Home |
Search |
Today's Posts |
#1
|
|||
|
|||
Soundcard/preamp noise levels
I'm using Cool Edit Pro 2.1. My hardware is an M-Audio Audiophile 2496
soundcard connected to a FMR Audio RNP preamp. The cables are regular RCA type with 1/4" adapters on the preamp end. I record acoustic guitar and vocals. I was previously using a Behringer 802 mixer to the card. The improvements in recording with the RNP are pretty obvious. I'm confused about level readings in CEP and was wondering if someone could explain them. With nothing connected to the soundcard I get levels of about -84 db, much better than a previous card. I assume the noise is due to electronics within the PC. With the RNP turned on and the gain on zero the levels stay about the same. With the gain turned up all the way to 60 db (an extremely unreasonable setting, I know) the CEP meters go up to -48 db. At a useful, real-world gain setting of 35db the noise level drops to about -75db. The actual db levels with the Behringer were close to the same but the recordings done with the RNP are much cleaner. I suppose what I'm asking is whether these numbers seem to be in the ballpark for the equipment I'm using or if there's something I can do to improve it. Or if it matters at all......... Thanks. |
#2
|
|||
|
|||
Soundcard/preamp noise levels
"George W." wrote in message
news I'm using Cool Edit Pro 2.1. My hardware is an M-Audio Audiophile 2496 soundcard connected to a FMR Audio RNP preamp. The cables are regular RCA type with 1/4" adapters on the preamp end. I record acoustic guitar and vocals. I was previously using a Behringer 802 mixer to the card. The improvements in recording with the RNP are pretty obvious. I'm confused about level readings in CEP and was wondering if someone could explain them. With nothing connected to the soundcard I get levels of about -84 db, much better than a previous card. I assume the noise is due to electronics within the PC. With the RNP turned on and the gain on zero the levels stay about the same. With the gain turned up all the way to 60 db (an extremely unreasonable setting, I know) the CEP meters go up to -48 db. At a useful, real-world gain setting of 35db the noise level drops to about -75db. The actual db levels with the Behringer were close to the same but the recordings done with the RNP are much cleaner. I suppose what I'm asking is whether these numbers seem to be in the ballpark for the equipment I'm using or if there's something I can do to improve it. Or if it matters at all......... I presume that you are using readings taken from the record level meter in CEP. That's one way to do audio measurements with CEP, but take a look at what happens when you highlight part of your recording and click on Analyze, Statistics. For one thing, the statistics are for a specific part of your recording. For another thing you can do this any time over the life of the recording. Unlike what you just did, it's highly repeatable. Finally, you've got a far larger variety of potentially meaningful numbers. For a real thrill, try Analyze, Frequency Analysis. That all said, noise measurements still aren't worth squat without some kind of fixed reference level that's meaningful in the real world. In the case of mic preamp measurements, the fixed reference level is often a highly-attenuated signal from a signal generator of some kind, set up in a certain way. Think of it as a simulation of a reference microphone picking up a reference sound. Both the RNP and the little Behr have one or more gain controls that among other things move the noise floor around pretty much at will. The usual way preamp noise floors are measured involves setting gains for a consistent level with a signal generator, and then terminating the preamp's input with a certain value resistor, and taking a measurement over a defined measurement bandwidth. Noise measurements also aren't worth squat unless referenced to some kind of relevant measurement bandwidth. This is because the narrower the band, the smaller the noise voltage A common measurement band is 3 dB down at 20 and 20 KHz, and flat in-between with first order Butterworth filtering. Another very popular one is called A weighting, which has a more complex frequency response curve that is something like that of the ear at low levels. You can do this all in CEP, but it takes a little work. You can do this all with CEP, your sound card and a few resistors. Ask and you shall be answered. Bottom line is that your current set of measurements seem to fail to follow the general rules I just pointed out. So, they are basically mystery meat and AFAIK they always will be. If you're really interested in noise measurements you are going to have to do a little homework and also do your actual measurements over again with some fairly cheap bells and whistles attached. |
#3
|
|||
|
|||
Soundcard/preamp noise levels
On Sat, 22 Nov 2003 13:11:08 -0500, Arny Krueger wrote:
"George W." wrote in message news I'm using Cool Edit Pro 2.1. My hardware is an M-Audio Audiophile 2496 soundcard connected to a FMR Audio RNP preamp. The cables are regular RCA type with 1/4" adapters on the preamp end. I record acoustic guitar and vocals. I was previously using a Behringer 802 mixer to the card. The improvements in recording with the RNP are pretty obvious. I'm confused about level readings in CEP and was wondering if someone could explain them. With nothing connected to the soundcard I get levels of about -84 db, much better than a previous card. I assume the noise is due to electronics within the PC. With the RNP turned on and the gain on zero the levels stay about the same. With the gain turned up all the way to 60 db (an extremely unreasonable setting, I know) the CEP meters go up to -48 db. At a useful, real-world gain setting of 35db the noise level drops to about -75db. The actual db levels with the Behringer were close to the same but the recordings done with the RNP are much cleaner. I suppose what I'm asking is whether these numbers seem to be in the ballpark for the equipment I'm using or if there's something I can do to improve it. Or if it matters at all......... I presume that you are using readings taken from the record level meter in CEP. That's one way to do audio measurements with CEP, but take a look at what happens when you highlight part of your recording and click on Analyze, Statistics. For one thing, the statistics are for a specific part of your recording. For another thing you can do this any time over the life of the recording. Unlike what you just did, it's highly repeatable. Finally, you've got a far larger variety of potentially meaningful numbers. For a real thrill, try Analyze, Frequency Analysis. That all said, noise measurements still aren't worth squat without some kind of fixed reference level that's meaningful in the real world. In the case of mic preamp measurements, the fixed reference level is often a highly-attenuated signal from a signal generator of some kind, set up in a certain way. Think of it as a simulation of a reference microphone picking up a reference sound. Both the RNP and the little Behr have one or more gain controls that among other things move the noise floor around pretty much at will. The usual way preamp noise floors are measured involves setting gains for a consistent level with a signal generator, and then terminating the preamp's input with a certain value resistor, and taking a measurement over a defined measurement bandwidth. Noise measurements also aren't worth squat unless referenced to some kind of relevant measurement bandwidth. This is because the narrower the band, the smaller the noise voltage A common measurement band is 3 dB down at 20 and 20 KHz, and flat in-between with first order Butterworth filtering. Another very popular one is called A weighting, which has a more complex frequency response curve that is something like that of the ear at low levels. You can do this all in CEP, but it takes a little work. You can do this all with CEP, your sound card and a few resistors. Ask and you shall be answered. Bottom line is that your current set of measurements seem to fail to follow the general rules I just pointed out. So, they are basically mystery meat and AFAIK they always will be. If you're really interested in noise measurements you are going to have to do a little homework and also do your actual measurements over again with some fairly cheap bells and whistles attached. Thanks for the explanation. I'm not sure if any of these numbers mean much in real-world terms. While the noise levels between the Behringer and the RNP seem pretty close the resulting recordings with the RNP are quite an improvement.....The 802 recordings sounded fine to me in the past but now sound "boxy" by comparison when recording acoustic guitar with an MXL 603. I've still got a couple of weeks to evaluate the RNP and I'd just like to be sure it's working as it should be. G. |
#4
|
|||
|
|||
Soundcard/preamp noise levels
|
#5
|
|||
|
|||
Soundcard/preamp noise levels
That all said, noise measurements still aren't worth squat without some kind of fixed reference level that's meaningful in the real world. In the case of mic preamp measurements, the fixed reference level is often a highly-attenuated signal from a signal generator of some kind, set up in a certain way. Think of it as a simulation of a reference microphone picking up a reference sound. Arne, Could you suggest a specific resistive attenuator to go from an unbalanced audio generator (like my HP) to a microphone preamp intended for 'low impedance balanced' microphones?? Thanks! -- Regards, Terry King ...In The Woods In Vermont "The one who dies with the most parts LOSES! What do you need??" |
#7
|
|||
|
|||
Soundcard/preamp noise levels
"George W." wrote in message
Someone mentioned in another post that you really have to learn to hear what's good and bad about a piece of equipment, especially one where improvements are more subtle than dramatic. I've recorded some short acoustic guitar tracks with the Behringer and the RNP, with a variety of mics and guitars. The RNP tracks are all easily distinguishable from the Behringer. All better to some degree (depending on the mic) though I find it hard to describe the difference. Even though I'm probably too old for this stuff I'm still learning, and I appreciate the input from everyone. I really don't know too much about the technical differences between a RNP and the little Behr 802. Mic preamp spec sheets generally suck. I can only recall seeing one mic preamp spec sheet that I felt represented the product reasonably well. The RNP tech information I've seen is a lot more wordy, but seems to have no more hard details than the vacuous spec sheet for the little Behr. My past experience suggests that were the comparison to be done rigorously, differences that seem more obvious under casual testing conditions would become less obvious if the test were repeated with more vigor. But, I would be a lot less surprised if mic preamps turned out to sound significantly different than power amps. There seem to be more variables. |
#8
|
|||
|
|||
Soundcard/preamp noise levels
|
#9
|
|||
|
|||
Soundcard/preamp noise levels
Listen to what Mike R. said: if you were testing the preamps with nothing
plugged into them, your numbers basically don't mean much. I also use a dummy plug with a 150-ohm resistor; it's not really that bad a representation. All that said, the RNP isn't the quietest preamp on the block -- the designer said that was one of his deliberate choices, sacrificing some noise performance for better sound on higher-level signals. But it's quiet enough for most applications involving condenser mikes. Peace, Paul |
Reply |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
rec.audio.car FAQ (Part 2/5) | Car Audio | |||
rec.audio.car FAQ (Part 1/5) | Car Audio | |||
Isn't noise cumulative? a technical question | Pro Audio | |||
hearing loss info | Car Audio | |||
Noise - alternator, shrieking, etc with Delphi XM satellite system | Car Audio |