Sunday, February 5, 2017

How a MM Phono Cartridge Works

How a MM Phono Cartridge Works

Phono amplifier is designed for a phono signal amplification while using Turntables amplifier inside for special sound equalization circuit (RIAA) for restoring vinyl, it cannot be used for other purposes. But do you know How a MM Phono Cartridge works -- the key component that pick up the signal from the LP vinyl which is amplified.

A MM phono cartridge is a micro-manufactured electromechanical device that tells your entire audio system what is happening along the half-mile groove that is cut into a typical analog disk.

Phono cartridges contain transducers that convert one form of energy into another. Phono cartridges do it by translating variations in the groove walls into electrical signals. Great inventer Thomas Edison pioneered this technology way back in 1877 using a stylus on a tinfoil or wax cylinder.

The stylus (needle) moves horizontally and vertically as the groove of the record travels underneath it. A coil of wire and magnet at its other end generates a small audio signal.

Since then, there are two main types of phono cartridges: moving magnet (MM) and moving coil (MC). A tiny magnet rests on the end of a stylus shank that is suspended between two coils. The vibrating magnet induces a small current in the coils. 

To decide which phono cartridge will work best for you that depends on a few factors.

You will need to know how the cartridge attaches to the turntable you have or are going to buy. There are two types as below.

Standard mount that is far the most common: Two screws, half an inch apart, thread through the cartridge body to secure it to the headshell, which then plugs into the tone arm.

P-mount that is The four prongs at the back of the cartridge plug directly into the tone arm. A setscrew goes through the side of the cartridge at the back to hold it in place on the tone arm.

Elliptical (Bi-radial) or Spherical Stylus

The stylus (or needle) is really the heart and soul of the cartridge and accounts for about 90% of the cost of it.  Almost all styli have industrial diamond tips. There are two needle shapes: elliptical and spherical. Elliptical needles pick up more information from the record groove and are typically the choice of audiophiles. DJs choose spherical needles because they sit higher in the groove and result in less record wear.

Finally, a LP Turntables Tonearm Signal Cable from the output of MM phono cartridge will be connected to phono stage amplifier to amply weaker signal.There is a HIFI LP Turntables Tonearm Signal Cable that is good partner for connecting them.

Tips for Adjusting Car Amplifier Gain

Tips for Adjusting Car Amplifier Gain

You will be happy after you buy a car audio amplifier, but it may be a little trouble when you set up or adjust its tone and gains after you connect it with the car speaker units according to the diagram. The article might help you set up it successfully after you read it. It is provide a general guide or tips, of course, you also shall refer to the manual.

Contrary to popular belief, car audio amplifier gain controls aren't volume controls. They are input sensitivity controls and are intended to allow the user to adjust the sensitivity of an amplifier to match the output voltage from the head unit. This is needed in car audio because there is no standard for head unit output voltage.

The purpose of properly setting the amplifier gain is three steps. 

First and most importantly, it is to allow the amplifier to reach max output when the head unit volume is at max without causing the amplifier to clip. 

Secondly, gain can be limited to prevent over-powering your speakers if the amp can put out more than the speakers can handle. 

Third, gains can be used to help balance a system, meaning adjusting the relative output levels between amplifiers so that they are operating at the correct levels for any given head unit volume setting. 

This guide is primarily aimed at addressing the first: achieving max output without clipping the amplifier. Here are a few things you'll need as below.

Power Amplifier HIFI 4 Channel 4 x 80W Brushed Aluminum alloy casing American Descent Silver 

Back View

Inside View

Hearing protection

You need ear plugs or muffs while setting gain as the system will be operating at high output levels. Hearing loss is very quick as sounds become louder, and you really need to protect your ears because building a good sounding sound system will be a waste of time if you can't hear it. Also since the output will be high while gain is being set you should perform this in a location and at a time when it won’t disturb other people.

A CD with proper test tones

You need a CD recorded at 0db reference level that contains various test tones. 50-60 Hz is good for setting subwoofer levels and 1000-1500 Hz is good for setting main stereo amp levels.

Basics setup

1. Fader, tone controls, loudness/expansion, etc. 

Fader and balance controls should be set to “normal” or zero or “in the middle.” Loudness and bass boost should be OFF and all EQ set to flat.

2. Dedicated subwoofer volume controls 

Many amps have outboard subwoofer volume controls and head units have dedicated internal subwoofer volume adjustments. These should be set to MAX.

3. Set all amp gains to their lowest point before starting. 
This is usually full counter-clockwise.

4. Input sensitivity switches
If your amp has a selector switch for different input sensitivities, start by setting it to the highest setting. These are typically expressed in voltages, for example .2-1v, 1-3v, 3-8v. Start with the higher numbers (ex. 3-8v which is the lowest sensitivity). If you can't get the amp to clip at those settings, try the next one down until you find the clipping point. You can disregard generally what the markings themselves say since there's no real standard for marking them. Never trust your system's well-being to those arbitrary numbers, they're just there for reference and are best ignored.

5. Work with one gain at a time.
For example, if you have both L&R gain for your front speakers, you'll set each side separately. If multiple amps, unplug (remove the signal from) all but the amp you're working with. If it’s a 4+ channel amp, typically you'll have only a single L & R gain, so treat it like a 2 channel. If it has multiple gains adjust each one separately.

After you set up them below, Now you can test it, the procedure as below.

1. Play the appropriate test tone

Put on your hearing protection and start your car. Select a test tone that is in the pass band of the amplifier channel you are setting. For example, if it’s a subwoofer amp select something audible below the subwoofer LP crossover setting. We like to use 60Hz. Set your CD player on its lowest volume setting and play the track in repeat mode.

2. Find the head unit clipping point

Slowly turn up the head unit volume and you should begin hearing the tone. Keep turning it up until you can hear the tone change. It will become “sharp” sounding and is an obvious change. This indicates the head unit preamp is now clipping. Note the volume level and slowly turn the head unit back down until the tone changes back to its original sound. Note this volume level. If the head unit clips at below its max level, you should NEVER turn it up past the point where the clipping begins.

If the head unit never clips, this is good and indicates you have a quality preamp. Set the volume control to about 75% or 80% of whatever its max might be.

3. Now find the amplifier clipping level

Turn off the system and disconnect all the RCA cables except for the amplifier channel you are setting. Now turn the system on and place the test tone in repeat, and turn the head unit up to the max unclipped volume discovered in the previous step. Move to the first amplifier gain control and SLOWLY turn it up until you hear the tone change quality like before. This step may get loud, so be prepared. Once you find the gain setting where clipping begins, slowly back it off until the clipping stops. This is your proper max gain setting for this amplifier channel. Leave it there. Now turn off the head unit and repeat the above step for all the other amplifier channels in your system.

After setting all the gains you can enjoy your system. 

There is also a car audio amplifier with tubes 6992 as preamplifer, if you like warm tube taste.

HIFI Car Amplifier 4 Channels Audio 6992 Tube Preamplifier Transistors Power Stage Class AB RMS Power 85 W x 4

If you like the car audio amplifier, please visit the links for details.