, we concluded that we had really hit the nail on the head. any differences in grit could be chalked up to slight battery voltage differences - the original had a 1.55v AA, our clone was running 9v but chopped down to 1.7 v using small bear's method. whichever unit had a hotter battery was the hotter sounding one in various tests.

our clone in action:

[John Lyons]

Yes sir, I like it. 

[joegagan]

thanks john.

to be more specific, in case it would be useful to anyone. the voltages in the tests were:

test 1

maestro at 1.55v.with lithium ion batt  sounded louder and stronger than our clone , which had a 9v that had dropped to around 8.5v ( did not measure the actual voltage post diode drop)

test 2

maestro at 1.45v sounded  not as loud as our clone when i jumpered two saggy 9vs together measuring 14.86 v . post diode drop  V was 1.88v.

[arawn]

sounds awesome

[smallbearelec]

Cool! I am glad that the perfboard tutorial was helpful. I have in my hairy paws several protos of this PCB:


and I am waiting to get back from pedalpartsplus the CNC-drilled proto of the enclosure. With that, I will be able to release a full kit.

Regards
SD

[Gus]

Joe

Did you see the 9VDC to 1.5VDC  circuit idea in this thread.
http://www.diystompboxes.com/smfforum/index.php?topic=93921.0
I would use a LED with about a 2VDC drop.  The 1 meg pot would then let you adjust up and down a bit around 1.5VDC.

I am going to sim a refined version of this idea.

[joegagan]

steve, congrats on your kit, looks great. thank you for the article, it really came in handy.

gus, yes, i saw that. funny how these things go in waves, john lyons has also been doing some of this vintage 1.5v stuff. if i didn't have a customer ask for it, i never would have gotten around to building an fz1. your adjustable voltage circuit would really come in handy as our comparison tests showed large differences when the voltage changed even by .15 volt.

[Gus]

http://www.national.com/ds/LP/LP2950.pdf

http://www.ti.com/lit/ds/symlink/tps7201.pdf

http://www.onsemi.com/pub_link/Collateral/MC78LC00-D.PDF

http://www.linear.com/product/LTC1844

Four links from a search.  I would guess even more companies make low power, low dropout,  low voltage regulators 

Search engines can be useful

[LucifersTrip]

using small bear's method.

sounds cool...regarding SB's method, are you referring to this?
http://www.smallbearelec.com/Projects/FuzzE-One/FuzzE-One.htm

Isn't that for an FZ-1A?

...and you're gonna leave us with that excellent video without giving us any specifics (transistors used, hfe's, leakages, voltage readings)

[joegagan]

LT, yes that is the article we used. i will try and amend the thread title, i was not aware of the designation difference.

zac followed the part values quite closely.  i don't think we wrote down the HFes of the transistors used, they were average but i don't recall any details. we had sockets and we swapped the 3 around till we found a combo that we liked, then carefully set them aside in proper order , removed the sockets and made the selection permanent. i recommend this method if you don't want to use or don't have a Ge tester.

thanks for the note on the video. two things to notice, 1. the amp was mushing out, at 1:40, i lean down and lower the pregain on the amp, it gets much nicer after this.
2. the amp was turned loud, listen to the echo off the building out 65 ft from our shop.

[petey twofinger]

my wife just found a fz-1b in our storage . its really old . the cable was bad so at one point i cut it and soldered a new conector on it  , other than that its original , i am pretty sure it runs on 9 volts . i have to open it up one of these days . curious if its noisy or not .

[DougH]

http://www.national.com/ds/LP/LP2950.pdf

http://www.ti.com/lit/ds/symlink/tps7201.pdf

http://www.onsemi.com/pub_link/Collateral/MC78LC00-D.PDF

http://www.linear.com/product/LTC1844

Four links from a search.  I would guess even more companies make low power, low dropout,  low voltage regulators 

Search engines can be useful

I kind of wonder how stiff you really want that regulated though. Also might want some impedance on the supply voltage bus. Not sure what the effect of being "too clean" might be.

[John Lyons]

The Diode shunt does have a bit of sag Doug.
I had to adjust it to get it in the Zone. Not sure it stiffening up the
power with a regulator would take some of the character away...
We'll see.

[boogietone]

Cool build. I have an original one and really like it. A bit temperamental but I can hit quite a groove with it.

[mac]

Today I breadboarded this circuit.
I have a bunch of AC187 (high gain, high leakage) and Texas Inst. 2N1114 (high gain, low leakage) for this task.
I used low leakage 2n1114 at Q1 and Q2 to get the right bias, and a high leakage AC187 at Q3.
I'll try to explain leakage bias later.
These are my readings, stock circuit except I used 330k instead of 470k at Q2, and 15k at Q3 collector.



Q1
(160, 226ua) RG test at 9v
(92, 80ua) ib: 10ua, rc: 1k at 1.54v

Ve: 0.43v
Vb: 0.35v --> but Vbe: 0.036v
Vc: 1.54v

Q2
(120, 119ua) RG test at 9v
(85, 54ua) ib:10ua, rc:1k at 1.54v

Ve: 0.00v
Vb: 0.07v at 50k; 0.01v at 0k
Vc: 0.80v at 50k; 1.43v at 0k

Q3
(220, 740ua) RG test at 9v
(191, 436ua) ib: 4ua, rc: 1k at 1.54v

Ve: 0.00v
Vb: 0.02v
Vc: 0.76v


It sounds amazing!!! With the drive pot at 0k it is almost clean, and at 50k full distortion. I can get satisfaction!!!  
Leaky germs at Q2 made the drive pot work in reverse.

To explain leakage bias I am going to use the following model,
ic = hfe*ib + iL
ic, ib: collector and base current, hfe:gain, iL: leakage

Let's start with Q1.
Note that the base current is flowing out of Q1 so it is negative. Kirchoff says,
ib*1000k + Vbe = (hfe+1)*(-ib)*10k + iL*10k
Using Q1 data
ib = (0.08ma*10k - 0.08v)/(1000k + 93*10k) = 0.000373ma
The effective current across the 10k is
ie = 93*(-0.000373ma) + 0.08ma = 0.0453ma
The voltage across the emiter resistor is
Ve = 0.453v, very close to my reading.

The base resistor shunts excess leakage to gnd, or from a different point of view, it makes ib negative to reduce effective ic, ie.
If the base resistor decreases you need a higher leakage device to bias near half Vcc. Q3 has a base resistor 100x smaller so you can expect a leaky germ to work there... but temperature is a big problem.

Let's calculate Q3. Remember that ib is flowing out of the base.
ib*10k = Vbe, so ib = 0.02v/10k = 0.002ma
ic = 191*(-0.002ma) + 0.436ma = 0.054ma
The collector voltage is
Vc = 1.54v - 0.054ma*15k = 0.73v
Again close to what I mesured.

The rule for leakage bias is: the higher the leakage, the smaller the base resistor to gnd, and viceversa.

Even though higher leakage devices works well at Q3, I'll use a low leakage there and increase the base resistor to 100k-1M to avoid thermal issues. But since it increases the amount of signal hitting Q3 I'll put a series resistor between Q2 and Q3.

Correction and comments welcome (it's 3am and the bottle of jack daniels is almost empty...)
RG, PPR?

Joe,
Next time put the cap over the amp. People walking on the street might put a few bucks on it  

mac

[joegagan]

mac, thanks for the report. we have 3 more boards etched, will try your findings in our next one and report.

taking tips in front of our store ona saturday? ha! ( someday i might share my horror story of being stuck in new orleans around 2001 with very little money and trying to busk. did not go well. one dollar 37 cents in 7 hours is not good.)

[DougH]

The Diode shunt does have a bit of sag Doug.
I had to adjust it to get it in the Zone. Not sure it stiffening up the
power with a regulator would take some of the character away...
We'll see.

I was just referring to the IC regulators.

[boogietone]

What is the black, wedge shaped thing around the stomp switch? It looks like the rubber piece from the backside of a wah or volume pedal.

[joegagan]

it is simply a decorative piece. it is cut from a FORD floormat from autozone.
it also hides the screw heads from the metal standoffs, i still like metal standoffs.

the black switch surround is ABS sheet plastic.

[John Lyons]

The Diode shunt does have a bit of sag Doug.
I had to adjust it to get it in the Zone. Not sure it stiffening up the
power with a regulator would take some of the character away...
We'll see.

I was just referring to the IC regulators.

Yeah, I know... I was just going along with you thinking that (possibly)
with a rock solid regulator it my cut out some of the good "funk".