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Welcome Overview Why Quality Audio? Goals Disclaimer Pictures of my Shack and other Hams
working in
Audio Where to get Audio Equipment Help with Audio Related Problems How to fix DSP-100 problems (NEW) in Questions answered #3
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Q.
Ok, I just listened to some amazing sounding stations and I was
referred to this website. How do I get to sound like “what’s his
name”? A.
This simple question has many layers of answers from over
simplistic to extremely complicated. You must understand many of the
fidelity stations you’re listening to have spent countless hours and
dollars to achieve what you hear. The intent here is not to discourage
you, rather keep your interest in perspective so you too in the future
can sound like those you’ve heard. You have lots of work to do so if
you’re ready let’s go! Q.
Ok I understand what you’re saying I have an average station,
you know, a few dipoles, a vertical, a medium range rig like say, a
Kenwood TS450 or, a Yaesu FT920, or an Icom 1C746. I have the stock or a
Heil mic. And of course the antenna tuner, no amp right now but some
day. So what’s first? A.
Slow down, before you buy anything you must go through a learning
cycle. This way you’ll understand what’s going on, realize your
station limits, and determine your attainable audio goals. You have lots
of required reading right now; some you might not understand at first.
There is a completely different world of techy stuff and jargon you’re
required to learn or at least be familiar with. Audio Jargon and Ham
Jargon are not quite the same. Study this website, then go to other
audio websites like NU9N, KC4PE, K6JRF to mention only three. Each one
provides necessary information to help you avoid some of the frustration
those before you, have encountered. Q.
Frustration? like what? A. The list, can be endless but a few key areas are: 1. Equipment selection 2. Equipment installation [placement] 3. Proper cable routing and signal flow 4. Local interference like hum, rfi, ground loops, buzz, room noise. 5.
Equipment settings [audio and radio] Q.
Ok, I get the idea, I’m ready, but I’m also over my head.
Everyone I talk to tells me similar stuff yet it’s very different and
confusing. Am I being flimflam'd? A. Actually no! Just as you’ll get opinions and advice for a radio or antenna, you’ll find the same with audio. In the early years of this mode, there was a very steep learning curve, which also was expensive. Today, there are devices recognized that will provide you with the results you’re looking for. The good news is, the selection today is actually greater and even cheaper in cost than as recent as 2 years ago. Some
of the flim-flam you may be experiencing is due to those who have
major dollars invested and they feel that unless you do exactly like
them the process is a waste of time. I’m sure you have been through
the same thing when asking about antennas. “ya need a 150’ tower
and mono band antennas for each band” You settled for a dipole and
for now you’re satisfied. The point here is to read the websites,
listen to the various stations, take copious notes to see the pattern
of equipment used with what radios. In fact, keep track of what the
preferred radios for audio are. You will shortly see a pattern of
equipment used. Q.
I don’t want the hassle of the “science experiment” of
audio. I just want to sound good, better than I do now, you know what
I mean? A.
I’ll try to help. You have one microphone, one radio, and all
you want is to sound better, oh and quiet some room noise. I recommend
you use the W2IHY 8 band EQ box with noise gate. It is a single box
“plug and play”. The unit will interface with almost every radio
and Ham microphone. You should not encounter any rfi problems unless
your station is not set up correctly (which is a different topic in
itself]. You will still require some on air assistance in adjusting
the 8 band equalizer. Q.
I hear about “HAMALYZER & SPECTRA PLUS” what’s that
all about? A.
These are computer programs essentially used as a spectrum
analysis tool to graph your audio bandwidth and response. The graph
can be very helpful in tailoring your audio adjustments to the
anomalies in your voice and even in your Ham Shack. This is optional
and there are many folks out there with the properly adjusted
receivers and skill to help you. Q.
I have lots of
boxes a new mic, WOW! Can I have your settings, since you sound, as I
want to? A.
My station set up is different, room noise is different, my voice is
different, my microphone is different, and perhaps I even have a
different radio than you... What works for me may not work for you.
Each set up is unique period! This web site and others, have developed
a “start-up” group of settings. Some of the websites discuss EQ
settings, and other “box” settings that will get you into the ball
park out of the box. Be aware, it may take you a while to find your
“audio nirvana”. Patience is key here! Q.
Hey what’s going on here? I listened to myself in the W2IHY box
and I sounded great, then I listened in the radio monitor and I sounded
Ok, then I had a signal report saying I sounded awful. What gives? A. The secret answer here is “audio bandwidth”. When you listen to the W2IHY box, the monitor circuit is designed to “hear” the entire audio bandwidth of the equalizer. You hear full fidelity. When you listen to your audio via the radio monitor, most often the signal is tapped off from an “IF” circuit giving you a snapshot and not a true representation of your audio. Some folks have modified their monitor circuits to eliminate this occurrence. If you feed your W2IHY box or other audio directly into your microphone input, often the first stages of microphone amplifiers have frequency design limits, again some folks have changed the capacitor values in those circuits to expand the audio frequencies passed. Finally, your transmit audio is a product of your “IF” filters. The filters can vary from 250~2.4khz to 0-3.1khz or in some radios even wider or narrower. This is where your skill as a Ham operator comes into play. You need to understand your equipment and know its limits. If you have a radio with a bandwidth of say, 2.4khz you will not pass anything higher than 2.4khz even though you have a 3200hz setting at 16db on the W2IHY box! This is oversimplification but for now I’d rather not get into a technically complicated explanation. Q. You have a nice fidelity SSB audio, but what I notice more is the fact you have such a quiet signal. How do you do that? A. NOISE is defined as: any sound that is undesired. We audiophiles spend as much time dealing with “room noises as we do adjusting our audio boxes. Simply put, many of us have “tuned our ham shack rooms for minimal noise”. The actual room used for your Ham Radio Station is important. This room should be “anechoic “, which means void of echoes or reverberation. The best way to “tune the room” is to purchase a “SPL METER” like the Radio Shack 33-2050 [about $35.00]. The meter will then help you determine the noise floor of the shack, specific equipment noise, and an average room noise your microphone is picking up. A typical recording studio will be quiet, 20-30 DbSPL. Learn how to use the SPL tester properly and measure the Ham shack, if it’s 50 DbSPL or less you have a reasonably quiet shack! Now how about the equipment? For example I have a small Mirage BD-38-G amp and the blower noise is 68 DbSPL. With my entire equipment running and a ceiling fan on high, I average a room noise of about 56-65 DbSPL. This measurement was taken at the location of my microphone. The microphone will process what it hears! I then adjust my “gating” to remove the room noise. A key to a quiet room is equipment placement. Loud devices like power supplies, amplifiers, and even computers should be placed away from the microphone pick up range. If your Shack is noisy, avoid an omni directional mic”, rather use only “cardioid types” and you’ll notice less room noise transmitted. Another way to reduce background noise is to maintain the appropriate levels in your audio chain. Average conversational audio is from 60-70 dBSPL so avoid shouting /yelling into the microphone. Gating is a device/control that fully attenuates a signal, which falls below a predetermined threshold level. You use gating to remove the room noise. Proper adjustment is critical and often we overdo this setting. Q. RMS or PEAK values? A.
Most of the time your
specs
will reflect
RMS levels. To review: 0
dBm is 1 milliwatt
which
equals 0.775 volts
RMS across a 600 ohm
circuit, and 0 dBV is 1 volt RMS.
When we wish to evaluate the loudness of a signal as
perceived
by a
human ear, the RMS value
corresponds more closely with the sensitivity of
our ears to
audio energy. The
exception
is
when we discuss the
broadcast limiter. A
momentary transient peak can
cause over modulation and consequent signal
splatter [spurious emissions],
in
this instance a peak detector/limiter
is used [and not an RMS
level] to address
the signal. Q. I’m confused, I hear everyone tossing around the term “Db this and Db that” What’s a Db? A.
Books are
written
about the “Db” so there is
really no truly simple explanation, but I’ll
try to
make some sense of the use
of “Db”in the fidelity SSB audio world
The “Db” is a unit
of audio measurement of sound
pressure level [SPLI, signal level, and
changes or differences in
signal level. The decibel is a logarithmic [log]
mathematical function that
reduces large numeric
values into smaller, more
manageable numbers. STAY WITH ME!
Decibel is
calculated as being 10
times the log of the ratio
of two powers
and 20 times the
log of the ratio of two
voltages. dBm=
decibels referenced to 1
milliwatt dBu
-or- dBv= decibels referenced
to 0.775 volt. [dBu is preferred] dBV = decibels referenced to 1 volt Keep in mind in the audio world we are looking at an impedance load of 600 ohms. So, 0.775v across 600 ohms equals 0 dBm. 1 volt across 1000 ohms equals 0 dBm some meters are calibrated in dBm so the meter indication is only accurate when across a 600 ohm load. Another unit of measurement is the dBu. This means 0 dBm= 0.775 volt across 600 ohms. Relating dBV, dBu, and dBm to specifications: In many products you see phono jack inputs and outputs rated in dBV [1 volt ref.] because that is the standard generally applied to such equipment. The XLR connector output level and some phone jack output levels [confusing huh?] are rated in dBm [1 milliwatt ref] or dBu [0.775 volt ref] Typically, line level phono jack inputs and outputs are intended for use with high impedance equipment, which is basically sensitive to voltage rather than power. So, their nominal levels may be specified as “-10 dBV” This is the standard used in consumer grade audio equipment for many years! Typical line level XLR connector inputs and outputs are intended for use with low or high impedance equipment. Since older low impedance equipment was sensitive to power, XLR connector nominal levels were often specified as " +4dBm or + 8dBm". These levels are characteristic of sound reinforcement, recording, and broadcast equipment respectively. Most newer Ham Radio’s utilize a 250 to 600 ohm microphone input impedance. Finally, matching impedance is important for proper signal levels, controlling distortion, and equipment overload. A low impedance line output can be connected to a higher impedance input with minima! level change. But, if a high impedance output is connected to low impedance input that output may be somewhat overloaded and the frequency response may be adversely affected. In some cases, the equipment could also be damaged. To truly understand the device specifications presented is in itself an amazing accomplishment. Most spec sheets are designed under specific parameters to advertise amazing results!!! Thus, sell more product [my opinion]. With that said, let me try approaching the Db from another angle. SIMPLY PUT: * The Decibel is a technical term that describes the difference in amplitude between two signals. *When a scale is specified, a DB can also refer to an absolute level. * dBSPL is used to measure an absolute volume [sound pressure levels] * The scale of your mixer's LED meter is marked in dBu [typically or selected to measure dBV ] which is a standard scale for measuring the amplitude of mic-level [or line-level] audio signals. · Audio signal levels fall into three ranges: 1. speaker-level, 2. line-level, 3. mic-level Mixers can work with line and mic levels. XLR connectors are usually designated mic-level and the TRS connectors are designated line-level. One of the mixer's functions is to bring the different signals into a roughly equal operating range. So, we have two signal levels, -10 dBV and +4 dBu that we have to work with: If you take the output of a –l0 dBV piece of gear and patch it into something expecting a + 4 dBu level input, the sound may be too soft, even when turned all the way up. The reverse is also a problem, because the output of a +4 DBu device may cause distortion in the input of a device designed for –l0dBV level signal. Some of our audio boxes can operate at either signal level by including a little switch near the input or output jacks marked “-10/+4”. Toggling the switch between these two positions calibrates that device’s inputs or outputs to conform to one or the other operating level standard. When possible, try to choose components that all use the same reference level-- all -10dB or all +4 dBu. Keep in mind -10 and +4 signals may be both referred or generically as “line level” signals even though the +4 level signals are of significantly higher amplitude.
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