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Choose DISCIPLINEChemical Engineering. Civil Engineering. Data Communications. Electrical Engineering. Electronic Engineering. Information Technology. Instrumentation. Mechanical Engineering. Project Management. Technical Q ANote  Some of the questions on this section of the website reflect my opinions, and they are just that my opinions, and not necessarily to be taken as the gospel truth. Everyone has different ideas of what it takes to build a good sounding, high quality amplifier. Some manufacturers will insist only on original parts, cloth wire, etc. Some insist only on aluminum chassis while others say steel is the only correct choice. Because tone is such a subjective thing, there can be no single right answer to some of these questions. Use your ears and formulate your own opinions. Q What is the best type of resistor to use metal film, carbon film, or carbon composition A It depends on what you are trying to accomplish. Descargar Libro Stop Ansiedad Pdf Editor on this page. If you want the absolute lowest noise, metal film is the only way to go. Here we are presenting a long range FM transmitter that can cover a reasonable distance of 5 kilometers 3 miles and beyond with a one watt RF power with full. Serial Number Perspective Rectifier Transformer' title='Serial Number Perspective Rectifier Transformer' />However, some people prefer the tone of carbon composition resistors, which they say are subjectively warmer. Unfortunately, carbon composition resistors have notoriously poor drift and noise characteristics, and are responsible for most of the crackling and frying sounds heard in most old Fenders and other type amps. Carbon film resistors are a good compromise between the low noise and excellent stability of metal film and the subjective warmth of carbon composition. Larger wattage resistors are quieter than smaller ones, due to the geometry of the part, so you should always use the highest power rating you can find, particularly in carbon composition resistors. Note Some of the questions on this section of the website reflect my opinions, and they are just that my opinions, and not necessarily to be taken as the gospel truth. ZYX. WARNING Please do yourself and us a favor and not buy a ZYX phono cartridge from someone you are not sure of. We have seen used cartridges sold as new, serial. Internet ExplorerIE. In addition, most lower power resistors, such as 12. W and 1. W units, are only rated for a maximum of 2. V to 3. 50. V.  I recommend using only 2. W 7. 50. V resistors for plate load resistors and other locations where large voltage swings or high turn on voltage surges are expected. The first stage of the amplifier and other low level stages, such as reverb recovery amps, are the most critical for noise, because the signal level is lowest at that point, so proper attention to the type of resistor used will have the most impact on overall amplifier noise performance. Q What kind of resistors do you recommend for power supply decoupling use A I recommend 5. Figure%201x600.png' alt='Serial Number Perspective Rectifier Transformer' title='Serial Number Perspective Rectifier Transformer' />W or a higher power rating if needed 1 7. V metal oxide resistors for this application. They have higher surgeoverload capability than the film types, excellent long term stability, and flameproof construction. Note that lower power metal oxides, such as 1. W and 2. W are usually only rated for 3. V and should be avoided for this application. Even though the voltage across the resistor in normal operation is only 5. Another good type to use is the Ohmite OXOY series ceramic composition resistors. These dont have the tight temperature coefficient or tolerance typically 1. Q What about screen grid resistors A  I recommend 5. W 1 7. 50. V  metal oxide flameproof resistors for this application. The flameproof cement box resistors are also good, but are usually only available in 5 and 1. W or 1. 0W in order to get an appropriate voltage rating, because the 5. W and lower units are usually only rated for 3. V.   In normal operation, the screen grid resistor only has a few volts dropped across it, so a 3. V resistor is overkill. However, in the event of an internal tube short, the voltage drop can be much higher, up to the level of the supply, and the current through the screen resistor will increase dramatically, increasing the voltage drop across it. Normally, the fuse will blow fairly quickly, but sometimes not before the screen resistor is toasted. There are two possible failure modes, over voltage and over dissipation due to the increased current from the short. If the voltage rating is too low, the resistor element will flash over and either burn up or carbon track and change value, leading to eventual failure down the road. If the voltage rating is made higher than the supply voltage, there is only one possible failure mode of the resistor, over dissipation. The metal oxide flameproofs or OXOY ceramics can usually take a higher than rated surge for a short time before they burn up. If the fuse is appropriately rated, it will blow before this over dissipation can harm the resistor. A quick fuse and tube swap and the amp is back in business, instead of having to replace the screen resistors. Q What kind of potentiometers do you recommend A  I prefer to use sealed RV4 mil style 2. W potentiometers. They are available in both hot molded carbon and conductive plastic elements. I originally used the conductive plastic Clarostat units, but their inconsistent torque and feel caused me to switch to the hot molded carbon types from PEC, which I now use exclusively. They are extremely well built units, even better looking than the Clarostat, but more expensive. These RV4 type pots are more expensive than other types, but their sealed construction, reliability, and precision feel makes them worth the extra cost. UPDATE   I have to admit I was wrong on this issue. After having quite a few amps in the field for going on 1. I am starting to see a few complaints of noisy pots from people who own my amps. Normally, I  would just tell them to open the amp up and spray some contact cleaner in the pots. Unfortunately, you cant do this with a sealed pot, so you have no choice but to replace the pot. No pots are going to last forever, so you may as well use a cheaper pot like the Alpha, that can be cleaned or replaced for a fraction of the cost of one PEC pot. The Alphas have a nice smooth torque feel to them. Q Why do you recommend polypropylene filmfoil capacitorsA Because they are the best, in terms of temperature stability, and, subjectively, tone. The interior of a guitar amplifier chassis tends to get very hot, particularly in a combo, where the tubes are hanging upside down beneath the chassis and the heat rises upward. Polyester and metallized film capacitors have very poor temperature characteristics compared to polypropylene filmfoil, which means the amplifier tone will change as the amplifier heats up. A 5 or 1. 0 drift in value can produce a very noticeable shift in tone, depending upon how the capacitor is used in the circuit, and all caps will drift in the same direction, which is determined by the characteristics of the dielectric material, so the effect is multiplied. Also, polypropylene capacitors are far better in terms of dissipation factor and dielectric absorption, which some people say makes them sound better. I use them because they have the best characteristics, even though they cost quite a bit more than the cheaper polyester caps. The long term temperature stability and quality construction makes them worth it, in my opinion. The most commonly used coupling cap, the Sprague Orange Drop, is available in polypropylene filmfoil, but only in a radial lead package. These are fine for PC board amplifiers, but some manufacturers use them for point to point boards by bending the leads out at the body of the capacitor. This usually leads to cracking of the epoxy seal around the lead entry points, which can allow moisture into the capacitor, leading to drift and potential failure. I use only axial leaded capacitors, because they are designed for point to point style mounting, and the epoxy end seals do not crack when they are mounted on the board. Q What type capacitor do you recommend for small values in the p. F range, such as in tone controls A Silver mica or polystyrene film capacitors are the best choices. They have the best temperature stability and most transparent tone. However, the polystyrene film caps in the p. F range usually have very tiny leads, which may not be robust enough to stand up to the rigors of road use. There are very few capacitor manufacturers making low p. F value film capacitors in other dielectrics, such as polypropylene or polyester, and they are nearly impossible to find.