Transistor swapping question



Moderator: Ghost Hip

Forum rules
The DIY forum is for personal projects (things that are not for sale, not in production), info sharing, peer to peer assistance. No backdoor spamming (DIY posts that are actually advertisements for your business). No clones of in-production pedals. If you have concerns or questions, feel free to PM admin. Thanks so much!

Transistor swapping question

Postby Paul_C » Thu Mar 07, 2019 3:36 pm

Sorry for another newbie question - part of the problem is there are so many forums and sites out there :)

Swapping transistors - is there a list or table somewhere which might give options to try, or is it just a matter of "try anything as long as it matches the one that came out regarding PNP or NPN" ?

I don't mind trial and error, and I'm sure after a while I might have some favourites which I'll try first in certain situations, but if there's something that can save a bit of time (and money, if there are some that rarely prove much use).

I've got my first batch of transistor sockets, so I'm eager to go but don't have too much time to waste right now.
Paul_C

User avatar
experienced
experienced
 
Posts: 845
Joined: Thu Jun 11, 2015 1:45 pm
Location: Northampton UK

Re: Transistor swapping question

Postby BetterOffShred » Thu Mar 07, 2019 3:51 pm

Typically circuits are designed to use a certain gain range of transistor, in either NPN or PNP. Some circuits are far more sensitive to this range, and will either sound like ass, or not work without a pretty exact gain.. most circuits are not like this and you can probably coax good shit out of a few substitutions.

So that being said you can look up the gain range of the specified transistor and see what else you have in that range etc.

Since we started talking about Devi circuits I'll bring them up again.. the Torns Peaker sounds so much better with some substitutions IMO. I think mine only has a single MPSA18 left .. the others are subbed.

So to answer the original question, both. There are certainly "try these instead" lists people have made.. but they are just based off gain ranges typically. Mind the pinout too, your component tester should help that
BetterOffShred

User avatar
IAMILFFAMOUS
IAMILFFAMOUS
 
Posts: 3155
Joined: Thu Aug 17, 2017 2:01 pm

Re: Transistor swapping question

Postby crochambeau » Thu Mar 07, 2019 4:36 pm

P vs N and pinout are the big ones.

I've found transistors to be surprisingly robust on the lower voltage (and resistance padded) circuits we generally find in effects pedals. I'd be wary of going willy-nilly with NOS Ge treasures, but cheap jelly bean parts are made for experimentation. I've grabbed from BCE stock to plant in EBC circuits, installed stuff wrong way around, etc. while playing about, you'd be surprised at some of the stuff that passes interesting signal.
D.o.S. wrote:This thing is like the Blue Box on the amount of acid that lands you in the ER pretending to play it straight while you try and ignore the fact that the walls are dripping oil.


Rochambeau Musical Apparatus
Reverb storefront
Shark Tank
crochambeau

User avatar
FAMOUS
FAMOUS
 
Posts: 1700
Joined: Mon Jul 20, 2015 12:49 pm
Location: Cascadia

Re: Transistor swapping question

Postby Jero » Thu Mar 07, 2019 5:00 pm

Jero

User avatar
IAMILFFAMOUS
IAMILFFAMOUS
 
Posts: 10426
Joined: Fri Mar 12, 2010 1:12 am
Location: here

Re: Transistor swapping question

Postby Paul_C » Thu Mar 07, 2019 5:23 pm

Thank you all for your help - it looks like transistor acquisition is needed, I only have three or four varieties :)
Paul_C

User avatar
experienced
experienced
 
Posts: 845
Joined: Thu Jun 11, 2015 1:45 pm
Location: Northampton UK

Re: Transistor swapping question

Postby eatyourguitar » Sat Mar 09, 2019 5:20 am

BetterOffShred wrote:Typically circuits are designed to use a certain gain range of transistor, in either NPN or PNP. Some circuits are far more sensitive to this range, and will either sound like ass, or not work without a pretty exact gain.. most circuits are not like this and you can probably coax good shit out of a few substitutions.

So that being said you can look up the gain range of the specified transistor and see what else you have in that range etc.

Since we started talking about Devi circuits I'll bring them up again.. the Torns Peaker sounds so much better with some substitutions IMO. I think mine only has a single MPSA18 left .. the others are subbed.

So to answer the original question, both. There are certainly "try these instead" lists people have made.. but they are just based off gain ranges typically. Mind the pinout too, your component tester should help that


I think this is all very good advice. I want to speak on the devi thing. she was using transistors with a Hfe 5000 (MPSA18) and piggybacking two transistors together to lower the gain. sometimes she would put a transistor in backwards sharing a socket with another transistor that was not backwards. death by audio had a pedal that was using reverse gain only found in some transistors. all of the transistors were intentionally installed backwards after they tracked down a bag or rare transistors that were tested to have gain in reverse. some of my early pedals had transistors installed backwards but they worked fine because of the reverse gain. or maybe the previous gain stages were driving the last attenuator stage hmmm?

swapping germanium transistors for other germanium transistors is pretty good practice. swapping silicon NPN for other silicon NPN is not always useful. it depends on the circuit. I think there are two things happening here. some people swap germanium out for other germanium of a similar gain to get different sounds. but swapping silicon for other silicon of similar gain will rarely change the sound. that is why you swap out a 2N3904 to a 2N5088. this will increase the gain. then you swap to a MPSA18 to increase the gain again (or to just try darlington transistors compared to BJT). there are an infinite number of part numbers for 2N3904 replacements of similar gain. I have tried a LOT of them from mouser, tayda etc...they are %100 compatible (they sound exactly the same).

swapping transistors is probably more useful if you understand the purpose of every component in a guitar pedal. if you understand how to change some resistors to make the higher gain transistor work in that circuit then you will be able to compare apples to apples as far as possible differences in sound between transistors. if there are no differences in gain, then the differences you hear are all related to some other property or some other interaction. this is usually explained by differences in linearity and to a lesser extent, leakage, and noise.
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF
eatyourguitar

User avatar
IAMILF
IAMILF
 
Posts: 2853
Joined: Sun Oct 03, 2010 12:37 pm
Location: USA, RI

Re: Transistor swapping question

Postby Paul_C » Sat Mar 09, 2019 7:02 pm

Thank you for that - it makes some sense to me now and will no doubt make even more sense once I've learned a bit more :)


In other news, I've found another supplier for components, some prices better than my main supplier (and they stock some things the other one doesn't), some a little more expensive, but the bit that amused me most is that the seller is only on the other side of town from me. It's cheaper to pay the postage (a flat rate for all orders) than drive over, but as they only sell online I doubt they'd want me going round to their house anyway.

I'll have to place an order soon to finish off my small stash of different transistors. The next thing I'm probably going to need is better storage for everything ;)
I've got a few small boxes separating capacitors from resistors etc. but everything is all jammed into one small toolbox and there's almost no room left already!
Paul_C

User avatar
experienced
experienced
 
Posts: 845
Joined: Thu Jun 11, 2015 1:45 pm
Location: Northampton UK

Re: Transistor swapping question

Postby eatyourguitar » Sat Mar 30, 2019 2:14 am

paper compact disc sleeves in bulk is my new method of storing passives like caps and resistors. this way you can put them in cases made for CD's and they will collapse down to nothing if one of the bins runs empty. I don't do this for caps of in production kits since those are all bulk of one value of cap.
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF
eatyourguitar

User avatar
IAMILF
IAMILF
 
Posts: 2853
Joined: Sun Oct 03, 2010 12:37 pm
Location: USA, RI


Return to DIY Effects



Who is online

Users browsing this forum: No registered users and 1 guest


Sponsored Ad. (Please no inflated/repetitive clicking. Thanks!)

Advertisements help support ILF


ilovefuzz.com is not responsible for user-submitted content. Users participate at their own discretion and risk.