A Sonic Wrapper Around A Vintage Pedal
Getting That Vintage Tone -  In Any Sequence
...
last update: March 15, 2021

Copyright 2021 by H. Gragger. All Rights Reserved. All information provided herein is destined for educational and D.I.Y. purposes only. Commercial re-sale, distribution or usage of artwork without explicit written permission of the author is strictly prohibited. The original units  with their associated  trade-names are subject to the copyright of the individual copyright owner. The Author is by no means affiliated with any of those companies. References to trade names are made for educational purposes only. By reading the information provided here you agree to the Terms of Use.
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Index


Sonic Idols
Examining The Vintage Sound Chain - As Far As It Is Known...
Examining The Vintage Sound Chain - Digging Deeper
Emulating The Vintage Sound Chain
Reference

Sonic Idols

Every aspiring musician has an idol, whose sound they admire. It is natural to try to use similar equipment to achieve this tone, while we elegantly choose to ignore the fact that most of the tone is in the hands.

Manufacturers mercilessly exploit this weakness, trying to sell their gear to you, but they are (sometimes) aware that there were more environmental parameters influencing tone, that are not so obvious and that are not always well explored, let alone well documented. Many of those were a fact or just not thought about back then.

Commercial demo videos demonstrating effects units are not fair.
#1: the musician is far better than you.
#2: the effect´s environment is highly optimized unbeknownst to you.
When technology has become a dominating fact in music making,
the musician has to have a certain technical knowledge.

This explains why some amateur people´s YT demo videos sound obviously amateur from a perspective of sound quality. This also explains why „professional“ videos sound so good, so much like the real thing, that you inevitably end up disappointed once you have the box at home. Of course you realize that you also need the rest of the gear they casually show you.
When technology has become a dominating fact in music making, the musician has to have a certain knowledge to shape their tone. Knowledge is power.


"Knowledge is power" 
    - commonsense

Many vintage effects and boutique re-issues (which re-issue the flaws with it) are plagued by impedance matching issues, so that they do not get on well with other effects in a certain sequence, or sound awkward, not as we heard them. This is particularly true for fuzz-face type effects (hereafter: FF), since these were invented very early in the semiconductor history and have been the ancestors of many dirt boxes to come for a long time.

Let´s wind time back to the Sixties.
  • There was a Fender amp, bright, mid deficient. There was a Marshall amp, mid-prominent, (originally) dark. Maybe a Vox, bright too,  to name just the most prominent. Even back then a particular effect would have sounded different into any of them.
  • An effect into an idling tube amp sounds different than into a stack at full throttle.
  • There was a curly cable with unholy capacity killing all treble on the onset.
  • There was high impedance inputs (tubes) and ultra-low impedance inputs (fuzz face). There was weak drive signals on the outputs (high impedance pots).
  • There was all sorts of incompatibilities and instabilities due to impedance mismatches
  • There was little knowledge in a newly arisen technological field. There was non reliable and expensive components
  • There was technical flaws and peculiarities in those components that lead to (today sought of) circuit designs that tried to make the best out of the situation.
  • This all lead to certain attempts of circumvention (like seemingly not-to-be-questioned sequence of effects)  and to a certain sound we are used to.

Nowadays, transistors of very high quality cost next to nothing in amounts. There is evolved amplifiers, technically correct input and drive impedances, low cable capacities and a lot of knowledge.


One would expect that with all that advance in knowledge the sounds of yesteryear should be able to be replicated with ease, while not sacrificing the goods.
But that does not seem to be the case.

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Examining The Vintage Sound Chain - As Far As It Is Known...

Let´s look at a typical vintage sound chain with a fuzz face. Although not all vintage effects use a FF topology, many suffer from low input impedance and high output impedance, so what is said will work on many vintage effects.

In pursuit of the holy tone of yesteryear people seek out unobtainium transistor circuits and make them exactly like the original.

Now this is a problem, because back then, few knew what they did. It is reported from Hendrix, that he went into the music store and tried dozens of units until he found one that sounded right. He had to learn the hard way that those units failed too when the temperature changed.

The intrinsic problems of GE transistors of the time like leakage and temperature instability (I have read that the Russians, who used GE well into the recent decades, had finally cracked the nut and produced units no longer plagued by those issues. But unfortunately, their days were over) were not understood, being too new a technology.

Even if they knew about buffering, two additional transistors in a FF topology would probably have doubled the price of the unit.

So the units were full of compromises, kind of doing what they were expected to within limits.

  • FF input impedance:
A FF thus has very low input impedance (some 8 kOhm, which is easily a factor of 100 smaller than a contemporary effects unit), and with a 500 k output pot a very weak drive. Indeed, they were prone to burst into oscillation with the wrong unit afterwards.
A FF has a current driven input, not voltage. It is therefore very sensitive to its driving impedance, which does change the tone to the dislike of people (to be more precise: not the way they expect, since in this mode they start to behave like other, well accepted units like the Tone Benders).

  • Guitar drive impedance:
A guitar has a weak drive too, and is heavily loaded by a fuzz face, which drives the FF softly.
  • Cable capacity:
Cables had a capacity maybe ten times higher than today´s, which even at the slightest deviation of the volume setting from max would inevitably result in a huge loss of treble (hence the modern treble bleed networks to counteract this…). At max the cable capacity would form a resonance peak in conjunction with the pickup induction, but even at slight deviation from max this would be a normal  low pass without Q peaking. Any parallel resistance would reduce the peak anyways, let alone a heavy load from a FF.

typical vintage soundchainA typical vintage soundchain: (click on the picture to download) So we have:
  • reduced treble content into the FF from a start,  treble decreasing with volume pot setting.
  • Reduced peaking (resonant circuit Q).
  • Altered volume pot behavior (its pot law is changed into super logarithmic with a maximum volume drop upon minimum rotation).
  • In case of another high capacitance cable (as it was common in the old days…) after the FF, additional treble contents removed dependent on the setting of the volume pot.

Together with the inherent problems of the FF´s design like heavy transistor hfe dependency and other flaws a design like that would nowadays probably be discarded at an instant.


"Even though Jimi [Hendrix] made them very successful, the actual design is a complete disaster when it comes to temperature stability and everything else. (...)
It could be best described as a minimum parts circuit, for sure. It wouldn’t be something you’d deliberately go home and design, you know?
"
 

    - Roger Mayer, Roger Mayer Talks Fuzz (Premier Guitar July 20, 2010) [1]

 Well known, FF´s used to be fed into a smoldering tube amp, which will act as a dynamic filter (similar to a multi-band compressor) for harsh frequencies.
  • Loudspeakers. Compression at high volume, overpowered, range-limited drivers.
  • Tube amp output impedance: 8-16 Ohms, yields a resonance boost (low frequency)
But that made the tone. A one-trick pony so to speak. And it better be in the sequence depicted if any effects are to follow.

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Examining The Vintage Sound Chain - Digging Deeper

But wait a moment. This is just the part we know from history, just what meets the eye. We gauge this by the recordings we hear, and the few pictures we see. Let´s take Hendrix, surely the man who made the FF broadly known.

We can definitely hear hints of a FF on the recordings, although some crafty engineers wonder, if what we hear were off-the-shelf units. [2]

But that is where the problem starts. Nowadays Germanium is being touted as the holy grail. It is nevertheless known, that Hendrix (or, rather his technician Roger Mayer) switched to silicon pretty early.  And still Hendrix sounds like Hendrix (note: we do not know what Mayer did to make the silicon version sound more like a germanium version).

Hendrix did by the way play other guitars than Stratocasters, and you would not hear the difference if you did not know. But you certainly do not want to hear that.

Also, what is not repeated like a sermon so often, Mayer knew about the technical background, and he said they used buffers when they tried to circumvent those problems [3]. Hendrix is reported to have used a bass-heavy JTM-45, lateron (probably) Superleads or whatever that were no longer so bass heavy. Just a matter of a different capacitor in the right position. Amps evolved, and they certainly responded to that to keep Jimi´s tone the way he liked it.

He also reportedly used Twins in the studio. Mayer tells us that they used different (low capacity) cables when they they wanted a different effect. He also mentions using buffers. So what other trade secrets did Mayer implement that does not meet the eye readily? He will have his reasons for not telling us all. But this proofs the fact that there was more to it even back then.


So what were those secrets? It does not matter, since it cannot have been much fancy. There was no fancy stuff available at the time, no crafty circuits, so it probably boils down to:
low and high end tailoring and impedance matching.

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Emulating The Vintage Sound Chain

So back to the beginning. Can a FF be made to sound well unconditionally? Absolutely.
  • Try starting to buffer the guitar. Instant gratification with consistent and repeatable control over volume and treble (and bass, as I prefer). Pristine Signal.
Many people will crucify you for this statement, because it has become a sermon, that a buffer into a FF sounds wrong. Read to the end. Remember Hendrix used modified units as Mayer leaked, and notice, the almost religious holy order of „fuzz face first!“ was quickly changed. Look at the pictures [4].
  • Possibly pickup voicing to move the resonance frequency or tame the peaking.
  • Possibly treble tailoring next (guitar tone cap).
  • Impedance matching fuzz face with alleged low impedance predecessor.
  • Possibly treble tailoring afterwards.
  • Possibly low impedance drive (buffer) into the successor (modern units usually have a „behaved“ input impedance anyways, but you never know…).
  • Next: possibly transparent overdrive to emulate what the tube stack does at full throttle, because you may want a fat „wall-of-sound“ tone in your bedroom. The latter is well known, but not the others.
  • Possibly some loudspeaker emulation.
So with all of that, conjuring up the vintage tone should be absolutely possible with a little thoughtfulness (and little money), so let´s think up a modern, versatile arrangement that lets us dial in those tones without sacrificing flexibility.

The method that intuitively comes to mind is using external units (EQ and impedance matching) before and after a FF, an external wrapper pack so to speak. This will be the method of choice for a given (commercial) effect if you don´t want to tinker with it. If you knit yourself, it would be much more practical to incorporate those improvements right into the effect itself, since those
things are usually very basic.

vintage soundchain emulation with
                                  external units Emulation for a vintage soundchain: (click on the picture to download)

Using external units such as a buffer dongle and buffered EQ units before and after the vintage effect makes up a nice wrapper around the vulnerable vintage effect that lets us dial in all vintage tones, while allowing for any desired sequence of effects.

A controlled drive impedance emulates the pickup´s effect into the FF.


I am a strong advocate for guitar buffering. Everybody who has heard their guitar through a buffer has been hooked so far. This delivers a consistent, reliable and repeatable tone into whatever comes afterwards.

However, there maybe some cable capacity inside the guitar necessary (right before the volume pot to avoid increasing treble loss over volume pot range) to tailor the desired tone. You decide upon a certain sound so to speak. This may be the only change you need in your guitar.

A buffer can be an unobtrusive external dongle, so no modification to a guitar is necessary.
This has to come immediately after the guitar, with a lead as short as possible. (This is automatically fulfilled with all wireless systems btw.)

I also like a less drastic treble cut (smaller tone cap, not shown in the picture) and an additional (passive) bass cut, since bass into a distortion unit (particularly vintage) not only changes bass content, but also distortion texture. (link) Having a continuously variable control rather than a series of switchable capacitors lets you dial in subtle shades of distortion. Any loss of bass caused by this (which may not be needed in band context anyways) can be counteracted with EQ afterwards.

Most of the time, the guitar´s treble cut is sufficient so that no further low pass shaping before the subsequent FF is needed (IF the FF is the first effect after guitar...) However, a HF protection input filter should be there mandatory to prevent Radio signals intruding (which drove Jimi nuts at Miami). No unit should ever be released with that (note that some FET buffers have high enough input capacity to take care of that by design…). Such a capacitor does not influence tone in the remotest, and it costs next to nothing. It even did cost very little back then, but they obviously were not aware of the problem initially.

A buffer built right into a FF+s front-end (like the Aion Solaris Germanium Fuzz [5] does it) is a brilliant idea, as long as there is a method to emulate a sort of „current drive“, which can easily be achieved with a series resistor in the order of the pickup´s DC resistance (their complete coil emulation may be unnecessary and may lead to hum intrusion. See my article Pickup Simulation With An Audio Transformer). This will guarantee consistent tone and behavior under all circumstances.

Using a variable series input resistor as many designers use it will allow for distortion shades different to the fuzz control settings by emulating a fully down guitar volume control. A divider may work similar. This restores the guitar´s volume control settings to a more useful range and opens up other creative options without sacrificing anything.

A buffer after the FF cannot do harm, but may not be necessary if a low value volume pot is used. A 50k drive is generally accepted as being sufficient. Note that Jeff Beck changed his volume pots to a lower value for increased treble for that reason. It is not that those things are not known…
Note also that Mayer uses low impedance output buffers on all the „voodoo“ versions of his effects.

As mentioned, post-EQ-ing with some sort of treble cut may be very useful. (BJFE implies cable capacity [6], which I consider a crude measure, trying to stay vintage at all cost). Typically, this will be a treble cut control. A silicon version should take care of HF range at the point of origin, which is directly at the transistors.

As mentioned before, any apparent loss of bass due to input bass shaping can be counteracted at this point, if the situation demands it.

Use any alleged amp simulation like overdrives afterwards to taste, but this certainly will be external (an exception being the Wampler Velvet Fuzz, which ends up being a one-trick pony).

Since those variables encompassing traditional bare FF´s are consistent, it amazes me that those are not put into some flexible wrapper, which innovative people like Atomium Amps ([7] reverting a CSO into a FF) and Joe Gagan in NVN designs made approaches to, allowing you to adapt the FF system (it is a system now) to any sequence or situation.


Thou shalt replicate the virtues, not the flaws.
(aquataur 8,15)

So we have now, for the modern, flexible stomp box system:
  • high impedance fullrange buffer with HF filtering
  • (opt.) Pickup simulation (e.g. series resistor)
  • Pre-Gain: (opt.) variable series resistor or input divider.
  • Pre-EQ: variable bass cut (switchable capacitors, continuously variable input capacity á la Gagan)
  • FF core, possibly with measures to smooth HF range for silicon versions.
  • Post-EQ (bass and treble)
  • optional, but recommended: buffered drive
The original CSO (color sound overdriver) uses a baxandall topology for post-EQ-ing, but the treble control is fairly inefficient.
Atomium Amps made the treble part of the baxandall stack fixed (with slight boost) and used a more efficient „stupidly wo
nderful treble control“ [8] after the make-up gain/buffer stage. This proved very effective. With this setup you should be able to master all situations.
Although Atomium does not like the Gagan bass input control, I do so. This may be covered in a forthcoming issue.
Pre-Gain is crucial for his setup of the fuzz-control maxed, but is very useful for all types of fuzz faces and simple enough.

You can use any type of a more fancy tone control like a BMP style control if you are pushed for space. This will be an improvement, although the BMP stack has its drawbacks.

Output buffers with a volume put afterward are kind of senseless, unless it were low resistance. 50K is generally deemed unproblematic and a good compromise, possibly saving you another active stage.

A system like that will fit any place in a sound chain with pleasing results and will let you replicate the conditions and sounds of yesteryear.


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Reference

[1] Tom Hughes, Roger Mayer Talks Fuzz, Premier Guitar, July 20, 2010
     
https://www.premierguitar.com/articles/Roger_Mayer_Talks_Fuzz
[2] see Björn Juhl´s musings on Moodysounds forum https://moodysounds.se/bjf-kits/
[3] Arbiter Fuzz Face, Michael Dregni, Vintage Guitar Magazine, August 2012
      https://www.vintageguitar.com/16117/arbiter-fuzz-face/
[4] The Ultimate Guide to Jimi Hendrix: Tone, Gear, Effects (Updated 2020), Guitargearfinder September 13, 2020
    
https://guitargearfinder.com/guides/ultimate-guide-jimi-hendrix-tone-gear-effects/

[5] AIONFX: Solaris Germanium Fuzz building documents,  https://aionfx.com/project/solaris-germanium-fuzz/
       and others like the Proteus. Also see EQD eruptor (clone: PCB Mania Volcano device)
[6] Björn Juhl: About cables and the influence they have on outputs of fuzzes and guitar pick ups
[7] Atomium Amps: Let’s talk about fuzz for a minute, (reverting a CSO back to a fuzz)
      https://atomiumamps.tumblr.com/post/157119810141/lets-talk-about-fuzz-for-a-minute-this-is-the,
[8] AMZfx: Stupidly Wonderful Tone Control 2: A Simple Passive Tone Control for Effects Pedals,
      http://www.muzique.com/lab/swtc.htm

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Update History
  • Mar 14, 2021  initial release
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