Author Topic: Mini-Muff: mids control vs Presence/Shift control?  (Read 2013 times)

thesameage

  • Electron Doctor
  • *****
  • Posts: 841
  • JR
    • View Profile
Mini-Muff: mids control vs Presence/Shift control?
« on: January 08, 2015, 10:45:49 AM »
I'm working on a pickdropper mini-muff and have been wondering whether to use the built-in mids pot or go for a pharoah/hoof version of the AMZ Presence knob, which seems to be a 25K pot on R19.

Any thoughts on this? Of course, I'll give both a try. But does anyone feel that one is better than the other? Background: I'm "not" going for a scooped mids classic muff sound.

juansolo

  • Electron Doctor
  • *****
  • Posts: 4704
  • John - Wakefield, UK
    • View Profile
    • Juan's Gnomepage
Re: Mini-Muff: mids control vs Presence/Shift control?
« Reply #1 on: January 08, 2015, 01:41:51 PM »
They both act differently. The AMZ control also has an effect on the bass and treble also. It's small, but it's there and it's noticeable. Put the values into Duncan's tone stack calculator to see what it does.

The Pharaoh/Hoof control doesn't work quite correctly if you use a 25k pot. You would think that all the way down it'd just give you the base cap, but the pot is never out of the circuit and affects the cap. So it's not what you get at all. Go with a C500K instead and you will get the response you want. The main advantage to the Shape knob over the AMZ control is that it only affects the mids.

Again, The Duncan Tone Stack Calculator is KEY to adding either of these controls effectively to get the cap/resistor values right.
« Last Edit: January 08, 2015, 01:46:10 PM by juansolo »
Gnomepage - DIY effects library & stuff in the Stompage bit
I excite very large doom for days - playpunk

thesameage

  • Electron Doctor
  • *****
  • Posts: 841
  • JR
    • View Profile
Re: Mini-Muff: mids control vs Presence/Shift control?
« Reply #2 on: January 08, 2015, 02:01:31 PM »
The main advantage to the Shape knob over the AMZ control is that it only affects the mids.

So, why do they use the AMZ control over a mids control?

juansolo

  • Electron Doctor
  • *****
  • Posts: 4704
  • John - Wakefield, UK
    • View Profile
    • Juan's Gnomepage
Re: Mini-Muff: mids control vs Presence/Shift control?
« Reply #3 on: January 08, 2015, 02:51:22 PM »
Easier to implement I would assume. It's simply an in-line add in and getting it to do what you want is simple as it's essentially just two resistors in series. The presence/shape control took some experimentation (as the maths involved in working out what it's doing is scary) and almost a complete abandoning of the Ultrastoner II project before we got it working correctly. BUT, now we know how it works (or doesn't work in the case of the Pharaoh/Hoof), it's dead easy to work out what it's up to.

Edit: Perfect example for you

The yellow traces are the AMZ control, the green traces are the shape control. The three traces are pot all the way up, centred and all the way down. You'll notice from the green shape trace that the bass stays nigh on the same no matter adn it only starts to roll off the highs at the extreme mid cut setting. Whereas with the AMZ control with the pot down you also lose bass and treble. With the pot all the way up you actually get a bass boost though the treble stays mostly put.

To my ears the shape control when implemented right sounds nicer. But as I say, it's much easier to add the AMZ control.
« Last Edit: January 08, 2015, 03:25:59 PM by juansolo »
Gnomepage - DIY effects library & stuff in the Stompage bit
I excite very large doom for days - playpunk

thesameage

  • Electron Doctor
  • *****
  • Posts: 841
  • JR
    • View Profile
Re: Mini-Muff: mids control vs Presence/Shift control?
« Reply #4 on: January 08, 2015, 03:48:16 PM »
Thanks for taking a look at this!

Overall goal for this pedal: Have a muff for bass guitar (it will have a blend) that is very versatile and good mix of low end, has good mids that cuts through the mix and can be used as both a warm overdrive and a fuzz pedal. As far as clipping goes, Id like  the fuzz to be smooth and useable in a mix without being as loud and aggressive as the Sabertooth or Brassmaster, but a few harder clipping settings would be nice--I'd like to give LED's a try.

Background: I have all of the parts for a Green Russian, so Im starting with that as my base.  I had a Pharaoh clone that I loved for its versatility, but did not care for the silicon or no diodes clipping or the hi/lo switch. I gave it to my guitar player. That said, Im looking to start with the russian and want to try out some ideas from the hoof and pharaoh. Maybe try to use the Hoof Focus knob, which creates a variable input resistor and looking at making it more germanium and will experiment with the Hoof germanium transistors but will give their LED clipping a try as well.

I have the board populated with the more common values and plan to socket the following tonight and experiment with them (between the Russian and Pharaoh values): R18, R19, C6, C9, R2, R5, C10, C11, C3


juansolo

  • Electron Doctor
  • *****
  • Posts: 4704
  • John - Wakefield, UK
    • View Profile
    • Juan's Gnomepage
Re: Mini-Muff: mids control vs Presence/Shift control?
« Reply #5 on: January 08, 2015, 04:43:37 PM »
Use doubled up germanium diodes in the 2nd clipping stage if you want smooth clipping (without too much volume loss). LEDs are about the most aggressive clipping you can get.

If you want it to cut you'll need to reduce the mid scoop dramatically. Again, Duncan's Tone stack calculator... Down load it, experiment with settings until you've got what you want, then build it and see what it does.

There is an excellent article out there in the interweb somewhere (you'll have to google as I can't remember where) that tells you what all the parts of a muff actually do. It's a ludicrously versatile and tolerant circuit. But start with the above and move on from there.
Gnomepage - DIY effects library & stuff in the Stompage bit
I excite very large doom for days - playpunk

thesameage

  • Electron Doctor
  • *****
  • Posts: 841
  • JR
    • View Profile
Re: Mini-Muff: mids control vs Presence/Shift control?
« Reply #6 on: January 08, 2015, 06:16:21 PM »
All good info... thanks!

I have to figure out how to run the tone stack calculator on a mac. Don't have pc access right now and can't dl it to parallels at work. I'll figure that out, though.

I gave you the short version above. I actually have the whole circuit mapped out as to what caps and resistors do what so that I'll know what I'm tinkering with.

thesameage

  • Electron Doctor
  • *****
  • Posts: 841
  • JR
    • View Profile
Re: Mini-Muff: mids control vs Presence/Shift control?
« Reply #7 on: January 09, 2015, 08:19:16 AM »
The Pharaoh/Hoof control doesn't work quite correctly if you use a 25k pot. You would think that all the way down it'd just give you the base cap, but the pot is never out of the circuit and affects the cap. So it's not what you get at all. Go with a C500K instead and you will get the response you want. The main advantage to the Shape knob over the AMZ control is that it only affects the mids.

This was helpful because it explains some of the different Pharoah values. From here: http://www.bigmuffpage.com/Big_Muff_Pi_versions_schematics_part4.html

A 25k pot was added to the tone stage in place of the R8 low pass resistor, yet another variant on the AMZ tone/presence control, allowing a boost to the highs. The low pass cap at C8 was enlarged to 2.2F to balance the low pass filtering. The large cap and resistor at C9 and R5 on the high pass sides allow for less mid range scoop than the "47" Ram's Head.