Why do capacitors sound different?

In the past capacitors were just capacitors and sound quality was determined by the dialectric material with polypropylene considered by many as "the best" seeing as this type of capacitor had the lowest losses. But technology of the 21st century has brought us new measuring techniques and insights and there seems to be more to it. We can now measure things that were not possible a few years ago. In a nut-shell: microphony is the keyword - the mechanical resonance, a key feature of audio capacitors. This is a physical deformation of the capacitor walls which occurs as a result of the audio signal passing through the component - much like an electrostatic speaker. This resonance is dependent on the size, shape, materials and manufacturing parameters of the capacitors. This effect has been known about for years as it plays a part in the impulse strength of capacitors. However, the effect has never been considered read the white paper on mechanical resonances inside capacitors. Another interesting article was written by Martin Colloms back in 1985 in which he tested several capacitors on their sonic differences. Also look at the equivalent circuit diagram of a capacitor, this also explains a lot!

Phase

Speakers are a complex electromechanical machine that vibrate and move air to produce sound. Sounds simple. But what many people do not understand is just how a speaker receives a signal from the radio or amplifier which powers it.

All electronics in a vehicle will operate on 12 Volts DC, or direct current battery voltages. But, a speaker will not operate properly if DC voltages are applied to a speaker. So what happens? The amplifier, whether internal to the radio or a separate amplifier connected to the radio, will convert an audio signal from the radio to a very low AC voltage.

For a speaker to make sound, it must move IN and OUT. But to do this, the audio signal that is given to the speaker through speaker wires must change polarity. Or more simply, the voltage waveform of the audio signal must switch between (+) positive and (-) negative polarities very quickly. When a this happens, the speaker will move in for (-) negative signal and move out for (+) positive signals. This is a simplified overview of how a speaker vibrates in and out, producing sound. This is a very important concept in mobile electronics.

POLARITY: is the part of the voltage waveform that is currently active. The part of the waveform that is (+) is considered positive polarity, and the part of the waveform that is negative is considered negative polarity. You might notice that speakers connections are marked (+) positive and (-) negative so that you connect the (+) positive speaker wire to the (+) positive speaker connection and that you connect the (-) negative speaker wire to the (-) speaker connection.

In reality, a speaker is NEUTRAL or doesn’t have a (+) positive or (-) negative to it. The marks on the speaker indicating (+) positive and (-) negative are there so that you connect ALL of your speaker the same way. WHY? Well, polarity. When all speakers are connected the same, all (+) positive speaker wires connected to (+) positive speaker connections, etc., then all speakers will move out at the same time and move in at the same time. When all speakers are connected the same, the speakers are said to be “in polarity”. What happens if speakers are “out of polarity”? Lets say there are (4) four speakers in a vehicle, (3) three of which are connected the same, but (1) one is connected “out of phase”. That one speaker will move opposite of the other three and cause problems. The amplifier that is powering the four speakers will, internally, see an “out of phase” problems. When an “out of phase” problem exists, the overall sound from the speakers will sound different. What happens inside the amplifier is that the AC voltage waveform powering the “out of phase” speaker will be opposite of the other “in phase” waveforms. When this happens, the “out of phase” waveform signal will CANCEL out one or more of the “in phase” waveform signals powering one of the “in phase” speakers. When two waveforms cancel each other out, a flat waveform exists. Speakers will reproduce this flat waveform in the form of dull or lifeless music.

Many amateur installers or listeners cannot tell when a speaker is out of phase. To these people, the music reproduced by the speakers sounds odd, but they do not know how to solve the problem - finding the speaker “out of phase” and flipping the wires until the speaker is “in phase” with the rest of the speakers. When this happens, the sound immediately improves and the amp is not fighting itself internally.

AC Voltage Audio Waveforms

Low ESR Capacitors

What is ESR?

ESR is an abbreviation for Equivalent Series Resistance, the characteristic representing the sum of resistive (ohmic) losses within a capacitor. While ESR is undesirable, all capacitors exhibit ESR to some degree. Materials and construction techniques used to produce the capacitor all contribute to the component's ESR value. ESR is a frequency dependent characteristic, so comparison between component types should be referenced to the same frequency. Industry standard reference for ESR is 100KHz, +25°C. ESR is an important characteristic, as the power dissipation (watts) within the capacitor, and the effectiveness of the capacitor's noise suppression characteristics, will be related directly to the ESR value.

What's driving demand for Low ESR?

An industry wide trend towards lower voltage - higher current circuit design, fueled by lower voltage silicon devices is causing designers to specify capacitors with minimal ESR. Higher levels of functionality in today's designs means that despite voltage level falling, circuit power levels have not dropped accordingly. Ohms law tell us, in every simple fashion, that at the same power dissipation level, lower voltage operation will mean higher current levels. This greatly increases the demands on the power management circuit (power supply or DC/DC converter) to deliver energy during periods of high current load stepping. Lower voltage circuit operation also imposes greater restrictions upon the output voltage variation level as well. The output capacitors or capacitor bank, used in the power management circuit, need to exhibit low ESR characteristics. Ripple voltage (noise) on the output supply voltage will be directly proportional to the ESR of the capacitor used. By considering the formula: Vr = I x R, where Vr is the ripple voltage and R is the ESR, we can see that if the current (I) increases from say 4A to 20A then the ripple voltage will also increase by a factor of five. Increased ripple voltage (Vr) cannot be toleranted in todays and next generation designs. This is fueling demand for very lower ESR capacitors.

What types of Low ESR Capacitors are available?

Capacitance values greater than 10ìF are often required to supply energy to today's electronic circuits, during load current stepping (low to high current stepping). This requirement is met through the use of single or multiple surface mount (SMT) electrolytic capacitors or combination electrolytic and high capacitance MLCC (ceramic chip) capacitor. Surface mount configurations are preferred as it allows closer component placement, reduces performance robbing series inductance and can reduce total PCB assembly costs. Recent low ESR electrolytic capacitor development has focused on techniques and materials designed to reduced the resistance of the cathode connection, either with a lower resistivity solid electrolyte. The cathode connection of electrolytic capacitors is the largest contributor to the electrolytic capacitors total ESR figure.

Low ESR SMT capacitors available today chiefly fall into 7 types.

ESR = Equivalent Series Resistance (ohm)

RCR = Ripple Current Rating (Amp)

1. LIQUID ELECTROLYTE, VERTICAL CAN CHIP ALUMINIUM ELECTROLYTIC CAPACITORS

Lowest cost solution.

Pros: High capacitance values, high voltage ratings, moderate to low ESR, moderate RCR and lowest cost.

Cons: Liquid electrolyte exhibits dry-out under high temperature, medium to large sizes.

2.HYBRID ELECTROLYTE, VERTICAL CAN CHIP ALUMINIUM ELECTROLYTIC CAPACITORS

Provides solid electrolyte performance (very low ESR) at much lower cost than solid electrolyte types.

Pros: Very Low ESR, High RCR, moderate capacitance values and moderate cost.

Cons: Liquid electrolyte component exhibits dry-out under high temperature, low voltage ratings and medium sizes.

3. SOLID POLYMER ELECTROLYTE, VERTICAL CAN CHIP ALUMINIUM ELECTROLYTIC CAPACITORS

Lowest ESR and highest RCR of the vertical can chip types, but at highest cost.

Pros: Very Low ESR, High RCR, moderate capacitance values and solid electrolyte for good long-term performance at high temperature.

Cons: High cost, low voltage ratings and medium sizes.

4. SOLID POLYMER ELECTROLYTE RESIN ENCAPSULATED FLAT CHIP ALUMINIUM ELECTROLYTIC CAPACITORS

Low ESR and high RCR, but at highest cost of all aluminium electrolytic types.

Pros: Very Low ESR, High RCR, Smallest size aluminium electrolytic type, moderate capacitance values and solid electrolyte for good long-term performance at high temperature.

Cons: High cost and low voltage ratings.

5. SOLID ELECTROLYTE, RESIN ENCAPSULATED FLAT CHIP MnO2 CATHODE TANTALUM ELECTROLYTIC CAPACITORS.

Standard tantalum chip capacitor construction processed for low ESR.

Pros: Moderate to Low ESR, Moderate RCR, Small size, Low ESR versions produced with manganese dioxide cathode (MnO2) construction and solid electrolyte for good long-term performance at high temperature.

Cons: Low voltage rating and limited transient (reverse or surge conditions) tolerance, could combust upon failure.

6. SOLID ELECTROLYTE, RESIN ENCAPSULATED FLAT CHIP POLYMER CATHODE TANTALUM ELECTROLYTIC CAPACITORS.

Standard manganese dioxide cathode (MnO2) is replaced by a highly conductive polymer (polypyrrole) cathode that considerably reduce ESR. The conductivity of polypyrrole is more than 100 times that of manganese dioxide.

Pros: Very Low ESR, High RCR, Small size, polymer cathode construction suppresses combustion = increased safety factor and solid electrolyte for good long-term performance at high temperature.

Cons: High Cost and low voltage ratings.

7. MLCC - SURFACE MOUNT CERAMIC CHIP CAPACITORS.

Capacitance values up to 100uF are available today in ultra-small sizes.

Pros: Ultra Low ESR, Moderate RCR, Smallest size, Non-polarized for applications where reverse operation or transient conditions occur, High temperature rating and good soldering heat exposure characteristics.

Cons: Low voltage ratings, Large effective capacitance loss under VDC operation, Capacitance decrease over time (aging), Piezoelectric effects.

Summary

Circuit designs incorporating lower voltage semiconductors and IC's are driving increasing demand for better and lower ESR capacitors. SMT low ESR type electrolytic capacitors offer the combined solution of high capacitance, to supply energy during high-speed load stepping, and low ESR to reduce the output filter ripple (noise) voltage to meet the needs of today's and tomorrow's power management design challenges.

Clarion DRZ9255 (HX-D2)

Enjoy your music like it was intended to be heard

No other source unit combines the DRZ9255’s dedication to pure sonic performance with signal processing power at this level. The 24-bit 96kHz D/A converter recreates music without any phase shift or attenuation - the result is silky smooth, incredibly life-like and detailed sound that deserves the name Clarion. The incredible accuracy of the time alignment, parametric equalization and built-in crossovers make it easier than ever to tune your system perfectly. Housed in a copper plated chassis and powered by an external DC-DC power supply, the DRZ9255 is the only choice for the true audio enthusiast.

• Dual 24-bit / 96 kHz Sampling Digital-to-Analog Burr-Brown Converters and DSP

• Built-In 4-Way Crossovers

• 5-Band Parametric Equalizer

• Digital Time Alignment for Each Line Level Output

• 8-Channel/4-Volt Gold Plated Oxygen-Free Copper RCA Outputs

• 0.5dB-Step Electronic Volume Adjustment Circuit

• Copper Plated Chassis

• External DC/DC Converter

• CeNET Control of Optional CD Changer, TV Tuner and iPod Interface

• Two 2-Channel AUX Inputs

• Zinc Die-Cast Faceplate

• Fiber Optic Input/Output

• Vacuum Florescent Display

• 18FM/6AM Presets

• Remote Control Included

Conventional CD Players Can Only Reproduce Frequencies Up to Around 20 kHz

The spiral pattern on CDs represents numbers (“digit” means “number”). These numbers represent measurements of an audio signal (and other data). When a digital recording is made, measurements can be made 44,100 times each second (per channel). At that sampling rate, frequencies up to around 20 kHz can be recorded… so the frequency range of conventional CD players barely extends over 20 kHz.

High-Frequency Harmonics Add Richness and Depth to Sound

Why can’t conventional CDs encode data for frequencies over the limit of around 20 kHz? Because the people who set the CD standard believed that no one could hear those high frequencies. If such frequencies were on a conventional CD, the filters in a conventional CD player would remove those frequencies. Furthermore, analog filters can cause phase distortion of the signals that go through them, causing the high frequencies that do come out of the player to come out at the wrong times. Ironically, high-frequency harmonics can affect the details and the depth of sound.

96 kHz Oversampling Enables Reproduction That Is More Faithful to the Original Source

The 96 kHz digital anti-imaging filter interpolates samples into the audio signal from the disc at a speed more than twice as fast as the CD standard sampling rate of 44.1 kHz. This is the first such digital filter designed for vehicle audio. Without oversampling, the signal from a CD must be filtered in the analog domain to reduce high-frequency noise, and such analog filters cause phase (time) distortion. Oversampling filters are free from phase distortion, so they deliver more musical detail and more of the realistic resonances of real live sound.

Copper Plated Chassis Reduces Distortion and Noise

The use of a copper plated chassis minimizes the creation of spurious electrical currents that could distort the audio signal. Additionally, the copper plating can reduce noise because it creates an insulating shield. Zinc has a high specific gravity, high rigidity, and low resonance, so a die-cast zinc panel can reduce distortion caused by vibration. Because components such as the power supply, VFD devices for the display, and the drive mechanism can cause noise in the signal, those components are externally positioned away from the audio signal.

Burr-Brown Advanced Segment 24-Bit Digital-to-Analog Converter

After the data from the disc goes through the 96-kHz filter, it is processed by a Burr-Brown advanced segment 24-bit DAC with superior dynamics and resistance to clock jitter. The Digital-to-Analog conversion is highly accurate because the DAC’s internal structure is a four DAC configuration operating on an L–R differential signal.

Turning the Display OFF to Turn Sound Quality ON

When the DRZ9255 plays a CD or other source, its display can be turned off to minimize interference from circuits that can otherwise degrade sound quality.

The DRZ9255’s DC / DC Converter Keeps Great Sound In and Keeps Noise Out

The DRZ9255 is truly an audiophile source unit. Its external DC / DC converter is comprised of components of the highest quality from its input wiring through its chassis to its output fuses. This power supply gives the DRZ9255 both strength and precision, and its six-sided shielded casing repels noise even during high-load bursts. To prevent even the smallest vibration, the power supply is wrapped in a die-cast aluminum casing and a copper plated chassis. Toroidal choke coils inside the power supply minimize induced vehicle noise and loss of power. A large capacity low impedance condenser allows this external component to supply pure power. Clarion takes this one step beyond by equipping this power supply with a gold plated connection terminal to further minimize power loss.

The World’s Best 0.7 Cm per Step Digital Arrival Time Alignment

This function lets you delay signals going through as many as eight channels so sound from all speakers can arrive at one location simultaneously. Arrival times can be optimized for the driver, front passenger, both front seats, rear seats, or all seats. You can quickly and easily select the system’s acoustic pattern… or choose settings based on the type of vehicle or number of passengers. Signals can be delayed for differences in distance of up to 500 centimeters (over 16 feet) in increments of 7 millimeters (approximately one forth of an inch).

TUNER SECTION
Frequency Bands
FM: (MHz) 0.2 MHz steps	87.9 to 107.9
AM: (kHz) 10 kHz steps	530 to 1,710
FM Usable Sensitivity (dBf)	9
FM 50 dB Quieting Sensitivity (dBf)	15
FM Alternate Channel Selectivity (dBf)	70
FM Stereo Separation @1 kHz (dB)	35
FM Stereo Freq. Resp. @ 3 dB (Hz)	30 to 15,000
CD SECTION
Wow/Flutter (WRMS)	Below measurable limit
S/N Ratio (dB)	112
Frequency Response (Hz)	5 to 20,000
Dynamic Range (dB)	100
Harmonic Distortion (%)	0.003
GENERAL
Dimensions (W × H × D), mm	178 × 50 × 178
DC/DC Converter (W × H × D)mm	175 × 43 × 99
Remote Control (W × H × D), mm	52 × 125 × 12
Power Consumption: less than	1.4A
Speaker Impedance	4 (4 to 8 allowable)

Car audio - Top 10 SQ Head Unit

We should start with the caveat that it's incredibly difficult to rank these units and it's almost unfair to each to compare them to another. Some of the products were made in different times, some are made to work as part of a system—especially in that case how do you put these products in any kind of order?—and they have different price points plus various levels of complexity to boot. Our top ten list is definitely not meant to be hierarchical. We'll let you decide. Go to our Forums page where you will see a longer list of source units and cast your vote. Or add to the list. We'll compile the numbers and present the enthusiasts' pick for best SQ source units later this year.

1. Alpine 7909
Introduced in 1989, Alpine's 7909 is still a sought after radio by audio enthusiasts. When you're talking about this CD player, we thought who better to ask than SpeakerWorks' Eric Holdaway who used one in his legendary Buick Grand National. He had this to say: "It was easy to use, good looking and sounded great.  It was the first unit I knew of that used Dual DACs, 18x oversampling and had an 18-bit processor instead of the regular 16 that all other CD players used. The AM/FM tuner was the very best tuner I have ever used. I wish Alpine would go back to that tuner!!! Looking back at a 7909, it is kind of funny that the unit was a pullout… Big ol' handle hanging off the face—man was I glad they had a lock in kit for those!!!"

2. Pioneer  DEX-P99RS
With sound quality increasingly taking a back seat to other aspects of car audio and electronics, it's nice to see a company like Pioneer continuing to maintain a high standard for audio playback. We recently evaluated their new top of the line CD player. Read Howie Liwanag's review here. 

3. Alpine DVI-9990 (plus PXI-H990 Multimedia Manager)
In some people's opinion, the most sophisticated source unit and processor ever made. The first-ever DVD-Audio system designed for in-car use, and the first to fully and properly implement digital signal processing entirely in the digital domain, without any unnecessary D/A and A/D conversions along the signal path. Also the first to implement auto-tuning and automatic road EQ-ing in real time. Ask any Alpine fan and they say that it remains the ultimate mobile audio source unit and processor system, not soon to be surpassed. Drawbacks? It was expensive and you have to use the H990. Read contributor Bob Norvelle's review here.

4. McIntosh MX4000/MDA4000
Legendary McIntosh heritage translated into the mobile audio realm. Classic and timeless McIntosh design and incredible build quality. The only head unit ever made with a silkscreened glass face and aluminum machined knobs. The looks and user interface are second to none! Of course, you either love or hate the looks of McIntosh products; not a lot in the middle. Those who love it say the head unit makes other head units look like silly toys with a myriad of useless LEDs and non-tactile buttons. The first source unit in car audio to use a separate state-of-the-art 20 bit D/A converter. This combo may be the most admired and respected source unit for CD sound quality in the history of audio. 

5 & 6. Pioneer 800/880 PRS and Alpine 9887 
Feature editor Bing Xu voted for these units for a very good reason: "I like these options because they are SQ heads for the common guy, very reasonably priced. And while their on-board processing capability is limited, you can still do a mild active system with them. As standalone head units, they are also very clean, especially considering the price points.  These two go hand in hand for me when I think of moderately priced SQ head units. That’s what makes them relevant on this list in my opinion."


7. Pioneer ODR system
The acronym stands for Optical Digital Reference, but needs no introduction or explanation to serious audio enthusiasts the world over. The audio signal stays within the digital domain from CD player to amp. No noise, no deterioration of sound. A legion of ODR fans swear by its sound quality. Then add to it one of the sexiest and most elegant cosmetic designs and you have perhaps the most desirable product/system of them all.

8. Clarion DRZ9255 (Clarion HX-D2)
This understated beauty is more than good looks with its Dual 24-bit / 96 kHz Sampling Digital-to-Analog Burr-Brown Converters and DSP. Clarion took the best of the DRX-9255, made it even better and then put it in a new package to create the DRZ-9255. Most will probably agree that its an improvement over its predecessor in terms of cosmetics and usability and, as Bing says, it also takes CDRs more easily. Aside from the setup side, it's very easy to use. However, trying to use it as an actual DSP is really slow and labor intensive, not to mention its capabilities are somewhat limited compared to a full outboard DSP.  Some say they are prone to certain noise issues. 

9 & 10. Denon DCT-Z1 and Nakamichi CD700 & MB100
We love the Denon for its looks and its SQ prowess. It has balanced ps2 style output jacks, very classy and solid looking design, exceedingly easy to use, but obviously, very pricey and has virtually zero expansion capability. The Nakamichi is similar to Denon in terms of attributes, but perhaps not as reliable, especially the CD transport system.