2 Si NPN HP like fuzz

[Gus]

I finally installed the board I built some time ago in a box and tested it today.  Interesting fuzz


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

[petemoore]

  Wow, that's different ! Q2/Q1 loop relationships...
   Very cool ! Haven't seen one with topology before...have I ?

[mac]

A barge concept percolator with a different ac signal path... or a silicon mu-amp???  

I'll try it with a couple of 2sc1213 of similar gain.

mac

[Gus]

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

[EATyourGuitar]

can I try this with 2n5088?

[Gus]

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

[EATyourGuitar]

thanks for your help. I'm gonna try it with some pots in series with some resistors and see what happens.

[EATyourGuitar]

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

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?

[EATyourGuitar]

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.

[John Lyons]

I'll have to fool around with this Gus, thanks.

[ayayay!]

Tone 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... 

[Derringer]

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?

[EATyourGuitar]

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?

[EATyourGuitar]

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.

[petemoore]

  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. 

[EATyourGuitar]

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.

[EATyourGuitar]

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

[EATyourGuitar]

100uf NON-POLAR
ceramic 6.7v mouser part #
tantalum 10v mouser part #


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.

[kvb]

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.

[EATyourGuitar]

I've been messing with it on the breadboard and two perf builds. I actually started a new thread and drew an oscillating version. 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.