I finally installed the board I built some time ago in a box and tested it today. Interesting fuzz
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=43462&g2_serialNumber=2)
The hfe readings in blue are from a HF purchased Cen-Tech DMM. I am guessing this is the type transistor tester some people use.
The voltages are the measured voltages.
I used 1n4001 clippers after the .1uf output cap and before R5 not shown in schematic
Tone is sensitive to input volume control setting. I used a 100k linear input and an 100k audio output.
Have fun
Wow, that's different ! Q2/Q1 loop relationships...
Very cool ! Haven't seen one with topology before...have I ?
A barge concept percolator with a different ac signal path... or a silicon mu-amp??? ;D ;D
I'll try it with a couple of 2sc1213 of similar gain.
mac
It is based off the harmonic percolator
The first stage(bottom transistor) sims at about 20Db gain and the 2nd stage at about 40Db gain. The voltages in the sim are close to the measured voltages
I have built a Si NPN PNP version
Fun little circuit C4 AC decouples the gain stages from each other, it is a tuning point
can I try this with 2n5088?
Yes but it will not be the same as lower hfe transistors
I just simmed it using a 2N5089 model it looks like you should change change R1 to 1.8meg and R2 to 3.9meg. You might need to adjust the resistor values from the two I posted.
http://www.fairchildsemi.com/ds/2N/2N5088.pdf
thanks for your help. I'm gonna try it with some pots in series with some resistors and see what happens.
I got some metal can 2n222 so I'm gonna try it with all the original values and the diode thing. my highest gains are 103 and 113 Hfe so I'm gonna use those. I'm using silicon 1N914 diodes
(http://farm4.static.flickr.com/3114/5789448216_405b989031.jpg)
not showing the pots that go before and after. I did this real quick and I tried to leave room for the transistors and electro. BTW I'm not sure if thats supposed to be non polarized 100uf but I couldn't find one at radioshack and I didn't want to wait for my next mouser order. it should be good with the neg side of the cap to ground right?
(http://farm6.static.flickr.com/5024/5790872745_ff9b72cf34.jpg)
this one is better for the size of the components I have. legs on the transistors I have are in a triangle so it has shorter leads this way. just check it against the original schematic if you use it. it flows right to left.
I'll have to fool around with this Gus, thanks.
QuoteTone is sensitive to input volume control setting.
Did you happen to try it with a bleed cap in that case? Man this thing is weird... :D
i will breadboard this when I finish with whats on the board now ... looks very cool
Does it sound very different from the HP? How?
I built it and stuffed it into a nice etched box but then it didn't work. I disconnected everything and I have only the V+ and ground hooked up to the circuit. this is my first time probing a non-working circuit for dc. I'm pretty sure I'm doing it right. I'm measuring VDC with one probe on ground. I got 9.5 on my battery and 9.4 after R3. then I tested the voltage drop across R3 just to be sure. its 22mV. in the schematic it should have a 5.5v drop across R3. then I tried a 100k in R3 and still the same. did I fry my silicon transistors with too much heat? also, I didn't have a 100uf non-polar so I used a 100uf electro with the neg to ground. is the non-polarized cap that important?
solved my own problem by testing all the leads of the transistors with an Ohm meter. all legs are 0ohms on both transistors. dead transistors. lesson learned. socket the transistors every time, no matter what.
At least if the transistors can be tested it might help solve whether there's just a bug elsewhere that needs d'd with.
It's possible but not all that easy to bake a transikstor.
Having cut them at the shins and shin-tacked new transistors quickly to the old ones lower legs, left in the board. It should take less than 1 second to bond prepared transistor leads [pretinned] without loosening anything left connected under the board. Wobblier than through-board mount, but quick, gets the job done without disturbing the pad side.
but what if I cook the new transistors lol. also, I used my last two metal can 2n2222 that were 113 and 103hfe. I can use fs3699(2n5133) I have 60hfe up to 250hfe. or i can drive to radioshack for the newer style black 2n2222. they spec at 120hfe+ up to like 160hfe. I'll report back
edit: I guess what your saying is its really quick touch of the iron to melt the pretinned solder. I could try that.
still not working.
V+ 9.55V
Q2 C 9.48V
Q2 E 9.1V
Q2 B 9.04V
Q1 C 9.08V
Q1 B 110mV
Q1 E ground
Q1vBE 370mV
Q2vBE 390mv
everything is the same. so changing from metal can 2n2222 to the TO-92 2n2222 its all the same. gains on these new 2n2222 are 255Hfe
100uf NON-POLAR
ceramic 6.7v mouser part # (http://www.mouser.com/ProductDetail/TDK/FK11Y5V0J107Z/?qs=sGAEpiMZZMuMW9TJLBQkXo1rviRUuaBKH%252bYl2NbviS0%3d)
tantalum 10v mouser part # (http://www.mouser.com/Search/ProductDetail.aspx?R=T350J107K010ATvirtualkey64600000virtualkey80-T350J107K010AT)
I'm guessing that this 100uf non-polar cap is needed for it to work. I'm also changing diodes to the 1n4001 gus mentioned. I'll report back when it arrives.
I've got this on the breadboard now. Works fine. I can hear the harmonics jump out as certain notes fade just like the HP.
The funny thing is that as I get closer to the speaker for feedback the note goes from low to high. With the HP the note goes from high to low as you get closer.
This cleans up well with the vol backed off but it seems like there is still something like a ghost of distortion in the background.
I think I'll build it.
Thanks Gus.
I have a multi-pole switch sitting around not being used. I'm considering building like three HPs and putting them in the same enclosure. This one, a non-typical transistor version of the HP, and one that remains to be seen. Because the controls are just input/output volume the box would still only have two pots plus the switch.
I've been messing with it on the breadboard and two perf builds. I actually started a new thread and drew an oscillating version (http://www.diystompboxes.com/smfforum/index.php?topic=92628.msg794972#msg794972). I definitely like 100n input cap. its also really high gain ish so I put a 100k for the V+ to decrease volume. its still loud. I used a tantalum 100uf in the final version. the schematic shows a non-polar 100uf. on the breadboard, flipped it around both ways and it sounds the same. next I'm gonna try aluminum electrolytic non-polar. I just found out they exist and are about the same size as any electro. these big caps are like $2 each.
what did you use for the 100uf? and did you have problems with noise? like a white noise that doesn't go away.
don't buy the non-polar cap. you can make a non-polar cap with two electrolytics. just connect the two negative ends. the result is a cap that can accept positive flow from either direction. I don't think the schematic intends to represent the cap as being non polar. If one lead is at negative ground then there's no need for a non-polar.
I wouldn't get too hung up on tantalums either. I think sometimes they are chosen for their small size. I've heard a few stories about bad tantalums causing problems. I think most people don't worry about it either way.
as far as noise is concerned there is something strange going on but I'm not sure if that is a breadboard issue or not. It is possible that there is some high frequency feedback happening that could be cured with a 100p cap somewhere. I won't know until I build it and put it in an enclosure. Honestly that probably won't be soon.
yeah I had crazy noise on the breadboard. sounded like heavy distortion on the tail end of the note. when I boxed it up it was less noisy but different. like a noise floor that is really high. almost like tape noise. the 15k shunt I put in my schematic helps but totally changes the sound and behavior of the pedal. 15k shunt is a bad idea. it affects every pedal on the board cause it lets any AC running on the ground right back up into the HP Fuzz where it gets amplified. it goes through cycles where it phases itself out to near zero volume and ramps back up again. I was gonna call it a fuzz trem but after I saw what it does to the pedal board, I want to just scrap the 15k and use shielded wire and board mounted pots.
another thing that is weird about this fuzz is how the transistors are not sitting at 4.5v base and yet it is actually really clean and loud without the diodes. goes against what I know about biasing a transistor.
Quote from: EATyourGuitar on July 22, 2011, 04:16:08 PM
yeah I had crazy noise on the breadboard. sounded like heavy distortion on the tail end of the note. when I boxed it up it was less noisy but different ...
"A solderless breadboard is probably the worst noise environment you can imagine" - amptramp
yeah thats true but my fuzz faces work fine on the bread board. depends on the circuit. and my finished pedal was noisy too FWIW