I'm planning to build a small custom fuzz box for a musician friend. It will have quite a few components including six 2N2222 (or MPS6531) transistors, etc.
One thing I noticed was that it calls for a 100uf 10volt electrolytic capacitor across the battery terminals (rail to ground). I'm wondering would this be necessary at all if you are just powering it from a 9v battery? My guess is that maybe they are including this to smooth out the power in case someone was using a wall wart instead. In that case, wouldn't a wide range of caps be suitable, even a 4700uf 16volt cap for example? I'm trying to get all the stuff from the same supplier, and that's the closest they have.
A few other very simple questions for those who have worked with these before, but I'll post them later. Just want to make sure I work up the best design, as I'll have to to send it by mail to him.
One thing I noticed was that it calls for a 100uf 10volt electrolytic capacitor across the battery terminals (rail to ground). I'm wondering would this be necessary at all if you are just powering it from a 9v battery? My guess is that maybe they are including this to smooth out the power in case someone was using a wall wart instead. In that case, wouldn't a wide range of caps be suitable, even a 4700uf 16volt cap for example? I'm trying to get all the stuff from the same supplier, and that's the closest they have.
A few other very simple questions for those who have worked with these before, but I'll post them later. Just want to make sure I work up the best design, as I'll have to to send it by mail to him.
frank754
i might be wrong but the cap may be needed to prevent your circuit from oscillating it is after all an amplifier(with lots and lots of distortion!)so some stability i think would be desirable.
i might be wrong but the cap may be needed to prevent your circuit from oscillating it is after all an amplifier(with lots and lots of distortion!)so some stability i think would be desirable.
Please include it. It is a nice low impedance path to ground from the 9V rail. What you don;t want is the signal from one or more stages causing little variations in the power supply, which can then be amplified, causing instability or undesired audio artifacts.
What sort of supplier are you using that doesn;t have 100uf caps? if they don;t have it in 10v, go to 16v or 25v.
What sort of supplier are you using that doesn;t have 100uf caps? if they don;t have it in 10v, go to 16v or 25v.
Yes - absolutely essential - if anything it's perhaps more important than with an AC supply.
Without it you will get drastically reduced battery life (10% or less), instability and motor-boating. It may also prevent the circuit working correctly, as any circuit releis on that capacitor for it's operation.
I usually use Antique Electronics, as they have a lot of parts for musicians and audiophiles as well, and carry a lot of tubes & supplies. My choices would be the 4700uf 16v (too high?), but they also have 25uf 25v, 47uf 35v (a lot in that range), also 220uf 50v (maybe that last one would be best if 50v is ok and 22 uf isn't too high.). I know that filter caps aren't always as critical, where the caps within the stages are finely tuned players. Within the circuit itself, it calls for eleven 10uf electrolytics but doesn't specify any voltage. I'm tentatively ordering 10uf 50v for these (that's the lowest voltage they have for 10uf). These are used interstage and also around a pair of clipping diodes. So I guess the voltage isn't critical on these since it's not specified? If not, I could go with Mouser or some place like that.
Anyway, thanks for your replies, I'm doing this for an out-of-town musician friend I've known about 20 years, and he's looking for certain vintage effects.
Anyway, thanks for your replies, I'm doing this for an out-of-town musician friend I've known about 20 years, and he's looking for certain vintage effects.
Considering 100uF is probably one of the most common values it's a bit strange they don't have those?.
220uF would be fine, or the 47uF - you don't need a 4700uF, and it wouldn't be a good idea.
Thanks, I think I'll just put 2 of those 47 uf caps in parallel, and that should be darned close to the original spec 🙂
Hi,
Care to explain any of the above utter nonsense ?
rgds, sreten.
Any reasonable value could be used, 100uF is just a standard
value you typically use on board rail to rail, but its no big deal.
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In what regard?, no nonsense there at all.
I never suggested the VALUE was critical, only that a suitable capacitor is.
What we are all wondering is how will battery life be seriously compromised without a reservoir capacitor?
I can only assume that you meant that if it was unstable, or even oscillating supersonically - battery current would be increased?
I can only assume that you meant that if it was unstable, or even oscillating supersonically - battery current would be increased?
Any electronic circuit is designed on the basis that there's a low impedance AC path between the supply rails, and that the supply itself has a low impedance.
The capacitor across the supply fills those two requirements.
Without the capacitor (or if it fails) it 'may' work when the battery is absolutely brand new, but in a relatively short time it will fail to do as, as the source impedance of the battery increases and the circuit starts to fail.
Remote controls are probably the best example? - if the capacitor goes O/C (and I've changed many over the decades) - the battery life drops from 2-3 years to only 2-3 weeks. If you replace the capacitor, the existing batteries work fine again, but not without it.
You have the "right" answer for the wrong reasons.
No way can the lack of a capacitor pull more current from the battery and cause its early failure!
What happens is the battery internal impedance goes up with age and, without a parallel charge storage cap or higher ESR of the existing one, the peak current to fire the infra-red leds is not available!
So the battery no longer works in that circuit with its higher ESR.
No way can the lack of a capacitor pull more current from the battery and cause its early failure!
What happens is the battery internal impedance goes up with age and, without a parallel charge storage cap or higher ESR of the existing one, the peak current to fire the infra-red leds is not available!
So the battery no longer works in that circuit with its higher ESR.
Hi,
Its all nonsense for a battery powered fuzz box.
Battery life - nonsense.
Motorboating - nonsense.
Instability - generally nonsense if the board has suitable
properly placed rail decoupling caps, typically 100nF.
rgds, sreten.
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Which I never suggested.
I never suggested anything different - and even said that fitting the essential capacitor would allow you to re-use the battery.
But it's not just remote's, that's just an extreme example, it applies to almost anything electronic.
What Nigel says clearly is that a low supply impedance is good/necessary (take your pick), doubly so in a *high gain* (any doubt about that?) , *crude* design (any doubt about that?) like a Fuzz.
An old tech 9V battery, carbon zinc is what we are talking about, will start with a relatively high internal resistance which will only go up, never down.
Which is a *known* cause for instability.
So one of those batteries will last, say, "X" days because instability raises its head, but many more days with the cap added.
Making so much fuss about that cap, which by the way was used from the beginning, as shown in the original schematic , well, *that*'s nonsense.
Or having very little to do.
Increased current consumption was never mentioned or implied, don't know where was that pulled from, *but* longer "usable" or "practical" life.
Which is the point, of course.
An old tech 9V battery, carbon zinc is what we are talking about, will start with a relatively high internal resistance which will only go up, never down.
Which is a *known* cause for instability.
So one of those batteries will last, say, "X" days because instability raises its head, but many more days with the cap added.
Making so much fuss about that cap, which by the way was used from the beginning, as shown in the original schematic , well, *that*'s nonsense.
Or having very little to do.
Increased current consumption was never mentioned or implied, don't know where was that pulled from, *but* longer "usable" or "practical" life.
Which is the point, of course.
OK, here's the image. I finished the prototype. It "sort of" works, but the problem is very low gain. Even with the 2 pots all the way up, the sound volume is attenuated by more than 60% when running the guitar into the box vs running it (bypassed position) directly into the amp. When going in "notch" position, there's virtually no sound at all, but skip that for now (that makes me assume the problem is "earlier" in the signal path). As you can see, the part specs are very vague. I used MPS-6531's for all the transistors rather than 2N2222's, as that's all I had available. I'm wondering if the problem is in the transistors, or perhaps a few of the resistors can be tweaked. Incidentally, I used a pair of 1N4001 diodes for the clippers near the bottom left. As far as the resistors go, could I try cutting down the 22k input resistor, or perhaps the ones around the first two transistors (proportionately to each other) at the top left? And which stage (Q1/Q2) or (Q3) or (Q4/Q5) (I'm assuming Q6 is doing its job) would be most suspect for causing performance issues like this? I'm not an engineer, and not quite the gizmo tech freak I'd like to be, but very good at construction, so any help is appreciated 🙂
You need to find out where you're losing the signal, if you don't have a scope, then use your amp as a signal tracer. For a start feed the amp from the output of the 'drive' control, this should be considerably louder than direct from the guitar.
So try that, and report back.
So try that, and report back.
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