BC108B transistors

[Fndr8875]

my buddy gave me a pack of 3 bc108b transistors he got from tayda. I had seen several things about bc108 fuzzes, but upon further research it seems as though what i find uses either bc108c and a bc109x, or bc108cs if i remember correctly. what comes to mind is a new MXR fuzz, but like i said i read it uses bc108c. The sole fuzz ive found is a Hofner buzztone and from tagboard effects blogspot , and it uses all three bc108bs in the build. Ive recently build some devi ever stuff, soda meiser with a mod to flip last transistor and it makes it a vintage fuzz master which is like octave fuzz, a hyperion 2 thats got a cool oscilation pot, Ruby which is supposed to be some sort of treble booster/fuzz. Any way, the hofner one sounded ok, but just wondering if anyone has any suggestions about what i can do with 3 bc108bs. Thanks for any suggestions.

[thermionix]

What are the gains like?  Several years ago I built a Si Fuzz Face just because I had a pair of NOS BC109Cs lying around.  I didn't know any better then, but they were too high gain.  I had just copied the common NPN schematic.  I didn't like it all, so I gave it to a buddy of mine.

[Kipper4]

Google npn silicon fuzz face.
http://fuzzcentral.ssguitar.com/fuzzface.php

Breadboard it. Swap out one of the transistors, maybe use a 10k bias trimmer in place of a std 8k2 t collector.
Experiment with a series input pot. Axis face.

Other options
NPN buffers.
Darlington pairs.

[Electric Warrior]

What are the gains like?  Several years ago I built a Si Fuzz Face just because I had a pair of NOS BC109Cs lying around.  I didn't know any better then, but they were too high gain.  I had just copied the common NPN schematic.  I didn't like it all, so I gave it to a buddy of mine.

How high were the gains? Dallas Arbiter was using BC108Cs back in the day. High gainers as well. Guess it helps with the bias. Q2's collector voltage in a silicon fuzz face mostly depends on Q1's hfe from what I understand.

[thermionix]

How high were the gains? Dallas Arbiter was using BC108Cs back in the day. High gainers as well. Guess it helps with the bias. Q2's collector voltage in a silicon fuzz face mostly depends on Q1's hfe from what I understand.

No clue on the gains.  I didn't know anything about FF biasing then either.  I just built it per the schematic, and didn't like the sound.  My buddy still has it, doesn't really use it, maybe I'll get to rework it at some point.

[Gus]

look at replies 10 and 37 for some ideas in the following link http://www.diystompboxes.com/smfforum/index.php?topic=111894.20 Look at what changes

What did the Tayda BC108s measure? 

Search this forum and the web, a lot of good posts at this forum. It can be a lot of reading.
There are FF programs that you enter beta etc and you get values on the web.
Don't get fooled by the web rule that Q2 needs to be 4.5VDC and adjusting Q2 collector resistor for biasing
One of my favourite NPN Silicon transistor FF like circuits has around 1.6VDC and 7VDC collector voltages
A fast way to adjust a FF like circuit is to use something like LT spice.  If you use programs like LT spice is you can do a simple sim of the guitar/bass cable and FF to graph how they interact.

LT spice and other programs like it make it easy to adjust a FF like circuit
Make a sim and change values and note what changes
Almost every resistor in a FF like circuit affects the biasing

[Fndr8875]

im unsure of what the hfe is on them, ive been interested in pedals for a while, but i struggle to understand alot of the concepts of why and how things work. I am familiar with all the parts and have gotten better at soldering, but i cant take a schematic and breadboard it. Its a love hate thing lol...im at a point where im obsessed with understanding everything, things are starting to make some sense, i love music and playing guitar, but seems like i spend all my time trying to make something work, and now that i actually have built a few pedals im planning the next one and barely using the few ive made. Any way im gonna build a tester tommorow and figure out what the gain is on each of them and if they have a good range. I got a 10k trim pot yesterday and wanna learn about biasing and all that and i guess itll be some fuzz face of some sort. I have been big into the devi ever stuff bc the circuits are small and use almost all the same components. Ppl can say whatever they want about her designs and simplicity but , to me , at tleast the soda meiser/vintage fuzz master and hyperion sound pretty incredible given there simplicity.

[duck_arse]

How high were the gains? Dallas Arbiter was using BC108Cs back in the day. High gainers as well. Guess it helps with the bias. Q2's collector voltage in a silicon fuzz face mostly depends on Q1's hfe from what I understand.

No clue on the gains.  I didn't know anything about FF biasing then either.  I just built it per the schematic, and didn't like the sound.  My buddy still has it, doesn't really use it, maybe I'll get to rework it at some point.

the BC108 comes in one of four varieties - BC108, BC108A, BC108B, BC108C. this actually applies to most of the "BCxxx range of transistors. the A, B, C is gain bucket divisions. the BC108 can appear in any of those gain bukkets, but the A bucket contains only the lower gain parts, after sorting.

this all appears in the datasheet.

mush as I dislike wikipedia, here is something to read - https://en.wikipedia.org/wiki/Pro_Electron

[brianq]

You can make anything you want with them, providing you've biased them correctly. There's a myriad of "transistor bias" threads on here if searched. Have you searched net for fuzz face calculators? Or read "technology of fuzz face" yet? I think there may be links in faq on transistor bias? Good luck tho

[Fndr8875]

I have read alot of those documents , but like i was saying they mainly make my head hurt lol.  I downloaded the data sheet and it covers bc107-109 and i guess all the A B Cs of all of them. The gain range on bc108 is 110-800. I found a breadboarding tutorial on smallbear diy that state good candidates are bc108 and 2n2222a. He uses 2n2222a. I got about half of it done and gonna finish it up when ive got a spare couple hours this week. I do have a multimeter with the transistor socket and hfe setting on dial. From what ive read ppl say that isnt an accurate or accetable reading, but at the end of the tutorial he has pics of his readings and swaps out one of the transistors, and then puts in a lower value 5k resistor in place of the standard 8.2k, he also shows how us can use a trimmer 10k and bias it to 4.5v. Anyway ill be excited to see if i can get it to work, and do the biasing thing. my multimeter shows 2 of my bc108s at exactly 342, and one at 320. It just seems odd though, because i tested a few other npn transistors ive got and some 2n2222 i have from radioshack all show exact same hfe. I highly doubt from things ive read ive got all these transistors that have the exact same hfe, not even off by one point. Any way got a shipment today with my pt2399s so i think my deep blue delay will happen before a 4th fuzz pedal. Thank god for veroboard, i tried several pad per hole builds and got a couple to work but was sooo tedious, and i was using radioshack board. I signed up for free amazon prime trial and have got some awesome stuff, at incredible cheap deals, free shipping ....lol 5 3pdt footswitches orderd at midight sat night and here when i woke up this moring for 11 bucks....two 3" x 6" sheets are veroboard, actual veroboard brand fr-4 for 6 bucks. That copper is so thick ive soldered , unsoldered, and resoldered over and over on mods or mistakes and over had any of it come loose from board. That tayda vero was easier to work with but seemed just a hair better than radioshack stuff. Anyway i had trouble finding a good source of actual vero brand board til i stumbled across it on amazon. Anyway i suggest to sign up for the free prime trial, these 3pdts  look high quality and there were ton of good reviews, and 5 for 11 ad change is the absolute cheapest ive found anywhere, and if u go that route your normally waitig weeks for it to be delivered, im pumped i found these deals gotta stock up before trial ends. There are lotta stuff no where to be found such as enclosures and certain components , and lotta sweet deals like switches and switchcraft jacks for $1.25, but u gotta do as ad on on $25 or more order for the switchcrafts, anyway im rambling...thanks for replies, I knew fuzz was what theyd be fore just was having trouble finding much online about any brand pedals that used them...my buddy said they were 3.99 for 3 of them, kinda expensive so figured thered be more out there on them, plus wasnt aware of the ABC catagories.

[zombiwoof]

All BC108's are manufactured the same, if they are labeled just BC108 they are unsorted and could have gains anywhere within the range you quoted.  Some are measured and sorted, and labeled by gain ranges (A,B,C, or low, medium and high gains). You can measure silicon trannies with your meter and get a good ballpark range, the complicated testing procedure is aimed at germanium transistors, which can vary greatly according to the ambient temperature, even being susceptible to changes in gain when handled with bare fingers.  Toss those silicons in your meter and check the gains, it will be close enough to the real gain to figure where to use them.
Al

[LightSoundGeometry]

BC108's work great but you hae to breadboard them and bias them out using the proper resistors and filter - these bc108's are from the Bear



* radiochack board is garbage, and taydas is cheap junk to; you need either one of these to make perf workable:

http://www.veroboard.com/

or I use this stuff now and love it as well

http://smallbear-electronics.mybigcommerce.com/perfboard-stripboard-1/

[Fndr8875]

yea i got a 3 pack of bc108bs from tayda. I have decided im not ordering anything from them any more. I buy veroboard brand off amazon, with prime you can get like 2 good size sheets for 6 bucks and free shipping in 2 days. Could you give me the schematic you used for your bc108bs? I built a hofner buzztone from tagboard veroboard site that uses all three 108s and it sounded like trash. there was a video from the guy who did layout ti think but idk he had to have done something different like biasing or maybe my 108bs just suck. Ive noticied the pots from tayda just dont have as smooth feeling turning radius compared to smallbear. also the hair on my head is thicker than resistor leads. to me if i gotta even order one or two things from other places then you got the added shipping, recieving at different times, at first i tried to find deals and stuff be @#$% it, spending all the time sourcing planning build, doing enclosure, spending money i wanna know at least im recieving quality stuff, if i @#$% it up well thats diff story, but small bear only from now on. Well other than hammmond enclosures from amazon. the prime thing is awesome for vero and hammonds, but tinned vero sounds very appealing.

[Gus]

In the link I posted there are resistor values for different hfe/beta transistors.  Maybe try the 2N5089 values I posted for the higher hfe/beta 108s

Changing just the 2nd collector resistor value is often not a good idea.

Look at the meathead, Vox amp fuzz, Colorsound one knob etc. schematics you can find with a web search for some ideas for resistor values.

Both Qs collector resistor values , Q2 emitter resistor value, The feedback/bias resistor value change the biasing.

Look for some of my fuzz posts I sometime post the hfe measured with different meters they often do not match.  So when transistor hfes/betas are posted the meter used should be posted as well.