Silicon vs Germanium transistor comparison

[Branimir]

Hey everyone...

I've been building and playing  fuzz faces for too long now and after two years - today, I took out the old tonepad layout fuzz face with AC128's and tried it versus two Axis Face silicons...

I used 2N2219A's in axis face since all other transistors that are available locally, BD139, 2N2222, had too high hfe's, so I messed around with a lot of 2N2219A's and tried those with hfe from 60 to 200 and seems to me the best "woolly" sound is around 130 for both positions.... But...

The Ge Fuzz Face still sounds different... It has different bottom (I put 220nF input cap into Ge FF like in Axis Face), the mids are a bit smoother, I tend to say it's a bit scooped compared to the AF's, and the whole fuzzyness is rich with harmonics and still there's no piercing highs or excessive treble.

On the other hand both of AF's (one has higher gain transistors, one has lower) have mids much more pronounced, sort of boosted a bit, and I would say it has a high-mid spike between 3kHz and 5kHz (my ear is the judge on this heh). I would say it sounds a bit "boxey" compared to the Ge FF, even with the hfe's in the same territory, the fuzzyness isn't the same, and there that high-mid spike that makes me turn the treble down on the amp...

In one AF I use 33nF to tame the highs, and on the other one I used 47nF, just for the sake of being different a bit...

In direct comparison, Ge FF makes me crank mids on the amp, as well as bit of treble, and still it sounds way "fuller" next to the AF. With AF I turn the mids lower than with Ge FF and for all that I know turning treble down on the Hiwatt Custom 100 doesn't get rid of that highmid spike that AF has. Frankly, I haven't tried it with the bass player on practice, the AF did his job for the last year and the half it works well with bass guitar, so there could be problem with the Ge FF it could just get lost against bass gutiar in those rich lows and lowmids it has (Ge FF). Bass player comes back from his bussines trip after the new year so I'll hear more then...

Question is - what other transistors should I take into consideration to try in Axis Face to get the similar sound to the AC128's? BC108?

I am aware and I have searched the forums and I saw the list of popular low hfe silicon transistors, but I'm curious about your experiences with Si trannies and impressions.

Thanks for the replies.

B.

[bumblebee]

I like BC109C's/BC108C's in my fuzz face based circuits, they sound a lot nicer than the lower gain A versions. I'm a big fan of silicon tranies, don't much have any use for Ge except in cases where the effect requires, I do like Ge tranies, they sound good but I make effects that mostly require Si. I feel that if you are using silicon and not Germanium you should increase the hFE a bit, but that's just me.

[brett]

Hi
try some higher power devices.
Like TIPs or MJE3055s.  Lower hFE => lower the input impedance => lower the cutoff frequency of the filter formed by the pickups and the input impedance of the fuzzface.
The 2N/PN 2369A is very popular for its effect on tone (hFE about 70).
cheers

[roknjohn]

Thanks for the notes on the comparison Banimir. I've built both circuits, but never did a side by side comparison. I think the Axis Face is as close as I've heard silicon come to duplicating a Ge Fuzz Face. It's not 100% identical mind you, but it comes pretty close to it in my opinion. I used a PN2369A and BD139 in my Axis Faces.

I also built an Axis Face for a friend, and at first it was a bit gritty sounding. I swapped out both transistors right away and the gritty sound disappeared, and sounded much smoother. My point being try more than one transistor of a particular type if you have them. I never did go back to find out which transistor (or both perhaps) was the problem with my buddys pedal.

One big reason I like the Axis Face so much is because I don't have the problem with drift. My Fuzz Face (AC128s) would drift as the temperature changed. Now I only use the FF indoors or where the temp is fairly stable. Maybe my AC128s are just bad, but I bought 20 at the time and used the pair that sounded the best.

If you are looking for the Axis Face to exactly mimic the Fuzz Face, that might be a tall order. Also keep in mind that Fuzz Faces varied widely from unit to unit as well.

Hope that helps.

[drewl]

The closest and best sounding silicones I've found are these weird old ones that have a brown rounded case material that doesn't seem to be like plastic.
I found a bunch in an old bench multimeter (I'll have to post some pix and numbers) but I put some in my Tychobrae clone, axis face and some other fuzzes and they just came alive in tone and feel.

[Branimir]

Back to page one...

The Ge FF with AC128 sounds "warmer" and "cleans up better".

Now... the readings of hfe's of those two AC128 are on the high side, one is somewhere around 120 and the other one is 170 ?!

The same 2N2219A hfe combo in Axis Face doesn't respond to picking dynamics or vol pot the same way so I digged a bit deeper into this issue...

With smaller hfe transistors in both places in Axis Face I lost the fuzzyness and "woollyness", but I noticed that when having a smaller hfe Q1, let's say - 80 and a higher hfe Q2, let's say 190 (silicon transistors), I get much better vol pot cleanup with guitar and picking dynamics are much better, and you still have nice amount of fuzz when vol pot on 10. By the way, I always bias the FF's to 4.5V. The Ge FF STILL cleans up better with a vol pot, but Axis Face is now passable in this territory. By knocking down middle knob on my amp, AF sounds quite similar/almost the same as the Ge FF. This is of course with 2N2219A's that I've used for testing...

Now I have to try some BC type transistors, maybe act different...

[Radamus]

Forgive me for being new to this, but could you guys be more specific which transistor is Ge and which is Si? I'm looking to make a fuzz face (I play bass, so it's just sort of a novelty) and I pulled the two normal FF's from GGG. There's three parts different (two being the transistors). I have honestly no idea which I wanted to build, but I'd like the option of both. I just can't tell which transistors are which. I hope this doesn't take the topic too far away.

Thanks

[petemoore]

  Avoid PNP Neg Gnd.
  PNP Pos Gnd. requires a power supply or some kinda workaround, many Ge's are PNP...this can make it more difficult to use, I used to use battery before I made and got a floating supply power system.
  Ge = Germanium, I think most of the schematics call the recommended transistors, or in the BOM.
 
 

[Radamus]

I know the the names (CHM 101 ftw), but you guys dropped a lot of numbers and I couldn't figure it out. I'll just look it up I guess. There's probably tons of fuzz face topics.
Thanks

[petemoore]

  In all that, Geo "Technology of the Fuzzface" wasn't mentioned ? or was it ?

[mac]

I have a 2n2219a FF (110,117), it behaves similar to a Ge FF except that it is brighter, which makes the fuzz somehow different. I have to play with the guitar volume.
Si high freq response is not a good thing; AC128 are a little dark so they are perfect for this fuzz.
Recently I bought some 2n2369a, gold legs, no brand name but there is a symbol like the "almost equal" (?). These are the most Ge-like transistors I heard. They sound fat and fuzzy, much more than 2n2369a from Motorola. But they are still bright.
Also Si higher Vbe makes Q1 collector voltage higher than a Ge. I like to gate Q1 by using a 47K - 68K instead of 33K.

mac

[Branimir]

Hey Mac!

Do you know any Si transistors that are darker?

How does increasing 33k reacts to sound/dynamics? I tried once with a 100k trimmer and haven't really heard any differences, although I may be mistaken and overseen/overheard some things....

[jrod]

Forgive me for being new to this, but could you guys be more specific which transistor is Ge and which is Si? I'm looking to make a fuzz face (I play bass, so it's just sort of a novelty) and I pulled the two normal FF's from GGG. There's three parts different (two being the transistors). I have honestly no idea which I wanted to build, but I'd like the option of both. I just can't tell which transistors are which. I hope this doesn't take the topic too far away.

Thanks

I can tell you this: ACXXX = Ge and BCXXX = Si. 2N2222, 2N2219A, 2N2369 are all Si. Hope that helps.

[Radamus]

Forgive me for being new to this, but could you guys be more specific which transistor is Ge and which is Si? I'm looking to make a fuzz face (I play bass, so it's just sort of a novelty) and I pulled the two normal FF's from GGG. There's three parts different (two being the transistors). I have honestly no idea which I wanted to build, but I'd like the option of both. I just can't tell which transistors are which. I hope this doesn't take the topic too far away.

Thanks

I can tell you this: ACXXX = Ge and BCXXX = Si. 2N2222, 2N2219A, 2N2369 are all Si. Hope that helps.

Thanks. That's what I was looking for.

[alex frias]

But I have some BC and 2N that are Ge...

[mac]

Hey Mac!
Do you know any Si transistors that are darker?

No. Post a new topic or do a search "low frequency, low gain" at datasheetcatalog.com or alldatasheet.com.

How does increasing 33k reacts to sound/dynamics? I tried once with a 100k trimmer and haven't really heard any differences, although I may be mistaken and overseen/overheard some things....

Some say that below 33k, say 22k, the FF spirit is gone. Above 33k things get more gated, obscure, sorry hard to describe it. If you want to hear the differences just breadboard a Si FF with a 100k pot, but take the output from Q1.

mac

[Branimir]

Hah! One of the local shops has 2N2369A's, I bought 10 and 8 of them have hfe between 46 and 59, one is 103, and one is 70. I put the last one (hfe=70) in the Q1 position, and it seems to me that its a bit darker, and fuzzier... I'll try it today at band practice on the big amp, and tell the results...

What's the deal with 100 or 200R resistor at Q1 emitter towards ground? Instead of grounding the Q1's emitter? I remember reading about it, but these forums get kinda hard to search sometimes... http://www.diystompboxes.com/smfforum/index.php?topic=64573.msg510185#msg510185

Think I saw some other thread it is mentioned that base voltage is higher then an clipping more asymetrical? Usually for hi gainer transistors, for low gain (2N2369A) it's not needed...

Damn that volume pot cleanup!! 

[mac]

The emiter resistor is for high gain Si. But you could use a lower one, say 10R for your 2369s, just for fun
One thing I never tried with high gain Si is a resistor between Q1 collector and Q2 base 

Damn that volume pot cleanup!! 

What about adding a small cap from Q2 emiter to ground, or from the pot center lug to Q2 emiter? It could increase the gain of high freqs and keep things more brighter when you roll back the pot 

mac

[Branimir]

So I messed around with those 2N2369A's that I bought...

The Q1's hfe iz 70 and I tried various other transistors for Q2, BC107 (hfe=122), 2N2219A (hfe=140), 2N2369A (hfe=103).

The 2N2369A are darker than the other types I've tried and the most "ge sounding" combination was with these two mentioned, the clean up was very very good, but the overall - it lacked a bit of fuzz and sustain, the 2N2219A is brighter and so is BC107, but the later one proved as a good compromise for good strong fuzz and a good clean up, wish I could find 2N2369A's that have gains around 120...

What about adding a small cap from Q2 emiter to ground, or from the pot center lug to Q2 emiter?

I don't use that 1k pot at all, I just put the 1k in parallel with the electrolyte so it work as if the fuzz control was crancked all the way

[alex frias]

I have used those 2N2369 and they behave very similar to BSX20, just a bit less hfe. Always I need some low gain Si, they are there. In my version of Harmonic Percolator, I use 2N2369 or BSX20 as the NPN Si tranny.