RNFR - SIKOVYA BS-III

RnFR · Post by **RnFR** » 04 Aug 2009, 19:04

hey guys-

here's a little project i've been working on lately. and yes, yet another FUZZ, because AFAIC you can never have enough!

this is basically a knocked up version of the Sekova FA-II. i've done a number of mods to add a gain control, switch the trannies from Ge to Si, more tone control parameters, adjust the bias, diode switching, and a Ge booster stage to bring up the low volume that the original had. it's a great sounding fuzz that is now much more tweakable than the original version and has plenty of output power. rolling back the gain, and switching in the LED's gives it a great crunch, and cranking the gain with the diodes brings it into superfuzz territory. this version is PNP, to go with the Ge boost at the end, but if you have an NPN Ge transistor an NPN version could be built up using a 2N5088 and a 2N222, or just switch the boost to Si. i am using some 15uF mil spec tants instead of the original 10uF electros(because i've got an assload of 'em.), but you could probably go back to the original specs without much difference there. have fun, pcb to follow shortly.

lolbou · Post by **lolbou** » 04 Aug 2009, 19:39

Interesting stuff! Can you go a little bit further on switching Ge for Si (or backwards)? What do you have to tweak basically?

devastator · Post by **devastator** » 04 Aug 2009, 20:17

interesting design ! actually all your fuzz design looks cool and insteresting, especially with explanations. .

rocklander · Post by **rocklander** » 04 Aug 2009, 21:01

lolbou wrote:Interesting stuff! Can you go a little bit further on switching Ge for Si (or backwards)? What do you have to tweak basically?

and what are the diode values.. am I missing that on the schem.. I just can't see that there?

lolbou · Post by **lolbou** » 04 Aug 2009, 21:06

I guess it doesn't really matter what type... The Si or Ge will give different Vd values, so you can go for any signal diode I think?

rocklander · Post by **rocklander** » 04 Aug 2009, 21:14

lolbou wrote:I guess it doesn't really matter what type... The Si or Ge will give different Vd values, so you can go for any signal diode I think?

yeah.. that was kinda my point.. what's a signal diode?

lolbou · Post by **lolbou** » 04 Aug 2009, 21:18

rocklander wrote:what's a signal diode?

http://www.electronics-tutorials.ws/diode/diode_4.html

There's even the very difference between Ge and Si ones...

rocklander · Post by **rocklander** » 04 Aug 2009, 21:24

lolbou wrote:
rocklander wrote:what's a signal diode?
http://www.electronics-tutorials.ws/diode/diode_4.html

There's even the very difference between Ge and Si ones...

sure I could RTFM, but is it wrong to expect the schem to have values on it (even suggested/optional).. I mean.. all the other components have them (bar the switch.. okay and the LED)

lolbou · Post by **lolbou** » 04 Aug 2009, 21:36

rocklander wrote:ure I could RTFM, but is it wrong to expect the schem to have values on it (even suggested/optional).. I mean.. all the other components have them (bar the switch.. okay and the LED)

Man, I have to google to find the meaning of RTFM... God bless wikipedia!

No, I guess you're right about the name of the diodes...

1N914 should be ok for Si ones... And I don't have any particular Ge diode in mind...

RnFR · Post by **RnFR** » 04 Aug 2009, 22:54

guys, this is DIY design, not a production pedal. i think i gave specific enough guidelines, but there are no rules here.

and since this IS DIY, do something yourself, and decide which freakin diodes you like best.

rocklander · Post by **rocklander** » 04 Aug 2009, 23:01

but.. but.. but.. I need rules.. how the hell am I supposed to break them otherwise?

RnFR · Post by **RnFR** » 05 Aug 2009, 03:50

lolbou wrote:Interesting stuff! Can you go a little bit further on switching Ge for Si (or backwards)? What do you have to tweak basically?

the only thing i did was lower R8 from 5K6 to 3K9. i was getting a bit of gating when i listened to the circuit without the diodes. this fixed it. when listening to the circuit with Ge transistors, it really didn't sound that great. i think you would have to rebias the circuit properly for whatever transistor you use. i just popped in some silicons, and the circuit came to life really. it wasn't hard at all.

BUT- if you want a real explanation on how to convert a circuit from Ge to Si, you should probably read this tutorial-
http://www.hawestv.com/transistorize/germanium1.htm

as far as the clipping circuit goes, it's really simple-

when the switch is in the OFF position, the LED's are conducting. when you switch to either the Si or Ge pair, they conduct, and the signal is clipped below the clipping threshold of the LED's. therefore, the LED's are effectively out of the circuit. so you could use just about any clipper you wanted- as long as the one with the highest Vf is in the LED position.

RnFR · Post by **RnFR** » 11 Aug 2009, 20:16

here's a layout i just finished. checked in eagle, but not built yet.

bobo · Post by **bobo** » 12 Aug 2009, 00:12

What's another transistor that equal to MP14B.?

RnFR · Post by **RnFR** » 12 Aug 2009, 02:18

you could probably use a gt308 or maybe a gt313. or just try any Ge transistor and adjust the collector resistor until it sounds good.

OR- you could just use a silicon tranny and lower the collector resistor to about 10K. that would probably work fine, too.

RnFR · Post by **RnFR** » 01 Sep 2009, 12:31

good news and bad news-

first the bad. there is a small error in the pcb that eagle didn't catch. it can easily be fixed with a jumper, but i'll update the layout soon anyway.

now the good news.this thing is a highly variable freakout fuzz machine. i hadn't built it up yet with the cut knob, and man, that thing makes a world of difference. between all of the available filtering and the clipping options, tons of crazy fuzz shapes can be had. anyone looking for something wild along the lines of some super doom, or maybe the DBA stuff, give this a shot. you won't be disappointed.

devastator · Post by **devastator** » 29 Nov 2009, 17:33

hi,

I've just tested it , interessting , even if that's not really my fav. fuzz tone, the tonestack section is a little bit weird. The extrem positions of the swell pot. give a kind of boost (bass and treble) and in the middle there's a kind of midscoop variable . The cut pot. does its role, it brings back some mids . For my taste 50KB is too high, maybe 25K or even less could be the job with all their curve.

I made it with 2N3904 transistor (I haven't Ge diodes), So maybe some tweaks are necessary to have a perfect baising. I used LED + zener for the clipping diode. The output level is very lood.

Just one question, what's the role of R15 ? I prefer the sound without it .

RnFR · Post by **RnFR** » 29 Nov 2009, 19:42

yes, you could definitely use a smaller pot there. when i first drew out the schematic, i hadn't tried that exact configuration yet, so i i just guessed on that value, going by similar designs. having built it, i had the same findings that you did. as far as the 100 ohm resistor, my guess would be that it allows a little bit of feedback back into the earlier part of the circuit instead off taking the 22K resistor straight to ground. just a guess though. removing it would probably add more gain, correct?

i have found that i tend to like this circuit a lot with the gain rolled back a bit. it gives a kind of lofi, nasty, overdrive sound that i find perfect for any type of punk or really nasty blues. LED's are definitely my fave clippers, liking them over Ge or Si. thanks for giving it a shot, it could probably use a bit of tweaking, it's just the fruits of a couple of sessions. i've also thought of raising the output cap and trying it for bass.

devastator · Post by **devastator** » 29 Nov 2009, 20:39

yeah removing R15 add more gain.

Led give a bigger and fatter sound, they're really flashy with strong attack on the strings. I haven't a lot of different diodes , so I can't see the changes produced by another clipping section.

I'd try more that circuit tomorrow, it's little bit late right now.

Otherwise, yes "nasty" and "dirty" are good words to describe the sound .

RnFR · Post by **RnFR** » 29 Nov 2009, 20:57

yeah, i like it because you can get a rather nasty type of sound without it being all blatty and gated like so many fuzzes that have that description tend to get. looking forward to hearing what you come up with!