Hypothetical resistor question?

[Ed Nice]

Ok, I'm looking at a Big Muff.

This is probably an obvious, dumb question to most of you guys, but here goes...

There is a 560R from the sustain pot to common (see, I must be learning. I wouldn't have had a clue where it went last week!). If I don't have a 560R, but have a 510R, what would this do to the sustain? Would it make a huge difference, given that theoretically the upper boundary of a 5% 510R and the lower boundary of a 560R overlap by a few Rs?

I know, they have alternate upper and lower boundaries respectively and these are quite far apart, but I'm considering that something like this may have a significant tolerance outside of the boundaries of the noted value. I'm just trying to get a feel for tolerances.

I know a resistor would most likely be more significant in, say a power or gain stage or an IC/transistor connection (there I go again with that there learning stuff!) so I'm pretty sure a suck it and see attitude wouldn't do any damage and I'm thinking changing the resistor here would simply govern the amount of signal taken to ground from the sustain pot so I'd see more or less sustain?

So, am I talking nonsense in my reading of what might happen and why and what would the effect be?

Thanks. :)

[Travis]

That resistor is just there so that the pedal isn't silent when you turn the sustain all the way down. You could use 510Ω no problem. You could even replace it with a link, 1k resistor, doesn't matter too much as long as you don't use a big resistor

[rocket88]

+1 to travis's comment. btw, which muff are you building? cause i'll warn you now, just like being Ge-curious, it's a slippery slop and you can never have enough muffs.

[Ed Nice]

Thanks guys. I guess I'm on the right track with my theory training then and the purpose of the resistor there is actually really obvious now you've said it!

Rocket, I'm looking at this: http://tagboardeffects.blogspot.co.uk/search/label/Electro%20Harmonix

It suggests a BC550C for the transistor, so I'm guessing this is where I can look to get jiggy with something a bit sweeter maybe? :)

There are a ton of variations out there, I know, but a mate of mine said 'Can you build me a Bigg Muff?' so I figured he was looking at a pretty vanilla original? As I haven't got one, I thought I'd build one for me too. I socket my trannies anyway, so should I be looking at a bit of experimentation with it?

:)  

[Travis]

I'm not rocket :P but nah that's not really a very effective place to tweak the muff. I'd probly just use the BC550C as they're pretty low noise and high gain

You could adjust emitter resistor values for more or less gain (smaller emitter resistor = more gain)

Adjust coupling cap values to get more or less low end (bigger = more low end)

Adjust the ceramic caps in the transistor feedback loops to adjust which frequencies are clipped most (bigger values may get muddy pretty fast and smaller ones may be noisier, but adjust to taste)

And of course you could adjust the values in the tone stack. Seymour Duncan site has a calculator that will help you pick values for the freq response you want

Change clipping diodes for different compression, distortion, etc

Just a few tips :P

[rocket88]

not a fan of that plan either to be honest. each one is very distinct from the other in its tone and have a different character. before you build the muff i would check out the guide below, link to guide



and check out the following site. it tells you all about every change you can do to the muff, and what you can expect from that change.

most of what i learned about circuits and designing comes from building a big muff. there's so much info out there about it that you really can get your hands dirty with the engineering aspect.

if you're building it for a friend, i would have them listen to a bunch of audio from different muffs to see what sound they would like and go from there. it might be that you can go with a stock muff from a specific generation. hell you could go with a tweaked muff like the BATW pharaoh, super collider, musket, etc.

[nocentelli]

Bigger emitter resistor = LESS gain: Standard muff has 100r or 150r in those spots. Increasing the collector resistors would give more gain, but it's unlikely to make a huge difference, since you already have four high gain stages in series. I found tinkering with the clipping diodes is a good place to experiment, e.g. replacing them with leds or two pairs in series. Also, the tonestack as mentioned, e.g. adding a mids pot to adjust the mid-scoop, or eveven give a mid boost.

[Ed Nice]

Thanks guys :)

I'm not really up to too much fettling just yet. My feeble brian is struggling enough! Just suggesting stuff that I don't really understand does motivate me to go and read up on things though so i appreciate all the help and suggestions, even though it's mostly falling on fallow ground at the moment.

I'm probably at about 2.9% known unknowns and about 97% unknown unknowns, but how can I say that if I don't know? All I know is I don't know nearly enough yet. On a positive note, my soldering is getting pretty good, especially since the incident with the electrified cat and the curtain fire.  

I'll probably do as mentioned and sit yer' man in front of various demos until he betrays some emotion in a positive way?

I'm gonna build me a standard Big Muff anyway. You know, just coz...

[nocentelli]

The bmp is a large circuit to start out on, but it's also nicely designed so you can use parts easily +/- 20% or more out of spec and it will sound good. It's a shame to see so many people start out on a germanium fuzzface and mess around trying to get it to work and sound ok. In many ways, you can't go wrong just building a stock version because I think they got it about right.

[rocket88]

for some odd reason while reading your post all i could think about is this from clue:


"Wadsworth: The game's up, Scarlet. There are no more bullets left in that gun.

Miss Scarlet: Oh, come on, you don't think I'm gonna fall for that old trick?

Wadsworth: It's not a trick. There was one shot at Mr. Boddy in the Study; two for the chandelier; two at the Lounge door and one for the singing telegram.

Miss Scarlet: That's not six.

Wadsworth: One plus two plus two plus one.

Miss Scarlet: Uh-uh, there was only one shot that got the chandelier. That's one plus two plus *one* plus one.

Wadsworth: Even if you were right, that would be one plus one plus two plus one, not one plus *two* plus one plus one.

Miss Scarlet: Okay, fine. One plus two plus one... Shut up! The point is, there is one bullet left in this gun and guess who's gonna get it!"

btw, i would read this. it's an explanation of how the big muff works, and it's something that really helped me get over the hump in my knowledge and understanding of circuits at the beginning. also, if you're so inclined you could check out this, which is a start of an analysis of each big muff version, and clones. it also has all the schematics for each model too.

remember, the problem is there really is no standard muff, because there really is so much variation between each version. shit, for me i built a violent rams head, russian green, 77 opamp, not to mention some of the variants like the iron bell, pharaoh, and swollen pickle just to name a few. i'm not even including the ones i own that were made by EHX. in case you couldn't tell the big muff is one of my favorite fuzzes. not saying it's the best, but there's something about it for me.

[Ed Nice]

Thanks Rocket.

That big muff page got posted by someone else a bit back and I had a read of it but I'm so junior at all this, I get about 8 words in and think, 'WTF does that mean?'. So off I go and read some more random stuff, get sidetracked, start chasing a fluffy tailed squirrel around the room, make a cup of tea, read 6 more words, . 'WTF is that supoposed to mean (again)', three datasheets and 7 wiki's later, I forgot the first bit... :p

It's slowly coming [mostly thanks to the patience of you Saints that hovver majestically under your omniscient halos on this here heaven of a forum!] but I'm not doing this in a sensible [linear] manner. I'm jumping round from point to point. But from experience, that's how I learn, by being a bit more action than theory, so it's ok...

I'm like that kid who just says 'why?' all the time. The origin of this train of thought simply came from me looking at the orginal muff whilst making a stocklist spreadsheet and thinking, 'I haven't got one of those. What if, why, etc...'. I have a similar (groan) hypothetical why about something in this: http://tagboardeffects.blogspot.co.uk/2014/04/fulltone-fatboost-v1.html. If I change the 3u3 in the output, does that add bass if I go up, treble if I go down?

I suppose I've got an inquisitive mind, which is probably a good thing in many respects. I am happy so far building from [these great] layouts, but inevitably I then have a growing desire to understand. *I have to know what Pandora keeps in her box?

*It's probably the old legs of components for jumpers?

[rocket88]

haha, i'm the exact same way. one of my first builds was a russian green muff, which is where a lot of the theory stuff clicked in my head. i mean, the light bulb went off and everything. so i have to agree, love it or hate it everyone should build a muff. try checking out the explanation again, just take it in pieces. so start with the explanation of one stage, once you get it down, move to the next, and so on and so on. trust me, you'll be happy you did and it will all make sense.

i took a look at the fatboost schematic, which is basically an AMZ mini boost with a tone control. i could be wrong, but if you wanted to raise the bass you'll want to increase 220nF cap that runs to the output, if you want to lower the bass lower the 220nF cap. this will only effect the amount of bass leaving, so you may want to add an input cap, in fact the original AMZ has a much higher 47nF input cap. the gain control basically just controls the amount of signal entering the effect.

no saint here, just a sinner with a helping hand, well at least for some people here. but, the again i would rather be hanging with the sinners, then singing with the saints. but, seriously i'm actually just glad to help and pay if forward for all the help i've been given over the years. not to mention we're all brothers of the soldering iron, and you're one of us, so you'll get help whether or not you like it.


btw, the ultimate answer to the question of why is always the same. QUANTUM MECHANICS!!!!! sorry, remember scientist here.

[Travis]

lo siento mi amor

Got a little dyslexic there

[rocket88]

what are you sorry for? you lost me. lol

[Travis]

Ah. nocentelli pointed out I had the emitter resistor gain thing backwards. I edited my post to avoid confusion

Also I was working at the shop today with Mexican radios the whole time