Why does a Tone Bender MkII sounds good? half a cent analysis...

[PRR]

> i'd stick 'em in the club's fridge or freezer for a bit.

Reminds me of a very old story. When Ampex went to the Big Show (AES? NAB?) to introduce their first prototype tape recorder, something got loose inside the head, and crapped-out when the room or deck got hot. They left a bag of bar ice on the heads, and took several firm orders based on the story that they could make it work without ice, someday.

[Steben]

Uhm..... this circuit is used as base for silicon version as well.... 
Just saying ..... biasing ..... less thermal influence ..... 

My favourite fuzz face is silicon though. I think I am biased. Lol pun intended.

[teemuk]

It would be interesting to see how they tackle the "leakage bias" of the first stage with silicon devices. Not that it's a sane design by a long shot.   

[Steben]

It would be interesting to see how they tackle the "leakage bias" of the first stage with silicon devices. Not that it's a sane design by a long shot.   

Probably a bleed resistor from collector to base.

[Greenwichpaul]

This circuit is debated often and we have had huge amounts of great information over the years.

But one quirk I've rarely seen discussed is the 100k resistor between the emitter of Q3 and the base of Q2. Its shown on Steben's OP and, irrc, the fuzzcentral circuit diagram - but as far as I can see isn't on most vero layouts, for instance Electric Warriors . As far as I've read, it's a negative feedback resistor that tames the gain when the attack is set low.

Is it like the negtive feedback i amps where it spills over to distortion more quickly but is smoother up to that point? Has anyone experimented with different values ?

[FSFX]

This circuit is debated often and we have had huge amounts of great information over the years.
But one quirk I've rarely seen discussed is the 100k resistor between the emitter of Q3 and the base of Q2.

This whole biasing arrangement can be traced back to an article by an engineer called J. Somerset Murray in the May 1957 edition of the magazine Electronic & Radio Engineer entitled 'Transistor Bias Stabilisation'.
That design was later adopted in the design of a tape preamp and published by P. F. Ridler entitled 'Transistor Tape Preamplifier' the following year, 1958, in the December edition of the UK magazine Wireless World.

All Tonebender and FuzzFace circuits are just a derivation of that.

[pinkjimiphoton]

It would be interesting to see how they tackle the "leakage bias" of the first stage with silicon devices. Not that it's a sane design by a long shot.   

Probably a bleed resistor from collector to base.

reverse biased ge diode, the idea was the diode would compensate for the ge q's leakage. britface mod it was called. well... part of it. i have it archived somewhere.

kinda works...if the temps aren't to extreme

[PRR]

... J. Somerset Murray in the May 1957 edition of the magazine Electronics & Radio Engineer entitled 'Transistor Bias Stabilisation'.

(no 's' in magazine title)
https://worldradiohistory.com/UK/Experimental-Wireless/50s/Electronic-&-Radio-Engineer-1957-05.pdf
PDF page 31 (magazine page 151)

https://worldwide.espacenet.com/patent/search/family/010336677/publication/GB809207A?q=pn%3DGB809207A

[FSFX]

(no 's' in magazine title)

I suppose I am allowed a typo now and again like everyone else.

Corrected my original comment. Thanks for adding the links. I would have done it had I really thought people were that interested but most just seem to think that guitar players and their mates designed or invented these things and never attribute the designs to the true inventors.

[PRR]

I noted the spelling because Google refused to find it at first, and I know Rob and several others here collect such trivia.

I have wondered where this hookup comes from.

It is in GE Transistor Manual 1960 pg 58, also the 3rd edition <1958?  GE does not analyze or attribute the idea.

I have a small pile of older phono preamps but it does not show there until the GE. A lot of terrible schemes existed those days.

It is not in RCA Transistors I.

[FSFX]

It is in GE Transistor Manual 1960 pg 58, also the 3rd edition <1958?  GE does not analyze or attribute the idea.

Similarly it is in the 1960 Mullard Transistor Reference Manual

https://nvhrbiblio.nl/biblio/boek/Mullard%20-%20Reference%20Manual%20of%20Transistor%20Circuits%201960.pdf

[PRR]

Murray's patent in USPO style:
https://patents.google.com/patent/US2959741
This seems to try to cover too many variants?

IAC, the bibliography looks promising:

Shea 1953 especially. (I may know where mine is.)

Owens: https://worldradiohistory.com/Archive-Radio-Electronics/50s/1956/Radio-Electronics-1956-09.pdf
I don't see the FF bias stabilization.
But the little girl on pg 2 is worth the price.

Lowry:
https://worldradiohistory.com/Archive-Radio-News/50s/Radio-News-1956-11-R.pdf
FF bias stabilization at V4 V5.
Page 64 has an excellent essay on audio tubes(!).

[antonis]

Owens: https://worldradiohistory.com/Archive-Radio-Electronics/50s/1956/Radio-Electronics-1956-09.pdf
But the little girl on pg 2 is worth the price.

I presume she should be a spooky old lady nowdays..

[FSFX]

Lowry:
https://worldradiohistory.com/Archive-Radio-News/50s/Radio-News-1956-11-R.pdf
FF bias stabilization at V4 V5.

Thank you for finding that. So it predates Murray.
So this looks like it could actually be the first ever implementation of the type of circuit that got used for the Tone Bender and fuzz Face?

[Electric Warrior]

But one quirk I've rarely seen discussed is the 100k resistor between the emitter of Q3 and the base of Q2. Its shown on Steben's OP and, irrc, the fuzzcentral circuit diagram - but as far as I can see isn't on most vero layouts, for instance Electric Warriors .

That would be a stupid mistake - and it's not a mistake I can recall making. Where did you find that layout?
The MKII always had a 100k feedback resistor.

[Steben]

Hi Steben,

Nice analysis! Do you also have a graph for the resulting frequency response hitting the drive stage (centered at 300 to 500 Hz) ? That would be nice stuff for people trying to emulate sounds with a wholly different schematic. For example:

I recently made an opamp schem with three inductors in the feedback loop of the first stage that allows me to adjust what frequencies hit the drive stage. Would be interested to try a tonebenderish frequency response as well. At the moment the inductors are centered at 300 hz, 1khz and 3khz. I can see what is happening in a ltspice Sim of my schematic.

Thanks in advance, Hans

I kinda skipped this remark. Yet, what I woud like to add is the change of character once you swap the input stage.
You will loose the classic volume roll off effect on the guitar. We ALL love the clarity one gets when backing off the volume no?
AH, guitar electronics.... full of paradoxes. We need high input impedance except when we need low impedance.

[Fancy Lime]

Lowry:
https://worldradiohistory.com/Archive-Radio-News/50s/Radio-News-1956-11-R.pdf
FF bias stabilization at V4 V5.

Thank you for finding that. So it predates Murray.
So this looks like it could actually be the first ever implementation of the type of circuit that got used for the Tone Bender and fuzz Face?

Also note the tone control arrangement that is similar to, but well pre-dates that of James (1949) and Baxandall (1952).

Sorry if I'm being dense but why does the to e control from 1956 pre-date 1949 or 1952?

[FSFX]

Sorry if I'm being dense but why does the to e control from 1956 pre-date 1949 or 1952?

Sorry, just got a bit too involved in looking at that circuit and was thinking 10 years off. That's what happens when you get to my age and have a few drinks at Xmas. It is easy to do when looking at early electronics as so much development took place between 1940 and 1960. Anyway, it is a bit different as it has swopped input and output of James.

Regardless of that, isn't it about time that DIY guitar pedal builders were informed that most of what they build was invented by engineers many years before some guys in the basement of a music shop just took an existing circuit and blasted it with a lot more input signal than was originally intended and then claimed it as their own.

[PRR]

....Shea 1953 especially. (I may know where mine is.)

No.

But it is on Archive.org

Principles of transistor circuits. by: Shea, Richard Franklin, 1953
https://archive.org/details/principlesoftran0000shea/mode/2up

You can only 'borrow' for an hour. And you do need to register with Archive.org. I did that years ago and I have not got any extra spam from that. Page 99 has what is often called the Shea Stability Criteria S. The next dozen pages show bias stabilization but not AFAICT the FuzzFace kind.

[PRR]

Lowry:
https://worldradiohistory.com/Archive-Radio-News/50s/Radio-News-1956-11-R.pdf  FF bias stabilization at V4 V5.

...it could actually be the first ever implementation of the type of circuit that got used for the Tone Bender and fuzz Face?
Also note the tone control arrangement that is similar to, but well pre-dates that of James (1949) and Baxandall (1952).

I've learned never to say "first ever". Significant chunks of the iconic Fender 5F6a Bassman were adopted from other brands.

The funny-bit of this early transistor tone control is that, relative to James et al, it is wiper input. Early transistor circuits often did this. (Not quite in honor of Fender Deluxe 5E3, but the Old Men could think both ways.)

FSFX> ..isn't it about time that DIY guitar pedal builders were informed that most of what they build was invented by engineers many years before some guys in the basement of a music shop just took an existing circuit and blasted it

No. Ignorance can be bliss. If they want to credit themselves or other intermediate prophets, let them.