Substituting Ge for Si Transistors

[Pavlos]

I know it is possible to use silicon diodes (LED etc) instead of germanium, albeit with a change in the character of the circuit, but is it possible to do the same with silicon transistors in place of germanium? and if so are there particular specifications to look for and would there be much modification of the circuit required?

Reason I am asking is that there are a few circuits that I like the look of but use Ge transistors, and with the relatively high (In some cases extortionate) cost of Ge components coupled with availability being somewhat more of a challenge it would be nice to know there is an alternative.

I expect that in some instances it may well make more sense just to build a different circuit, but I'm also hoping that it might be possible, with minimal effort to make a workable alternative 'flavour' of an existing circuit, much as using a variety of different diodes can yeild a lot of really good results.

If it's just a crazy unworkable idea then at least it's good to know

[Travis]

Of course it is. Look at the fuzz face for example

As for what specifications to look for, it depends on the circuit. Some circuits rely on the leakage from germanium transistors to bias correctly, and these generally are not good candidates for Si transistors. Otherwise, you basically just need to experiment and hear for yourself.

Of course you need to be mindful of PNP vs NPN. Two different types of Ge transistors with the same hfe and leakage often do not sound the same.. Same goes for Si transistors. So there isn't really a single answer here as much as we would like to give one. You need to use some sense when it comes to approximating hfe and beyond that you need to use your ears

[rocket88]

just to add a little to what travis already said. when replacing Ge with Si transistors ignoring all other factors already mentioned you will most likely have to adjust bias to get the transistor to act as it should. case in point the Ge Giant, which started life as a modified Elektra distortion made by Nick Greer, which uses an Si transistor. Swapping to Ge the resistor has to be rebiased to get it to act properly, which is why i made the layout with a trimmer rather then a specific resistor value. the funny thing is that most Elektra distortion clones are made with Si, when the pedal originally was Ge.

the other thing as far as price of Ge transistors is concerned, there are ways around the price. option 1 is buy in bulk. typically the more you buy the cheaper they are, which is how i have the relatively massive stock i do. if you buy in bulk you'll have to sort them to figure what they are good for, and in some cases you'll get some that aren't really usable for other then Ge buffers or clipping diodes. you could also buy pre-sorted transistors for specific builds, which will cost more. the benefit to buying in bulk is you potentially will have many transistors for different builds. but no sorting or guessing. another option is to realize you don't need the specific model and brand transistor to get a good effect, and have it sound right or even better. check out the germanium thread and you'll see tons of options and "reviews" as far as batch quality, gains, sounds, etc.

[Sphere80]

Should I replace the collectors with trimpots?  I had luck substituting  inexpensive silicon transistors  on a few builds, but I'd like to get  closer to the original sounds.

[rocket88]

Depends on the build. You can either replace the collector resistor or emitter resistor or both.

[Beaker]

There are a whole heap of fuzz pedals that started off with a Ge version, and then swapped to a Si version. The Mosrite Fuzzrite is a good example, as there are layouts on the main page for both versions, as well as several variants. Look at both versions and you will see the differences are minimal.

So yeah, with a bit of tweaking you can pretty much build a Silicon version of any Germanium pedal.

Just be aware that you can generally expect a Si version to sound louder, more compressed, more focused, tighter, fiercer and more agressive sounding, and with more treble (and sometimes bass) than the Ge version. (At least when comparing fuzzes!)

[Pavlos]

great responses everyone, thank you 
reading through various topics in the forum I had sorta guessed it was possible, and that re-biasing would be necessary, just like in any circuit if you were to use substantially different transistors than specified, or everyones favourite ultra variable the JFET!

As Travis mentioned to be mindful of NPN and PNP, that makes perfect sense to me as (Unless I'm mistaken) the fundamental layout isn't any different between Ge and Si? but rather the operating parameters?
 

Beaker wrote

Just be aware that you can generally expect a Si version to sound louder, more compressed, more focused, tighter, fiercer and more agressive sounding, and with more treble (and sometimes bass) than the Ge version. (At least when comparing fuzzes!)

Am I right that Ge typically have lower hfe than Si? and if so would it be worthwhile to aim for lower hfe Si transistors as a starting point to use as substitutes? working on the assumption that the closer the spec the more likely it to work with minimal tweaking? accepting of course that it won't sound exactly the same as Ge even with a lot of tweaking. Will have play with the breadboard on some simple circuits to see what the results are though

rocket88 wrote

the other thing as far as price of Ge transistors is concerned, there are ways around the price......another option is to realize you don't need the specific model and brand transistor to get a good effect, and have it sound right or even better.

Hmmm, the temptation to turn to the dark side lol
Buying bulk is definitely a good way to keep costs down for commonly used components unfortunately, as I'm only building for my own use, there just aren't enough Ge transistor builds that I'm intrested in at the moment to really justify buying in bulk without having lots of unused ones gathering dust. Which, along with the cost of buying smaller quantities and sets for specific builds is what got me wondering about substituting Ge with Si in the first place.........though I might bite the bullet and get some Ge diodes at some point.......it's easy use a lot of diodes for clipping


note to self, experiment with the breadboard and..........investigate the germanium thread

[rocket88]

The description beaker have if the difference between sealing Si for Ge is a lot of different reasons, and I wouldn't worry about boiling it down to all the reasons tbh.

As for buying in bulk, you don't have to buy 100 or then, but you can get Russians in sets of 10 and up, but I would get like 25-50. You'll have more then enough for a few different builds. Remember to think long term more then short term. Right now maybe you want to build a Ge fuzzface, then a few months from now you think about trying a fuzzrite, then maybe a tonebender. It's just like you don't only buy components for a single build, cause you may need some of the same components for others that pop up. I'm not just saying that because I'm the emperor or the Ge Deathstar.

As far as going between PNP and NPN, the only think you have to typically do is reverse any polarized component, diode or electrolytic, and -9V becomes ground and ground becomes +9v.

[Pavlos]

haha, yes oh dark lord of the Ge Deathstar
Jeez! I don't think I'm quite ready to start flipping between PNP and NPN just yet, I'm still very much at the novice end of the scale so trying to learn in small, fairly easy stepssome things make more sense than others and some stuff is way off in the land of noideawhatonearththatis! I'm enjoying the process of learning though, especially because I'm ending up with some really good sounding stuff to play with

I hear what you say about thinking ahead, I've built up my stock of components to the point now where I can now build most of my wish list at will (It's not a stupidly massive list thankfully) mostly by working out what I needed and ordering a few extras of the comon use parts just to make sure. It's saved me quite a lot doing that because even with something as cheap as resistors, we use loads of them especially certain values so a difference of a couple of pence each when buying in small quantities soon looks ridiculous when you can get them for a fraction of the cost each if you buy a hundred or more at a time! I'll certainly have a look at what smaller quanities of Ge stuff is available for not too silly money though, because it's so easy to think oh I only need to get for two builds, only to find a week later that you've just added another five to the wish list.....oops in fact I might just put a separate Ge build wish list together to see what I might/might not be realistic....damn this temptation

[rocket88]

Welcome to the darkside.

But in all seriousness I hear you. When I started out I just built layouts I wanted, ordering for a few pedals I wanted at that moment, but quickly realized that bulk for a lot of what I commonly used was cheaper and if something new came along that really interested me I could do it 7/10 the time.

As far as being in the land of of not rally knowing what you're doing it takes time to come out. Taking it slow to understand what different sections of a circuit look like, then how different circuit sections work together, then how to change them and why X modification causes Y effect in the circuit, then keep building from there. That's how I did it. I did a lot of reading, asking questions, and breadboarding. Always ask, you'll never get beaten up too bad, lol. But seriously, I think you've got the right idea and attitude.

If you want to do some Ge build and need something specific or what to look for and don't want to post it, you can always shoot me an email. If I can get you what you need or have it handy I'm sure I can send it to you, or direct you where/what I'd suggest ito get f you don't want to buy a bunch and try sorting to figure it all out yet.

[Beaker]

Beaker wrote

Just be aware that you can generally expect a Si version to sound louder, more compressed, more focused, tighter, fiercer and more agressive sounding, and with more treble (and sometimes bass) than the Ge version. (At least when comparing fuzzes!)

Am I right that Ge typically have lower hfe than Si? and if so would it be worthwhile to aim for lower hfe Si transistors as a starting point to use as substitutes? working on the assumption that the closer the spec the more likely it to work with minimal tweaking? accepting of course that it won't sound exactly the same as Ge even with a lot of tweaking. Will have play with the breadboard on some simple circuits to see what the results are though


Yes, NPN Silicon transistors are generally much higher. Ge transistors tend to measure roughly from 50 - 130 hfe. Silicons usually start at around 200.

No, its not a good idea to try and match the hfe readings. Not only sub 100hfe silicons rare, they often don't sound great - you need a much higher gain.

Take the Fuzzrite for example, I've built versions using 60 (ish) Germanium NPN MP38a, and Silicon versions using 2N2222a around 220 hfe, and 2N5088 around 400 hfe.

[Pavlos]

haha, the dark side is quite a well populated place already I think, still, strength in numbers eh!

That's what is so good about this site, it's not just for the braniacs, even an absolute beginner can ask a question, or for some help without feeling stupid, and the answers that come back are brilliant. In less than a year I've managed (With a lot of trawling through the site) to go from having no idea at all to knowing a little bit, and every time I read someone elses questions, and the replies they receive, I learn a little bit more.......I don't think I've seen anyone getting beaten up on here though?.....a little bit of gentle humour here and there........even a bit of ribbing.......but nothing harsh

Thanks for the offer of help, very much appreciated I may well ask at some point to be steered towards suistable parts/sources.....in the mean time I just need to figure out what looks promising first

[Pavlos]

Thanks Beaker, I wasn't sure how viable it would be to try to match up hfe or other specs, kinda made sense but I had doubts as well, after all Ge is not Si, petrol isn't diesel etc it's all good to know though and having a play with this on a breadboard will do me the world of good to better understand how circuits work and component interactions which is something I'm rather lacking at the moment.......stiull, keep on learning!

[Pavlos]

Well it's a bit of a cold, wet and wintery weekend here in the UK so I thought I'd do something constructive with my time, so I got myself a coffee and did some reading.......did some searching.....more coffee, more reading etc.........and it turns out there might be a few more Ge transistor circuits that spark my interest than I thought.......seventeen of the blighters! hmmm a number that seems to keep cropping up in my life for some reason.......birth date.....house number......album by  the cure...........maybe it's a sign ok so a few of them are Si/Ge hybrids, and about seven of them are tonebender variants.........but even so that's a few more than I expected, and I was aiming at relatively small and simple.......oops looks like my wish list just grew again

So according to my list (below) if I got round to building all of them (Probably not but depends on breadboard results of course) it looks like I'd need at least 30 + transistors, and just to get enough with suitable specs for maybe half of them, I'd probably need something like that anyway even from a reliable source. Now I've seen various mentions of 'our Bulgarian friend' so I'm assuming there are some reliable sources for useable spec Ge transistors out there? I've also seen a lot of mention of good results with eastern European/Russian Ge transistors as subsitutes for the orignals, but as this is a new area of experimentation I've no idea what is likely to work well in these circuits, and what is a reasonable price? Likewise with Ge diodes, another area that is probably worth me looking into, but again, what is worth using for good results and consistancy? and reliable sources?

One of the things that was really bugging me about most of the Ge transistor circuits wast that they are +ve ground......but I think I might have that one figured out? either use batteries (Which I've never been keen on) some kind of +ve ground PSU (Err what? sounds a bit too easy to confuse and end up with smoke signals) or use one of these?
http://tagboardeffects.blogspot.co.uk/2013/02/ne555-voltage-inverter.html
http://tagboardeffects.blogspot.co.uk/2012/05/negative-voltage-inverter.html
Maybe mounted in a separate box with enough outlets to power a handful of +ve ground pedals, label everything up nice and clearly and use different coloured power plugs? I could of course tag one on to each build but it can be nice to have the option?


http://tagboardeffects.blogspot.co.uk/2013/08/bjfe-bearfoot-pink-purple-fuzz.html               2N1308 x 1
http://tagboardeffects.blogspot.co.uk/2014/04/bearfoot-emerald-green-distortion.html         2N1308 x 1
http://tagboardeffects.blogspot.co.uk/2013/05/earthquaker-devices-crimson-drive.html        AC128 x 1
http://tagboardeffects.blogspot.co.uk/2016/10/earthquaker-devices-tone-reaper.html          AC176 x 1  
http://tagboardeffects.blogspot.co.uk/2014/05/roger-mayer-page-1.html                            AC128 x 2
http://tagboardeffects.blogspot.co.uk/2012/04/sola-sound-tone-bender-mkiii-3-knob.html    PNP x 3
http://tagboardeffects.blogspot.co.uk/2012/03/tone-bender-mkii-pnp-with-negative.html      PNP x 3
http://tagboardeffects.blogspot.co.uk/2012/02/sola-sound-tone-bender-professional.html     PNP x 3
http://tagboardeffects.blogspot.co.uk/2012/02/marshall-supa-fuzz.html                              PNP x 3
http://tagboardeffects.blogspot.co.uk/2013/03/vox-tonebender-compact-version.html         PNP / NPN x 2
http://tagboardeffects.blogspot.co.uk/2013/02/prescription-electronics-yardbox.html           PNP x 3
http://tagboardeffects.blogspot.co.uk/2016/02/pro-analog-mkiii-fuzz.html                           PNP x 3
http://tagboardeffects.blogspot.co.uk/2016/08/carlsbro-fuzzbox.html                                  PNP x 3
http://tagboardeffects.blogspot.co.uk/2012/02/baldwin-burns-buzzaround.html                    PNP x 3
http://tagboardeffects.blogspot.co.uk/2016/08/tone-factor-cream-pie.html                          PNP x 1
http://tagboardeffects.blogspot.co.uk/2015/08/germanium-giant.html                                 PNP / NPN x 1
http://tagboardeffects.blogspot.co.uk/2014/02/monolith-oracle.html                                  NPN? x2

[Beaker]

That's quite a list!


I'll keep this as short and to the point as possible - basically just a list. If you want more info, just ask.

For NPN circuits, try MP38A and MP38 (MP38A only crop up occasionally now - if you find any, grab them. MP38 are the same but unsorted, so gain range is a lot bigger.
103NU71 and 104NU71 are fantastic too.

For Ge diodes, any of the D9 series, D310, D311 and D18. All these are Russian and great alternatives to 1N34A.

Voltage inverter is a good way to go.

Suppliers - bg-manue is our Bulgarian friend, I've used nearly all the East European suppliers at some point, and never had a problem.

Any more questions, just ask.

[Pavlos]

haha, yes it is a bit of a list sin't it, though in my defence almost half of them are tonebenders or very close cousins and I was basically just looking to see what looked interesting to me, and trying to make sure that I knew what I'd need to get, and what quantities to have a fighting chance of getting decent results. Also with how variable Ge componets can be it would be very easy to jump in and blind buy a small quantity for silly money, only to find they are too far out of spec to be useable and give up in dissappontment. So many thanks for all the info and help so far very much appreciated

Am I right that the suggested transistors are all broadly interchangeable with each other in the same way that similar spec Si ones? also, I know it's probably not an easy one to answer but on average how much variance is there with for example the unsorted MP38? in batch of say 50, approximately how many are likely to be near or outside the extremes of useablity?



is this the seller you mention?

dbat69 wrote

The service is as good as if not better than before.   There are three seller names
pulsar8882
bg2014-manue
ml-electronics

http://www.ebay.co.uk/usr/bg2014-manue?_trksid=p2053788.m1543.l2754
http://www.ebay.co.uk/usr/ml-electronics?_trksid=p2053788.m1543.l2754


And is this the other seller mentioned in the same thread?
http://www.ebay.co.uk/usr/elecments13?_trksid=p2053788.m1543.l2754

Again, thanks for the help

[Travis]

As far as inexpensive Ge goes, I like the MP20A for MKII ToneBenders. I've gotten lucky and just popped a (hfe tested) trio in a MKII and it sounded flawless, usually I've had to do a little swapping to get the noise and sustain/decay in balance. Generally I think it's possible to use the MP20A to make a very respectable sounding MKII for cheap.

For the MKIII ToneBenders the Russian Ge tends to be a little low leakage for Q3. The tungsram AC125 is an inexpensive option for a leakier transistor. Now that I have a lot more options for leakier transistors, I can't say the tungsram AC125 is my favorite sounding, but they were inexpensive and useful for me when I was starting out.

Usually the battery is the best sounding way to power most of the classic fuzz circuits. Most of the people on here will disagree with me on this (which is ok), but just relying on my ears I have had a lot of issues with charge pumps in the past.. They are particularly no bueno when it comes to fuzz faces. The fuzz face is easy to build but very sensitive to modifications..

[Pavlos]

just wondering about the folowing? thoughts if you would be so kind please
And my apologies if it's a bit of bombardment of information

http://www.ebay.co.uk/itm/MP38-Qty38-NpN-Russian-Ge-Transistors-15V-HFE-35-75-Vintage-NOS-2N1304-/171755276584?hash=item27fd698928:g:sjAAAOSwLnBX7VqM
http://www.ebay.co.uk/itm/41-pcs-MP41-Russian-Germanium-PNP-Transistor-AC128-AC178-Vintage-NOS-/171769224011?hash=item27fe3e5b4b:g:13kAAOSwIBBUbPRo
http://www.ebay.co.uk/itm/MP21A-lot-of-21pcs-Vintage-RU-PNP-Ge-Tr-hfe-50-150-Military-grade-Nos-/182334902628?hash=item2a7401d164:g:PuIAAOSwkNZUccpz
http://www.ebay.co.uk/itm/50-pcs-MP20-Vintage-Russian-Germanium-PNP-triodes-50V-HFE-50-150-military-/182293699756?hash=item2a718d1cac:g:3G4AAOSwGzlTsdQl
http://www.ebay.co.uk/itm/20x-MP20A-Vintage-Russian-Germanium-PNP-Transistors-50V-HFE-50-150-military-/182297106135?hash=item2a71c116d7:g:tJcAAOSwNRdX7WB~
http://www.ebay.co.uk/itm/GT313B-V-Qty30-USSR-Germanium-transistor-PNP-HF-450MHZ-hFE-20-250-15V-/172391428102?hash=item2823547006:g:fs0AAOSwIBBUbPoA
http://www.ebay.co.uk/itm/D9V-Russian-USSR-military-Germanium-diode-9-lot-of-20-pcs-/172393731065?hash=item28237793f9:g:x18AAOSwepJXbago

I also found these
http://www.ebay.co.uk/itm/20-pcs-Elorg-D9E-9E-Russian-small-signal-general-purpose-GE-diode-military-/262682138757
http://www.ebay.co.uk/itm/100pcs-Elorg-D9B-9-Russian-small-signal-general-purpose-GE-diode-military-/262519649109
http://www.ebay.co.uk/itm/D18-Lot-of-100-pcs-Russian-USSR-military-Vintage-point-contact-Ge-diodes-/252593952137
http://www.ebay.co.uk/itm/D311-Qty-100-in-box-USSR-Germanium-diodes-30V-40mA-meza-diffusion-pulse-/262704477399
http://www.ebay.co.uk/itm/SFD112-Qty50-Tungsram-Military-grade-general-purpose-fast-switching-Ge-diodes-/252593952145

and these
http://www.ebay.co.uk/itm/25x-P416a-416-Military-Germanium-PNP-Transistors-Ge-PNP-12V-25mA-100Mhz-/351748740545?hash=item51e5dbd5c1:g:w4MAAOSwnFZXUBlz
http://www.ebay.co.uk/itm/100x-RARE-D9B-10V-40mA-USSR-Soviet-Military-GERMANIUM-Ge-DETECTOR-DIODE-9-/351864441935?hash=item51ecc14c4f
http://www.ebay.co.uk/itm/200x-RARE-D9B-10V-40mA-USSR-Soviet-Military-GERMANIUM-Ge-DETECTOR-DIODE-9-/351853658902?hash=item51ec1cc316
http://www.ebay.co.uk/itm/MP15A-15-LOT-OF-20-RUSSIAN-MILITARY-GERMANIUM-PNP-TRANSISTOR-0-15-W-0-02-A-/281417616152?hash=item4185cc0b18:g:kS8AAOSwL7VWpOZ2
http://www.ebay.co.uk/itm/MP42A-42-LOT-OF-50-RUSSIAN-MILITARY-GERMANIUM-PNP-TRANSISTOR-0-2-W-0-15-A-/271584125595?hash=item3f3bace29b:g:eKEAAOSwq7JT92uT
http://www.ebay.co.uk/itm/MP26B-Vintage-Russian-Germanium-Transistors-ACY17-2N1188-20pcs-/252421415722?hash=item3ac57d232a
http://www.ebay.co.uk/itm/30x-GT313V-313-Soviet-Military-Grade-Germanium-Transistors-Ge-15V-30mA-100mW-/351747880485?hash=item51e5ceb625:g:2voAAOxyFjNSTpGn

[Travis]

First off I meant to say I prefer the MP20A in the MKII ToneBenders, edited my post to reflect that.

If you read Zach's Ge transistor thread he has posted a lot of info about those Russian parts already.

For the circuits that you mentioned you are interested in, I would go for MP20A (MKII benders), Tungsram AC125 for a cheap leakier tranny, MP38A for the NPN parts.

I don't want to give you the impression that these are my favorites or the greatest parts for every build, but they're good cheap parts to get you off to a good start.

One thing I will say is that the QTYs for the transistors you linked to are light. Remember you will need to sort these and they won't all be what you're looking for..

[rocket88]

Hey figured I would chime in, on a break from studying and from the anatomy lab.

Definitely check out the germanium thread, and look at what I wrote about the  Russian and Eastern European germanium transistors. I wouldn't say I'm an expert with them, but I've really stocked up and experimented with them, and worked hard to put all those descriptions up to help others out. So you don't have to waste money on stuff that's not really worthwhile.

While I've got a few British ones, thanks to Travis and I going in on a nice bulk buy, I really like the Russians. As a whole they're still dirt cheap, low leakage, and sound great, a little dark but I like that.

Travis is spot on about the tonebender. I built one for Kelly from mothership, MP20A Q1-Q2, and used a leaky Eastern European for Q3, I think it was a high gain super leaky sft306. Travis helped to tune it through audio samples to get it right, he's a fucking tonebender whisperer.

I try to avoid the ones without a suffix, i.e. I'd get MP41A, but not MP41. I find those without the suffix to be rather wider in their gain spread then I expect, and also typically lower hfe then expected. If you get from our Bulgarian MP38 should be good, people have a lot of luck with his batches.

I would make the following suggestions based on your build list:
MP21A - good general all around PNP Ge, good for tonebender Q1-Q2
MP38/MP38A - good all around NPN Ge
AC125 - can be a little more pricey, but good and usually nice leakage for tonebenders
IT308/GT308 - IT is military spec of the GT308