getting a fuzz face to work with buffered pedals

[mr.adambeck]

correct me if I'm wrong, but, if I put something like this http://en.wikipedia.org/wiki/Voltage_divider as the first stage in a fuzz face, would it then work with buffered pedals?  Or am I misunderstanding the problem...  I'm a bit of a noob here! 

[Gus]

It will work with a voltage divider volume as drawn but you are shunting some signal to ground away from the input via the wiper to ground part of the volume pot.
  A series resistor works with the FF type circuit.  The first schematic I saw posted on the web using this was one of the early Fulltone fuzzes the 69 fuzz IIRC.

You can try it both ways.

People often use a pot wired as a variable resistor for 0 to 10K or 0 to 50K etc.

The use of a series input resistor is in a fuzzface article at GEOFEX there is a link to GEOFEX at the top of this page.  Look for "The Technology of the Fuzzface"

[edvard]

Somewhere I saw a particular method using one side of a transformer.
Aha! There it is...

Effects circuit will respond differently to an input from a low impedance signal source such as an op-amp output than when driven directly from a guitar pickup. This can be especially evident with certain types of simple transistor circuits. The classic fuzz face is a good example of a circuit that has a low impedance input which produces a significantly different sound when connected to a guitar pickup than when it is preceded by a buffer or another effects box.
...
As shown here, an inductor, resistor and capacitor are configured to duplicate the inherent pickup components. The primary winding of a small transformer is used as the inductor.

http://www.muzique.com/lab/pickups.htm

[mr.adambeck]

Does a series resistor also work in other fuzzes with the same problem?  Or is it specific to the fuzz face?

thnx

[edvard]

I would say it should work for any fuzz in which loading your pickups is fundamental to it's operation.
I'd recommend building it into a small box (it doesn't need batteries) and plug it into a few things.

*edvard goes hunting for an empty tuna can. 

[petemoore]

  The interaction of the FF input with the PU's and thier volume control[s offers a variety of sounds and control other Distorter fuzzes can't offer.
  That variety is lost [or changed] when the input is other than a passive pickup, this makes the FF interaction with other active sources an 'if you like it, use it'...it tends a bit more toward Tonebender sound, or harsher, but doesn't tend to clean up at the guitar volume control.
  I'm ~always using <90% volume when the FF is on, and keep telling myself I'd like a resistor which mimics this setting when the control is slapped to CW stop, that last 10% isn't anything I ever really use or need anyway.
 

[RedHouse]

...A series resistor works with the FF type circuit....

Works well in fact.

Try in the 1K -to- 20K range.

[BAARON]

Or you could build a "Fox Rox wah retrofit" buffer to put on the input of your fuzz, rather than at the output of a wah... That would work too.  You can find the schematic for it at the "other site" for sure.

[wavley]

I just started tinkering with Jack Orman's pickup simulator in my fuzz face last night and I'm getting really nice results, I'm still tuning things but it's very promising.

[brett]

Hi
IMO series resistances don't emulate pickups well because they lack the capacitive and inductive characteristics necessary for that lovely FF "bloom".  Highs and other tonal features emerge with a a sustained note from a pickup straight into a FF (as well as the volume bloom, which is all you get with series resistance).  Therefore, I like a coupling transformer.  It should have an output impedance similar to a pickup (ie about 15k) and lowish resistance. 

Someone around here will know the resistance, capacitance and inductance of different pickups.  Matching all 3 parameters in your transformer will give best results.

good luck

[wavley]

Here is a link to Jack Orman's article on the subject I'm pretty sure he hangs out here so you might be able to ask him directly about it.  http://www.muzique.com/lab/pickups.htm

[brett]

Thanks for the link.  All good stuff.  If I were to build Jack's circuit, I'd have a switch to choose between 330pF and 660pF.  Modern pickups and cables might total 330pF, but old cables sometimes had 100pF per foot, so the pickup and cable capacitance must have been around 1000pF for many setups(!).

[wavley]

Thanks for the link.  All good stuff.  If I were to build Jack's circuit, I'd have a switch to choose between 330pF and 660pF.  Modern pickups and cables might total 330pF, but old cables sometimes had 100pF per foot, so the pickup and cable capacitance must have been around 1000pF for many setups(!).

Over the last couple of days I've been tinkering with this circuit's values to adjust to my taste and I've been getting really great results with it, it really is a great jumping off point.  I use a different transformer, the triad magnetics TY-141P, it's about a dollar more than the xicon one but has a wider frequency response

[R O Tiree]

IIRC, a "vintage" Strat pickup should be about 2.5H, 6k winding resistance and have a resonant peak at around 3kHz or so. Both the Xicon transformer in Jack Orman's article that edvard and wavley linked to and the Triad Magnetics series only have an impedance quoted in ohms in their datasheets. It doesn't say at what frequency they measured this impedance, but the 42TL019 and the TY-141P are both quoted at 10k impedance and there are references to "1.0kHz" elsewhere in the specs, so I'm assuming that they measured it at that frequency.

Unless I'm missing a trick, that comes out at 10000/(2*pi*1000) = about 1.5H. If that is so, then the TY-144P might be a better choice, as that comes out at 2.5H almost exactly, using the same calculation and assumption as to frequency. Put that in series with a 4k7 or so (10k trim pot?) and then we're close?

Maybe we could put a really transparent buffer as an input stage so we have a known output impedance from that buffer. If I'm going along the right lines, then we can possibly assume that this can be represented as:

A voltage source (from out of the input buffer)

"Winding resistance" = output impedance from the buffer + TXfmr winding resistance + trim pot = 6k

Coil inductance = 2.5H

As Jack says in his article, the parasitic capacitance inherent in the pickup is small, so perhaps it can be ignored?

Of course, if any of my assumptions are out to lunch, then more thinking is required...

[R O Tiree]

Oops - we still need a cap to ground (as per the diagram showing the "basic representation" in Jack's article, at the top of the page) so we get the 3kHz resonant peak. 1nF seems to do the trick in a SPICE simulation. As stated elsewhere, smaller values will raise the resonant frequency and vice versa.

Add the Tone and Vol components from Jack's update from 2006 at the end of his article...

It was getting late when I posted previously and, after sleeping on it, I knew as soon as I woke up that I'd forgotten the peak. The subconscious had clearly been chuntering away while I was in the Land of Nod

The other thing to do is to ensure that the buffer has a bi-polar power supply, so Vref is truly "signal ground" instead of the "virtual ground" that we habitually use in stomp-boxes - we don't want to have to put a DC blocking cap in there, because that might mess with the resonant frequency and, if we didn't have a cap, there'd be one he!! of a BANG whenever we engaged it .

[R O Tiree]

bump... Question for R.G., Mark H, etc - Am I way off base, here, or perhaps I'm making it too complex?

[earthtonesaudio]

Maybe this:
Add a low-value (<100 ohms) resistor between Q1's emitter and GND.
Add a separate (stereo) input jack, labeled "buffered input."
When you plug into this input, the sleeve/ring connection shorts the "normal input" cap to ground through some low/medium resistor, and the tip of this connection goes through a cap to the top of the newly added emitter resistor.
Total parts added: 4 including the extra jack.

...But, other than the output being inverted compared to the "buffered input," I have no clue what this would sound like.