How transistors act as amplifiers for acoustic guitars

New spacecraft aim to solve them. Here we have three separate types. But it's facing supply. Free Shipping. Best Offers for 3g lure lot brands and get free shipping.

We are searching data for your request:

How transistors act as amplifiers for acoustic guitars

Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

Content:

• Tube Amps vs. Solid State: How to Choose the Right Amp
• How Do Guitar Amps Work? Simply Explained, Easy To Get
• How Tube Amplifiers Work
• A Guide To Effects Pedals | Guitarbitz
• A brief history of bass amplification
• Pro Audio Reference (A)
• Guitar Contact Microphone Preamp
• Power Amplifier Design Guidelines
• Understanding Impedance
• Passive Amplifiers Vs. Active Amplifiers (Sound & Audio)

WATCH RELATED VIDEO: Easy DIY Pre-Amp for Acoustic Guitar

Tube Amps vs. Solid State: How to Choose the Right Amp

I am amazed at the number of amplifier designers who have, for one reason or another, failed to take some of the well known basics and pitfalls of amp design into consideration during the design phase. While some of these errors whether of judgement or through ignorance is uncertain are of no great consequence, others can lead to the slow but sure or instantaneous destruction of an amplifier's output devices. When I say 'of no great consequence', this is possibly contentious, since a dramatic increase in distortion is hardly that, however in this context it will at least not destroy anything - other than the listener's enjoyment.

Even well known and respected designs can fall foul of some basic errors - this is naturally ignoring the multitude of 'off the wall' designs e. This is not including valve amps, these are a 'special' case and in many areas, such as guitar amps, as far as many players are concerned they remain unsurpassed. In this article, I have attempted to cover some of the areas which require their own special consideration, and the references quoted at the end are excellent sources of more detailed information on the items where a reference is given.

Reference Amplifier My reference amplifier is shown in Project 3A , and is a hard act to follow. As I have been refining these pages and experimenting with simulations and real life, I have found that this amp is exemplary.

It does need a comparatively high quiescent current to keep the output devices well away from crossover distortion, but this is easily accommodated by using decent heatsinks.

Even a Class-A system Death of Zen fails to come close at medium power, and is barely better at low power. It is stable with all conventional loads, capable of 80W into 8 Ohms, and simple to build. Using only commonly available parts, it is also very inexpensive.

Note: This article is not intended to be the 'designers' handbook', but is a collection of notes and ideas showing the influences of the various stages in a typical amplifier. Although I have made suggestions that various topologies are superior to others, this does not mean to imply that they should automatically be used. If one were to combine all the 'best' configurations into a single amp, this is no guarantee that it will perform or sound any better than one using 'lesser' building blocks.

There is a school of thought that the fewer active devices one uses, the better an amp will sound. I do not believe this to be the case, but my own design philosophy is to make any given design as simple as possible, consistent with the level of performance expected of it.

Regardless of these claims, most amplifiers actually work just fine, and do not have to do any of the things that the claimants may imply. The vast majority of all the off-the-wall claims you will come across can safely be ignored. It's also worth noting that making a design more complex more parts doesn't necessarily mean that it will have better performance.

More active parts in the signal chain tend to add delays, and this can make it very difficult to keep the final circuit stable. No-one wants or needs an amplifier that has marginal stability, meaning that it may be on the verge of oscillation during normal operation. Connecting a speaker lead with above average capacitance may cause spurious and intermittent oscillations on parts of the waveform. This is always audible, but might not show up when the amp is on the test bench.

There are two main possibilities for an input stage for a power amplifier. The most common is the long tailed pair, so we shall look at this first. While this makes the circuit appear to be fully symmetrical, it isn't, because the NPN and PNP transistors will never be exact complements of each other. Long Tailed Pair It has been shown [ 1 ] that failing to balance the input Long Tailed Pair properly leads to a large increase in the distortion contributed by the stage.

Some designers attempt to remedy the situation by including a resistor in the 'unused' collector circuit, but this is an aesthetic solution - i. See Figure 1a Note that the 'driver' transistor is simply there to allow us to make comparisons between the circuit topologies, and to provide current to voltage conversion.

It is worth noting that even though this resistor serves no purpose electronically, it can make the PCB layout easier. Use of the long-tailed or differential pair in an amplifier means that the amplifier will operate with what is generally called 'voltage feedback' VFB. The feedback is introduced as a voltage, since the input impedance of both inputs is high and approximately equal , and input current is relatively speaking negligible.

The feedback resistor and capacitor are selected to allow the circuit to operate at full open loop gain for the applied AC, but unity gain for DC to allow the circuit to stabilise correctly with a collector voltage at or near 0V. Different simulators will give different results, but the trends will be the same.

Simply by reducing the value of R1 it is possible to improve matters, but it is still not going to give the performance of which the circuit is capable. Again, as shown the gain of the LTP is a rather dismal 32 as measured at the collector of Q2.

The inclusion of R3 is purely cosmetic. It does provide a convenient means to measure the gain of the LTP, but otherwise serves no purpose. Changing R1 for a current source does not help with gain, but provides a worthwhile improvement in power supply hum rejection, and in particular improves common mode rejection. A common mode signal is one that is applied in the same phase and amplitude to both inputs at once.

The overall gain of this configuration measured at the collector of Q3 is , but by reducing R2 to 1. This also improves collector current matching in the LTP, but the value will be device dependent, and is not reliable for production units. The circuit shown in Figure 1b has improved overall gain to 6,, a fairly dramatic improvement on the earlier attempt.

A further improvement in linearity is to be had by adding resistors Ohm or thereabouts into the emitter circuits of the current mirror transistors. This will swamp the base-emitter non-linearities, and provide greater tolerance to device gain variations. Overall gain is not affected. Proper selection of the operating current will improve matters considerably, and also help to reduce distortion, especially if local negative feedback as shown in Figure 1b is applied.

This has been discussed at length by various writers [ 1 ] , and a bit of simple logic reveals that benefits are bound to accrue to the designer who takes this seriously. Since the value of the transistor's internal emitter resistance r e is determined by the current flow -.

For example, at 0. Although this will introduce local feedback and reduce the available gain , it is non-linear, resulting in distortion as the current varies during normal operation. Increasing the current, and using resistors which are nice and linear to bring the gain back to where it was before will reduce the distortion, since the resistor value - if properly chosen - will 'swamp' the variations in the internal r e due to signal levels.

At small currents where the current variation during operation is comparatively high , this internal resistance has a pronounced effect on the performance of the stage. Simple solutions to apparently complex problems abound. Use of a current mirror as the load for the long-tailed pair LTP again improves linearity and gain, allowing either more local feedback elsewhere, or more global feedback.

Either of these will improve the performance of an amplifier, provided precautions are taken to ensure stability - i. There is another not often used these days version of an amplifier input stage. This is a single transistor, with the feedback applied to the emitter. It has been claimed by many that this is a grossly inferior circuit, but it does have some very nice characteristics. Technically, it uses current feedback, rather than the more common voltage feedback.

Figure 2a - Single Transistor Input Stage. So what is so nice about this? In a word, stability. An amplifier using this input stage requires little or no additional stabilisation the 'Miller' cap, aka 'dominant pole' which is mandatory with amps having LTP input stages.

An amplifier using this input stage is referred to as a 'current feedback' CFB circuit, since the feedback 'node' the emitter of the input transistor is a very low impedance. The base circuit is the non-inverting input, and has a relatively high input impedance - but not generally as high as the differential pair.

CFB amplifiers are used extensively in extremely fast linear ICs, and are capable of bandwidths in excess of MHz that is not a misprint! There is one basic limitation with this circuit, and this was 'created' by the sudden requirement of all power amplifiers to be able to faithfully reproduce DC, lest they be disgraced by reviewers and spurned by buyers.

This input stage cannot be DC coupled at least not without using a level shifting circuit , because of the voltage drop in the emitter circuit and between the emitter-base junction of the transistor. Since these cannot be balanced out as they are with an LTP input stage, the input must be capacitively coupled. In addition, some form of biasing circuit is needed, and unfortunately this will either have to be made adjustable which means a trimpot , or an opamp can be used to act as a DC 'servo', comparing the output DC voltage with the zero volt reference and adjusting the input voltage to maintain 0V DC at the output.

The use of such techniques will not be examined here, but can provide DC offsets far lower than can be achieved using the amplifier circuit itself. There is no sonic degradation caused by the opamp assuming for the sake of the discussion that decent opamps cause sonic degradation anyway , since it operates at DC only it might have some small influence at 0.

It has also been claimed that the single transistor has a lower gain than the LTP, but this is simply untrue. Open loop gain of the stage is - if anything - higher than that of a simple LTP for the same device current.

I simulated a very simple pair of circuits shown in Figure 2b to see the difference between the two. Collector current is approximately 1mA in each, and the output of the LTP shows a voltage gain of 1, from the combined circuit the input stage cannot properly be measured by itself, since it operates as a current amp in both cases. In neither case did I worry about DC offset, since the effects are minimal for the purpose of simply looking at the gain - therefore offset is not shown.

This in no way invalidates anything, they are just different. By comparison, the open-loop gain of the single transistor stage is 2, - this perhaps unexpectedly is somewhat higher.

Admittedly, the addition of a current mirror would improve the LTP even more dramatically, but do we really need that much more gain? A quick test indicates that we can get a gain of 3, This looks very impressive, but is only an increase of a little over 4. By the same logic, the single transistor only has a 1. Because the single transistor stage requires no dominant pole Miller capacitor for stability, it will maintain the gain for a much wider frequency range, so in the long run might actually be far superior to the LTP.

Further tests were obviously required, so I built them. Real life is never quite like the simulated version, so there was a bit less gain from each circuit than the simulator claimed. The LTP came in with an open loop gain of , while the single transistor managed Distortion was interesting, with the LTP producing 0. The single transistor was slightly worse for the same output voltage with 0. This is an open loop test, so it's really an examination of the 'worst-case' performance.

If the gain is reduced with feedback, distortion falls dramatically. However, it doesn't necessarily fall in a direct relationship. Quite unexpectedly, the single transistor also required a Miller cap, but only when running open-loop. When it was allowed to have some feedback the oscillation disappeared. The LTP could not be operated without the Miller capacitor at any gain, and as the gain approached unity, more capacitance was needed to prevent oscillation.

The next step was a test of each circuit providing a gain of about 27, since this is around the 'normal' figure for a 60W power amp. Here, the LTP is clearly superior, with a level of distortion I could not measure.

How Do Guitar Amps Work? Simply Explained, Easy To Get

AmpliTube has always been about realism, and now that extreme commitment to accuracy is a part of its completely redesigned cabinet section. The new Cab Room feature is the most advanced cabinet section ever made, giving you a new level of customization and flexibility never before seen in software or reality. Never before has such a level of control and customization been available for fine-tuning tones from the speaker section. AmpliTube 4 ushers in some amazing control features when it comes to fine-tuning and tone sculpting one of the most important components in the signal chain: the speaker cabinet. Plus you can use any available cabinet with any amplifier — impedance matching in AmpliTube 4 is automatic so you never have to worry about blowing up your power amp!

How Tube Amplifiers Work

Bass players are understandably infatuated with the bass itself. Get a group of bass players in a room, and the conversation will eventually circle toward basses. But then the conversation turns to bass amps. If innovation is a good catalyst for conversation, amps give us much more to talk about. While there have been many stabs at revolutionary change, the bass guitar has basically stayed the same since it was invented. Sure, there are many approaches to each facet, but to change any one would essentially reorient the very instrument itself. Amps, on the other hand, are a venue for truly radical change.

A Guide To Effects Pedals | Guitarbitz

AAAF American Academy of Audiology Foundation Their mission: "To promote philanthropy in support of research, education, and public awareness in audiology and hearing science. They perform using instruments that date from the time when the music was composed. AB Microphones. A stereo recording technique whereby two microphones are spaced apart anywhere from about 3 feet to as much as 10 feet to create a time difference between them that the human brain perceives and translates into stereo localization and imaging.

A brief history of bass amplification

By popular demand well, at least one of you asked for it , a growing index of topics found on the Truth About Vintage Amps…. Episode 2. Episode 3. Episode 4. Episode 5.

Pro Audio Reference (A)

When we think of electric guitars, it is hard to imagine one without an amplifier. The amp is an electronic device used to strengthen the signal coming out of the guitar. If you ever tried playing an electric guitar without one, you quickly realized that it would be impossible for anyone to hear what you play. So how do guitar amps work? The guitar amp contains a power amplifier inside the box or a preamp. There are several ways you can amplify the sound coming from the guitar, and the most common ones are using transistors or vacuum tubes.

Guitar Contact Microphone Preamp

Amplifiers can be found all around us if we choose to look for them. Though we may think of active amps when we think of amplifiers, there are also passive amplifiers that are common enough in our daily lives. What is the difference between a passive and active amplifier? Amplifiers are essentially devices that increase the amplitude of a quantity.

Power Amplifier Design Guidelines

RELATED VIDEO: The transistor as an amplifier (Part 1)

The modern amp is enough to create real "tone" which usually requires a very strong amp to produce. But with amp-in-guitar its possible without waking the house. From there you can find videos of the other models as well as links to other forum discussions where my assertions are discussed at length. Elliott Dean www. Here's a few more benefits of amp-in-guitar with a slightly more acoustic-portability backbone than most: 1. Enhanced acoustic capabilities louder, warmer, sweeter 4.

Understanding Impedance

Beginner Guitar HQ. One question that plagues many guitar players of all levels is what type of amp to buy. This guide will help you make an informed choice on what type of amp you will be looking for. It will also answer any questions that you may have about the process and how to tell the types apart. Solid state amps are often rated far higher due to headroom. Tube amps overdrive at a lower volume but analogue clipping is a soft clipping which is pleasant on the ear. Solid state amps are transistor clipping which is harsh.

Passive Amplifiers Vs. Active Amplifiers (Sound & Audio)

Solid state guitar amps use transistor technology rather than tube technology to amplify the signal of the guitar. Early guitar amps used vacuum tubes to amplify the sound, but when the transistor was invented, amplifier manufacturers found a more reliable and cheaper technology. Solid state amplifiers are considered to be more reliable than their tube counterparts, but problems can occur in solid state amps.