21st Century Big Muff

roseblood11 · Post by **roseblood11** » 05 Dec 2010, 09:57

Dirk_Hendrik wrote:Other than that, what's the reason for the series-connection of those 1n and 10n caps?

Because buying large quantities of one size is cheaper, I guess...

Has anyone already made a layout?

MicMicMan · Post by **MicMicMan** » 05 Dec 2010, 12:52

Dirk_Hendrik wrote:Thus the question remains, why is a gain control called "level"? (while the only reason it will suggest level is because that tonestage gives such an attenuation that with a make up gain of 2 it will still suggest being turned all the way down)

Oh

perhaps I should pay attention to the poster's nickname

I suppose it's to fit the original big-muff controls, or stay somewhat close to.

mictester · Post by **mictester** » 05 Dec 2010, 13:07

roseblood11 wrote:
Dirk_Hendrik wrote:Other than that, what's the reason for the series-connection of those 1n and 10n caps?

Because buying large quantities of one size is cheaper, I guess...

Has anyone already made a layout?

Correct about the component choices! I always choose to repeat the same few values throughout a circuit - when you're making a batch of them, it's a lot cheaper.

I've got layouts here (Vero and PCB) which I'll post when I've converted them into readable form.

Dirk_Hendrik · Post by **Dirk_Hendrik** » 05 Dec 2010, 20:03

....
but to publish a circuit as such...?

mictester · Post by **mictester** » 05 Dec 2010, 22:51

Dirk_Hendrik wrote:....
but to publish a circuit as such...?

Why not? If you want to use 4n7 instead of two 10n in series, feel free. However, it's much cheaper to stock large numbers of a smaller range of components.

I don't stock (for example) 30k resistors, but have loads of 33k. I needed 30k for a potential divider (the other values worked out to more standard values) so I used 33k // 330k which worked fine, and didn't take up much more board space. I mostly just stock the E12 values.

By the way - try the "James" passive tone control. The values I gave were right for guitar (double the capacitors for bass). The range of control is remarkable (try simulating it), and you can get the "classic" scooped mids, extreme treble boost , woolly bassiness, and even a flat response. It's one of the best tone controls I've ever used, despite being lossy.

DrNomis · Post by **DrNomis** » 05 Dec 2010, 23:33

mictester wrote:
Dirk_Hendrik wrote:....
but to publish a circuit as such...?
Why not? If you want to use 4n7 instead of two 10n in series, feel free. However, it's much cheaper to stock large numbers of a smaller range of components.

I don't stock (for example) 30k resistors, but have loads of 33k. I needed 30k for a potential divider (the other values worked out to more standard values) so I used 33k // 330k which worked fine, and didn't take up much more board space. I mostly just stock the E12 values.

By the way - try the "James" passive tone control. The values I gave were right for guitar (double the capacitors for bass). The range of control is remarkable (try simulating it), and you can get the "classic" scooped mids, extreme treble boost , woolly bassiness, and even a flat response. It's one of the best tone controls I've ever used, despite being lossy.

You could probably overcome the lossiness of the James Tone Control by putting a gain stage after it,maybe something like a FET Cascode Mu-Amp circuit as used in the Brown-Sound-In-A-Box,only needs three 10M resistors,a 100N Capacitor,and two N-Ch J-Fets (say a couple of MPF102),and then use appropriate value coupling Caps....

The thing I like about the FET Cascode Mu-Amp is that when you overdrive the circuit,it soft-clips and the corners are quite rounded,plus I read somewhere that it typically has a Frequency Response flat from DC to 1Mhz.....

roseblood11 · Post by **roseblood11** » 06 Dec 2010, 00:27

DrNomis wrote:You could probably overcome the lossiness of the James Tone Control by putting a gain stage after it

A very interesting idea...

irfrench · Post by **irfrench** » 20 Dec 2010, 22:02

Evening.

Ok so I took the dive into creating PCB layouts.

This seemed complicated enough to start with!

I've attached the schematic, layout and pnp as .pdfs so they'll be to scale.

Mictester (or anyone!) - please take a look over this to make sure all appears correct.

As I say, it's my first layout so be gentle!

Please note the jumper inline with C15.
Also this is minus the bi-colour LED and Millenium Bypass.

THANKS FOR THE SCHEMATIC MICTESTER!

Cheers,

Ian.

mictester · Post by **mictester** » 21 Dec 2010, 00:22

irfrench wrote:Evening.

Ok so I took the dive into creating PCB layouts. This seemed complicated enough to start with!

I've attached the schematic, layout and pnp as .pdfs so they'll be to scale.

Mictester (or anyone!) - please take a look over this to make sure all appears correct.

As I say, it's my first layout so be gentle!

Please note the jumper in line with C15.
Also this is minus the bi-colour LED and Millenium Bypass.

THANKS FOR THE SCHEMATIC MICTESTER!

Cheers,

Ian.

You're welcome, Ian. You might want to have the option to break a connection to the 10n in the input stage - you might also want to be able to change it. It looks mostly OK so far, and I'll keep checking it for you. Also - think about another board for the bypass indicator!

irfrench · Post by **irfrench** » 21 Dec 2010, 11:17

Mictester - thanks.

I've updated the layout to include a C1 (10nF) lift. Not sure if this is what you meant.

Either way it's included now!

This has been a valuable learning experience in laying out PCB's (unsuprisingly the Bazz Fuzz didn't push my layout construction 'skillz' hard enough

) so thanks. If there is anything I can improve on let me know. I was a bit worried about the size of the board to begin with but I've condensed it down to this.

Critique welcome!

Cheers.
Ian

P.S> I'll have a look at the bi-colour indicator. It's a nice touch to have so if this is correct I'll do a daughterboard.

PPS> Just noticed I have not labelled C2 ... 100nF says I.

mictester · Post by **mictester** » 02 Apr 2013, 20:40

I revisited this circuit over the last few days. It occurred to me that one of the biggest changes that you can make to the clippers in a Big Muff if to vary the collector resistors (try 4k7 or 5k6 all you "low gain" freaks and prepare to be pleasantly surprised!). I had a supply of 100k dual log pots (used in my mixers), and decided to try making the collector resistors for the clippers variable. My first attempt tried using a single pot (I'm cheap like that) but it wasn't terribly good. Going for the dual pot, wired as two variable resistors is amazing - it goes from less than the usual Big Muff tones right up to an uncontrollable screaming monster! It occurred to me to reduce the collector resistors in series with the pots - 6k8 was found to be a good minimum. The pots can be 47k (or 50k) or you can put 100k resistors across them if you find that the maximum gain is useless (I did).

It will be interesting to see how soon this pot configuration turns up in some Boutique version of the BMP!

: Copyright 2013 Mictester for FSB (though there's no such thing as "Copyright"!); BMP21v2.png (11.7 KiB) Viewed 3629 times

Nocentelli · Post by **Nocentelli** » 03 Apr 2013, 20:00

I just so happen to have some 100kB dual-ganged pots on the way to me, I will give this a try. I've messed about with the BMP a bit, but have never played with the collector resistors, just always used 12 or 15k.

V1nce69 · Post by **V1nce69** » 02 Apr 2017, 08:33

mictester wrote:I decided to put an op-amp "wrapper" around the standard BMP clipper stages, and add my favourite tone control for real versatility. As drawn, it sounds really good, but has more top end than a normal BMP because there's no input loading effect. The capacitor in the feedback around the first op-amp stage could be increased in value (I have 47 nF there at the moment), to give a roll off similar to that which the original transistor input stage would cause, but other players like the brighter top end, so I've left the diagram as originally drawn (on a napkin, in a pub!)

This is a "halfway" design - I was going to add electronic switching, and some other modes of operation to the "full" version. You'll see that it can be switched to "Jumbo Tonebender" mode in this version.

In the next version, there will be "Stock Old", "Stock New", "Russian", "Creamy", "Jumbo", "Swollen" and may be other modes too. These will be selected by electronic switching. It also occurred to me that it might be worth allocating two sounds to two foot switches, so that it was easy to switch between a low gain "Russian" mode and a screaming "Creamy" mode.... The possibilities are endless, and I know I'm going to end up building loads of these with preset resistors inside and DIP switches to select sounds, and no external controls except the bypass footswitch!

Here's the circuit schematic as it stands today, and this is a really worthwhile version:
The attachment BMP21.png is no longer available
Enjoy!

mictester wrote:I revisited this circuit over the last few days. It occurred to me that one of the biggest changes that you can make to the clippers in a Big Muff if to vary the collector resistors (try 4k7 or 5k6 all you "low gain" freaks and prepare to be pleasantly surprised!). I had a supply of 100k dual log pots (used in my mixers), and decided to try making the collector resistors for the clippers variable. My first attempt tried using a single pot (I'm cheap like that) but it wasn't terribly good. Going for the dual pot, wired as two variable resistors is amazing - it goes from less than the usual Big Muff tones right up to an uncontrollable screaming monster! It occurred to me to reduce the collector resistors in series with the pots - 6k8 was found to be a good minimum. The pots can be 47k (or 50k) or you can put 100k resistors across them if you find that the maximum gain is useless (I did).

It will be interesting to see how soon this pot configuration turns up in some Boutique version of the BMP!

The attachment BMP21v2.png is no longer available

Hi Mictester,

Randomly searching for some Muff mods, I stumbled on this old post of yours. It looks like something very interesting and not yet done, afaik, to play with the collectors' resistors like this. Thanks for publishing your schematic.

Still something makes me wonder here

: in the clipping sections both 47n capacitors are placed after the diodes in your schematic.
Any reason you did this as in the original schematic they are placed before the diodes (their value define the frequencies that are clipped, usual 100n, 47n in Green Russian)

roseblood11 · Post by **roseblood11** » 02 Apr 2017, 11:58

It doesn't make any difference.

soggybag · Post by **soggybag** » 04 Jul 2022, 18:18

I just built this. Has anyone else built one of these?

The gain pot is not is not very dramatic. I'm using a linear pot, it's all I had on hand.

soggybag · Post by **soggybag** » 04 Jul 2022, 18:29

Here’s a picture of my build.

: 218F69D0-CA82-4208-BDB8-8B28E7EAFE3E.jpeg (144.21 KiB) Viewed 1829 times

: CC13E913-BBE9-44D0-9C19-D69F2FB703D0.jpeg (100.85 KiB) Viewed 1829 times

mictester · Post by **mictester** » 06 Jul 2022, 03:00

You'll find that all the action is bunched up at one end of the pot. Try reducing the 6k8s on the collectors, to 3k3, and remove the 100k bypass resistors. You'll find that it becomes wildly unstable at one extreme setting!

soggybag · Post by **soggybag** » 06 Jul 2022, 16:41

Thanks for the reply Mictester! I'll give this a try! I notice on some settings the gain control doesn't seem to do a lot. Depending on the Sustain setting it can have a larger effect.

Glad to see your'e still around! I did a PCB for your Silicon Tonebender recently and posted it here!

Guroots · Post by **Guroots** » 09 May 2023, 17:41

Hey mictester,

I am really insterested in your work to make my own BM. I just want to understand the aim of the first stage espacially the sound shapping and gain.

So may you explain how it has been designed ?

The gain of this stage is 100/22 = 4,5 where on BM is close to 10 -> I am right about gain calculation ?

100K/10n is a low pass filter with cut off frequency of 159 Hz ?

I do not really understand what is the 22K/10uF : is it High pass filter ? But the cut off ferq has no sence 0,07 Hz..

See you

21st Century Big Muff [documentation]