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#41
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Low Noise Sound card
"Mr.T" MrT@home wrote in message ... "Ian Bell" wrote in message ... If you REALLY can achieve 120dB INSIDE a PC then you can certainly achieve it outside. Sure, you can do it EITHER way, that's the point. All through the magic of mixed-signal design. |
#42
Posted to rec.audio.tech
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Low Noise Sound card
"Mr.T" MrT@home wrote in message
"Arny Krueger" wrote in message ... I fail to see how that is any more difficult than using the soundcard digital attenuator which WILL reduce your S/N ratio at it's output, whilst an analog attenuator will reduce both signal and noise keeping the S/N ratio the same. Not necessarily. Both the sound card and the amplifier are properly modeled as a fixed noise source and a variable signal. Therefore, as you turn the signal down, the SNR of both the sound card and the amplifier will get worse because there is less signal but the same amount of noise. Do tell how a passive analog attenuator will reduce the signal but leave the noise untouched? Quite easily if the most significant noise source is downstream of the attenuator, which is often the case. This is one of my favorite "audiophile myths". The audiophile has a power amplifier with 80 dB SNR, attached to a CD player (93 dB SNR @ FS) with a digital attenuator. He's beside himself with anxiety over the issue we are discussing. He *solves* his alleged problem by introducing a passive attenuator. In fact, the best case is that he did not further muck things up. Of course you can't *improve* on the amplifiers s/n, but a digital attenuator does have a fixed noise floor greater than a passive analog one, which is only governed by it's thermal noise floor. Yes, but the amplifier's noise floor is often the weakest link, particularly if the amp is tubed. Many integrated amps often have actual input sensitivities on the order of 200 mV, so their SNR in Db isn't all that great, either. My rule of thumb for a good SS power amp is around 100 dB, which is about the same as a good CD player. |
#43
Posted to rec.audio.tech
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Low Noise Sound card
"Arny Krueger" wrote in message ... Both the sound card and the amplifier are properly modeled as a fixed noise source and a variable signal. Therefore, as you turn the signal down, the SNR of both the sound card and the amplifier will get worse because there is less signal but the same amount of noise. Do tell how a passive analog attenuator will reduce the signal but leave the noise untouched? Quite easily if the most significant noise source is downstream of the attenuator, which is often the case. Arny I'm really surprised I have to spell it out for you, a passive analog attenuator reduces both signal AND noise at *it's output* (amplifier input) The OP *wasn't* complaining about his amplifiers noise! IF that was his problem, asking for a low noise sound card is even more stupid! This is one of my favorite "audiophile myths". The audiophile has a power amplifier with 80 dB SNR, attached to a CD player (93 dB SNR @ FS) with a digital attenuator. He's beside himself with anxiety over the issue we are discussing. He *solves* his alleged problem by introducing a passive attenuator. In fact, the best case is that he did not further muck things up. ****, it's a pretty woeful amplifier that only gets 80dB S/N these days! Hardly "audiophile" quality!!!! Of course you can't *improve* on the amplifiers s/n, but a digital attenuator does have a fixed noise floor greater than a passive analog one, which is only governed by it's thermal noise floor. Yes, but the amplifier's noise floor is often the weakest link, particularly if the amp is tubed. For a tube amp perhaps, but power amps with over 100dB S/N are easily obtained these days. My rule of thumb for a good SS power amp is around 100 dB, which is about the same as a good CD player. Exactly! (well actually no CD player can really do 100dB wide band since it's above the theoretical maximum for 16bits, but let's ignore the slight difference) However it can easily be degraded by running the amp gain flat out and using the soundcard digital attenuator as the OP said he was doing! MrT. |
#44
Posted to rec.audio.tech
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Low Noise Sound card
"Mr.T" MrT@home wrote in message
"Arny Krueger" wrote in message ... Both the sound card and the amplifier are properly modeled as a fixed noise source and a variable signal. Therefore, as you turn the signal down, the SNR of both the sound card and the amplifier will get worse because there is less signal but the same amount of noise. Do tell how a passive analog attenuator will reduce the signal but leave the noise untouched? Quite easily if the most significant noise source is downstream of the attenuator, which is often the case. Arny I'm really surprised I have to spell it out for you, a passive analog attenuator reduces both signal AND noise at *it's output* (amplifier input) Of course, but read what I wrote: it does nothing to reduce the noise at the output of the amplifier which is often the weakest link. The OP *wasn't* complaining about his amplifiers noise! In this case he had an amplifier with atypically low noise. IF that was his problem, asking for a low noise sound card is even more stupid! The problem of coming up with an audio interface with dynamic range and SNR 108 dB was solved long ago. This is one of my favorite "audiophile myths". The audiophile has a power amplifier with 80 dB SNR, attached to a CD player (93 dB SNR @ FS) with a digital attenuator. He's beside himself with anxiety over the issue we are discussing. He *solves* his alleged problem by introducing a passive attenuator. In fact, the best case is that he did not further muck things up. ****, it's a pretty woeful amplifier that only gets 80dB S/N these days! Hardly "audiophile" quality!!!! Look at the spec sheets for some modern integrated amps. I'm here to tell you that many power amps that spec 100 dB are a little optimistic. Of course you can't *improve* on the amplifiers s/n, but a digital attenuator does have a fixed noise floor greater than a passive analog one, which is only governed by it's thermal noise floor. Yes, but the amplifier's noise floor is often the weakest link, particularly if the amp is tubed. For a tube amp perhaps, but power amps with over 100dB S/N are easily obtained these days. They can be obtained, but 100 dB is not a low mark, especially if you test them on the bench. Also consider that most CD players are attached to integrated amps, not power amps. Exactly! (well actually no CD player can really do 100dB wide band since it's above the theoretical maximum for 16bits, but let's ignore the slight difference) However it can easily be degraded by running the amp gain flat out and using the soundcard digital attenuator as the OP said he was doing! Like I said, the OPs specific problem is in my views resolved days ago. |
#45
Posted to rec.audio.tech
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Low Noise Sound card
"Arny Krueger" wrote in message ... Arny I'm really surprised I have to spell it out for you, a passive analog attenuator reduces both signal AND noise at *it's output* (amplifier input) Of course, but read what I wrote: it does nothing to reduce the noise at the output of the amplifier which is often the weakest link. Read what I wrote, I never said it did. But the OP thinks his amplifier is not the problem. The OP *wasn't* complaining about his amplifiers noise! In this case he had an amplifier with atypically low noise. So why bring up something irelevant to the actual discussion then? IF that was his problem, asking for a low noise sound card is even more stupid! The problem of coming up with an audio interface with dynamic range and SNR 108 dB was solved long ago. Never in dispute. ****, it's a pretty woeful amplifier that only gets 80dB S/N these days! Hardly "audiophile" quality!!!! Look at the spec sheets for some modern integrated amps. Yep, "audiophile" grade pretty much around 100dB these days. Your definition of "audiophile" grade may differ of course. I'm here to tell you that many power amps that spec 100 dB are a little optimistic. Sure, and many that aren't, and I've measured quite a few. For a tube amp perhaps, but power amps with over 100dB S/N are easily obtained these days. They can be obtained, but 100 dB is not a low mark, especially if you test them on the bench. Also consider that most CD players are attached to integrated amps, not power amps. Irrelevant to the current discussion. You are free to make a completely separate point of course, but don't drag me into it. Like I said, the OPs specific problem is in my views resolved days ago. Years ago in fact, but he doesn't seem to realise it. MrT. |
#46
Posted to rec.audio.tech
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Low Noise Sound card
Mr.T wrote:
"Arny Krueger" wrote in message ... Arny I'm really surprised I have to spell it out for you, a passive analog attenuator reduces both signal AND noise at *it's output* (amplifier input) Of course, but read what I wrote: it does nothing to reduce the noise at the output of the amplifier which is often the weakest link. Read what I wrote, I never said it did. But the OP thinks his amplifier is not the problem. The OP *wasn't* complaining about his amplifiers noise! In this case he had an amplifier with atypically low noise. So why bring up something irelevant to the actual discussion then? IF that was his problem, asking for a low noise sound card is even more stupid! The problem of coming up with an audio interface with dynamic range and SNR 108 dB was solved long ago. Never in dispute. ****, it's a pretty woeful amplifier that only gets 80dB S/N these days! Hardly "audiophile" quality!!!! Look at the spec sheets for some modern integrated amps. Yep, "audiophile" grade pretty much around 100dB these days. Your definition of "audiophile" grade may differ of course. I'm here to tell you that many power amps that spec 100 dB are a little optimistic. Sure, and many that aren't, and I've measured quite a few. For a tube amp perhaps, but power amps with over 100dB S/N are easily obtained these days. They can be obtained, but 100 dB is not a low mark, especially if you test them on the bench. Also consider that most CD players are attached to integrated amps, not power amps. Irrelevant to the current discussion. You are free to make a completely separate point of course, but don't drag me into it. Like I said, the OPs specific problem is in my views resolved days ago. Years ago in fact, but he doesn't seem to realise it. MrT. And both of you please stop using s/n when you mean dynamic range - they are not the same thing not to mention simply quoting a totally unqualified dB figure is quite meaningless. Cheers ian |
#47
Posted to rec.audio.tech
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Low Noise Sound card
"Ian Bell" wrote in message
And both of you please stop using s/n when you mean dynamic range - they are not the same thing not to mention simply quoting a totally unqualified dB figure is quite meaningless. If you could read and remember what other people write for more than a few seconds Ian, you would see that I used both terms non-interchangably. And of course totally unqualified dB figures is meaningless, but its one of those things that happen all the time on online forums that you kinda sorta have to step over to get to the meat of the problem. You know, like the self-important luddite ijiots who think that good audio can't come out of a PC chassis. |
#48
Posted to rec.audio.tech
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Low Noise Sound card
Arny Krueger wrote:
"Ian Bell" wrote in message And both of you please stop using s/n when you mean dynamic range - they are not the same thing not to mention simply quoting a totally unqualified dB figure is quite meaningless. If you could read and remember what other people write for more than a few seconds Ian, you would see that I used both terms non-interchangably. And of course totally unqualified dB figures is meaningless, but its one of those things that happen all the time on online forums that you kinda sorta have to step over to get to the meat of the problem. You know, like the self-important luddite ijiots who think that good audio can't come out of a PC chassis. LOL |
#49
Posted to rec.audio.tech
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Low Noise Sound card
On 15/03/2010 10:03, Ian Bell wrote:
Mr.T wrote: "Arny Krueger" wrote in message ... Arny I'm really surprised I have to spell it out for you, a passive analog attenuator reduces both signal AND noise at *it's output* (amplifier input) Of course, but read what I wrote: it does nothing to reduce the noise at the output of the amplifier which is often the weakest link. Read what I wrote, I never said it did. But the OP thinks his amplifier is not the problem. The OP *wasn't* complaining about his amplifiers noise! In this case he had an amplifier with atypically low noise. So why bring up something irelevant to the actual discussion then? IF that was his problem, asking for a low noise sound card is even more stupid! The problem of coming up with an audio interface with dynamic range and SNR 108 dB was solved long ago. Never in dispute. ****, it's a pretty woeful amplifier that only gets 80dB S/N these days! Hardly "audiophile" quality!!!! Look at the spec sheets for some modern integrated amps. Yep, "audiophile" grade pretty much around 100dB these days. Your definition of "audiophile" grade may differ of course. I'm here to tell you that many power amps that spec 100 dB are a little optimistic. Sure, and many that aren't, and I've measured quite a few. For a tube amp perhaps, but power amps with over 100dB S/N are easily obtained these days. They can be obtained, but 100 dB is not a low mark, especially if you test them on the bench. Also consider that most CD players are attached to integrated amps, not power amps. Irrelevant to the current discussion. You are free to make a completely separate point of course, but don't drag me into it. Like I said, the OPs specific problem is in my views resolved days ago. Years ago in fact, but he doesn't seem to realise it. MrT. And both of you please stop using s/n when you mean dynamic range - they are not the same thing not to mention simply quoting a totally unqualified dB figure is quite meaningless. s/n as in max voltage output with an input of 0dB to the voltage output with no input signal. -- Dirk http://www.transcendence.me.uk/ - Transcendence UK http://www.blogtalkradio.com/onetribe - Occult Talk Show |
#50
Posted to rec.audio.tech
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Low Noise Sound card
"Dirk Bruere at NeoPax" wrote in
message On 15/03/2010 10:03, Ian Bell wrote: Mr.T wrote: "Arny Krueger" wrote in message ... Arny I'm really surprised I have to spell it out for you, a passive analog attenuator reduces both signal AND noise at *it's output* (amplifier input) Of course, but read what I wrote: it does nothing to reduce the noise at the output of the amplifier which is often the weakest link. Read what I wrote, I never said it did. But the OP thinks his amplifier is not the problem. The OP *wasn't* complaining about his amplifiers noise! In this case he had an amplifier with atypically low noise. So why bring up something irelevant to the actual discussion then? IF that was his problem, asking for a low noise sound card is even more stupid! The problem of coming up with an audio interface with dynamic range and SNR 108 dB was solved long ago. Never in dispute. ****, it's a pretty woeful amplifier that only gets 80dB S/N these days! Hardly "audiophile" quality!!!! Look at the spec sheets for some modern integrated amps. Yep, "audiophile" grade pretty much around 100dB these days. Your definition of "audiophile" grade may differ of course. I'm here to tell you that many power amps that spec 100 dB are a little optimistic. Sure, and many that aren't, and I've measured quite a few. For a tube amp perhaps, but power amps with over 100dB S/N are easily obtained these days. They can be obtained, but 100 dB is not a low mark, especially if you test them on the bench. Also consider that most CD players are attached to integrated amps, not power amps. Irrelevant to the current discussion. You are free to make a completely separate point of course, but don't drag me into it. Like I said, the OPs specific problem is in my views resolved days ago. Years ago in fact, but he doesn't seem to realise it. MrT. And both of you please stop using s/n when you mean dynamic range - they are not the same thing not to mention simply quoting a totally unqualified dB figure is quite meaningless. s/n as in max voltage output with an input of 0dB to the voltage output with no input signal. So far, so good. No noise measurement is complete without a statement of the measurement bandwidth. Dynamic range measurements are performed with a test signal present, as it also includes spurious responses. A typical measurement would be made using a -60 dB 1 KHz sine wave. |
#51
Posted to rec.audio.tech
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Low Noise Sound card
Dirk Bruere at NeoPax wrote:
On 15/03/2010 10:03, Ian Bell wrote: Mr.T wrote: "Arny Krueger" wrote in message ... Arny I'm really surprised I have to spell it out for you, a passive analog attenuator reduces both signal AND noise at *it's output* (amplifier input) Of course, but read what I wrote: it does nothing to reduce the noise at the output of the amplifier which is often the weakest link. Read what I wrote, I never said it did. But the OP thinks his amplifier is not the problem. The OP *wasn't* complaining about his amplifiers noise! In this case he had an amplifier with atypically low noise. So why bring up something irelevant to the actual discussion then? IF that was his problem, asking for a low noise sound card is even more stupid! The problem of coming up with an audio interface with dynamic range and SNR 108 dB was solved long ago. Never in dispute. ****, it's a pretty woeful amplifier that only gets 80dB S/N these days! Hardly "audiophile" quality!!!! Look at the spec sheets for some modern integrated amps. Yep, "audiophile" grade pretty much around 100dB these days. Your definition of "audiophile" grade may differ of course. I'm here to tell you that many power amps that spec 100 dB are a little optimistic. Sure, and many that aren't, and I've measured quite a few. For a tube amp perhaps, but power amps with over 100dB S/N are easily obtained these days. They can be obtained, but 100 dB is not a low mark, especially if you test them on the bench. Also consider that most CD players are attached to integrated amps, not power amps. Irrelevant to the current discussion. You are free to make a completely separate point of course, but don't drag me into it. Like I said, the OPs specific problem is in my views resolved days ago. Years ago in fact, but he doesn't seem to realise it. MrT. And both of you please stop using s/n when you mean dynamic range - they are not the same thing not to mention simply quoting a totally unqualified dB figure is quite meaningless. s/n as in max voltage output with an input of 0dB to the voltage output with no input signal. LOL, that's is awful. 0dB has no meaning. Input termination in both cases is unspecified Output termination is unspecified. No bandwidth is specified. No weighting or not is specified. No mention of whether the measurements are rms, peak, quasi-peak etc Variations in the way the above are specified can make a large difference to the 'measured' value and I bet you can guess which set the marketing department will want to choose. Cheers ian Cheers Ian |
#52
Posted to rec.audio.tech
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Low Noise Sound card
"Ian Bell" wrote in message ... And both of you please stop using s/n when you mean dynamic range - they are not the same thing Who said they were? not to mention simply quoting a totally unqualified dB figure is quite meaningless. Neither should be "unqualified", but ANY figure that isn't qualified is meaningless of course. MrT. |
#53
Posted to rec.audio.tech
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Low Noise Sound card
On 15/03/2010 22:17, Ian Bell wrote:
Dirk Bruere at NeoPax wrote: On 15/03/2010 10:03, Ian Bell wrote: Mr.T wrote: "Arny Krueger" wrote in message ... Arny I'm really surprised I have to spell it out for you, a passive analog attenuator reduces both signal AND noise at *it's output* (amplifier input) Of course, but read what I wrote: it does nothing to reduce the noise at the output of the amplifier which is often the weakest link. Read what I wrote, I never said it did. But the OP thinks his amplifier is not the problem. The OP *wasn't* complaining about his amplifiers noise! In this case he had an amplifier with atypically low noise. So why bring up something irelevant to the actual discussion then? IF that was his problem, asking for a low noise sound card is even more stupid! The problem of coming up with an audio interface with dynamic range and SNR 108 dB was solved long ago. Never in dispute. ****, it's a pretty woeful amplifier that only gets 80dB S/N these days! Hardly "audiophile" quality!!!! Look at the spec sheets for some modern integrated amps. Yep, "audiophile" grade pretty much around 100dB these days. Your definition of "audiophile" grade may differ of course. I'm here to tell you that many power amps that spec 100 dB are a little optimistic. Sure, and many that aren't, and I've measured quite a few. For a tube amp perhaps, but power amps with over 100dB S/N are easily obtained these days. They can be obtained, but 100 dB is not a low mark, especially if you test them on the bench. Also consider that most CD players are attached to integrated amps, not power amps. Irrelevant to the current discussion. You are free to make a completely separate point of course, but don't drag me into it. Like I said, the OPs specific problem is in my views resolved days ago. Years ago in fact, but he doesn't seem to realise it. MrT. And both of you please stop using s/n when you mean dynamic range - they are not the same thing not to mention simply quoting a totally unqualified dB figure is quite meaningless. s/n as in max voltage output with an input of 0dB to the voltage output with no input signal. LOL, that's is awful. 0dB has no meaning. http://jtauber.com/decibels/ "There are actually two reference voltages in use. 1V and 0.775V. When using the former as the reference, we write 'dBV' and when using the latter we use 'dBu'. " Either would do. Input termination in both cases is unspecified As per manufacturers guidelines Output termination is unspecified. As per manufacturers guidelines No bandwidth is specified. We are talking "audio" so perhaps we can suggest it just might be somewhere between 20Hz and 20,000Hz? No weighting or not is specified. True. No mention of whether the measurements are rms, peak, quasi-peak etc Well, maximum Music Power obviously! [not] Variations in the way the above are specified can make a large difference to the 'measured' value and I bet you can guess which set the marketing department will want to choose. -- Dirk http://www.transcendence.me.uk/ - Transcendence UK http://www.blogtalkradio.com/onetribe - Occult Talk Show |
#54
Posted to rec.audio.tech
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Low Noise Sound card
"Ian Bell" wrote in message
0dB has no meaning. Actually, it does. In the digital domain 0 dB is commonly equated with FS. While the units are arbitrary and may be confusing to people who still think 100% analog, it is both meaningful and commonly used. Input termination in both cases is unspecified. If the input is a mic input, then the usual standard of 300 ohms applies. If the input is a line level input, then the source impedance is usually such that system performance is not affected that much by probable variations. Output termination is unspecified. The noise performance of line level outputs is minimally affected by probable and reasonable variations in load impedance. No bandwidth is specified. Relevant and already mentioned No weighting or not is specified. Relevant and already mentioned No mention of whether the measurements are rms, peak, quasi-peak Both SNR and DR are ratios of two measurements. It is most important that both measurements be done under the same circumstances. Variations in the way the above are specified can make a large difference to the 'measured' value Some yes, some no. and I bet you can guess which set the marketing department will want to choose. One other benefit of the solid state/digital revolution is that SNR and DR performance is often so good ( 100 dB) that most variations in how they are mentioned don't matter that much. |
#55
Posted to rec.audio.tech
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Low Noise Sound card
Dirk Bruere at NeoPax wrote:
On 15/03/2010 22:17, Ian Bell wrote: Dirk Bruere at NeoPax wrote: On 15/03/2010 10:03, Ian Bell wrote: Mr.T wrote: "Arny Krueger" wrote in message ... Arny I'm really surprised I have to spell it out for you, a passive analog attenuator reduces both signal AND noise at *it's output* (amplifier input) Of course, but read what I wrote: it does nothing to reduce the noise at the output of the amplifier which is often the weakest link. Read what I wrote, I never said it did. But the OP thinks his amplifier is not the problem. The OP *wasn't* complaining about his amplifiers noise! In this case he had an amplifier with atypically low noise. So why bring up something irelevant to the actual discussion then? IF that was his problem, asking for a low noise sound card is even more stupid! The problem of coming up with an audio interface with dynamic range and SNR 108 dB was solved long ago. Never in dispute. ****, it's a pretty woeful amplifier that only gets 80dB S/N these days! Hardly "audiophile" quality!!!! Look at the spec sheets for some modern integrated amps. Yep, "audiophile" grade pretty much around 100dB these days. Your definition of "audiophile" grade may differ of course. I'm here to tell you that many power amps that spec 100 dB are a little optimistic. Sure, and many that aren't, and I've measured quite a few. For a tube amp perhaps, but power amps with over 100dB S/N are easily obtained these days. They can be obtained, but 100 dB is not a low mark, especially if you test them on the bench. Also consider that most CD players are attached to integrated amps, not power amps. Irrelevant to the current discussion. You are free to make a completely separate point of course, but don't drag me into it. Like I said, the OPs specific problem is in my views resolved days ago. Years ago in fact, but he doesn't seem to realise it. MrT. And both of you please stop using s/n when you mean dynamic range - they are not the same thing not to mention simply quoting a totally unqualified dB figure is quite meaningless. s/n as in max voltage output with an input of 0dB to the voltage output with no input signal. LOL, that's is awful. 0dB has no meaning. http://jtauber.com/decibels/ "There are actually two reference voltages in use. 1V and 0.775V. When using the former as the reference, we write 'dBV' and when using the latter we use 'dBu'. " Either would do. Indeed, and most professional equipment operates at +4dBu and some at +8dBu and then again a lot of commercial power amps have an input sensitivity of 2V for full output. Any of these would do, the point is we are not told which. Input termination in both cases is unspecified As per manufacturers guidelines I very much doubt the manufacturer says how the input is terminated when he measures the amp output noise but I very strongly suspect he short circuits it to give him the lowest noise figure. Of course you will not achieve this figure when connected to a real source. Output termination is unspecified. As per manufacturers guidelines Which are what? No bandwidth is specified. We are talking "audio" so perhaps we can suggest it just might be somewhere between 20Hz and 20,000Hz? Yes, but when measuring noise it is very important. Often a 15KHz bandwidth with well defined slopes is used because it gives a total equivalent noise bandwidth of 20KHz which is not the same as a flat response from 20Hz to 20KHz but is does give a better figure. No weighting or not is specified. True. No mention of whether the measurements are rms, peak, quasi-peak etc Well, maximum Music Power obviously! [not] LOL Cheers Ian Variations in the way the above are specified can make a large difference to the 'measured' value and I bet you can guess which set the marketing department will want to choose. |
#56
Posted to rec.audio.tech
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Low Noise Sound card
Arny Krueger wrote:
"Ian Bell" wrote in message 0dB has no meaning. Actually, it does. In the digital domain 0 dB is commonly equated with FS. No, that is 0dBFS. While the units are arbitrary and may be confusing to people who still think 100% analog, it is both meaningful and commonly used. No it is not. Input termination in both cases is unspecified. If the input is a mic input, then the usual standard of 300 ohms applies. It is a power amp, it does not have a mic input. 300 ohms is NOT the 'usual standard for a mic input' If the input is a line level input, then the source impedance is usually such that system performance is not affected that much by probable variations. You miss the point. How is the input terminated when noise is measured - obviously it is not left open circuit is it? Output termination is unspecified. The noise performance of line level outputs is minimally affected by probable and reasonable variations in load impedance. No bandwidth is specified. Relevant and already mentioned No weighting or not is specified. Relevant and already mentioned No mention of whether the measurements are rms, peak, quasi-peak Both SNR and DR are ratios of two measurements. It is most important that both measurements be done under the same circumstances. In fact they generally are not since a signal and noise have quite different characteristics. The signal will be measured rms. The noise can be measured in several ways each giving a different figure. Variations in the way the above are specified can make a large difference to the 'measured' value Some yes, some no. and I bet you can guess which set the marketing department will want to choose. One other benefit of the solid state/digital revolution is that SNR and DR performance is often so good ( 100 dB) that most variations in how they are mentioned don't matter that much. Rubbish. Once again, SNR and DR are different animals. Achieving a 100dB DR is not hard but unless you run your amp close to clipping all the time you will not achieve that as a SNR. The marketing guys are as active as ever in trying to make their product appear superior to its competitors and will choose the measurement methods that best do that. Cheers ian |
#57
Posted to rec.audio.tech
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Low Noise Sound card
"Ian Bell" wrote in message
Indeed, and most professional equipment operates at +4dBu and some at +8dBu and then again a lot of commercial power amps have an input sensitivity of 2V for full output. What you've missed is that there is only a few dB between all of these numbers. The difference between an objectionally noisy system and an aceeptable system is generally far more than just a few dB, no matter how you measure things. Any of these would do, the point is we are not told which. It's a hair-splitting, misleading point. I very much doubt the manufacturer says how the input is terminated when he measures the amp output noise but I very strongly suspect he short circuits it to give him the lowest noise figure. Of course you will not achieve this figure when connected to a real source. Again, there are only a few dB difference in the noise floor of line-level products with reasonable variations in source impedance or load. Output termination is unspecified. As per manufacturers guidelines Which are what? No bandwidth is specified. We are talking "audio" so perhaps we can suggest it just might be somewhere between 20Hz and 20,000Hz? Yes, but when measuring noise it is very important. Often a 15KHz bandwidth with well defined slopes is used because it gives a total equivalent noise bandwidth of 20KHz which is not the same as a flat response from 20Hz to 20KHz but is does give a better figure. Again, there are only a few dB difference in the noise floor of line-level products with reasonable variations in measurement bandwidth. Many of these issues are bigger issues for legacy vacuum tube equipment, where the noise levels were generally closer to the edge of perception. |
#58
Posted to rec.audio.tech
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Low Noise Sound card
Arny Krueger wrote:
"Ian Bell" wrote in message Indeed, and most professional equipment operates at +4dBu and some at +8dBu and then again a lot of commercial power amps have an input sensitivity of 2V for full output. What you've missed is that there is only a few dB between all of these numbers. The difference between an objectionally noisy system and an aceeptable system is generally far more than just a few dB, no matter how you measure things. Any of these would do, the point is we are not told which. It's a hair-splitting, misleading point. I very much doubt the manufacturer says how the input is terminated when he measures the amp output noise but I very strongly suspect he short circuits it to give him the lowest noise figure. Of course you will not achieve this figure when connected to a real source. Again, there are only a few dB difference in the noise floor of line-level products with reasonable variations in source impedance or load. Output termination is unspecified. As per manufacturers guidelines Which are what? No bandwidth is specified. We are talking "audio" so perhaps we can suggest it just might be somewhere between 20Hz and 20,000Hz? Yes, but when measuring noise it is very important. Often a 15KHz bandwidth with well defined slopes is used because it gives a total equivalent noise bandwidth of 20KHz which is not the same as a flat response from 20Hz to 20KHz but is does give a better figure. Again, there are only a few dB difference in the noise floor of line-level products with reasonable variations in measurement bandwidth. Many of these issues are bigger issues for legacy vacuum tube equipment, where the noise levels were generally closer to the edge of perception. And you add up these several instances of 'a few dBs' as the marketing guys will certainly do, plus the judicious choice of weighting for the noise and your 100dB DR spec suddenly becomes in reality in the 80 to 90dB region. The point is, using several unqualified specs of differing pieces of connected equipment made by differing manufacturers is not going to tell the whole story by a long way. Cheers ian |
#59
Posted to rec.audio.tech
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Low Noise Sound card
"Ian Bell" wrote in message
Arny Krueger wrote: "Ian Bell" wrote in message 0dB has no meaning. Actually, it does. In the digital domain 0 dB is commonly equated with FS. No, that is 0dBFS. Yes, so your use of the word "no" must be some kind of terrible mistake on your part. While the units are arbitrary and may be confusing to people who still think 100% analog, it is both meaningful and commonly used. No it is not. Assertion without support, which should be immediately dismissed. Input termination in both cases is unspecified. If the input is a mic input, then the usual standard of 300 ohms applies. It is a power amp, it does not have a mic input. 300 ohms is NOT the 'usual standard for a mic input' Good modern power amps are common, and do not have that much variation in their noise performance with normal variations in source impedance. If the input is a line level input, then the source impedance is usually such that system performance is not affected that much by probable variations. You miss the point. How is the input terminated when noise is measured - obviously it is not left open circuit is it? I guess you've never measured the actual noise coming out of a good modern power amp with the normal range of source impedances. They often don't vary all that much. Remember, this is not legacy vacuum tube equipment which was generally far noisier. Output termination is unspecified. The noise performance of line level outputs is minimally affected by probable and reasonable variations in load impedance. No bandwidth is specified. Relevant and already mentioned No weighting or not is specified. Relevant and already mentioned No mention of whether the measurements are rms, peak, quasi-peak Both SNR and DR are ratios of two measurements. It is most important that both measurements be done under the same circumstances. In fact they generally are not since a signal and noise have quite different characteristics. The signal will be measured rms. The noise can be measured in several ways each giving a different figure. While people could be stupid and compare a noise level measured in peak-to-peak volts to a signal measured in average volts, I know of no actual cases where this happens, except perhaps in your mind, Ian. There could be equipment noise that has a high crest factor, but nature does not usually go down that path. What is then left is a few dB of ambiguity, and most good modern equipment (which is common) is not so noisy that a few dB is a deal breaker in actual use. Variations in the way the above are specified can make a large difference to the 'measured' value Some yes, some no. and I bet you can guess which set the marketing department will want to choose. One other benefit of the solid state/digital revolution is that SNR and DR performance is often so good ( 100 dB) that most variations in how they are mentioned don't matter that much. Rubbish. Dismissive, unsupported claim, again itself worthy only of dismissal. Once again, SNR and DR are different animals. A truism - therefore something that actually sheds no signficiant light. Why do you obsess over these things, Ian? Achieving a 100dB DR is not hard but unless you run your amp close to clipping all the time you will not achieve that as a SNR. Another truism. The marketing guys are as active as ever in trying to make their product appear superior to its competitors and will choose the measurement methods that best do that. The myth is that some equipment is head-and-shoulders better than its competition. Everybody pretty much feeds from the same trough. |
#60
Posted to rec.audio.tech
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Low Noise Sound card
Arny Krueger wrote:
"Ian Bell" wrote in message Arny Krueger wrote: "Ian Bell" wrote in message 0dB has no meaning. Actually, it does. In the digital domain 0 dB is commonly equated with FS. No, that is 0dBFS. Yes, so your use of the word "no" must be some kind of terrible mistake on your part. No, 0dBFS refers to full scale signal in a digital system. It is common, especially in live recording to set '0dB' to -15dBFS so as to ensure sufficient headroom. In other words, 0dB can be anything you like and therefore on its own without context is meaningless. While the units are arbitrary and may be confusing to people who still think 100% analog, it is both meaningful and commonly used. No it is not. Assertion without support, which should be immediately dismissed. OK, then we will dismiss your original unsupported assertion that 'it is both meaningful and commonly used'. Input termination in both cases is unspecified. If the input is a mic input, then the usual standard of 300 ohms applies. It is a power amp, it does not have a mic input. 300 ohms is NOT the 'usual standard for a mic input' Good modern power amps are common, and do not have that much variation in their noise performance with normal variations in source impedance. If the input is a line level input, then the source impedance is usually such that system performance is not affected that much by probable variations. You miss the point. How is the input terminated when noise is measured - obviously it is not left open circuit is it? I guess you've never measured the actual noise coming out of a good modern power amp with the normal range of source impedances. They often don't vary all that much. Remember, this is not legacy vacuum tube equipment which was generally far noisier. A 'good modern one' should not vary much. We have no idea if the OPs's device falls into this category. However, if the noise is being minimised then a point will be reached when the source impedance is relevant because if the amp was extremely noise free that would be the ONLY source of noise. OTOH, it will not vary much with source impedance if the amp is very noisy to start with, like an old tube amp. SO precisdely the coinverse of what you state is in fact true. Output termination is unspecified. The noise performance of line level outputs is minimally affected by probable and reasonable variations in load impedance. No bandwidth is specified. Relevant and already mentioned No weighting or not is specified. Relevant and already mentioned No mention of whether the measurements are rms, peak, quasi-peak Both SNR and DR are ratios of two measurements. It is most important that both measurements be done under the same circumstances. In fact they generally are not since a signal and noise have quite different characteristics. The signal will be measured rms. The noise can be measured in several ways each giving a different figure. While people could be stupid and compare a noise level measured in peak-to-peak volts to a signal measured in average volts, I know of no actual cases where this happens, except perhaps in your mind, Ian. No, but as I keep saying, manufacturers will show their product in the best light and judicious use of weighting and bandwidths will alter the 'measured' value considerably. 'A' weighting, which is pretty commonly used by manufacturers will often improve and amplifiers noise spec. by 10dB. There could be equipment noise that has a high crest factor, but nature does not usually go down that path. What is then left is a few dB of ambiguity, and most good modern equipment (which is common) is not so noisy that a few dB is a deal breaker in actual use. It is more than 'a few dB' Variations in the way the above are specified can make a large difference to the 'measured' value Some yes, some no. and I bet you can guess which set the marketing department will want to choose. One other benefit of the solid state/digital revolution is that SNR and DR performance is often so good ( 100 dB) that most variations in how they are mentioned don't matter that much. Rubbish. Dismissive, unsupported claim, again itself worthy only of dismissal. As I have said before DR and SNR are not the same and they have little relation to the actual level of noise heard in the speaker. The OP's amp for instance has an output power of 800W. Suppose this is into a load of 4 ohms then this requires over 56V rms output signal. The DR is 100dB so the noise at the output is 100dB below 56V rms which which works out at a mere -65dBu. The original all tube Leak Point One in 1949 had a measured output noise and hum of -80dB below 10W into 15 ohms which works out at just over 12V rms. So its output noise is 80dB below 12V rms which works out to be a mere -58dBu. So in 60 years of development there's been only 7dB (oh sorry I should have said 'just a few dB') of improvement due to the digital revolution. Once again, SNR and DR are different animals. A truism - therefore something that actually sheds no significant light. Why do you obsess over these things, Ian? Achieving a 100dB DR is not hard but unless you run your amp close to clipping all the time you will not achieve that as a SNR. Another truism. Excellent, so then you must agree that SNR is always less than DR. So to get back to the OP's original problem, having a DR of 100dB is irrelevant. What matters is what his SNR is. The fact he can hear hiss from an 800W amp with his ear right next to it further demonstrates this because that is not where listeners will be when the spekaer pumps outn 800W. The marketing guys are as active as ever in trying to make their product appear superior to its competitors and will choose the measurement methods that best do that. The myth is that some equipment is head-and-shoulders better than its competition. Everybody pretty much feeds from the same trough. In reality, marketing departments will aim to make crappy equipment appear much better than it is using specmanship which is what they have always done. Cheers ian |
#61
Posted to rec.audio.tech
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Low Noise Sound card
"Ian Bell" wrote in message ... No, 0dBFS refers to full scale signal in a digital system. It is common, especially in live recording to set '0dB' to -15dBFS so as to ensure sufficient headroom. In other words, 0dB can be anything you like and therefore on its own without context is meaningless. You are welcome to state your context that would make a 24bit "live recording" on a 110-120dB souncard at -15dBFS peak level have more noise than the ambient noise? :-) And you know what I do in the studio, (and even live if I have a spare channel) simply record two channels at different peak levels and select from the one that gives me the highest level with no clipping, for each song!! It's easy to make sure you do NOT waste that 15dB headroom with minimal effort, by simply inserting a 20dB pad in one channel and running the other "hot". In any case if I ever attain a *true* 100dB DNR recording I consider myself very happy. (assuming no other problems of course :-) But then we get people like Neil Young who considers a 16-44 CD as not good enough for the release of an old 2 track 1/2" live analog reording that is so far below ultimate CD quality as to make him a complete ******! I bet he is the only one who considers 24-192 actually necessary in this case. I'd really love to see a recent hearing test of his! :-) (still love his old music though) No, but as I keep saying, manufacturers will show their product in the best light and judicious use of weighting and bandwidths will alter the 'measured' value considerably. 'A' weighting, which is pretty commonly used by manufacturers will often improve and amplifiers noise spec. by 10dB. Sure, and a manufacturer who doesn't specify it as dBA, should be scorned and avoided. Reputable manufacturers however provide both weighted and unweighted figures. As I have said before DR and SNR are not the same and they have little relation to the actual level of noise heard in the speaker. The OP's amp for instance has an output power of 800W. Suppose this is into a load of 4 ohms then this requires over 56V rms output signal. The DR is 100dB so the noise at the output is 100dB below 56V rms which which works out at a mere -65dBu. The original all tube Leak Point One in 1949 had a measured output noise and hum of -80dB below 10W into 15 ohms which works out at just over 12V rms. So its output noise is 80dB below 12V rms which works out to be a mere -58dBu. So in 60 years of development there's been only 7dB (oh sorry I should have said 'just a few dB') of improvement due to the digital revolution. Ah, but IF you turn down the gain on the 800W power amp so that it's output power matches the Leak for the same input voltage, you may find it's DNR now exceeds the Leak by a MUCH bigger margin! The choice is often in the hands of the user, higher power, lower noise, or somewhere in between. Some are too dumb to comprehend that higher power outputs require more gain of course. Excellent, so then you must agree that SNR is always less than DR. Nope, you must specify all your test conditions. Obviously there will be at least one set of conditions where they *must* be equal for a start. And if you measure DNR with an applied signal (as is usually the case for soundcards) SNR may be *greater* than DNR, given any distortion products. (and no headroom above 0dBFS like there was in the days of analog recorders, that will actually add to the DNR) So to get back to the OP's original problem, having a DR of 100dB is irrelevant. What matters is what his SNR is. The fact he can hear hiss from an 800W amp with his ear right next to it further demonstrates this because that is not where listeners will be when the spekaer pumps outn 800W. Exactly. In reality, marketing departments will aim to make crappy equipment appear much better than it is using specmanship which is what they have always done. So true, but then the use of the term "Audiophile grade" was used frequently in this thread. Your definition of "audiophile grade" may differ from mine if it includes crappy equipment from disreputable manufacturers! :-) MrT. |
#62
Posted to rec.audio.tech
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Low Noise Sound card
"Ian Bell" wrote in message
Arny Krueger wrote: "Ian Bell" wrote in message Arny Krueger wrote: "Ian Bell" wrote in message 0dB has no meaning. Actually, it does. In the digital domain 0 dB is commonly equated with FS. No, that is 0dBFS. Yes, so your use of the word "no" must be some kind of terrible mistake on your part. No, 0dBFS refers to full scale signal in a digital system. Of course! It is common, especially in live recording to set '0dB' to -15dBFS so as to ensure sufficient headroom. In other words, 0dB can be anything you like and therefore on its own without context is meaningless. Ian, you seem to be fascinated with telling people that they are wrong, and then explaining it by reciting either the exact same facts they did, or paraphrasing them. While the units are arbitrary and may be confusing to people who still think 100% analog, it is both meaningful and commonly used. No it is not. Assertion without support, which should be immediately dismissed. OK, then we will dismiss your original unsupported assertion that 'it is both meaningful and commonly used'. Tit for tat? Input termination in both cases is unspecified. If the input is a mic input, then the usual standard of 300 ohms applies. It is a power amp, it does not have a mic input. 300 ohms is NOT the 'usual standard for a mic input' Good modern power amps are common, and do not have that much variation in their noise performance with normal variations in source impedance. no response from Ian If the input is a line level input, then the source impedance is usually such that system performance is not affected that much by probable variations. You miss the point. How is the input terminated when noise is measured - obviously it is not left open circuit is it? I guess you've never measured the actual noise coming out of a good modern power amp with the normal range of source impedances. They often don't vary all that much. Remember, this is not legacy vacuum tube equipment which was generally far noisier. A 'good modern one' should not vary much. We have no idea if the OPs's device falls into this category. However, if the noise is being minimised then a point will be reached when the source impedance is relevant because if the amp was extremely noise free that would be the ONLY source of noise. Baseless speculation. OTOH, it will not vary much with source impedance if the amp is very noisy to start with, like an old tube amp. SO precisdely the coinverse of what you state is in fact true. I thank you for substantiating a point I make below. Output termination is unspecified. The noise performance of line level outputs is minimally affected by probable and reasonable variations in load impedance. No bandwidth is specified. Relevant and already mentioned No weighting or not is specified. Relevant and already mentioned No mention of whether the measurements are rms, peak, quasi-peak Both SNR and DR are ratios of two measurements. It is most important that both measurements be done under the same circumstances. In fact they generally are not since a signal and noise have quite different characteristics. The signal will be measured rms. The noise can be measured in several ways each giving a different figure. While people could be stupid and compare a noise level measured in peak-to-peak volts to a signal measured in average volts, I know of no actual cases where this happens, except perhaps in your mind, Ian. No, but as I keep saying, manufacturers will show their product in the best light and judicious use of weighting and bandwidths will alter the 'measured' value considerably. 'A' weighting, which is pretty commonly used by manufacturers will often improve and amplifiers noise spec. by 10dB. Believe it or not, "A" weighting has a reasonble justification. It weights the noise in accordance with the response of the human ear at the levels that noise from a reasonably clean piece of equipment is likely to be heard. It properly focuses on noise at frequencies where the ear is more sensitive, and tends to give less weight to noise at frequencies where the ear is less sensitive. There could be equipment noise that has a high crest factor, but nature does not usually go down that path. What is then left is a few dB of ambiguity, and most good modern equipment (which is common) is not so noisy that a few dB is a deal breaker in actual use. It is more than 'a few dB' Baseless assertion. Variations in the way the above are specified canmake a large difference to the 'measured' value Some yes, some no. and I bet you can guess which set the marketing department will want to choose. One other benefit of the solid state/digital revolution is that SNR and DR performance is often so good ( 100 dB) that most variations in how they are mentioned don't matter that much. Rubbish. Dismissive, unsupported claim, again itself worthy only of dismissal. As I have said before DR and SNR are not the same and they have little relation to the actual level of noise heard in the speaker. Ian, I've shown many ways that just your say so is not relevant or binding. Come up with some authority other than yourself, or watch your whole discussion flush down the toilet. The OP's amp for instance has an output power of 800W. Suppose this is into a load of 4 ohms then this requires over 56V rms output signal. The DR is 100dB so the noise at the output is 100dB below 56V rms which which works out at a mere -65dBu. The good news is that nobody in their right minds hooks 800 watt power amps up to lines where 0 dBu is the reference level. IOW Ian, your example is irrelevant to good, reasonable practice. The original all tube Leak Point One in 1949 had a measured output noise and hum of -80dB below 10W into 15 ohms which works out at just over 12V rms. So its output noise is 80dB below 12V rms which works out to be a mere -58dBu. And the point of equating 10 watt amps to 800 watt amps is????????????? So in 60 years of development there's been only 7dB (oh sorry I should have said 'just a few dB') of improvement due to the digital revolution. ????????????????????? A claim that comes about due to the incredible folly of equating a 800 wpc amp to a 10 wpc amp. Once again, SNR and DR are different animals. A truism - therefore something that actually sheds no significant light. Why do you obsess over these things, Ian? no answer Achieving a 100dB DR is not hard but unless you run your amp close to clipping all the time you will not achieve that as a SNR. Another truism. Excellent, so then you must agree that SNR is always less than DR. It can go either way. The most common current standard for measuring DR involves the presence of a test signal and the inclusion of nonlinear distortion. Depending on the piece of equipment, either SNR or DR can be the larger number. So to get back to the OP's original problem, having a DR of 100dB is irrelevant. What matters is what his SNR is. The fact he can hear hiss from an 800W amp with his ear right next to it further demonstrates this because that is not where listeners will be when the spekaer pumps outn 800W. The sentence itself is a non-sequitor, but if your point is that judging amps by putting your ear right next to the speaker is questionable, then I have to agree with that in general. OTOH, if there is some real world connection between this test and actual use in the real world, then we have to give the OP a pass. The marketing guys are as active as ever in trying to make their product appear superior to its competitors and will choose the measurement methods that best do that. The myth is that some equipment is head-and-shoulders better than its competition. Everybody pretty much feeds from the same trough. In reality, marketing departments will aim to make crappy equipment appear much better than it is using specmanship which is what they have always done. That's just it, the general quality of audio gear has improved signficantly since the days of the Leak Point One. |
#63
Posted to rec.audio.tech
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Low Noise Sound card
Arny Krueger wrote:
"Ian Bell" wrote in message Arny Krueger wrote: "Ian Bell" wrote in message Arny Krueger wrote: "Ian Bell" wrote in message 0dB has no meaning. Actually, it does. In the digital domain 0 dB is commonly equated with FS. No, that is 0dBFS. Yes, so your use of the word "no" must be some kind of terrible mistake on your part. No, 0dBFS refers to full scale signal in a digital system. Of course! It is common, especially in live recording to set '0dB' to -15dBFS so as to ensure sufficient headroom. In other words, 0dB can be anything you like and therefore on its own without context is meaningless. Ian, you seem to be fascinated with telling people that they are wrong, and then explaining it by reciting either the exact same facts they did, or paraphrasing them. While the units are arbitrary and may be confusing to people who still think 100% analog, it is both meaningful and commonly used. No it is not. Assertion without support, which should be immediately dismissed. OK, then we will dismiss your original unsupported assertion that 'it is both meaningful and commonly used'. Tit for tat? Input termination in both cases is unspecified. If the input is a mic input, then the usual standard of 300 ohms applies. It is a power amp, it does not have a mic input. 300 ohms is NOT the 'usual standard for a mic input' Good modern power amps are common, and do not have that much variation in their noise performance with normal variations in source impedance. no response from Ian If the input is a line level input, then the source impedance is usually such that system performance is not affected that much by probable variations. You miss the point. How is the input terminated when noise is measured - obviously it is not left open circuit is it? I guess you've never measured the actual noise coming out of a good modern power amp with the normal range of source impedances. They often don't vary all that much. Remember, this is not legacy vacuum tube equipment which was generally far noisier. A 'good modern one' should not vary much. We have no idea if the OPs's device falls into this category. However, if the noise is being minimised then a point will be reached when the source impedance is relevant because if the amp was extremely noise free that would be the ONLY source of noise. Baseless speculation. OTOH, it will not vary much with source impedance if the amp is very noisy to start with, like an old tube amp. SO precisdely the coinverse of what you state is in fact true. I thank you for substantiating a point I make below. Output termination is unspecified. The noise performance of line level outputs is minimally affected by probable and reasonable variations in load impedance. No bandwidth is specified. Relevant and already mentioned No weighting or not is specified. Relevant and already mentioned No mention of whether the measurements are rms, peak, quasi-peak Both SNR and DR are ratios of two measurements. It is most important that both measurements be done under the same circumstances. In fact they generally are not since a signal and noise have quite different characteristics. The signal will be measured rms. The noise can be measured in several ways each giving a different figure. While people could be stupid and compare a noise level measured in peak-to-peak volts to a signal measured in average volts, I know of no actual cases where this happens, except perhaps in your mind, Ian. No, but as I keep saying, manufacturers will show their product in the best light and judicious use of weighting and bandwidths will alter the 'measured' value considerably. 'A' weighting, which is pretty commonly used by manufacturers will often improve and amplifiers noise spec. by 10dB. Believe it or not, "A" weighting has a reasonble justification. It weights the noise in accordance with the response of the human ear at the levels that noise from a reasonably clean piece of equipment is likely to be heard. It properly focuses on noise at frequencies where the ear is more sensitive, and tends to give less weight to noise at frequencies where the ear is less sensitive. There could be equipment noise that has a high crest factor, but nature does not usually go down that path. What is then left is a few dB of ambiguity, and most good modern equipment (which is common) is not so noisy that a few dB is a deal breaker in actual use. It is more than 'a few dB' Baseless assertion. Variations in the way the above are specified canmake a large difference to the 'measured' value Some yes, some no. and I bet you can guess which set the marketing department will want to choose. One other benefit of the solid state/digital revolution is that SNR and DR performance is often so good ( 100 dB) that most variations in how they are mentioned don't matter that much. Rubbish. Dismissive, unsupported claim, again itself worthy only of dismissal. As I have said before DR and SNR are not the same and they have little relation to the actual level of noise heard in the speaker. Ian, I've shown many ways that just your say so is not relevant or binding. Come up with some authority other than yourself, or watch your whole discussion flush down the toilet. The OP's amp for instance has an output power of 800W. Suppose this is into a load of 4 ohms then this requires over 56V rms output signal. The DR is 100dB so the noise at the output is 100dB below 56V rms which which works out at a mere -65dBu. The good news is that nobody in their right minds hooks 800 watt power amps up to lines where 0 dBu is the reference level. IOW Ian, your example is irrelevant to good, reasonable practice. The original all tube Leak Point One in 1949 had a measured output noise and hum of -80dB below 10W into 15 ohms which works out at just over 12V rms. So its output noise is 80dB below 12V rms which works out to be a mere -58dBu. And the point of equating 10 watt amps to 800 watt amps is????????????? So in 60 years of development there's been only 7dB (oh sorry I should have said 'just a few dB') of improvement due to the digital revolution. ????????????????????? A claim that comes about due to the incredible folly of equating a 800 wpc amp to a 10 wpc amp. Once again, SNR and DR are different animals. A truism - therefore something that actually sheds no significant light. Why do you obsess over these things, Ian? no answer Achieving a 100dB DR is not hard but unless you run your amp close to clipping all the time you will not achieve that as a SNR. Another truism. Excellent, so then you must agree that SNR is always less than DR. It can go either way. The most common current standard for measuring DR involves the presence of a test signal and the inclusion of nonlinear distortion. Depending on the piece of equipment, either SNR or DR can be the larger number. So to get back to the OP's original problem, having a DR of 100dB is irrelevant. What matters is what his SNR is. The fact he can hear hiss from an 800W amp with his ear right next to it further demonstrates this because that is not where listeners will be when the spekaer pumps outn 800W. The sentence itself is a non-sequitor, but if your point is that judging amps by putting your ear right next to the speaker is questionable, then I have to agree with that in general. OTOH, if there is some real world connection between this test and actual use in the real world, then we have to give the OP a pass. The marketing guys are as active as ever in trying to make their product appear superior to its competitors and will choose the measurement methods that best do that. The myth is that some equipment is head-and-shoulders better than its competition. Everybody pretty much feeds from the same trough. In reality, marketing departments will aim to make crappy equipment appear much better than it is using specmanship which is what they have always done. That's just it, the general quality of audio gear has improved signficantly since the days of the Leak Point One. Arny, you seem more interested in argument than technical discussion so I am going to waste no more time on you. Cheers Ian |
#64
Posted to rec.audio.tech
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Low Noise Sound card
"Ian Bell" wrote in message ... Arny, you seem more interested in argument than technical discussion Seems to me his argument is your lack of accurate, relevant, technical discussion. MrT. |
#65
Posted to rec.audio.tech
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Low Noise Sound card
"Mr.T" MrT@home wrote in message
u "Ian Bell" wrote in message ... Arny, you seem more interested in argument than technical discussion Seems to me his argument is your lack of accurate, relevant, technical discussion. Exactly. I've read some great technical posts from Ian, but there have been some pretty serious technical problems in this thread. |
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