help| knowledge.

[itai12]

Hi ,

sup ?
i am kind of new to this topic,.
alrdy did once a amp project 1w .
i been read lot about it so i got som basic knowledge. [like value of resistor\cap , um +- radial axdial, how to wire footswitch, read scehmatic. u know basic things to build pedals\amp]
but i want to learn what each part do , like how the resistor at LPB-1 help the sound or what those resistor doing.
where can i learn more about this or how?


rlly tnx

itai .

[Thecomedian]

I want to make sure that I understand clearly.

You are new to this forum.

You have done a 1 watt project amp before.

You want to know what parts do inside amplifiers, and how each part affects the sounds or output.



try a search engine, and look for websites that talk about transistors, amplifiers, and AC current.

The Ideal amplifier transforms the voltage from small to large, with no distortion or coloring of sound. Pure amplification is the ideal. Sound coloring is an artifact of simpler amplifier builds or intentional choices with components.

Getting simulators and trying the values yourself is the second quickest way to learn. The first would be having some frequency selective meter to check voltages as you go through them all, but that is less useful than having a true oscilloscope.

Someone posted a good simulator that can show frequency values all side by side, somewhere around here. Just try searching the internet.

[J0K3RX]

google is your friend... 

[oskar]

http://homepage.ntlworld.com/g.knott/index1.htm

[Thecomedian]

maybe it's just me, but the part where they say painting a  heat sink black will increase radiation sounds fishy.

Where's their reasoning or evidence? Black will absorb more energy from light spectrums, which can only be used for adding heat using, most simply and efficiently, the sun, but I have no idea why it would allow radiation of heat from an object which is generating heat.

[R.G.]

maybe it's just me, but the part where they say painting a  heat sink black will increase radiation sounds fishy.

It is an old comment that contains some truth. It's only not true on a technicality.

Where's their reasoning or evidence? Black will absorb more energy from light spectrums, which can only be used for adding heat using, most simply and efficiently, the sun, but I have no idea why it would allow radiation of heat from an object which is generating heat.

The details and reasoning require some physics and math, but a surface that is a "black body" will in fact both absorb and radiate heat more efficiently than a surface that is non-black. The worst surfaces for radiation, just like for absorption of incoming heat, are shiny reflective surfaces.

In a vacuum, a surface that is black in the infrared spectrum is the best practical radiator, since broad-spectrum "black" is hard to get. Most organic paints, regardless of color, are effectively black in the infrared, so they qualify as "black" for radiation purposes. Organic paint heavily loaded with carbon soot might be somewhat better. A shiny surface in a vacuum will neither emit nor absorb nearly as well.

The reason vacuum matters is that radiation is not as efficient for heat transfer as convection. In air, the air gets heated, rises, and sucks new, cool air in. Moving air across a heated surface moves a lot more heat per unit area than radiation gives you. In air,  you want a "black" (and hence absorptive/radiative) surface that does not have the heat-flow resistance of a layer of paint. This is one reason that all aluminum heat sinks designed to work in natural convection instead of forced air mode are black anodized. The black anodized layer is much thinner than paint, has much lower thermal resistance than a layer of paint, and is made black by soaking black dyes into the coating, which helps radiation without incurring the resistance to flow of a layer of paint.

So - yeah painting a surface black is a definite "maybe" in air, but is effective in vacuum.

[PRR]

> Black will absorb more energy from light

It's reversible. True-Black radiates light (infrared) better.

> radiation is not as efficient for heat transfer as convection

Radiation improves as _3rd_Power_ of temperature difference; convection not so fast.

If it "glows" in a dark room, radiation is probably dominating. Soldering-irons and vacuum tube plates are on-the-edge of where radiation "typically" dominates the heat transfer.

For practical size/shape objects at "reasonable" temperatures (Silicon don't leak much), convection always dominates.

(As you say: assuming we got air. I don't work in places that don't have air; I don't even like being above 10,000 feet.)

And FWIW, many-many aluminum heatsinks are silverish (or golden).

I have a suspicion that many are black because it tips-up the *extreme* end of the power vs temperature graph and gives a better spec-sheet number (nevermind that you would rarely want to work that hot). (And sinks are always anodized, black dye is cheap, and black does not show anodize blemishes as much as 'bare' or golden.)

Black radiators are like chicken soup. It won't hurt. Sometimes it helps.

[R.G.]

If it "glows" in a dark room, radiation is probably dominating. Soldering-irons and vacuum tube plates are on-the-edge of where radiation "typically" dominates the heat transfer.

If it glows in a dark room, the paint question is usually moot, too. 

And FWIW, many-many aluminum heatsinks are silverish (or golden).

That's a reliable guide to them being either not designed for natural convection, or poorly executed. There is a difference in fin design for natural convection, radiation, and forced air (or other coolant). Heat sinks designed for pure radiation are quite thin, maximizing surface area per material used, and are angled so that one fin does not radiate onto another, which would defeat the purpose of radiating. The thin heat conduction material reflects the fact that heat output per unit area is low at temperatures that are usable for most materials, so the surfaces are at essentially the same temperature at the root and at the tip; the fin efficiency is high for thin fins.

You want the fin to be at nearly the same temperature at the root of the fin where the heat goes in as it is at the tip, even though it's losing heat all the way out to the tip. If the tip is a lot cooler than the root, the surface area near the tip is transferring significantly less heat because of the lower temperature difference.

In natural convection, the fins are still thinnish, but are not necessarily angled not to radiate at one another. The lower amount of heat transferred by radiation makes this a smaller point than pure-radiation sinks, which are almost only used in vacuums.  The fin efficiency requirements make for more fins, thicker fins somewhat closer together. Color is modestly important, not critical like for radiation-only fins.

In forced air cooling, so much heat is transferred by conduction/convection by the air flow that the fins cool noticeably along the length of the fin, and the fins have to be thick and stubby to minimize the temperature difference between root and tip. Surface color is not important at all, as conduction/convection with the cooling medium is so much larger than for either natural convection or radiation that color matters not a whit, just as long as the coloring, if any, does not materially decrease the heat flow out the surface by being a high thermal resistance film. It's the analogy of high currents needing thick wires and low-resistance connectors to avoid having the current flow choked by high resistance to flow; just heat flow and thermal resistance, not current flow and resistors.

I have a suspicion that many are black because it tips-up the *extreme* end of the power vs temperature graph and gives a better spec-sheet number (nevermind that you would rarely want to work that hot). (And sinks are always anodized, black dye is cheap, and black does not show anodize blemishes as much as 'bare' or golden.)

Matte black sinks are pretty... everything looks better in basic black. 

Lies, d@mned lies, and datasheets.

[markeebee]

Hi Itai

Bet you're glad you asked now  

This thread is great, it explains what all the parts in an LPB-1 are for:

http://www.diystompboxes.com/smfforum/index.php?topic=47572.0

[itai12]

rlly tnx guys

this forum really awsome =]

[Thecomedian]

TINA from the TI.com website is a powerhouse sim. LTspice is another sim, but it has less functionality, although with less functionality it is also easier to learn to use quickly.