Frequently Asked Questions - Electronics

Here are our answers to the questions we get asked the most. If the answer to your question isn't here, send us an email and we'll add the most popular new questions.

Things to consider when (before) installing your electronics.

What to look for when buying a turntable.

What to look for when buying a CD/DVD/SACD player.

What to look for when buying an amplifier.

Are Tubes better than Transistors?

What’s the best type or “class" of amplifier?

I can hear hum, how can I get rid of it?

I can hear hiss, how can I get rid of it?

My CD is so much louder than my vinyl, always have to turn it down.

Every time I turn it up, it sounds real harsh.

I’m getting radio interference, what can I do?

I don’t like that loud thump every time I turn on or off.

I’m blowing fuses, popping breakers.

What’s the difference between 16 and 24 bit digital audio?

How can I tidy up the back of my rack?

After 15 minutes of loud music, the sound changes

I hear ghost sounds that suddenly appear in the sound.

Things to consider when (before) installing your electronics.
Here is a list of things that have tripped me up in the past:

• Is there ample room for floor standing speakers?
• For wall mount speakers, how and where will you mount the speakers?
• How do you compensate for deviations from the standard “rectangular” room set up.
• How many audio sources do you have?
• Where will you put all the players, amps and controls?
• What about cables? Do they need to be hidden? Where do they run?
• Do you have enough power, where you need it?
• What to do with all those remote controls, how do you control it all?
• Who will be using the system, are they technically savvy, how easy/intuitive?
• Will the neighbors complain, will you wake the baby?

Specific installation problems include:
Vibration
Vibration from movement in the room and other general building vibration is really only a problem for turntables. The error correction on CD’s and DVD’s will cause the sound to cut-out if optics wobble gets too bad. Jitter really isn’t a problem these days. The biggest problem with vibration I’ve had is the electromechanical vibration of the mains transformers resonating a sheet metal panel and spoiling the inter-song silence with an offensive hum. A sturdy rack for your gear and an assortment of books to dampen panel resonance (without blocking cooling vents of course!) should fix most problems.

Power
All electronic devices need a stable power supply to operate properly and reliably. Add up the power requirements of all your components and check against power strip ratings and breaker circuit ratings. Look for other outlets around the home that are daisy-chained on the same outlet you’re using for the sound system; plugging a vacuum cleaner into the same circuit could cause some high peak currents.
Watch out for long lengths of extension cords. The resistance of thin gauge wire over long hauls can cause a wide range of “brown-out” related problems such as hum, distortion, drop-outs, noise-bursts and whistles. Long distances need thick wire. Make sure all extension cords are three wire and connect to three prong outlets, check with an electrician if you’re not sure of an outlets’ ground integrity.

Heat dissipation
Power amplifiers, computers, monitors and TV’s all generate lots of heat. Wifi access points also run hot. If you’re putting a lot of gear in a closet, think about air flow. Convection can handle a modest installation, but if you’re doing something special, consider how you’re going to get the heat out. Every 10°C temperature rise halves the life of your electronics.

What to look for when buying a turntable.
Accurate replay of a vinyl record requires the following conditions:

• A platen, rotating at a constant rate on a constant axis
• A correctly sized, shaped stylus in a critically damped mechanical mount oriented identically in 3D and moving identically to the cutting tool used for the master.
• A specific impedance matching and RIAA equalization pre-amplifier.

Unlike CD players and pre-amps, you can’t always plug a particular cartridge into any phono input; each cartridge has it’s ideal loading impedance so one phono amp cannot match all cartridges - check the specs of both to make sure. The dynamic range requirements of the RIAA equalization make noise figures in excess of 70dB difficult to attain. The noise from the thermal activity of the electrons in the cartridge coil should be the limiting factor in a good pre-amps design. The next weak link will be the mechanical system. Keeping rumble out of the spindle bearing assembly and platen drive chain is a key design challenge. Following that vibration from the surface supporting the turntable and also from acoustic pressure waves (if you like it loud) can be coupled into the reproduced signal. All these thing make choosing and installing turntables correctly very important.

Turntable require intricate set up that can be very difficult without the use of special tools. Adjustments include: overhang, vertical tracking angle, azimuth, tracking weight and bias. It is also essential the the turntable be perfectly level.

Generally, good turntables are very expensive but then again the best made turntables of the last decade should still be giving faithful service at auction prices. Their demise is surely due to the difficulties of aligning the cartridge and correctly loading the coils which requires the use of a test LP and a dual channel scope.
I read somewhere that the bandwidth and dynamic range of a vinyl record exactly matches that of human hearing.

What to look for when buying a CD/DVD/SACD player.
There are so many formats available for digital audio. You need to make sure your player supports all the formats you use.
Choices: mp3, cda, wma, wav, CD, CDR, CDRW, DVD, DVD-R, DVD+R, DVD+RW, SACD, DCD,
If you have MP3 compressed audio that you want to play on your system and you’re recording them on a CD-R then you need a player that can play this type of media. There’s a difference between DVD-R and DVD+R, some players only play the +R format. A little up-front research can save money and frustration later.
There are many types of connection from a player to the rest of the audio or home theatre system. There’s regular composite video using the standard RCA plug, then there’s S-video using the mini-DIN plug, component video using multiple jacks and now HDMI digital interface. There’s regular line level audio again using RCA plugs and then there’s S/PDIF and TOSLINK. You should consider how you want to connect the player into your system.
There is much discussion these days on the relative merits of single bit oversampled converters vs. multibit converters. I believe both are capable of excellent quality audio, it’s the implementation that counts. I recommend auditioning the player using good quality headphones first using music that you re familiar with. Do some research on the various reviewing web sites.

What to look for when buying an amplifier.
First thing to check is weight. True power capacity comes from big, heavy components so lightweight amplifiers are just that, lightweight. Unless you have a special need for super high power efficiency to justify the noise generated by switching power supplies and class D amplifiers, go for traditional iron transformer and large capacitor designs.
Next important is inputs. Unless you are buying a component specifically to select and pre-amplify all your sources,  the amplifier (aka receiver) is where all the sources come together. You’ll want individual inputs for some combination of tape, CD, DVD, PC, vinyl, gaming console, cable, satellite, FM/AM radio, guitar, synthesizer, microphone, telephone etc.etc. Some of these inputs need special  handling, for instance, vinyl cartridges need RIAA equalization filters and digital audio connections like S/PDIF need special inputs.
Directly related to cost is, number of channels. How many you need depends on whether it’s stereo or home theater, are you bi-amping/triamping, how many zones do you want to put audio in and whether they are all playing the same program material.
Many current designs use integrated amplifiers. These are large semiconductor “chip” modules that integrate the entire channel on a single package. They have at least 5 pins, usually more and bolt to the heatsink. The quality of these modules has improved over the years so that they can achieve comparable performance to a well designed discrete amplifier.  I think that excellent performance can be achieved with less than 20 transistors per channel and I prefer the ability to understand the design, ease of repair and the thermal benefits that come from discrete amplifier design.  Circuit designs such as those by Douglas Self set a high bar that not all amplifiers step up to today.
Remote control. Will you want to control this amplifier from another room? Remote control of amplifiers is painful to work out after you’ve installed your system. Another thing to consider: what are you going to do with all those handheld controllers? Are you going to program a universal with all the components commands or do you want an integrated system where the manufacturer provides cross-component compatibility for remote control?

Are Tubes better than Transistors?
It’s hard to justify tube amplifiers these days. Biggest negatives against tubes are: power consumption, heat dissipation, dangerous voltages and cost. But there’s something about the warm glow of the filaments lighting up the room at night. In a tube, you can relate to the electrons; they’re right there whizzing off the cathode at close to the speed of light. A transistor just sits there  all smoke and mirrors in a black plastic blob.
If you’re asking this question, you should probably just get yourself some good quality silicon amplification. Tube amplifiers need to be carefully matched to the system and you should fully research each component of a tube-amplified system before purchasing.

What’s the best type or “class" of amplifier?
My personal preference? A well designed class B transistor amplifier can easily deliver power with inaudible distortion any way you can measure it. That makes the loudspeaker the weak link in the electronics chain with 4% THD commonly achieved in challenging music situations. Class A is always more musical for the same distortion level, but environmentally I can’t get behind the constant 2KW rms dissipation needed for class A to match my tri-amped class B. Class D concerns me because it’s such a noisy way of making music. It’s all ultrasonic but I haven’t read anything on long term exposure to low level, broadband RF emissions. If it needs to be small and portable then absolutely, class D is a winner. For a home audio system, I’m not so sure.
Here’s one perspective on the different amplifiers out there:

• Class A

AKA current dumping. Class A amplifiers were the first amplifier topology or configuration to be designed. Their roots lie in the tube era where economy of design was utmost. A single tube was all that was allowed for an amplifier due to cost and power consumption so class A was the only way. It involves configuring an active device, a tube or a transistor, to pass a constant current. The audio signal acts to proportionally divert some of this current into the speaker by effectively turning the active device more on or off. At the time it was considered the best because it’s distortion products are all even and therefore musically related to the sound being produced. It is horribly inefficient as you are always dissipating the rated power of the amplifier if not in the speaker then in the active device. They are heavy and get hot but they still have a large following.

• Class B

AKA push-pull. With the advent of transistors, multiple active devices became economical and so class B was born. In this topology, one device drives positive while the other drives negative. Every half cycle of sound they take turns conducting and hand off to each other in turn. The key advantage is they only conduct the power that is needed for the speaker and so run a lot cooler, at least at low levels. The problem is the hand off. It is very difficult to get the different devices to switch conduction at exactly the same time; usually you have a small band where they both conduct (which is better than having a dead band.) They are characterized by having odd order harmonic distortion which requires large amounts of feedback to keep controlled to acceptable levels. It is because of badly designed class B amplifiers (particularly those of the early ‘70’s) that many audiophiles dislike negative feedback.

• Class C

Not generally used in audio applications

• Class D

While class B is more efficient than class A because the active devices only conduct when needed, there is still significant power wasted in the active devices because they have to absorb the difference between the power supply voltage and the actual output voltage delivered to the speaker. In effect, the devices are never fully on, they’re only partially on. Class D maximizes power efficiency by only ever turning the devices fully on. They work by using the speaker as a current regulator; they switch hard on until the current in the speaker rises to the required level and then turn off while the current in the speaker subsides. This switching is done at a very high frequency (typically 100’s of KHz) so that the switching frequency is inaudible. Care is needed to prevent excessive RF radiation interfering with other appliances.

I can hear hum, how can I get rid of it?
First of all, never use a ground lift plug to fix a hum problem. The ground pin on the home mains wiring serves as a safety barrier to protect you from electrocution in the event of a fault. Never defeat this safety barrier!

Hum and buzz problems are caused when the alternating current of the power supply interferes with the signal path in some way. It is impossible to completely eliminate power line hum from a sound system (unless it's battery powered), but you can make it inaudible through careful installation. There are many ways the power AC signal can get in and troubleshooting this problem needs a strategy.

Start by turning the volume controls up and down, one by one. Does the hum get louder and quieter as you turn the knob? If so, then the hum is being introduced at a point earlier in the signal chain. Focus your attention to the pre-amplifier and sources.

Check all cables. They should be securely plugged in to their respective sockets or jacks. The insulation or jacket should be unbroken. Pay particular attention to the point at which the cable enters the plug; this is weak spot in all cables. You can usually feel a break in the internal conductors as the break will flex differently compared to the rest of the cable. Has the cable been run over and sliced by something on wheels; feel the length of the cable for roughness. If in doubt, swap it out to see if the problem goes away.

Try disconnecting your various sources one by one. Does the hum go away when a particular source is disconnected? If so, then there’s a problem or incompatibility with that device or its cables. Has ground been defeated anywhere?

If everything looks good then there could be a problem with gain. Are any of the volume controls in the system set very low? High powered amplifiers can also have high levels of background hum and hiss
Disconnect input cables to the power amplifier. Has the hum gone away? If it has, you’re in luck, you can add a 20dB or even a 40dB pad between the pre-amplifier output and the power amplifier input and turn the volume up. If the hum is still there then you probably need a different, less powerful amplifier better suited to the room, speakers and preferred listening level.

One last thing to check. Occasionally, a sound system can end up being powered by two separate phases of the house electric supply. This can happen when the sources are on one wall, plugged into an outlet on that wall and the power amplifiers are located on a different wall and plugged into that walls outlet. The two outlets are wired to different circuits at the breaker panel and can be opposite phase. This can cause significant leakage current to flow in the audio cables connecting the different equipment and in the process add hum. The solution is to run all equipment on the same breaker panel circuit either by using a power strip with sufficient length to reach the remote equipment or moving the equipment to a single location and outlet.

Ground loops – facts and fiction.
Most discussion of system grounding is outdated. The concept of the star point or single point grounding dates back to days when high voltage power rails with poor regulation easily coupled (capacitively) into high impedance circuits in an RF-quiet environment. Today, the synthetic materials in our homes cause big ESD problems and the proliferation of wireless products means most homes have easily 6 or more household appliances operating in the RF band. Semiconductor technology has conquered low voltage, low impedance design so now current flow and inductive coupling is important.

Single point grounding philosophy requires breaking the ground path at various points along the signal path. Whenever a signal path passes over a break in the ground path, bad things happen. In order to minimize inductive coupling in a circuit, the signal path and the return path or ground path must follow each other as closely as possible throughout the entire circuit. As the path loop increases in area, ESD events and radio interference signals as well as power line hum are coupled in causing problems in the adjacent circuits. The old practice of connecting shield only at the input or only at the output is thus no longer valid. Neither is the star point amplifier grounding where connecting audio ground reference at the power source always caused problems. Walk away from any system where a ground pin has been snapped off the power cord plug.

A consideration of system signal integrity in the entire spectrum (DC to light) makes you design for the lowest impedance to “ground” at all points. In fact, it really is GROUND because on this planet, the only true reference is the ground under your feet (maybe the old school really did understand the concept.) Multiple connections less than ¼ wavelength at 10GHz are needed for perfection, that’s just over ¼”, anything greater will develop voltage.

All this leads to the realization that balanced (a.k.a. differential) design is the only way to guarantee consistent performance in all environments. There is only one ground, and it is your friend. Get close!

I can hear hiss, how can I get rid of it?
Hiss is the noise electrons make when they’re warm. As temperature goes up, the electrons bounce around more and more energetically, creating random localized currents. When these currents flow through a resistance, such as the input resistance of an amplifier, noise voltages are developed which in turn are amplified by our sound system and the result is hiss. Obviously, we can’t make the resistances zero, this would be a short circuit and not good for anything. All that can be done is to ensure that the circuits at the front end or beginning of the signal path are well designed which usually, although it doesn’t have to, means expensive. As we move along the signal path, the signals typically get larger and larger and therefore less and less sensitive to thermal noise.
Ideally, the first circuit in the signal path should amplify the signal cleanly up to a useable level therefore making the signal immune to noise from there on. However, in some complex systems with multiple gain stages, the gain distribution (or volume settings) for each stage can accentuate noise or hiss. What you don’t want, is wild fluctuations in the settings; this is poor gain distribution and once the thermal noise or hiss has been introduced, it’s impossible to eliminate. Every volume/gain control in the signal path should have a similar setting in the high mid range.
If you have a noisy component in your system, check to see that it is connected to an appropriate input on the pre-amplifier or receiver. For instance, you wouldn’t plug a moving coil turntable into an auxiliary or CD input on the receiver; the mismatch in levels would require the volume control to be set very high possibly accentuating hiss and noise in the receiver. Consult the manuals for both components and check that the input and output are compatible. Try a different input or alternative component on that input to test sensitivity.
Finally, make sure that you are only listening to a single source. This usually only happens on DJ systems where you can fade between sources but if one of those sources is an empty cable channel or a radio in between stations and it’s turned up, your system will be noisy. Also check monitor selectors if you have a recording set up as these can inject noise as well.

My CD is so much louder than my vinyl, always have to turn it down.
This is a common problem due to the fact that every manufacturer has a slightly different standard for signal levels. For example if your phono pre-amp puts out 300mV typical while your CD player puts out 1V typical then when you switch from the phono to the CD, the volume will jump up 10dB.
If you are choosing equipment to buy for a system then the problem can usually be prevented by buying all the source players from one manufacturer. On the whole manufacturers make sure that all their components play well together.
If you are solving a problem in an existing system then check the following. First, read the manual for your amplifier to see if the different inputs have a level trim. It could be a screwdriver adjustment on the back panel or a hidden menu on the set up screen. You may need a combination of turning the loud channel down as well as turning the quiet channel up to get a good balance. If your amplifier doesn’t have this adjustment then try the various different inputs.  The AUX, TAPE and RADIO inputs are all essentially interchangeable and they may have different sensitivities. Swapping the inputs probably won’t completely balance the inputs but may make the difference more acceptable.
Failing all this, the only solution is to build some custom attenuators. If there’s enough interest I’ll make some standard values available for sale on this site but for now, if you can operate a soldering iron, here’s how to make your own.
First work out how much attenuation you need on the loud component. You can do this by putting a constant tone through the amplifier and taking a voltage reading of the output at the two volume control settings you use. Divide the loud level by the quiet level and this is the attenuation you need.  Get the appropriate resistor values from the following table:

Tools:
Cable cutters/strippers
Soldering iron
AC voltmeter with 100mV scale
Parts:
1 stereo RCA to RCA extension cable, shortest you can find
2 RCA plugs, not too small, you need to get some components in here.
4 resistors,  1/8  or ¼ Watt is fine, get the values from the table below.

Cut the RCA to RCA cable at about 6” from the female connector end, keep the 6”section. Strip the ends and thread the screw caps of the RCA plugs over the bare ends (I always forget to do this) Solder the resistors to the RCA plug as shown and ten solder the cable to the resistor/plug assembly as shown. Screw the caps on, connect into system, enjoy.

Every time I turn it up, it sounds real harsh.
Harshness is usually associated with distortion and if it gets worse when you turn the volume up then this is a confirmation.
This could be caused by the room acoustics. If your room is particularly bright it may be that the room is over-accentuating the high frequencies and when you get to a certain level the reverberation becomes overwhelming. For now we’ll assume it’s a system problem.
First thing to check is whether the speaker power rating matches the amplifier. If you bought the amp and speakers at the same time from the same manufacturer then they are probably OK. If you picked them out yourself there could be a difference. To ensure that clipping distortion cannot occur, the speaker power rating should exceed the amplifiers. You may need to find the manuals or search the web to get this information. A quick check: if your amp weighs more than your speakers combined you could have problems.
Next, check that your amp has enough power for the volume you are trying to listen at. 20 to 40Watts should be plenty for all but the most aggressive listening levels with modern speakers. If your amplifier has single digit power ratings or you can easily pick it up with one hand – it’s probably a bit weak.
Make sure your speakers are wired up correctly and you’re not parallelling up multiple speakers off the same output channel. This can overload amplifiers and cause distortion.
Finally, you may need to face the fact that you’ve blown a speaker. GENTLY, push the cones in and make sure the motion is smooth any friction, rubbing or knarliness is a bad sign. Smell the speakers, any burnt odors are not good. If the distortion is only from one channel, swap he speakers and make sure he distortion follows the speaker. This would be confirmation of a blown driver.

I’m getting radio interference, what can I do?
Radio interference problems can be tricky to solve especially when it only happens once a week.  The first step in solving these problems is to be able to reproduce the problem and to do this you need a radio frequency source. Fortunately, many of us have such sources right at hand, a cordless phone, walky-talky or cellphone are all excellent candidates. Remember that phone devices generally have to be in an active call to continuously transmit.
The technique is to set the system up in the mode that the interference was last noticed (was it a phono source or CD) and set the levels similarly. Then start waving the radio frequency source around the system paying special attention to connectors, cables and jacks. It may be that you only have a poblem at a certain radio frequency in which case you may have to try multiple devices in order to reproduce the problem.
Once you can cause interference you can start to trace it.  Is it at the input or output of a component? Does the level go up and down with volume controls, Is it only present on one selected source? Does it go away when various components are turned off?
Hopefully, you have traced the problem to a particular input or output. The first thing is to check the shield connections at these points. Make sure that the screen/shield is soldered securely and the jacks are tightly screwed to the chassis. Has the ground terminal of the power plug been defeated? Replace immediately if it has!
If all is well then some additional filtering may be needed. Ferrite beads can be added around the cables at these inputs/outputs. These come in a variety of styles from tubular beads to fat doughnuts to intricate clamp on devices. Look for the highest resistive value and the broadest bandwidt when choosing. They’re usually quite cheap so buy a selection to try. If you are handy with a soldering iron you can try adding a small 100pF to 1nF capacitor between the signal wire and ground/shield in the plug of the offending connection.
Still no solution? Then the susceptibility could be in the component itself.  Without engineering skills to troubleshoot the circuit, the only solution may be to install the equipment in a grounded, shielded cabinet.

I don’t like that loud thump every time I turn on or off.
You should not hear anything when you turn your system on or off. All good systems these days have power on/off muting as these transients can be quite damaging to speakers. When you first turn on a power amplifier, all the various circuits need to charge up and the output drive is totally uncontrolled. One output device will turn on before the other and drive the output to one power rail or the other effectively delivering full power to the output. This can burn out voicecoils quite quickly. The other problem is with sudden transients which can literally cause to voicecoil to jump out of the airgap.
If your amplifier has just started thumping on power on/off but didn’t used to then it needs repair before your speakers do as well. The relays may have stuck or the delay circuit may have blown.
If your amplifier has always thumped then you need to install one of my power-on delay modules immediately. Email today

I’m blowing fuses, popping breakers.
Circuit Breakers:
What else is on this circuit? Turn the circuit breaker off and see what else in the house isn’t working. If it’s a high powered device or appliance such as a refrigerator or space heater then you’re just pulling too much power off that circuit. If your home theater is run off the same breaker (which is ideal) check to see what the total consumption is. A large TV can easily pull 5Amps and the turn on current for your large 600Watt surround sound amplifier could be in excess of 10Amps. Add a couple of lamps, sources and a gaming computer and you could easily exceed a 20Amp breaker's rating.  The solution is to split the power over two breakers. This will require a little detective work to see where an outlet on a separate breaker is located and you should try to make sure the two breakers are on the same phase. If you don’t know, then try and keep all your audio components on one breaker.
Fuses:
If you’re blowing fuses in your home fuse panel, see above for circuit breakers. If you’re blowing fuses on your individual component pieces then something is wrong that needs immediate attention. You should switch the entire system off and sit down for a think.
What’s changed since this started?

What’s the difference between 16 and 24 bit digital audio?
Increasing the number of bits in the digital audio stream increases the resolution or granularity of the signal. 16 bit audio breaks the signal up into 65,536 individual levels while 24 bit audio is divided into 16,777,216 individual levels; much higher precision and accuracy. This resolution or precision is known in specification terms as Dynamic Range. The question is: does it sound better? Whether you can hear a difference between 16 bit and 24 bit audio depends as much on the recording, your equipment and your listening environment as much as it does on your hearing acuity and preferred listening level. Achieving acoustic dynamic range greater than 16 bit is quite challenging due to aoustic ambient noise .

How can I tidy up the back of my rack?

Another perennial problem. Unless you are custom making all your interconnect cables, they will always be too long. What do you do with the surplus cable? With so many cables going in so many directions, how do you keep them straight and tidy?
You need a method and some cable management devices.

First,  install all the equipment in the position or location where you want them. Next run all the power cords into a common power strip and find a good place for the power strip to reside. Many power strips have keyhole mounts on the back which allow you to screw the strip to the back of the rack or cabinet. This greatly assists the assembly. As you plug in each power plug, coil up the surplus cable in the middle of the cord, flatten and tie using a tie-wrap or electrical tape.
Next, to keep all the cables straight, you need work from the central component, the one that connects to everything. This is usually the power amplifier/receiver. Plug all the cables into their respective jacks on the back of the receive only and lay them straight down to the floor. Next, group them into their different destinations; this could be a particular shelf in the cabinet or a particular location within the room. For each group in turn, plug in the loose end of each cable in it's respective socket, route the cable bunch together, away from the power cords aready installed. Loop any surplus cable in the middle of the run and tie-wrap or tape the group together. You can mount the group to the rack or just leave it supported by itself. Repeat until the back of your rack looks professional.

After 15 minutes of loud music, the sound changes
The culprit here is most likely heat and a careful exploration around the heat fins of your amplifier will quickly confirm this. Proceed with caution though as heatsinks can get hot enough to cause painful burns.
Having confirmed the problem, the next step is to understand why the amplifier is overheating. First, make sure that there is good airflow around the amplifier and heatsinks. If the amplifier is in a closed cupboard of cabinet then some method of getting cool air in and hot air out is needed. Natual convection (a hole in the bottom and another in the top) is a good start and may be all that is needed. If not, then some fan assistance is needed.
If there is good air circulation then the next problem could be the speaker impedance. This will probably not be the case if the amplifier and speakers were bought as a complete system as the manufacturer will have matched the amplifier to the speakers. If you have bought individual speakers you should check the impedance. A DC measurement of resistance will give you an indication. An 8 ohm speaker will usually measure around 5-6 ohms on a handheld multimeter. Anything lower than this, especially in a three or more way speaker with high order crossover could indicate trouble. High order crossovers in multi-way speakers have a habit ot presenting very challenging loads requiring additional power capability in the amplifier. The only solution in this situation is to buy a more powerful amplifier, add some forced air cooling or listen at lower levels.
Finally, it may be that your amplifier just isn’t up to the job of playing at your desired levels. If you’re playing at levels where you have to shout to be heard and your amplifier doesn’t need both hands to lift then an amplifier upgrade is needed.

I hear ghost sounds that suddenly appear in the sound.
Mysterious sounds that appear and disappear that you know aren’t in the recording are due to intermodulation effects and can be caused by a number of problems.
In analog systems such as amplifiers, they are caused by non-linearity in the electronics circuits. Modulation causes frequencies to be created at sum and difference values whenever two or more frequencies are present in a non-linear stage. All ampliying devices, tubes, transistors, FETs , are non-linear and it is the designers task to cancel or reduce these non-linearities as much as possible.  If this hasn’t been done well, then fixing the problem can be very difficult as the basic design is flawed. You’d want a very good reason to attempt this.
Heat can cause changes in the bias conditions of the output devices causing non-linearity and modulation. The cure here is to turn the volume down or get some more cooling air flow.
In digital systems, if frequencies outside the range that is supported by the sample rate are allowed into the converters, then those frequencies are folded back into the audio band effectively mirrored around the nyquist frequency. So in CD audio, a frequency of 22100 Hz becomes 22000 Hz while 30100Hz becomes 8050 Hz. Similar effects can occur with oversampling DACs where interaction between noise shaping techniques and digital anti-aliasing filters can produce strange artifacts in poorly designed systems.
These unwanted sounds which are, by definition, distortions, are difficult to meaure and quantify due to their intermittent nature. Complex test methodology is needed to track these problems down and fixes can be equally complex.