Anyone ever heard of UTS transistors?

[lowbrow]

Picked some of these up this week. They look, measure and spec identical to my RCA 2N270s and I could believe that's what they really are. Even the tooling marks on the hardware is exactly the same, from the can to the plugs in the bottom. I can find nothing on UTS googling. Anyone ever hear of them? These look like they could be from 1957?

[digi2t]

I think it's the house branding of UTSource (http://www.utsource.net/). Seems to make sense to me insofar as the "UTS" moniker is concerned. They have these in stock.

I've ordered from them before. I've found some rare stuff there.

[lowbrow]

Interesting, thank you! I was testing them sound wise yesterday in a FZ-1. Couldn't hear any difference between the UTS and a RCA in Q1 and Q3, but could hear a difference in Q2. Close, but a little darker, more compressed and lacked a quality I have yet to figure a good name for...perhaps "clank"? What ever your call it, its important for that vintage garage fuzz sound, IMHO.

[LucifersTrip]

The difference between the tone when you tried different Q2's is most likely the difference in hfe/leakage between the two.

You'll notice that with an FZ-1/1A, the hfe/leakage is the bigger indicator in tone than transistor model #, which makes very little difference....and what you have in Q1 will make a [edit] smaller difference than what you put in Q2 or Q3.

When you experiment, it'd be a cool idea to take & report voltages when you try different hfe/leakages in different positions. That'll help everyone...

hope you get it to sound killer

[lowbrow]

As a emitter follower...or buffer, really...I find Q1 to make little difference in sound, as long as it has enough leakage to give you the proper voltage gain on the emitter. Usually something north of 150 microamps. It is the least important transistor of the three in my experience. Q3 adds some to the sound, but is most responsible for the overall level. If you can find enough leakage to drive the collector down, the closer to 2volts the better, its going to sound good and work well...assuming you have a good Q2 situation. In my testing I had three UTS and three RCA transistors that where within 10% on both leakage and gain, so I just held everything else constant and compared those three pairs.

[LucifersTrip]

As a emitter follower...or buffer, really...I find Q1 to make little difference in sound, as long as it has enough leakage to give you the proper voltage gain on the emitter.

sorry, I actually edited that sentence twice and forgot I swapped the Q1 and Q2/3 positions in the sentence. It should say "smaller", not "bigger."

"and what you have in Q1 will make a smaller difference than what you put in Q2 or Q3."

Though, you can trim the emitter resistor on Q1 to kind of set the gain, like on a TB MKI. The attack pot on Q2B just sets the bias for Q2, so you can also alter that pot for the best sweep....and yes, Q3 is probably the most important for tone...but it's much more about the collector voltage it gives you than the model.

[lowbrow]

I've put a trimmer on Q1 before but found it superflous since such a wide range of devices can do that job. I disagree about Q3 being most important to the sound, I think its Q2. You can take a output from the collector of Q2 and it will sound very much in the ballpark of the FZ-1, just very low output and not quite as fuzzy as you wish. I think setting the envelope within which the Attack pot biases Q2 provides the best sound and most usefulness, so I put a trimmer on Q2 collector and stick with the stock values on the Q2 base to ground network. Changing the value of the Attack pot and leaving that 470k in place accomplishes much the same thing I'd wager, but I prefer setting that bias envelope from the power rail with the trimmer as it seems easier to me....or more flexible, if you will. I'll try to post a sounclip of one of my builds later.

[lowbrow]

Here's a clip of one of my typical Fz-1 builds using RCA 2N408 transistors. They get extremely close to the RCA 2N270 equipped pedal I have in my little collection.

http://lowbroweffects.com/wp-content/uploads/2013/06/New_FZ1_clip.mp3

[LucifersTrip]

I've put a trimmer on Q1 before but found it superflous since such a wide range of devices can do that job.

With a trimmer on Q1, you can use an even wider range of devices...

I think setting the envelope within which the Attack pot biases Q2 provides the best sound and most usefulness, so I put a trimmer on Q2 collector and stick with the stock values on the Q2 base to ground network. You shouldn't need to do any more than Changing the value of the Attack pot and leaving that 470k in place accomplishes much the same thing I'd wager, but I prefer setting that bias envelope from the power rail with the trimmer as it seems easier to me.

I think what you're doing is actually redundant....using 2 pots on the same transistor. I'll have to do this test again, but according to notes I made on a previous build, changing the bias via a collector resistor, changes the actual tone more than via the base to ground. It would seem like that's the reason they've chosen to bias it via the base.  BTW, in the end, what is the voltage range you have on that attack pot?

Exactly as they've done for Q2, a trimmer on Q3 base is excellent and can set how close to gating (higher voltage, closer to 3V) and how much noise (lower voltage) you'll have.

But again, do whatever works best for you. I never had an original FZ-1 to compare to. I've only had FZ-1A's and knockoffs, so I'm not 100% sure the subtle differences between the two.  There is the demo record, but not enough for the guitar.  I don't know what setting you're at when you're getting that choppy, gated sound from around 3:30 on in your clip and not sure if the original actually chopped that much.
https://www.youtube.com/watch?v=VAWwBEx3Qkc

[lowbrow]

Ah, now we arrive at the philosophical question...what did they sound like...or what where they supposed to sound like? There really aren't a lot of clips out there. We have the Pinstripe clip (which is probably my favorite), a few known recordings and  couple of youtube demos and the recent demo of two Fz-1s that appeared on the DAM forum. Interestingly, none of them sound the same. I've talked to a few local owners as well and they all said much the same...some sounded better than others. I think, as designed, the pedal more often than not didn't sound very good...or at least didn't have much range. That's demonstrated by those recent DAM forum clips... the Attack knobs have a spot where they make their best fuzz tone...and it's not all that great IMHO...and outside that setting they either are strangled or simply don't work. That played right into a thought I'd had about the pedal for a while now....most of the Fz-1s produced would work at some level or other, but none realized the potential of what the circuit could be. I think the same goes for the Fz-1a.

I've done A LOT of testing with this circuit. Studying each transistor position individually and as part of the whole. Everything lead me to Q2. In testing the stock circuit, no trimmers, I subbed Q2s of the same make and model of transistor with a focus on leakage, not gain (though I was able to hold gain within +/- 15% roughly). I started at about 150µA and went up. As I got into the 1mA (yes, 1000µA) range I started to get very good control over the bias envelope. At around 1500µA I could pretty well take the transistor from saturation to cut off with the Attack knob. That provided a huge range of tones, from a fairly hairy overdrive/mild  distortion to a ultra compressed ragged fuzz. Oddly, you don't get a lot of extraneous noise at that high a leakage. It's probably more temperature unstable, but I'm guessing on that point. I'm personally on the cusp of coming to grips with the math and understanding of what's occurring between Vce, Vbe, etc...but I thought what was happening with that huge leakage was more or less equivalent to decreasing the voltage drop from the power rail to the base. That, coupled with the clue that David Maine builds his MkI Tonebenders with a 180K resistor in place of the 470K on Q2 lead me to sticking a trim pot there.

Now, as long as I have something over 250µA of leakage in Q2, I can set that trim pot so that the Attack knob goes from Zero and a collector voltage of -2.7 to -2.8 Volts all the way up to Ten and a voltage of just over -0.2 Volts...or from close to cut off to close to saturation. The full potential of what the pedal CAN sound like is realized. The sound of any one vintage pedal is in there...because all the possible collector voltages are attainable. As for how I bias mine...I set Attack on maximum and dial in around -0.3 volts on the collector of Q2. If my leakage is in the correct range, then the minimum Attack setting takes care of itself and is usually around -2.7 Volts or so.

[LucifersTrip]

Ah, now we arrive at the philosophical question...what did they sound like...or what where they supposed to sound like?

the demo record actually gives you a good idea of what they were shooting for. it would seem doubtful that they were going for anything strangled or gated.

There really aren't a lot of clips out there. We have the Pinstripe clip (which is probably my favorite), a few known recordings and  couple of youtube demos and the recent demo of two Fz-1s that appeared on the DAM forum.

I've gotta check out the DAM ones. Though I love those Pinstripe clips, most are not very good as demos since they're mixed with other instruments & you don't get to see the pedal settings.

Interestingly, none of them sound the same.

exactly...isn't that what makes ge fuzz so much of a blast!  ...and more challenging.

the Attack knobs have a spot where they make their best fuzz tone...and it's not all that great IMHO...and outside that setting they either are strangled or simply don't work. That played right into a thought I'd had about the pedal for a while now....most of the Fz-1s produced would work at some level or other, but none realized the potential of what the circuit could be. I think the same goes for the Fz-1a.

remember, it's just a bias control more than a fuzz. when you're close to 3V there's no fuzz, then the fuzz turns on shortly after usually within 25% turn. Probably, like the MKI, the fullest tone will be at around 1/2 supply. When you drop the voltage lower, it starts to get thinner and more compressed.  And here's where it's up to personal taste. Do you want that attack to go from 3V right up to the point you thinks it's max or best fuzz...or do you want to continue to .2V where it's more compressed. That's probably what you're referring to about it's potential.

I've done A LOT of testing with this circuit.I started at about 150µA and went up. As I got into the 1mA (yes, 1000µA) range I started to get very good control over the bias envelope. At around 1500µA I could pretty well take the transistor from saturation to cut off with the Attack knob. That provided a huge range of tones, from a fairly hairy overdrive/mild  distortion to a ultra compressed ragged fuzz.

exactly...the higher leakage, the lower the collector voltage, so the easier it will be to drop that voltage low with the attack.

Oddly, you don't get a lot of extraneous noise at that high a leakage.

right...it's high leakage in Q3 that will give you more noise since you'll make it hotter, closer to 1/2 supply. with the FZ-1A, you'll get more noise at .8V than with 1.2V, for instance.

...but I thought what was happening with that huge leakage was more or less equivalent to decreasing the voltage drop from the power rail to the base. That, coupled with the clue that David Maine builds his MkI Tonebenders with a 180K resistor in place of the 470K on Q2 lead me to sticking a trim pot there.

I thought you put the trim on Q2 collector.  The larger you make that base to -9V rail resistance, the tougher it'll be to drop Q2C voltage with the attack (same as if you use low leakage).  So yeah, if you use a 180K, you'll get the full sweep on a MKI from 9V down to <1V much easier than with a 470K, which may only get you down to around 3-4V (which is close to max fuzz, 1/2 supply). it's the same idea for the FZ-1, of course.

I set Attack on maximum and dial in around -0.3 volts on the collector of Q2. If my leakage is in the correct range, then the minimum Attack setting takes care of itself and is usually around -2.7 Volts or so.

sounds like you enjoy that whole sweep...cool. remember, that attack pot just has a 22K across it, so it's basically a 15K pot, but not linear. It's weighted more towards the beginning of the sweep and the fuzz "turns on" in the first part of the sweep, also. so, if you just use a 20K log pot, you can get a more even sweep.

[lowbrow]

the demo record actually gives you a good idea of what they were shooting for. it would seem doubtful that they were going for anything strangled or gated.

I'm familiar with that record, yes, and that's probably true, but it is often the sound of what they actually produced...think of "Satisfaction" and that record demo...I don't think Keith's sound can be found on that little record...yet he used the Fz-1 to make that sound. But my memory may be failing me on that point.

I've gotta check out the DAM ones. Though I love those Pinstripe clips, most are not very good as demos since they're mixed with other instruments & you don't get to see the pedal settings.

Here are the two I was speaking of:

exactly...isn't that what makes ge fuzz so much of a blast!  ...and more challenging.

Agreed! I also like that there is a lot of room for interpretation...what may be "correct" to you may not be "correct" to me. Vive la différence!

remember, it's just a bias control more than a fuzz. when you're close to 3V there's no fuzz, then the fuzz turns on shortly after usually within 25% turn. Probably, like the MKI, the fullest tone will be at around 1/2 supply. When you drop the voltage lower, it starts to get thinner and more compressed.  And here's where it's up to personal taste. Do you want that attack to go from 3V right up to the point you thinks it's max or best fuzz...or do you want to continue to .2V where it's more compressed. That's probably what you're referring to about it's potential.

Indeed. At half supply you're working more like a ideal linear pre-amp...which the circuit is a adaptation of in reality....i like having those outer edges of the envelope available because some interesting tones can be found there.

I thought you put the trim on Q2 collector.  The larger you make that base to -9V rail resistance, the tougher it'll be to drop Q2C voltage with the attack (same as if you use low leakage).  So yeah, if you use a 180K, you'll get the full sweep on a MKI from 9V down to <1V much easier than with a 470K, which may only get you down to around 3-4V (which is close to max fuzz, 1/2 supply). it's the same idea for the FZ-1, of course.

I do put the trimmer on Q2 collector. I find if I have leakage around 400µA my trimmer often ends up at around 150K. The higher the leakage, the more resistance you need to run between Q2 collector and the power rail. If you can find a Q2 with about 1500µA of leakage or more you can just leave the 470K in place. I have a couple RCA 2N270s that meet that criteria and still have north of 100 Beta. I have not commited them to a pedal as of yet, but I'll bread board them occasionally and they sound excellent!

sounds like you enjoy that whole sweep...cool. remember, that attack pot just has a 22K across it, so it's basically a 15K pot, but not linear. It's weighted more towards the beginning of the sweep and the fuzz "turns on" in the first part of the sweep, also. so, if you just use a 20K log pot, you can get a more even sweep.

I do, yes I've subbed a single resistor in for that Q2base to ground network before (both at max Attack and min) but I've never actually experimented with different pot values. I'm not sure it effects the tone available approaching the overall bias envelope from the ground rail or the power rail..I suspect it does not. But for my purposes it's simpler to leave that base to ground network as is and sub a trimmer in for the 470K.

I just want to say thank you for such a interesting discussion on this. I'm very much enjoying myself!