[slightly o.t.] R.G. inspires Electrical Engineering M.Sc. on the Fuzz Face

[gaussmarkov]

DIGITAL CIRCUIT-LEVEL EMULATION OF
TRANSISTOR-BASED GUITAR DISTORTION EFFECTS
A Thesis
Presented to
The Academic Faculty
By
William E. Overton
In Partial Fulfillment
Of the Requirements for the Degree
Master of Science in Electrical Engineering
Georgia Institute of Technology
May 2006

here's the link:  http://smartech.gatech.edu/bitstream/1853/10566/3/overton_william_e_200605_mast.pdf.pdf

[zjokka]

had a quick scan... especially at the references...
I didn't think I would feel capable of studying again...but still, if this is what it takes to get a degree.. lemme have some...

but it looks like a great PDF online summary!

[gaussmarkov]

when i scanned this document, i found myself looking to see how much R.G.'s stuff was used and how much it was cited.  i think it is important to explain where you found things, even if those sources are not the original sources of the ideas.  the writer should always distinguish their thoughts from borrrowed thoughts so that the community can track ideas.  and it's nice to give credit where credit is due. 

i think section 2 relies more heavily on R.G.'s "Technology of the Fuzz Face" than is explained in the text.  in that section, R.G. gets two explicit references: one for noting that "the two transistors in the Fuzz Face make up a voltage feedback biasing circuit" and one for suggesting additional mods to the Fuzz Face.  yet this section is organized in the same way as R.G.'s article, describing Mayer's mods, Fuller's mods, and then R.G.'s mods.  that looks like a bigger intellectual debt than those two references acknowledge.

in the reference section, there are a bunch of citations but at least one seems to be missing.  R.G.'s circuit for measuring transistor gain with leaky Ge transistors is described, down to the detail of choosing the exact resistor values that make beta proportional to a difference in voltages.  there is no reference to this in the text or the reference section.  this may be a simple idea for electrical engineers, but i think you should still cite your source.  otherwise, as in this case, it looks like the author dreamed up this nifty method.

i did not do an exhaustive read.  these are just the two things that jumped out at me as i scanned through the document.  and, i admit, i don't like them.  it is the responsibility of the author to get such items properly cited.  and these look fairly obvious, at least to me.

[ohm1163058]

So he took the Fuzz Face circuit and simulated it in PSpice to generate a transfer function then made a digital filter in Matlab to process a recorded signal with. Cool, I did something similar last term for home work, we were given the paramiters for a low pass filter and had to design it in Matlab and test it, kinda fun to play with.

[gaussmarkov]

So he took the Fuzz Face circuit and simulated it in PSpice to generate a transfer function then made a digital filter in Matlab to process a recorded signal with. Cool, I did something similar last term for home work, we were given the paramiters for a low pass filter and had to design it in Matlab and test it, kinda fun to play with.

yes, it's nice to see that worked out.  it looks like all the matlab code is in an appendix, too.  which is great.  also, if you look around, i am sure that i saw some of the .wav files posted on line.  i haven't listened to them ... i just looked and found a link to the .wav files:  http://smartech.gatech.edu/handle/1853/10566

[Arno van der Heijden]

Right now, I'm busy doing my Msc. thesis research myself (Mechanical Engineering -> Dynamics & Control).
No offense to anyone, but the research of William E. Overton doesn't seem to be of particular high level (by Msc. standards). He doesn't even refer to one single scientific textbook or journal paper. 

I would expect something better from GeorgiaTech...

[mac]

I posted the math solution to the bias problem of a FF circuit at my site last year, and wrote a public program to calculate the bias resistors. Can I add an EE degree to my physics one with that?     



mac

[stm]

I enjoyed reading the article, however it looks more than an EE graduation work rather than a MSc Thesis.

Apart from the lack of references to scientific publications, it seems most of the ideas were borrowed from existing ideas, and I agree the original sources are not properly recognized.  If the work as a review of the state-of-the-art of the fuzz face circuit were to be complete, it might have included Phillip Bryant's Axis Face (both Si and Ge) as well, and also some article at Pisotones website where the author states that you can get the magic FF tone with transistors with almost any beta if you properly bias BOTH collector resistors in the circuit until you get the magic sound.

This, of course, would have posed an interesting contradiction to one of the statements of the thesis: "Germanium Fuzz Faces are better than Silicon FF's".  Nevertheless the sole fact of doing a "decent" digital modelling of such a circuit is still interesting by itself, more over if you consider tha fact that FF's still require hand selected transistors with special betas.

Finally, this work is mostly theoretical (yes I know there are MATLAB simulations with a few audio samples), however an actual realtime DSP implementation would have been more in accordance to a MSc degree level of difficulty, together with real listening performance testing done by a panel of musicians in order to validate the quality of the digital implementation.

Here in my country you not only need to write your thesis, but also make a publication in a reputed scientific magazine (IEEE) as well.

[zjokka]

I posted the math solution to the bias problem of a FF circuit at my site last year, and wrote a public program to calculate the bias resistors. Can I add an EE degree to my physics one with that?     
mac

http://www.diystompboxes.com/smfforum/index.php?topic=38135.msg269554#msg269554

I didn't know about that: and even a mac version 
great! thanks

I cannot believe why that thread didn't receive one intelligent reply.
zj

[mac]

I posted the math solution to the bias problem of a FF circuit at my site last year, and wrote a public program to calculate the bias resistors. Can I add an EE degree to my physics one with that?     
mac

http://www.diystompboxes.com/smfforum/index.php?topic=38135.msg269554#msg269554

I didn't know about that: and even a mac version 
great! thanks

I cannot believe why that thread didn't receive one intelligent reply.
zj

zjokka,
I hope to finish a new version which will include the effect of leakage. My approach to treat leakage is similar to RG test, ie, ic* = ic + iLeak, but since I am not an EE, I will welcome any help. Maybe I'm in the wrong path here. More:

http://www.diystompboxes.com/smfforum/index.php?topic=45481.0

Hopefully the program will include the bias of Big Muff and voltage divider stages, and will be MacOSX and Win.


mac