Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Preamps and Effects => Topic started by: LJN on December 04, 2014, 07:06:39 PM

Title: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 04, 2014, 07:06:39 PM
Hello. In the years since I've been on here, I've learned a little bit about building fuzz pedals. So, I thought I would post about the mosrite fuzzrite. This isn't the easiest circuit to build because there's not a whole lot of accurate information about it. I built one, and it took me over a year to get it straightened out. First, the pots should both be 500k log or audio taper. Second, transistor shouldn't be selected by hfe, but frequency as well. This is a very picky circuit. Select a transistor with a frequency around 110-140 MHz. Third, you'll have to experiment with smaller value collector resistors. I used 10k. There will be some radio static,  but don't worry. Just put a .002 uf cap on the board from input to ground. This is a very versatile fuzz, and is very underrated.  I use mine for everything I play. Make sure you put the 22k high pass resistor in there too. You may choose to put it on a switch. I did, but usually, I leave it connected. It's a very bright fuzz with only 14 seconds of sustain. It has become my favorite.  I hope this helps anyone who is having trouble building this great sounding fuzz. I used C1740 transistors in mine, by the way.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: Roly on December 05, 2014, 02:07:59 PM
Quote from: LJN
This isn't the easiest circuit to build

...and not made any easier by the lack of a circuit to refer to.

Quote from: LJN
Select a transistor with a frequency around 110-140 MHz.

Yawot?  Would you care to explain?   8|

(The datasheet typical fT of a 2SC1740 is 180MHz)
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 05, 2014, 07:20:59 PM
Okay. So there's not much in this circuit.  Two transistors, and not very much else. Some people will tell you that any transistor will work. That's wrong. The gain can be perfect, but if the frequency is too low, you get those weird decay sounds. If it's too high, it won't decay at all. The output will just cut off to dead silence as soon as the input signal drops. So what you have to do is find some middle number. Now, this circuit doesn't have much sustain. Only about 14 seconds. But it's more versatile than people think. Especially if you put the high pass resistor on a switch. With the transistors I used, the collector resistors had to be changed to 10k. This will cause radio static. To get rid of that, put a .002 uf on the board from input to ground. One last thing. The pots should both be 500k log taper. 33k and 350k are wrong.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: J M Fahey on December 06, 2014, 01:47:28 AM
Still no schematic  ::)
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: Roly on December 06, 2014, 01:58:04 AM
Okay, let me put it another way - how did you measure the fT of the transistors you used?
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 06, 2014, 04:11:52 PM
I don't have anything to measure transistors with. I just looked up the data sheets of the ones I had tried and the typical frequencies of those were all between 80 and 90, which is a bit too low. I originally used the schematic from fuzzcentral, which does work, but has some errors. I kept tweaking it until I finally got a good sound out of it. Now, I'm not knocking fuzzcentral.  Their fuzz face schematic works perfectly. But, the fuzzrite is a different story. I have a schematic of mine, which I drew by hand. I'll post it for you later.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 06, 2014, 04:30:19 PM
Okay. Here's my schematic. Transistors are C1740, collector resistors are 10k, pots are 500k log taper. The parts in red indicate all the changes that I made. It's a great sounding fuzz, but requires some getting used to. It's nothing like a fuzz face, or big muff. You'll be using the volume control on your guitar alot more, and your pickups will affect the sound quite a bit.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: Roly on December 07, 2014, 01:18:30 AM
Well the 2SC1740 datasheet I have gives a figure of 180MHz.

At the risk of sounding a bit testy, let me pose the question a third and different way; what makes you think that the transition frequency of a transistor in the hundreds of megaherts would have any influence at all on its behaviour in the audio spectrum?

Do you understand what the fT of a transistor is?

You say;
Quote from: LJN
transistor shouldn't be selected by hfe, but frequency as well

Do you understand how the fT and hFE relate to the dominant pole in an audio circuit?

I want to know how you came to the idea that the fT of your transistors would be as, or more, important than their hFE (which I'll bet you didn't measure either).
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 07, 2014, 05:07:51 AM
Look. I can't really give you a scientific answer to this. All I know is that when I tried these, they worked. The data sheet showed a higher frequency, so it occurred to me that this is an important factor. Have you ever tried some transistors in a fuzz circuit that just didn't sound right even though the hfe was perfect? All I can say is try them and see if you like the way they sound. I wish I knew how to answer your question, but I'm just not that familiar with the scientific aspect of electronics. I can't do math, either. But the data sheets will tell you. Just look at some. What transistors have you tried? Look them up and compare the frequencies. It's worth it.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 07, 2014, 05:22:22 AM
By the way, did you even read what I wrote? If you had, you'd see where I said that I went by the numbers on the data sheets because I don't have anything to measure transistors with. Go back and read this thread very carefully. I tried to explain it as best I could. You're right. I didn't measure hfe. Because I don't have the equipment,as I previously stated. I can understand your frustration. Just read the thread again, and when you have, then you may understand. It's not always about measuring every little thing. It's about experimenting with different parts until you get the right sound.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: Roly on December 07, 2014, 01:05:44 PM
The problem here is that I have read your posts carefully.

Some of your advice, such as;

Quote from: LJN
Select a transistor with a frequency around 110-140 MHz.

...has no actual factual basis, they are guesses, and not good ones.

Trust is an important issue.

Some sites such as Redcircuits and Runoffgrove post circuits and information that are simply bulldust, amplifiers that will always self-destruct at first power up for example.

This site has become trusted by many to give sound technical advice backed up by hundreds of man-years of collective experience, some fifty years in my case alone.  That trust must be carefully nurtured by making sure that incorrect or misleading information isn't posted without correction, and even members of the Brains Trust, the expert group, correct each other from time to time.

Sites such as R.G.Keen's geofex, Rod Elliot's ESP, or Steve Bench's DIY Audio Projects are trusted because they provide solid, accurate and tested information that people can hang their hats on, but that trust is hard to earn and easy to lose if they don't maintain high standards, and part of maintaining high standards is technical accuracy.

Your OP doesn't ask for help or information, rather it attempts to provide advice and information useful to anyone else attempting to build a Mosrite Fuzzrite clone, however some of the information you provide with a sound of authority is actually misleading.

It is trivial to measure hFE, and only slightly more difficult to measure fT, yet you make this very definite statement;

Quote from: LJN
Second, transistor shouldn't be selected by hfe, but frequency as well.

...when in a year you haven't measured either parameter of your particular individuals and therefore couldn't have any way of knowing which parameters were doing what to your circuit.  This is no small point when the 2SC1740 datasheet gives a production range of hFE from 120 to 560.

There is already a large amount of electronic mythology floating about in musicians circles, some of it imported from the world of know-nothing hyper-fi, and none of it is any practical use to musicians - it leads them astray and actually subtracts from the sum of human knowledge.

So, to a first approximation it would go like this:

Assume for a 2SC1740;
hFE = 100
fT = 200MHz

dB = 20 Log10 (Av)

therefore DC gain = 40dB

If we assume that the rolloff from the corner frequency fC is 6dB/octave or 20dB/decade, and work backwards remembering that fT is effectively the unity gain frequency, then the dominant pole fC is 40/20 = two decades below fT, or 2MHz for this device.


Put another way, this transistor is gain flat up to 2MHz which is itself two decades above the highest frequency you can possibly hear.  This means that hFE is an important parameter in an audio circuit, and that the effect of different fT would be entirely swamped by circuit strays, literally just breathing on your circuit will produce larger changes.

I have seen hundreds of circuits that must have wasted millions of hours of peoples time trying to get them to work as claimed, only to discover in the end that they are a total crock.  Your circuit isn't a total crock, but after saying;

Quote from: LJN
there's not a whole lot of accurate information about it. added to the pile of inaccurate information about it, which is rather unfortunate given your intent.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: g1 on December 07, 2014, 01:52:45 PM
  You may well have found some transistors that sound better for this circuit than others.
  However, you can not jump to the conclusion that the frequency spec. is what is responsible for the difference.
  Roly has shown how this is the case.  There are many other aspects of transistors that could be responsible for the difference you hear.
  It could also just be a coincidence.  You would need to try many samples of each type of transistor to reach any kind of conclusion.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 07, 2014, 03:12:27 PM
If my information seems misleading, I apologize. That wasn't my intention.  I merely wanted to point out that hfe isn't the only important factor. My circuit does, in fact work. I use it every day with no problems. Maybe I should try to learn more about electronic theory, but I'm no good with numbers. I found something that works great and I wanted to share it with people.  But if all you can trust is numbers, and say this is a coincidence, you're entitled to your opinion. I'm sorry that I'm not that familiar with these equations. I did try a number of different transistors. All of which I looked up the data sheets for. The hfe were all very similar according to the data sheets, but the frequency was different. If hfe was all that mattered, then wouldn't every fuzz circuit use the same ones? Further more, if that's the only thing that matters, wouldn't every circuit use the exact same transistor? Just think about that.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 07, 2014, 03:34:23 PM
That being said, I'm curious. Have you ever built a fuzzrite? If so, what transistors did you use, and how did it sound? Surely, in your 50 years of experience, you've seen some odd things, haven't you? If I can find a way, I'll try to get you a video of mine. Then you can be the judge.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 07, 2014, 05:03:58 PM
The video wouldn't go through, so here's some pics.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: J M Fahey on December 07, 2014, 06:51:39 PM
FWIW I have built tens of thousands discrete transistor circuits and never ever had problems with Ft limiting my designs.

60MHz/100MHz/180MHz is the same , always well above audible frequencies.
Speaking of silicon transistors, of course.

Now on Germanium ones, which have Ft measured in KHz , not MHz, yes, you audibly lose highs if you use them with high gain , which happens for example in old Fuzz circuits and Treble Boosters used by a few old time Guitar Gods, and which justifies the "smooth/warm sound" label.

I'd call that "lack of treble" and in fact can simulate it very well by adding a few 100pF (or 220/470/1000 pf) caps here and there, go figure.

Back to the Fuzzrite, not only I built clones but also had an original one, when they were new  :o  (now where's the [mummy]  emoticon? :( )

A friend of mine's Mother travelled to Miami (remember I'm from Argentina)  and he asked her to buy a Gibson 335 , unavailable here.
To make certain, he gave her a picture.
Boy, was he disappointed!!
She brought back a similar shape Mosrite "335" , which "the nice young salesman told her was better" , and who to sweeten the deal threw in a Fuzzrite, "free of charge/gift" .

Obviously I opened and traced it, and built clones. 8|
We are in an "European Culture" country, so I used what's standard here, BC147/8/9 transistors, not Japanese or American types.

All worked like a charm and had the exact same sound.

That's how uncritical that simple circuit is.

FT?  never cared about it (since all far exceed what I need for Audio).

Hfe? I always bought BC147/8/9 C types, factory guaranteed between 250/500 and in fact clustered around 500, so after the initial tests I stopped measuring them, only checking a few samples every time I buy a new batch (I buy 500 unit lots) .

Thats why we tell you that:

1) we agree that you built your Fuzz properly and it sounds good. :dbtu:
Congratulations.  :dbtu:

2) we agree that different transistors may sound different.

3) we do not agree that Ft is the main parameter affecting sound, quite the contrary, and we worry that somebody building his own clone gets worried about Ft and that snowballs appearing in other Forums (mainly Pedal related ones) and "confirmed true" , because "I saw in SSGuitar and those guys are very serious" .
Just that. :)

PS: in fact I can easily picture pedal supply shops, as, say, Small Bear (just the first one which came to mind) or EBay sellers offering "premium selected 2SC1740 transistors, Ft 140 MHz, as recommended in SSGuitar"   :o
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 07, 2014, 10:07:17 PM
Thanks for being a little more reasonable about it, Juan. I didn't mean to cause any trouble. I have compared my clone to videos of original units, and it sounds very close. So, you had an original? Nice.  I looked up the data sheet to the BC147. It specified hfe of 110, and frequency at 150 MHz. Are these still available? I'd be interested in trying them. Mine already has a buzzy sound, but cleans up quite well when the guitar volume is backed off. It's very responsive. I'd like to hear more about your experience with the original. How long did it sustain? And was it noisy? I couldn't find much information about the original units. So, I'd really like to hear some details from someone who has owned one. Thanks.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 07, 2014, 11:56:53 PM
I'm also planning to build the Ge version, but I don't have all of the parts yet and I have other projects going on. I'm trying to fix up a motorcycle. I'm gathering parts for three other pedals, as well. So, I'd really like to hear about your experience with an original fuzzrite.  :tu:
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: phatt on December 08, 2014, 02:38:39 AM
Hi LJN, Hey we understand your enthusiasm and we don't want to destroy that desire  :tu: but in this trade there are as many ways to make sound/distortion/buzz/fuzz or plain old good tone, as there are technicians. I remember the first time I worked out how back to back diodes made sustain and crunch and for a short time I glowed with the thought of becoming a tone god but my momentary delusions went poof once a kind old chap gave me a small pile of real technical books, (the ones you have to
purchase to study at Uni).

I then plowed through each type of transistor design explanation looking for the holy grail trick to make a wow circuit. Then one fine day as I pondered what I had learned the heavens opened as it dawned on me that there is NO Best circuit.  :o :o
Why yes,, it finally dawned on me that ALL these circuits have there benefits but come with limitations and quirks. the trick is understanding which ones to use where and that takes time to learn 8|

In the case of guitar sound if you build the best (HiFi standard) amplifier it will likely be a very bland and uninteresting sound which you will probably hate. xP
Fuzz circuits like the one you mention  only tend to work well in front of real tube amps.
In other words the fuzz circuit is actually rather more dependent on the amp that comes after the pedal.
The mojo is a combination of both but the hype tends to focus attention on the pedal. :loco

Reminds me of the old SRV tone thang where everyone ran out to purchase a TS9.99999 or some derivative assuming with that pedal you could access the famous sound. durh??

Sorry kids the mojo factor was the combination of the amplifiers used, any half decent pedal
of similar design would yield the same effect. +/- an electron or 3. ;)

Same goes for Brian May's famous setup.
Check the signal path,, He used the *Normal channel* NOT the other channels.

Signal went TB pedal > one triode stage > a 500K pot (Volume) > power amp.
Even if you used Brian's pedal it would sound vastly different if you used the other channels or another amplifier.
You need an exact combination (or close to it) for the sound to work.
In saying that be aware that other quite different combinations may well deliver the same end result.
Takes years to work that out but comes in handy if like me you need to save a dollar. :-X

In my personal case where a limited budget forces me to use whatever is on hand or cheap to
build/purchase you soon learn there are many ways to get the sound you desire. Sadly pedals are
mostly over rated and vid clips are often misleading because they often don't explain the signal
chain which means you have no way of knowing what it will sound like with your rig. :grr

From that hopefully you will come to realize that pedals are a good way to get some learning
but there is no one pedal known that will sound/perform the same through ANY Amplifier/Guitar
combination. sorry :blank:

Meantime keep at it you are heading in the right direction and with the help of the teck guys who are kind enough to share there wealth of experience and knowledge and you will likely get ahead a lot faster than I did,, no internet in my day so hence a lot of perfectly good transistors went to magic smoke heaven before I got things to work right. :crazy2:

Read up as much as you can, inet is good but too darn easy to get side tracked so a good book
keeps you focused.

Cheers, Phil.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: J M Fahey on December 08, 2014, 02:54:49 AM
OK :)

1) you got BC147 "no letter" which basically are the leftovers :(

That said, even those work well :)

2) There is a whole "family" of basically the same general purpose transistor, factory selected  <3)  with certain guaranteed parameters.
What's not to like about that?  :)

So, just because we are talking about that, originally there's BC107/8/9 , standing respectively 45V/20V/20V (in a 9V pedal they are all the same) .

Besides, they are graded by Hfe , and given a letter A/B/C (as said before, no letter means ungraded)


"No letter": "ungraded" :  Hfe 110 to 450 ... which in many cases does not matter.

"A" : guaranteed 110/220

"B" : guaranteed 200/450

"C" : guaranteed 420/500

See that BC108/109 look the same ... in fact BC109 are selected for low noise  8)

There's more:  they are also available in different casings:

BC107 (just to name one type) used an expensive, metallic case  :o

BC147 used a weird polygonal plastic case , with special short, arrow pointed legs, to make automatic insertion easier for machines (remember this was invented more than 40 years ago  :o )

BC547 is what I use today, in a conventional plastic TO92 case:

Still popular in the 21st Century  :tu:  now they are available in SMD packages:

I guess now you know why we LOVE "Cherman Enchineerink"  <3)
These were originally Siemens/Telefunken/Philips developments .

No other company we know is so thorough offering all kinds of possibilities to all manufacturers, without special ordering.

3) Small world indeed :)

Searching around I found a guy who built a Fuzzrite with BC109C  :o (what I did in the early 70's)


4) you ask me about the sound?

That was over 40 years ago, and there was nothing to compare it with (no MXR Dist+ , nor Tube Screamers, nor Big Muff, etc.) .

A friend had a VOX Distortion Booster, the kind which plugs straight in the guitar  :loco , which was very buzzy / "mosquito" sounding.


I liked the Mosrite better.

Sorry can't be more precise .
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 08, 2014, 03:03:31 AM
Thank you for your kind words, Phil. I've been wanting to get some of those books. I have a very limited budget too (actually, no budget). My amp is solid state. It's a 1970 sears 125 XL. It's noisy, but I love it. I sorta came to that conclusion about frequency after looking at all those data sheets. I didn't mean to cause any trouble.  I don't like to cause trouble.  I meant to help. Oh. My guitar is a beat up epiphone Les Paul standard. It has the stock pickups. I always leave my uni vibe clone hooked up, as well. I get a nice cocked wah sound that way when I back off the guitar volume. The pedal, and my amp are all treble. There's hardly any low end. That being said, I have tried this pedal through four different amps. Including my old sears amp. I also have a peavey. The pedal did sound quite different through that one ( think maestro fuzz tone) . I've also tried it with a few different guitars. Stronger pickups tend to make it sound pretty raunchy.
Title: Re: Mosrite Fuzzrite (si version) build tips
Post by: LJN on December 08, 2014, 03:17:55 AM
Thanks, Juan. I can't blame you. I love my fuzzrite clone. I did try some C1815(said to be BC109 equivalent)  . They sounded awful, but they worked great in my fuzz face clone. Maybe they're not exact replacements, then. I have to use whatever I can find in scrap electronics. Old TVs, radios CB 's, and stuff like that. So, getting the "right" parts is usually very difficult. I really wanted to build a tonebender mk II, but still haven't found the parts. I always wanted a fuzzrite,  ever since I heard " In-A-Gadda-Da-Vida" when I was 12 or 13. I just loved that sound. If you say these other transistors will work, it's worth building another one someday. Thanks again.