Big Muff Resistors

[bettsaj]

simple question really....

I'm gathering the components to make 2 v2 Big Muffs, and I've been offered a load of 1/4w carbon comp resistors. I know in the Big Muffs in the 70's they used 1/2w resistors..... Is there anything i should be concerned about, or just go ahead and use the 1/4w resistors. i've been offered them cheap, but the intention was to be true to the original pedals.

[PRR]

> in the 70's they used 1/2w resistors.

Well, they used CHEAP resistors.

In the 1970s, 1/2W was the cheapest size.

In the 1980s, 1/4W was the cheapest size.

Today 1/8W are generally cheapest.

This is all part-cent differences. If you build a million, like Mike, you have to count part-cents. In DIY you don't.

I can't think of anywhere in a Big Muff that needs even 1/4W parts.

You want parts big enough to handle (I have fat fingers), that look good (in DIY, you know what it looks like and that affects your perception), and affordable for your budget/profit situation.

[GibsonGM]

Any chance that using larger resistors, such as 1/2W, would increase hiss over 1/4W?  I know in amps, running at far far higher voltages, that can hold true...how about at low voltage?   

My guess is no, but thought it worth asking...

[bettsaj]

that look good (in DIY, you know what it looks like and that affects your perception), and affordable for your budget/profit situation.

i guess that's why over thinking it.. The circuit board i'll be using is a one to one copy of the standard v2 board... See attached...



i suppose what i'm really worried about is whether the smaller 1/4w resistors will look right on that board... Like you say, it's all perception. It won't sound any different i'm sure, but in my own mind i'll know they're smaller and therefore not right.

[bettsaj]

I think I've just answered my own question.... The 1/4w will be fine. They couldn't have used 1/2w as they would have been too big.

I've just laid a 1/4 watt resistor on the printed trace and it fits perfectly, so i was worrying needlessly

[bool]

Well, it's a big muff after all. So try to use bigger so to keep a tighter fit, heh ...

[Plexi]

If you want a 100% vintage correct Big Muff...use what the hell you have on hand...
No, really: they've never used what the schematics says...very inconsistent.

If you want quality, go for 1/2 metal film...or at least 1/4.
I prefer 1/4 or 1/6 due the size...but its the same to me

[bettsaj]

I know the exact circuit i'm copying... It's this one on the Kit Rae web site







In his opinion, the closest he's found to what Gilmour uses. i'll try this circuit, and see how it goes

[DeusM]

Like Plexi said. They used what they had in hand so the sound between different versions and in the same versions too may differ. Just keep in mind that although David Gilmour may have used one version doesn't mean that you'll get the same sound as he. Keep in mind that the sound in records is altered, EQed, compressed and all that stuff. I would recommend that you made that version in a breadboard and start messing around with the values to see if you can get a sound that you like. In Kit Raes's page there's a section where he specifies how different values affect the tone and the sound. Also, keep in mind this: that circuit doesn't have polarity protection, nor pull down resistor, nor caps for noise reduction.

[PRR]

> larger resistors.....  would increase hiss ....?

As a super general thing: hiss tends to go down as parts get larger. Think: hiss is the randomness. More atoms, the random averages-out to less hiss. This is almost un-measurable for all the parts we use: they are near-infinite atom-count. It has been seen in very sensitive circuits using the smallest SMD parts with truly microscopic guts.

And the *type* can make far more difference. Metal-film is solid metal. Carbon-film is near solid carbon. "Composition" resistors are coal-dust and clay sorta packed together, and tend to much more hiss than other types, and some factories worse than others.

[thermionix]

Though I've been considering it for a while, this thread was the final inspiration to breadboard a BMP.  So I did that late last night.



I followed the Kit Rae/Gilmour schematic above, I had already been eyeballing that one.  I'm not really a BMP enthusiast, but that seemed like a good first one to try.

My only real departure was that I used 2N5088s.  Three of them had hFEs around 445 and the fourth about 535.  No I don't remember where I put the high one.  I didn't know if this circuit was picky about hFEs or would need resistor values tweaked to bias properly.

Well, plugged it in and - big surprise - it sounds like a Big Muff.  I reckon a pretty good one, too.  At least as good as any I've played before, but admittedly that's not many and it's been years.  Got up today, hacked out the first couple sections of "The Grobe" and spent about 20 minutes playing that.  Put the wah in front and that's pretty awesome too (I have a FoxRox type output buffer in the wah so maybe that's a factor).  Singing, sustaining lead lines.  Maybe I'm a BMP fan after all.

So did I get lucky?  Or is this circuit not really picky about transistors and hFE?  I didn't check any voltages (nothing to compare them to) but it really doesn't sound like any bias adjustment is needed.  Is there something more to be had by tracking down the "correct" transistor types, or should I just build it as it is?

[DeusM]

Though I've been considering it for a while, this thread was the final inspiration to breadboard a BMP.  So I did that late last night.



I followed the Kit Rae/Gilmour schematic above, I had already been eyeballing that one.  I'm not really a BMP enthusiast, but that seemed like a good first one to try.

My only real departure was that I used 2N5088s.  Three of them had hFEs around 445 and the fourth about 535.  No I don't remember where I put the high one.  I didn't know if this circuit was picky about hFEs or would need resistor values tweaked to bias properly.

Well, plugged it in and - big surprise - it sounds like a Big Muff.  I reckon a pretty good one, too.  At least as good as any I've played before, but admittedly that's not many and it's been years.  Got up today, hacked out the first couple sections of "The Grobe" and spent about 20 minutes playing that.  Put the wah in front and that's pretty awesome too (I have a FoxRox type output buffer in the wah so maybe that's a factor).  Singing, sustaining lead lines.  Maybe I'm a BMP fan after all.

So did I get lucky?  Or is this circuit not really picky about transistors and hFE?  I didn't check any voltages (nothing to compare them to) but it really doesn't sound like any bias adjustment is needed.  Is there something more to be had by tracking down the "correct" transistor types, or should I just build it as it is?

Hey! That thing you did with the pots and the jacks seems awesome! I'm struggling every time in testing the circuit so I'll try building something like that i the future. In the Electro Smash page there is a section talking about the BMP and how every value should be. But I messed around with my prototype and I like how it sounds. Some values are "wrong" but changing to the right values don't seem to change a bit (I'm talking about the shunt feedback, in this case R9). I don't know if I should correct some things. Even ended up using MPSA58 for the first three stages. Is like to know if I should use more correct values but as long as it sounds (and keeps sounding good), I think that you should follow your ears as I did.

[thermionix]

Hey! That thing you did with the pots and the jacks seems awesome!

Thanks, definitely inspired by other people's setups I've seen here.  I already had the aluminum angle pieces so it was just a matter of drilling some holes.  Makes it much easier to tote the breadboard around between the workbench and amp.

I think that you should follow your ears as I did.

That's what I'm thinking.  I still might keep track of which transistor is in which position, just in case I've got a "happy accident" that won't sound as good in a different order.  That's really why I asked about it.  It sounds good to me, but I'm no Big Muff connoisseur.  Maybe it's even better with different transistors or gains?  I'd rather not use sockets, if I know I'm good to go.

[stringsthings]

My only real departure was that I used 2N5088s.  Three of them had hFEs around 445 and the fourth about 535.  No I don't remember where I put the high one.  I didn't know if this circuit was picky about hFEs or would need resistor values tweaked to bias properly......

So did I get lucky?  Or is this circuit not really picky about transistors and hFE?  I didn't check any voltages (nothing to compare them to) but it really doesn't sound like any bias adjustment is needed.  Is there something more to be had by tracking down the "correct" transistor types, or should I just build it as it is?

There are others who know more about the subject, but I recall reading about the BMP and it's transistors.  The choice of transistors in the circuit is not critical,
as long as the hfe is high enough.  There are many choices that work equally well, as far as the circuit is concerned.  2N3904, 2N5088, 2N5089, and their BC### equivalents
are just some of the more commonly available choices out there.  Back in the production days of the original BMP's, EHX used the cheapest available transistors that would work
in the circuit. 

[DeusM]

There are others who know more about the subject, but I recall reading about the BMP and it's transistors.  The choice of transistors in the circuit is not critical,
as long as the hfe is high enough.

Definitely. I'm not an expert neither, but I read the same thing and also tried different transistors. They don't make too much of a difference, specialy in the last stages where they only interact with the tone and the output volume, but you can get the same results (and even more) by changing other components. I don't think that it won't sound as good if you arrange them in different order, specially considering you are using all of the same type (I think you mentioned that, can't find the quote). But, hey, I'll keep track of the order too just to make sure I'll get the same thing I head when I was testing it.

Put the wah in front and that's pretty awesome too (I have a FoxRox type output buffer in the wah so maybe that's a factor).  Singing, sustaining lead lines.  Maybe I'm a BMP fan after all.

I didn't know neither untill I made one 

[thermionix]

The choice of transistors in the circuit is not critical,
as long as the hfe is high enough.

Thanks, that's what I was suspecting.  Just stuck in random transistors and it sounded right.  Played it more today and I don't think I want to change anything.