Russian Germaniums?

[JakeFuzz]

I got a pair of the ac128's from byoc and they sounded pretty good.  For 12 bucks, definitely worth a shot. I also ordered 150 ac125's from ebay.  I bought ten first and they were low leakages in useable gain ranges, so i went for a crap ton.  Theyre great sounding transistors for fuzz faces and particularly tonebenders as they were created as a replacement for the mythical oc81d.  I have been tempted to buy some of those 308's and 309's, but have yet to pull the trigger.  Let me know how they turn out.  If you have any extra pairs, i'll swap you for some of mine. (if you're interested)

Definitely. I would love to try some ac125's. I cant wait to try these ac128' too, I hear good things but have never seen Sony brand. Ill let you know how the batch turns out.

You know what? If i find a combination that I like and I have a few extra Ill just send you a pair so you can try them out. Hopefully I will have a bunch of good ones! Wish I had a camera so I could record how they sound.

Wow, that would be awesome if you can. I appreciate you doing that, let me know how much to send you.

Dont worry about it, I know how it is wanting to try a few trannies without having to buy bulk quantities.

[Meowy]

I also got some AC125s on eBay to try out in a treble booster. Gains are all over the map from under 125 to well over 300. The usable ones are decent, but to my ear not as musical as an OC75. Probably better suited to a Fuzz than a Treble Booster

[jimmybjj]

Well, thats mighty fine of ya Jake! I certainly appreciated it

[dwstanford]

Yeah, an oc75, 76, 71, or 44 would be a better choice for a treble booster.  The ac125 sounds pretty decent in a rangemaster, for instance, but you wont get quite as much harmonic distortion as one of the others i mentioned.

[lloyd17]

For what it's worth I've got a Monsterpiece Ge with Rus gt320b's in it and it sounds pretty terrific.

[JakeFuzz]

Well the Russian germaniums haven't come yet but I just tested the BYOC AC128's and they sound decent. They sound very similar to the 2N404's Julien sold me. They are very trebley and don't have as much sustain as my other FF's, this could be because byoc sent me gains of 77 and 103 which is a little low for Q2. They have slightly more bottom end than the 2n404's. They do sound good but I may hybridize these as well. I am hoping to get a really dark transistor one of these days so I can combine them and see what happens. I am hoping the Russians are a little darker; more on this in a few days.

[brainbender]

You guys got me really into this, i think i'll also buy some of these Russians!

[JakeFuzz]

You guys got me really into this, i think i'll also buy some of these Russians!

Ill let you know how mine turn out. I've heard mixed reviews about the IT308B but I paid like 11 bucks for 50 so I think ill get something useable out of it. I've only heard good things about the gt309's. I really want to buy a batch of the GT402's those get really good reviews too, higher gain ranges than most everything else it seems.

On a different note I submitted a query for more info to NXP for the CV7112. I really doubt they'll give me things like litho mask layouts and process details or if they still even have the files for them. Here is how things evolved with these, Philips-signetics made these for a company called Valve Technology. Philips semiconductor was split and formed NXP semiconductor well after the CV line was discontinued. So it is pretty wishful thinking that the data on these has survived all this history or that NXP would just give me something like that (I said it was for research purposes  ) but I figured it was worth a shot.  

A little more info: Valve Electronic was just a brand front for certain British military parts. These were made by Mullard (whom Philips completely owned at the time). The CV7112 was classified as a high switching speed, high current device and was used in military avionics "computers". The destination for end use was stated as "MOA" or Ministry of Aviation. CV stands for Communication Valve. The CV line (and all other military parts) were usually existing product designs with a greater degree of quality control. A footnote does state that while equivalencies are listed (eg, the CV7112 and the OC140) they are not necessarily the same parts. My guess is that Valve used the topology of the OC140 but altered some of the materials (and consequently the fabrication process). Unfortunately information on this specific device is tough to come by. Where does all this information go to die? Sitting in the back store-room in one of Mullards old fab facilities perhaps... 

[brainbender]

Wow, that's a detailed report!

[dwstanford]

I got my ac125's today and i went through and tested them.  I got 150 of them for 40 bucks and i was suprised to see how many useable transistors there were in the lot.  The gains averaged from about 110-160 hfe with a few strays above or below that.  The leakages averaged about 400u with several in the 200-300 range.  There were more than an average amount in the 140 hfe range with about 500u of leakage.  Id say about half of them fall into that category.  Overall, it was a good haul.

[jimmybjj]

I got my ac125's today and i went through and tested them.  I got 150 of them for 40 bucks and i was suprised to see how many useable transistors there were in the lot.  The gains averaged from about 110-160 hfe with a few strays above or below that.  The leakages averaged about 400u with several in the 200-300 range.  There were more than an average amount in the 140 hfe range with about 500u of leakage.  Id say about half of them fall into that category.  Overall, it was a good haul.

If you don't mind my asking where did you get them?

[dwstanford]

I got them on ebay from minifux.  They are tungsrams.  I ordered ten from them initially to see if id like them, and they were awesome.  Im on a tonebender kick right not and these sound great for those circuits.  The only trouble is, you need some lower gains for tonebenders traditionally (except for maybe the vox tonebender)  The first batch were between 60 and 120 so they were perfect.  Ill probably use these for fuzz face or fuzzrite style circuits. 

[JakeFuzz]

Well, these Russians are pretty much garbage as far as DC gains go. I tested a little over half and the highest gain was about 70. The majority are in the low 50's range. Ridiculously low leakage. Maybe at DC they just test poorly. Ive heard that even though these are low gain if they are biased up correctly they sound decent. Ill give it a shot maybe this weekend and see how they sound. The 309D's are even worse at an average of 45. Sorry guys hope you weren't getting your hopes up about these. 

[JakeFuzz]

But wait... there's more! They sound good! Not a huge wall of fuzziness but I tweaked my bias resistors until I got something and it sounds very good. Very smooth and decent sustain. There isn't a ton of gain but for a low gain bluesy fuzz it does very well. Strange   I really had to crank those bias resistors, I am pretty sure one of them is almost at zero ohms and the other one makes everything really boomy if I turn it up too high. I actually like them better than the AC128's (but I like really bassy wooly fuzz). I think I will try a few combination with 2n404 and ac128 next.

BTW the gains I used were both about 50. Ill measure the actual bias resistor values a little later

Okay I was wrong (my trim pot is backwards), the Q1 is at about 47k and the Q2 is looking good at about 10k. Unfortunately when I built this board I put in a 10K trimmer so I cant go any higher. The sound was getting sweeter at higher values of the Q2 collector resistor so maybe somewhere around 12 or 15k is the sweet spot for these low gainers. Didn't measure collector voltages before I threw them back in the pile. Ill do a hybrid test with a Si in Q1 this weekend too, something tells me it is going to sound really cool.

[JakeFuzz]

In fact they sound similar to the opening licks of this video which makes sense since this has an IT308B in Q2: