Great series man. I absolutely appreciate the info.

Thanks for the info..Bro.. I live in the Caribbean and there's not interest in this stuff here so I am working in a vacuum.. your videos are much appreciated.

I have used those 2SB75 transistors in a Fuzz Face ,they sounded really good

I got a bag of 150 AC125 Uz VI just about after you posted this way back when and I am finally getting a chance to test them and you're spot on with the gains... they have low leakage and most are in the 100s gain. I also have 150 AC125 Uz V and those are approx in the 60-80 range for me. good to have both types As I said, just now got around to testing the lot.

Cheers! Unfortunately the only way i know for testing freq response is to plug them and listen. Sorry.

thanks for the great info

What about wiring up si and ge as composite darlingtons and sziklai pairs? I've had a bit of luck doing that with low gain Russian MP11's and 38's with 2n5088's for darlingtons and ac127's for sziklai pairs. Leakage and thermal stability seem to be less of a concern. Might be a good use for otherwise junk transistors.

Nah its all good, i was agreeing with you :) The FSH1 is an awesome effect stil one of my favourites. Thats amazing timing man because I just finished, not 5 mins ago, a 'fault diagnosing' revisit on the FSH1. The FSH is a diy killer, this video is meant to assist people building it. Its a pretty complicated build. It's worth it though imo. The vid will be uploaded in a few days time. Thanks for all the compliments and all the best.

THANKS for these vids - I have collected quite a few Ge transistors AND definitely agree with what you say about not getting too hung up on hfe & leakage (so long as it's not huge). Test 'em and see if they sound ok in a Range Master or FF TB etc.. I've bought crap "NOS" from e-bay too BUT also some gems (best finds are sellers getting rid of old radio / electronics hobbyist's stock piles - as they often have decent amounts of Ge stuff - if you look carefully at the photos)

Difficult subject matter to keep organized in your series of videos, very detailed and informative - learned more about GE transistors here than in most of the research I have done over the last 6 months. And, an honest review that helps us not only pick the right transistors, but also the right sellers. Of course there always is a downside, I think that the sellers & products you recommended may have caused the sellers to TRIPLE their prices, unfortunately - UNLESS, I misunderstood what you said - you said (when you were holding up the packing slip, that you paid $50 for 150 of the AC125z @ 75-150, Orphius is asking $150 for 150 of those now, but he is asking around $70 for 150 for the AC125Uz, rated at 75-150 (these are the first type listed on the datasheet, the only difference is the "U" inserted before the "z" . Question - Have you tried and/or noticed a difference between the Tungsram AC125Uz - type VI (75-150) vs. the type you bought (label show in video) AC125z, @ 75-150 - difference the letter "U". Same hfe, same part number - what significance is the "U" - I also noticed that the bag and packing slip looks different - and half the "Buy It Now" price.. One other question - I found one you tube video demonstrating the Russian transistor that you recommend as Number 1 - GT402V(B) - first - do you have any sound samples/comparisons using this transistor, Second - the video I found - listening to this transistor, it is one of the best or possibly, the best transistor I have ever heard for fuzz, clean overdrive/boost, frequency response - it seems to do it all and it sounds unbelievable - since it is not one of your videos, I am suspicious as to its authenticity - almost sound too good to be trueFinally, a couple of quick questions on fuzz/overdrive pedal construction -:1) What size blank box do u typically use/recommend for pedal builds (2 &/or 3 transistor pedals)2) Do you use/recommend only non-alkaline 9V batteries/ brand?3) Do you use/recommend external DC power jack for GE transistor based pedals? If no - why not? and if yes - do you also recommend installing internal (installed as part of pedal circuit) sophisticated voltage regulation, isolation and filtering circuits or just a dedicated regulated separate wall-wart power supply (not part of pedal circuitry) with no additional internal pedal circuitry added like voltage regulator/isolation and filtering?I have read so much conflicting information on this subject - where some say absolutely no external power and battery must be old type non-alkaline, to others (reputable manufacturers and boutique builders) who either recommend dedicated regulated DC transformers to the extreme, where they have actually built and installed sophisticated user adjustable voltage regulators (adjustable for varying line voltages), isolation and filtering (capacitor) circuitry inside the pedal, adds $$$$$$ and affects size of pedal. ThanksChris

Those Roman Numerals. I've got some Silicon (a1015-c1815) With GR331 and yeah.. 400HFE The Complimentary Pairs but also I've been having great luck with GT320A as Sziklai pairs in the second stage of fuzz face using the same silicon in q1 and then paired for q2. Bazz Fuss as well(using a much higer HFE combo) Very hifi when biased right. But like 20-40 HFE in the ones I got If you have heating up issues with Germanium use Sziklai with a Silicon driving it.. with a 1kr and you'll have better stability

Yep. I said it 1000 times in the video. I think frequency response is more important then hfe. That said alot of below 50 hfe transistors i have tried havent cut the mustard. Biased correctly etc. Those GT308V's are an exception. Alot of people have reported they sound higher hfe then they actually are. I would say the MN21D's are the same in that respect. Just my opinion anyway...

Yeah definitely! I'd almost be tempted to pay extra and get japanese transistors as well. I've had good experience with those. Its a gamble everytime you buy some though, you just never know what your going to get. Part of the fun i guess :)

Reviewing "Orphius" Ebay transistor items for sale again, I think I figured out the difference between the various AC125z series types - AC125z, AC125Fz, AC125Kz and AC125Uz. Besides the hFe output related to "type V, VI, VII, there is also a "letter" before the "z" in the AC125 transistor model number and It has to do with operating voltage, Here is what I was able to discover: AC125z & AC125Fz are both rated at 32 Volts, AC125Kz = 40 Volts, and AC125Uz = 60 Volts. I haven't seen any other letters or voltage ratings other than these 4. I wonder if the AC125Kz and AC125Uz will behave the same way as the AC125z & AC125Fz?? and provide the hfe/gain levels you experienced using the 32 volt versions of these transistors - there is a price difference, I wonder why?

Ive read a few times about using a germanium diode to thermally stablise the germanium transistor, i think it was from base to emitter. But you have to match leakages or something. I think germanium transistors are still too cheap to worry about any of this though. People are digging them up all over the place, and probably for a lot longer as well.

Great stuff man! most informative :)

I hope you don't feel like I was trying to correct you or something, no...I just wanted to leave a comment so that people can read it and decide to let their ears decide when making anything. :) Good job Paul! And you play guitar nice as well. One of the few projects that I never made an attempt to is the Maestro sample and hold filter. I can see that you did a stellar job at this. Would you say that the sound is very dependent on the wiring, and the project is really difficult? Thanks

Caribbean, nice :) You should hang out at the forums (diysb, freesb, madbean etc) if you arent already. Lots to learn / talk about.

Another superb video Paul, well done mate. Full of really useful info that will make my wallet weep :-)

Nice informative info, thank you. You mentioned the importance of frequency response but didn't get into what specs correspond to get into the good freq response range?! Could you shed some insight on this aspect please?

Yeah not sure, most of the datasheets i have seen dont list frequency response. I was refering mainly to how the transistors sound in a circuit.

Wow, that's great, I can't wait for that vid to come out, thank you man. "A DIY killer" hahaha, yep, you got that right. I've heard from a friend that he is building one...that was a year ago :D

Nice videos and very helpful informations. Could you please post a link to the datasheet from the Tungsram AC125z VI, because I can't find it online. Cheers

Thanks. I thought it might be listed with the transistor's specs and there'd be a range or low end minimum to look for?

Oh yeah! Germanium Transistors (and of course, diy guitar pedals) are an expensive hobby :)