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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 15th Sep 2017, 7:45 pm   #21
Radio Wrangler
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Default Re: Transistors for Fuzz Pedals.

The design of the circuitry of a fuzz pedal is crude in the extreme. This is where the distortion comes from. However this also makes the biasing very crude and very dependant on the current gain of the transistors. So the bias currents vary significantly from unit-to-unit, and the bias currents set where the onset of distortion happens and the subsequent amount of it.

Did the guitar greats each buy a load of pedals and pick the ones they liked? or did they keep their roadies swapping transistors? Or maybe they got invited to the pedal factories to trawl through six months produce to cherry pick the one that sounds right?

I don't think building one replica fuzz face to try to replicate a magical sound. I think you also need the right tranistor from their manufacturing spread.

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Old 15th Sep 2017, 8:11 pm   #22
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Default Re: Transistors for Fuzz Pedals.

I've heard that Hendrix bought 20 at a time, and presumably other performers with sufficient resources did something similar.
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Old 15th Sep 2017, 9:15 pm   #23
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Default Re: Transistors for Fuzz Pedals.

Pedals or transistors Paul?
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Old 15th Sep 2017, 9:39 pm   #24
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Default Re: Transistors for Fuzz Pedals.

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Originally Posted by Lucien Nunes View Post
Noise is a significant nuisance in music amplification and if people would select components more on their contribution of noise, they would probably get a better subjective result as it is rare that one actually wants the noise as part of the recreated sound.
Yes this is entirely true. Especially since these pedals/effects devices run at the input of high gain guitar amplifiers. This is why it surprised me that people making the latter day replicas of these devices, if they did want to stick to germanium transistors, didn't opt for the lower noise versions like the AC107,2N2613 and Japanese 2SB440 etc. Instead, they choose the cheaper options of various transistor radio transistors, like many (but not all) of the original manufacturers did, to save money at the time. Some of the original manufacturers did use the 2N2613 in the USA.

There is another error often made too. Significant noise contribution can come from the collector load resistors, especially if they are the old carbon type. Yet I have seen replica pedals were these have been used to make it "sound original" but its much better noise wise to use a modern metal film resistor.
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Old 15th Sep 2017, 9:42 pm   #25
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Default Re: Transistors for Fuzz Pedals.

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Originally Posted by paulsherwin View Post
I've heard that Hendrix bought 20 at a time, and presumably other performers with sufficient resources did something similar.
Pedals or transistors Paul?
Pedals
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Old 17th Sep 2017, 12:38 am   #26
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Default Re: Transistors for Fuzz Pedals.

I try not to bias my mind beforehand when im trying out components in pedals.
Fuzz is a different animal than someother effects like delay and reverb. Like some people have mentioned here earlier. The character of the fuzz and especially with germanium it's in the weakness of the transistor. Noisy, unstable, and so forth. My electrical knowledge isn't that good, and the things I have learned has come from experimenting with different ciurcits. Mostly diiferent guitar fx and so forth.

I have buildt around 30-40 fx pedals over the last 15 months or so. So im really beginner at this. The thing im noticing when I try out different germaniums in my fuzz ciurcut is that they sound a bit more "organic" In that sense that there's more dirrence what the pedals sounding like when you turn the levels, volume and so forth. I've had one of the best sounding fuzz pedals, i ever built that's all silicon transistors. 've had germanium transistors that had good specs when I measured them. What I see for is a transistor that has enough gain for the specs of the ciurcut and low leakage. Not all of these has to my ears sounded good. There has been time with this "mojo" parts that I've gotten fm radio coming out through my amp, because of a germanium diode I used in one pedal.

I am aware that many builders say's that the only good transistor in a fuzz is NKT275 period. That is just ignorance in my opinion.
Since there has been guys starting up "botique" pedal brands, and buying up lots of the transistors, of course the price for these components will increase in value since there's a demand for it. Especially when some companies is doing extremely well selling these to well known artist.

Just a wild guess, I bet that Roger Mayer's Fuzz Face pedal wouldn't be as popular as it is today if not Hendrix used those? Or the Vox Wah pedal for that matter.
Of course you can't get the same sound as Hendrix with the same pedals, even originals, since there's hundreds of other critical factors that is way more crucial.
But the curiosity in me wants those things, like some of the legendery stuff like fenders, gibsons ans so forth. I want to try those "mojo" transistors and fooling around with crusty old components that has been stored in a damp old smelly basement for decades. Just like some of you want those old Nos tubes, Mullards from the 60's and so on. Is it better that quality new parts you can get today? I don't know. Probably not. I swear I can hear a difference.
It's like whan you buy a new 2000 dollar guitar, and someone comes in with a 200 dollar guitar. Just the fact that you paid 10 time the money for yours make your better in some way or another. It as to right?
I think it's one of the hardest things to do admitting to yourself, that you spent ten times the money for one thing you could get equally good or at least very close for just one tenth of the price.

I come foward and admit at least I try to justify my 2000 dollar purchase, with specs of my guitar beeing painted with nitrocellulose laquer, a specified copperwound pickups, and all these fancy words for just plain normal things on a guitar, the business is a crude unforgiving business, ready to pry your money out of your hands. And I hate to be the sucker that paid ten times for my guitar than I really needed.
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Old 17th Sep 2017, 9:19 am   #27
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Default Re: Transistors for Fuzz Pedals.

The NKT275 does seem to be in ridiculously high demand from FX builders. It's nothing special at all, just a fairly low gain AC125/6 type. I can't believe the original builders selected this type for any reason other than it being cheap. It was used in quantities in a number of early 60s British computers, and became obsolescent as the technology moved to silicon so would have had a low price.
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Old 17th Sep 2017, 10:24 am   #28
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Default Re: Transistors for Fuzz Pedals.

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I can't believe the original builders selected (nkt275) this type for any reason other than it being cheap.
It really is the old subjectivity vs objectivity dilemma that faces humanity.

The cult status of some electronic technology, especially that associated with music & good times, is a subjective phenomenon.

Often there is a sentimental or emotional attachment to it. All about the feelings & memories it invokes. No scientific or controlled data is required for the appreciation of it. If anything, trying to apply objectivity and scientific principles to it detracts from the experience. Paralysis by analysis if you like .

On the other hand, from a scientific & engineering perspective, where science is king, it all makes little sense and it all seems nonsensical & lacking any real meaning.

Since I fall more into a scientific than artistic camp myself, I sometimes struggle with the emotive notions attached to some technologies. Yet, since I was born very prematurely and spent my early life in an incubator, I think this explains why I was always attracted to the humming sounds of machinery and instrument panels with lights, meters & switches. I'm sure I bonded with the incubator.

I could submit that practically everyone on this forum is attracted to vintage radios and TV's because of early childhood experiences interacting with them in some way or another.

So while I'm convinced from the scientific perspective that it is much better to make FX pedals from low noise high gain silicon transistors, I can sort of understand, perhaps even sympathize, why there is this cult following for germanium FX pedals and things like NKT275's, when really they are just AC125's and definitely technically inferior (especially noise wise) to a silicon transistor.
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Old 17th Sep 2017, 11:32 am   #29
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Default Re: Transistors for Fuzz Pedals.

Low gain is good for effects pedals because the transition from amplification to clipping is less harsh.
The same is true of valve amplifiers.
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Old 17th Sep 2017, 11:33 am   #30
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Default Re: Transistors for Fuzz Pedals.

The only *really* important factor is the beta of the transistors, and the original circuits worked "best" - however that is defined for a circuit whose whole purpose is the distort - for beta between about 70 and about 110.

The secondary factor is fT, which ranges from about 1MHz to 5MHz. That may seem well outside the audio range, but since hard fuzz involves driving the transistors from hard off to saturation the lousy slew rate of germanium, which is linked to fT, makes for a softer edge to the sound.

But there are silicon transistors available with the same sort of characteristics. Just as an example the 2N1480 in a TO5 package, which has an hfe of typically 20-60 and an fT of 1.5MHz and a switching time of 25us. Current production at a not so cheap 2.83 from Mouser. But without all the grief to do with germanium leakage.
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Old 17th Sep 2017, 11:51 am   #31
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Default Re: Transistors for Fuzz Pedals.

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Low gain is good for effects pedals because the transition from amplification to clipping is less harsh.
The same is true of valve amplifiers.
Yes that is true, but of course the gain is easily controlled downward, for a higher gain device, by adding simple emitter degeneration which also has the useful effects of elevating the input impedance and making a range of devices with varying beta parameters behave more uniformly. On balance though, it is in the noise department where the silicons win out
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Old 17th Sep 2017, 11:53 am   #32
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Default Re: Transistors for Fuzz Pedals.

I still build effects for musicians - mostly for friends these days. I've been doing it since 1968, and designed effects for a few manufacturers in the 1970s and 80s. All component choice was entirely pragmatic - cost mattered more than function!

Today we have deluded "boutique" effects manufacturers seeking out "JRC" 4558 dual op-amps to make their variants of the venerable "Tube Screamer" effect (a mid-boosted soft(ish) clipper circuit with a crude tone control). I found that I had several tubes of JRC 4558s with early 80s date codes. I released these on to Ebay in small quantities, and had people competing to pay as much as $10 for a chip that cost me <$0.02 when they were new.

Putting one of the "magic" ICs into a Tube Screamer circuit and comparing it with a modern dual op-amp results in two devices that sound (and measure) entirely identically, but the deluded fools insist on the "original" parts....

It's much the same with germanium transistors. There are audible differences between a Fuzz Face made with germanium and silicon transistors, but addition of a couple of small value ceramic capacitors to the silicon version will make them sound (and measure) identically..... The silicon ones don't drift with temperature!

There are several more "musical" circuits than the Fuzz face, but the old FF can't really be beaten for economy!
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Old 17th Sep 2017, 12:14 pm   #33
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Default Re: Transistors for Fuzz Pedals.

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There are audible differences between a Fuzz Face made with germanium and silicon transistors, but addition of a couple of small value ceramic capacitors to the silicon version will make them sound (and measure) identically.....
Yes, as Craig Sawyers pointed out the fT is an important parameter for the application, but as you say a silicon transistor's fT is easily shifted downward by adding a small amount of base to collector capacitance to make it behave like a germanium in terms of its frequency response.
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Old 17th Sep 2017, 1:00 pm   #34
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Default Re: Transistors for Fuzz Pedals.

I suspect that not all the range of goodness/badness is a direct effect of the transistor's gain. With the simple bias arrangements used, the change in gain will move the collector voltage around some will be close to saturation, some close to cut-off and some may be around the middle.

Playing about with the base resistor value could extend the range of transistors which are reckoned to produce good results. The yield could be better than just blindly swapping transistors. Doing the same with a 'god' transistor and looking at the collector voltage would shed light on whether the best sounding pedals are nearer cutoff or nearer saturation.

David
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Old 17th Sep 2017, 1:08 pm   #35
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Default Re: Transistors for Fuzz Pedals.

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Yes, as Craig Sawyers pointed out the fT is an important parameter for the application, but as you say a silicon transistor's fT is easily shifted downward by adding a small amount of base to collector capacitance to make it behave like a germanium in terms of its frequency response.
Indeed. Fiddling around on Spice with a common emitter stage with an Ic of 1mA, a supply of 10V and a gain of 20dB, adding 33pF collector emitter reduces the 3dB point to around 800kHz regardless of the fT of the transistor.
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