Blog e página pessoal de Tiago Charters de Azevedo (Blog and personal webpage of Tiago Charters de Azevedo)

Setar geometric construction


Simple geometry using an real setar.
Simple geometry using an real setar.
Geometric construction.
Geometric construction.
Geometric construction (more detail).
Geometric construction (more detail).
Geometric construction (more detail).
Geometric construction (more detail).


Etiquetas/Tags: setar, geometry

Romanillos guitar geometry



Etiquetas/Tags: Romanillos, guitar, geometry

Various instruments geometry


Etiquetas/Tags: math, music, instruments




Setar r is one of the Iranian plectrum-type string instruments, which is plucked by the player's forefinger's nail. Sehtar or Setouyeh is a three-cord instrument, which was converted into a four-cord instrument under the reign of the Qajars. It is, in general, an ancient and gnostic instrument usually played at the gathering of dervishes most often held at Khaneqahs (monasteries or houses of dervishes), which makes the listener feel high. In view of its special vocal features, Sehtar is known as the instrument appealing to the listener's heart and the Iranian musical instrument ranking second among Iranian musicians. It is simpler than other instruments both in appearance and the method of playing. Its low tune, compactness and tenderness are the main reason for its great appeal in the course of the past centuries. It is made in various types and sizes including large, small, flat and zir-abai. Tars are made in two methods: Turkish (in many pieces) and scraped kasdani (in one piece). Sehtar is generally made from berry wood, while at some occasions that of pear or walnut tree might be used as well. Its bowel is a pear-shaped semi-sphere, while its thin and delicate handle is tenderer than that of other instruments. (http://www.orientalinstruments.com/oriental/joomla/index.php?option=com_content&view=article&id=49)

(click to enlarge)

Etiquetas/Tags: Setar, Sehtar



Ref.: http://farabisoft.com/Pages/FarabiSchool/InstrumentsDetails.aspx?lang=en&PID=4&SID=31

Etiquetas/Tags: instrument, musica, iran

An Fet/Bipolar voltmeter


Etiquetas/Tags: electronics, diy, voltmeter

Favorite way to clip a signal?


Etiquetas/Tags: clip, signal

Audio Kitchen Little Chopper


Este é dos meus preferidos! Gosto muito da abordagem da construção do amplificador, especialmente o último botão "Power". Controla o bias do estágio de output. Very clever!

Etiquetas/Tags: guitar, amplifier, class a

On water



Não custa fazer a experiência.

Etiquetas/Tags: flop, water, experiment

Symmetry breaking -- Claiming directionality of cables


Symmetry breaking describes a phenomenon where (infinitesimally) small fluctuations acting on a system which is crossing a critical point decide the system's fate, by determining which branch of a cable is plugged into the guitar. To an outside observer unaware of this, the choice will appear arbitrary. This process is called symmetry "breaking", because such transitions usually bring the system from a symmetric state into one definite state. Symmetry breaking is supposed to play a major role in guitar playing[clarification needed].

Etiquetas/Tags: guitar, cable, amplifier

Moondog - The Viking of 6th Avenue



Etiquetas/Tags: speakers, audio

Burning Speaker Amplifier


Have fun!

Etiquetas/Tags: amplifier, guitar, preamp, mosfet, IRF

Hyperdrive amplifier


Have fun!

Etiquetas/Tags: amplifier, guitar, preamp, mosfet, IRF

Bad Flu Blues


Can we do this using solid state devices? ;)

Etiquetas/Tags: guitar, dumble, solid state, question, tube, amplifier

Guitar speaker cab with a Kevlar cone speaker


I've build a simple cab for a cheap Skytronic Kevlar cone speaker

Skytronic: 5 1/4'' Kevlar cone speaker
Skytronic: 5 1/4'' Kevlar cone speaker

Although it sounded ok, a bit of math would benefit the sound that it produces. Note that this is not a typical guitar speaker. In what follows I will try to convince you that regular speakers (namely woofers) can be used to make great guitar cabs!

The specs for this speaker are these.

Item No. 902.420
Re 7
Le ?
Fs 55
Qms 5
Qes .44
Qts .41
Sd(cm2) 81
Vas(L) 5.6
Cms(uM/N) 605
Mms(g) 14.5
B x L 8.7
SPL_1W/1m2 84.8
Prms(W) 100
Pmax(W) 200
Xmax 3.5

The quantity that really one should look, because I'm doing a synthesis, is total Q; this value is a combination of the properties of the speaker taken conjointly with the cab.

The best reference to learn how to design speaker enclosures is still the papers by Richard H. Small and Neville Thiele. So the relevant equations are the electrical Q (taken into account the output impedance of the amplifier latex2png equation, latex2png equation the total Qts, combines Qe and Qms, like two resistors in parallel latex2png equation and the volume of the enclosure latex2png equation where latex2png equation is the total Q of the enclosure and speaker system.

The predicted Fc frequency of the system is then latex2png equation

The design process can be simplified by using a dimensionless parameter latex2png equation called the system compliance ratio, that can be written as latex2png equation

A simple GNU/Octave script will allow us to get a more clear view about the choices we are about to make.



Qts=1./(1./Qe + 1/Qms)


ylabel('F (Hz)')
title(sprintf('Rg = %i',Rg))


ylabel('Vb (l)')

Before choosing the dimensions of the enclosure let us look at some graphs.

The next figure shows the values of Fc, Qtc and Vb as a function of alpha.

Left:Amplifier output impedance Rg=0, high damping factor (infinite).Right: Amplifier output impedance Rg=8,  damping factor equals 1.
Left:Amplifier output impedance Rg=0, high damping factor (infinite).Right: Amplifier output impedance Rg=8, damping factor equals 1.

The next plot shows the frequency response of a typical high damping output amplifier (not for this particular speaker).

Left plot: Rg=8. Right plot: Rg=0.
Left plot: Rg=8. Right plot: Rg=0.

We see that a non-null output impedance permits the speaker to shine through, and also gives us a clear separation of bass and treble regions. This feature somewhat tames the distortion and gives the a good spectrum that we all like in guitar amplifiers (that can be found in tube/valve guitar amplifiers). This fact is one of the main reasons that a typical solid state hi-fi amplifier is found to sound terrible when fed with a distorted guitar signal.

So I'm aiming at a Rg=8 amplifier and a Fc around 80Hz (low E string), this gives latex2png equation and latex2png equation for latex2png equation which will give a warm and dark tone (for smaller Qtc the Fc will be smaller and although it gives a clearer tone, due to the low Fs of this speaker, the final tone would be somewhat a bit mushy).

(to be continued)

Etiquetas/Tags: DIY, guitar, speaker, kevlar

Voltímetro para electricistas amadores


Etiquetas/Tags: electricidade, DIY

L-Pad attenuator (15W)


Sometimes the simplest thing is the the most useful one! A L-Pad attenuator (15W):

It changes the output response of the amp after the 12 o'clock position, but works nicely.

Etiquetas/Tags: DIY, amplifier, attenuator, guitar



Com projectos interessantes para o DIY: http://www.bloguetronica.com/

Etiquetas/Tags: electrónica, DIY, PT

Tim Escobedo's Circuit Snippets


Etiquetas/Tags: Tribute page to Tim Escobedo's Circuit Snippets

Palavras chave/keywords: página pessoal, blog, vida-exacta

Última actualização/Last updated: 2014-07-29 [09:49]

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