oscillators

  • Thread starter Thread starter antispatula
  • Start date Start date
ok yeah, it's actally xlr UNbalanced, so making a cable is no big deal. Which side L or R should I use as the conductor into the XLR?

One more thing I don't get is how is it going to affect my signal when the computer is -10db(? I'm assuming) and my machine takes a +4 signal. I don't get how those numbers effect the signal. Does that mean it ADDS 4 DB when it goes into the machine, or what?
 
Well, there are actually two different differences at hand.

-10 vs +4 is actually closer to a difference of 12 db.

and 0db on the computer is actually -12 db in the analog world.

so; if your computer outputs 0 db at -10 digital, this should actually be very close to +4 analog. I suggest getting the meter hooked up to get a reading. I plan on doing this soon and I will let you know my results.

what kind of machine are you calibrating again?
 
well I'm sure the manual is taking into account the +4 part, all it's saying is to send the machine a -18db, so I think all I need to do is send a -18 db signal, and assume that they have already taken into account the line level.

So if my computer sends a -10 signal, and I need a -18 signal, I need to make a -8 db signal on the comp.

So -8 plus the added -10 from the output of my computer should make a -18 db signal......right? :D

Is that how it works? When a machine says it sends out a -10 signal, it ADDS -10 to the signal right, or if if a machine is +4, it ADD's +4 to the signal, right? I don't know why I don't know this already.
 
dB is a ratio of 2 signals. Typically one of the signals is a reference. If yuo are compairing dB levels that are referenced to the same reference you can just add together. (-10 dBv plus +2dBv equals -8dBv)

Take a look at: http://www.jimprice.com/prosound/db.htm for a quick review.
 
antispatula said:
Is that how it works? When a machine says it sends out a -10 signal, it ADDS -10 to the signal right, or if if a machine is +4, it ADD's +4 to the signal, right? I don't know why I don't know this already.
Click to expand...

no. -10 or +4 are simply two different operating levels. They are not even on the same decibel scale. one is dbfs and the other is dbv or something like that. I believe +4 literally means 0db = 1 volt and -10 literally means 0db = .3 volts (roughly). so, "pro" or +4 gear runs at a higher voltage level. that's all.

don't worry about why you don't know it already. you are leaps and bounds beyond anyone else at your age. I've actually been sitting here thinking "damn this kid is asking some advanced stuff!"
 
Snippin out of the web page....



Understanding dB
dB is an abbreviation for "decibel". One decibel is one tenth of a Bel, named for Alexander Graham Bell. The measurement quoted in dB describes the ratio (10 log power difference, 20 log voltage difference, etc.) between the quantity of two levels, the level being measured and a reference. To describe an absolute value, the reference point must be known. There are a number of different reference points defined. Here are a few:
dBV represents the level compared to 1 Volt RMS. 0dBV = 1V. There is no reference to impedance.
dBu represents the level compared to 0.775 Volts RMS with an unloaded, open circuit, source (u = unloaded).
dBm represents the power level compared to 1 mWatt. This is a level compared to 0.775 Volts RMS across a 600 Ohm load impedance. Note that this is a measurement of power, not a measurement of voltage.
dbFS - relative to digital full-scale.
dB SPL - A measure of sound pressure level.

A few easy-to-remember facts that may help:
If you're dealing with voltage measurments, convert from dBV to dBu: 1dBV equals +2.2dBu.
+4dBu equals 1.23 Volts RMS.
The reference level of -10dBV is the equivalent to a level of -7.8dBu.
+4dBu and -10dBV systems have a level difference of 11.8 dB and not 14 dB. This is almost a voltage ratio of 4:1 (Don't forget the difference between dBu and dbV !!)

dBFS - dB Full Scale

0 dBFS represents the highest possible level in digital gear.
 
thanks, evm.

question - how can you add decibels together?

say -10 + 3 . is this simply -7 or is it more complicated?
 
FALKEN said:
question - how can you add decibels together?
say -10 + 3 . is this simply -7 or is it more complicated?
Click to expand...
Yes, if the reference is the same. So -7dBV is 3dB more than -10dBV.
 
FALKEN said:
no. -10 or +4 are simply two different operating levels. They are not even on the same decibel scale. one is dbfs and the other is dbv or something like that. I believe +4 literally means 0db = 1 volt and -10 literally means 0db = .3 volts (roughly). so, "pro" or +4 gear runs at a higher voltage level. that's all.

don't worry about why you don't know it already. you are leaps and bounds beyond anyone else at your age. I've actually been sitting here thinking "damn this kid is asking some advanced stuff!"
Click to expand...

haha hey thanks, yeah but believe me, I barely understand the questions I ask :D

So I downloaded a digital oscillator, and for the amplitude or the output, it just says DB. Which one are they talking about?! :rolleyes: Is there one that is more likely than they other that they are using?
 
probably dbFS. what you should do is hook up your meter to the output and just adjust the volume on your soundcard to get to the right voltage. at least that's what I'm doing. someone want to verify this?


edit: crap...this doesn't seem to be working right. in the PC; I need different amounts of gain to get 400 hz and 7 khz to come out at .3 volts; but when that same .3 volt signal is fed into the inputs of the reel machine, each frequency reads differently on the VU meter, even though the voltage is the same.....

So, Should I reference 1k to .316 V and then adjust the frequencies,

or should I readjust to .316 V for each frequency?

Thanks.
 
Last edited:
FALKEN said:
probably dbFS. what you should do is hook up your meter to the output and just adjust the volume on your soundcard to get to the right voltage. at least that's what I'm doing. someone want to verify this?


edit: crap...this doesn't seem to be working right. in the PC; I need different amounts of gain to get 400 hz and 7 khz to come out at .3 volts; but when that same .3 volt signal is fed into the inputs of the reel machine, each frequency reads differently on the VU meter, even though the voltage is the same.....

So, Should I reference 1k to .316 V and then adjust the frequencies,

or should I readjust to .316 V for each frequency?

Thanks.
Click to expand...

yeah it's no big deal what the db reading it states on the computer, I'll just adjust till I get the right level on my voltmeter......If my voltmeter would read in millivotls AC!!!!!! Man, just another thing to go searching for...... I have a digital voltmeter, but it only reads in millis on the DC setting. How inconvinent is that! Don't MOST voltmeters allow you to read millivolts on an AC signal? What big name stores would sell them? All the "electronics" strores now are so commercial, it's hard to find places nowadays to get the things you need if they don't fall under the category of cell phones or video games or rap.
 
I got mine from radio shack. what I found is that if I set 1 khz to be .3 volts, then no matter what I switched the tone to on the PC, the VU meters stayed at zero but the voltmeter jumped around. weird, eh?
 
well it's not as if I know what I'm talking about, but it's most likely just that you're reading in millivolts so you can see the minute change, but the vu meters are perhaps not sensitive enough to pick up the change? Don't know.

Haha ironically enough, I WORK at a "radio shack." (just an after-school job kind of thing) We're now Strawflower Electronics (we were a RS franchise) because on our 25th year anniversary, they cancelled our contract illegally, and my boss is deep in a lawsuit with them at the moment actaully. Haha actaully, the CEO of RS has resigned because he lied on his resume back in the day, and turns out he never graduated college ect ect and people finally figured that out. :D But anyways, we don't even have a meter that reads in mV's, at least I don't THINK. I might as well double check next time I go in.
 
looking at my manual, i nee to have a load on the output of 10kohm.

that is probably why my head is about to explode and why non of my readings make any sense :mad:



AAAAAAAAAAHHHHHHHHH!!!!!!!!!
 
My Name said:
looking at my manual, i nee to have a load on the output of 10kohm.

that is probably why my head is about to explode and why non of my readings make any sense :mad:



AAAAAAAAAAHHHHHHHHH!!!!!!!!!
Click to expand...

A 10 k load is not really a load but more of a lack of load. What they are saying is that you need a load that is not less than 10K.

The greater the load (less ohms) the more power is needed to source the same voltage. Many output stages cannot drive that much power so they must drop the voltage. :eek:

Having too much of a load leads to inaccuracies.

Driving 100K load is not much different from driving a 10 k load. But driving a 5k load may introduce significant errors.
 
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