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#41
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Arny,
Sometimes. There still seem to be soundcards out there with analog input gain controls. Thanks for clarifying. I know you have experience with a lot of consumer grade cards. --Ethan |
#42
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Arny,
Sometimes. There still seem to be soundcards out there with analog input gain controls. Thanks for clarifying. I know you have experience with a lot of consumer grade cards. --Ethan |
#43
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On Thu, 2 Dec 2004 18:07:45 -0500, "Arny Krueger"
wrote: "Preben Friis" wrote in message "Joseph Raymond" wrote in message If the level control actually controlled the gain of the analog preamp, then some control words would have to be sent to the sound card's ADC to either change the reference voltage or to change the sound card's preamp gain. Based on economic considerations, I doubt that that is the case. Actually, it is the case for most audio chipsets. Take a look block diagram in the datasheet below. Between the input selector and the A/D there is a small block called PGA (Programable Gain Amplifier) that can be set from 0 to 22.5 dB gain in 1.5 dB steps. And this is for a part that costs $3...! http://www.analog.com/UploadedFiles/...7AD1881A_0.pdf Unfortunately, I've got quite a bit of experience with this device. Not exactly the device of choice for high quality audio production: Anything made for the AC-97 spec is of course made for the cheap and high-volume (as in number of manufactured units, not loudness) consumer PC soundcard/motherboard market, and I'd be surprised to find any such chip with really good specs. Furthermore, the "phat stereo" blocks don't endear me to think this is high quality. There's this quote from that datasheet: "SoundMAX is a registered trademark and PHAT is a trademark of Analog Device, [SIC] Inc." I can only wonder if Analog Devices has ever sued anyone in the Hip Hop community for use of AD's trademaked word PHAT. Test results for a typical device from the SoundMax series: Frequency response (40 Hz - 15 kHz), +9.68, -12.97 dB I can only wonder how that can be so bad in ANY piece of electronics (and I can't even think of how an improper test condition could do that either), but let's not go there for now... Noise level, -84.6 dB (A) Dnamic range, 82.0 dB (A) HD, 0.0044 % Intermodulation distortion, 11.441 % The HD and IM figures appear wildly incongruous. How is that? I can't imagine how the IM figure could legitimately be so large with the HD figure so small. Were the peak values the same in each test? I could see where clipping in the IM test could cause a big number like that. ----- http://mindspring.com/~benbradley |
#44
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On Thu, 2 Dec 2004 18:07:45 -0500, "Arny Krueger"
wrote: "Preben Friis" wrote in message "Joseph Raymond" wrote in message If the level control actually controlled the gain of the analog preamp, then some control words would have to be sent to the sound card's ADC to either change the reference voltage or to change the sound card's preamp gain. Based on economic considerations, I doubt that that is the case. Actually, it is the case for most audio chipsets. Take a look block diagram in the datasheet below. Between the input selector and the A/D there is a small block called PGA (Programable Gain Amplifier) that can be set from 0 to 22.5 dB gain in 1.5 dB steps. And this is for a part that costs $3...! http://www.analog.com/UploadedFiles/...7AD1881A_0.pdf Unfortunately, I've got quite a bit of experience with this device. Not exactly the device of choice for high quality audio production: Anything made for the AC-97 spec is of course made for the cheap and high-volume (as in number of manufactured units, not loudness) consumer PC soundcard/motherboard market, and I'd be surprised to find any such chip with really good specs. Furthermore, the "phat stereo" blocks don't endear me to think this is high quality. There's this quote from that datasheet: "SoundMAX is a registered trademark and PHAT is a trademark of Analog Device, [SIC] Inc." I can only wonder if Analog Devices has ever sued anyone in the Hip Hop community for use of AD's trademaked word PHAT. Test results for a typical device from the SoundMax series: Frequency response (40 Hz - 15 kHz), +9.68, -12.97 dB I can only wonder how that can be so bad in ANY piece of electronics (and I can't even think of how an improper test condition could do that either), but let's not go there for now... Noise level, -84.6 dB (A) Dnamic range, 82.0 dB (A) HD, 0.0044 % Intermodulation distortion, 11.441 % The HD and IM figures appear wildly incongruous. How is that? I can't imagine how the IM figure could legitimately be so large with the HD figure so small. Were the peak values the same in each test? I could see where clipping in the IM test could cause a big number like that. ----- http://mindspring.com/~benbradley |
#46
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Loren Amelang wrote in message . ..
On 1 Dec 2004 14:42:55 -0800, (Joseph Raymond) wrote: I don't know for sure the answer to your question. But I have wondered about the very same thing and believe that it is math. In other words, when you change the settings on the mixer on the PC screen, you perform either a multiplication or division on the digital word at the output of the ADC. And the level is the level at the output of the mult/div relative to the number of bits available. If the level control actually controlled the gain of the analog preamp, then some control words would have to be sent to the sound card's ADC to either change the reference voltage or to change the sound card's preamp gain. Based on economic considerations, I doubt that that is the case. In any event, the question is what is the 0 dB input setting of the software mixer? Is it with the slider in the middle or some other position? In other words, how can you set the mulitplying factor to 1? Then, keeping that fixed, adjust the output level of your mic mixer going into the LINE IN while monitoring the software VU meters for the largest signal without clipping. To add complexity to these questions, the level control you see in your recording app is not always a second view of your Windows Volume Control. When I start Audiotools, its sliders are at 0dB, regardless of where my input Windows Volume Control sliders are set. I find that cutting the gain at the Windows Volume Control provides much better results than an equivalent reduction within Audiotools. Even though the analog input to my sound interface is constant, if I crank the Windows Volume Control up and make a comparable gain reduction within Audiotools, the waveform appears compressed. Crank the Windows Volume Control even higher and the recorded waveform is clipped, even though the values in the digital file are nowhere near maximum. Same behavior is observed recording with Audacity. I've been assuming this is all happening in the digital domain, where one would hope math is math, but it clearly it is not! Either the Windows Volume Control must operate in the analog world before the ADC, or it must be able to multiply as well as divide, and it must be able to multiply so much that it can clip in the digital domain. Another way of saying that would be to say that the (possibly digital counterpart of the) "0dB" setting of the Windows Volume Control must be well below its maximum setting. (At least with some audio hardware...) To add one more variable, I've found that Alex Mina's AC97 Mixer app, which talks directly to AC97 audio hardware, can reach gain settings the Windows Volume Control does not offer. At least with some hardware... According to its datasheet, the AKM AK4584 chip in my Transit USB has a +18dB Input Programmable Gain Amp (0.5dB steps) ahead of the ADC. With this IPGA set at 0 dB, it is supposed to take 3.0 Vpp of audio to produce digital full scale. Cranking the gain up to +18 raises the noise floor 10dB, so it sounds like this really is an analog amplifier. And I can clearly get clipping with way less than 3.0 Vpp, so the Transit drivers must have this IPGA set above 0 dB. Then there are the 0/14/20/26 dB steps that M-Audio offers as "Mic Boost" in their control panel. I don't see how that is implemented, or how it relates to the +18 dB IPGA in the audio chip. And I haven't a clue how the input Windows Volume Control is hooked up to all of this. So is there a way to tell whether the Windows Volume Control for a particular interface is operating before or after the ADC? I have a feeling it is different for different audio devices, and possibly for different driver versions... Loren That is the $64 question! Aside from doing it indirectly by experimentation and analyzing the digitized waveform, I imagine that there exists a Windows Audio API that defines all the possible commands that Windows can send to the audio chip. I see in the chip below that they say it meets MS PC2001 audio requirements. Perhaps knowing what MS PC2001 is is a place to start. http://www.cirrus.com/en/pubs/proDat...CS4205_PP3.pdf Then you would have to know which chip is on your PC or sound card. And I guess lastly, you would have to know if the chip has met Windows Hardware Quality Labs testing. I have no idea what that entails. And, when you loaded your drivers, it would be nice to not see any messages appearing asking whether you want to proceed because it does not meet Windows something or other. Lately I just started using a Tascam US-122. It has an LED indicating whether the front end is being overloaded and pots to adjust the input level. It would be nice if this were the only way to adjust the input level into the ADC. However, after this discussion, I have some doubts! Joe |
#47
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"Ethan Winer" ethanw at ethanwiner dot com wrote in message
Arny, Sometimes. There still seem to be soundcards out there with analog input gain controls. Thanks for clarifying. I know you have experience with a lot of consumer grade cards. I believe that the best analog attenuator *ever* was the CS 3310, which was developed for high end consumer cards. It had over 93 dB dynamic range and could handle like 20 or 30 vrms, and cut it down into something palatable for your typical sound card ADC. |
#48
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"Ethan Winer" ethanw at ethanwiner dot com wrote in message
Arny, Sometimes. There still seem to be soundcards out there with analog input gain controls. Thanks for clarifying. I know you have experience with a lot of consumer grade cards. I believe that the best analog attenuator *ever* was the CS 3310, which was developed for high end consumer cards. It had over 93 dB dynamic range and could handle like 20 or 30 vrms, and cut it down into something palatable for your typical sound card ADC. |
#49
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#51
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(Mike Rivers) wrote in message news:znr1102117998k@trad...
In article writes: Lately I just started using a Tascam US-122. It has an LED indicating whether the front end is being overloaded and pots to adjust the input level. It would be nice if this were the only way to adjust the input level into the ADC. However, after this discussion, I have some doubts! Those are real pots and actually attenuate the signal going from the input jack to the A/D converter. I don't think that it uses the Windows mixer for record level adjustments. Thanks for that info Mike. That suits me just fine Btw, I bought this box partly on what you posted in this NG and am quite pleased with it especially since it has 24 bit DACs. The only bad thing is that dog **** Cubasis software they threw in which didn't work well with my XP machine. Fortunately, my old SoundForge Studio 6.0 worked very well with it. Then, to get the full 24 bits I bought n-Track Studio which is working quite well so far. Sooooooo for $275 it's a good deal IMO. Joe |
#52
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(Mike Rivers) wrote in message news:znr1102117998k@trad...
In article writes: Lately I just started using a Tascam US-122. It has an LED indicating whether the front end is being overloaded and pots to adjust the input level. It would be nice if this were the only way to adjust the input level into the ADC. However, after this discussion, I have some doubts! Those are real pots and actually attenuate the signal going from the input jack to the A/D converter. I don't think that it uses the Windows mixer for record level adjustments. Thanks for that info Mike. That suits me just fine Btw, I bought this box partly on what you posted in this NG and am quite pleased with it especially since it has 24 bit DACs. The only bad thing is that dog **** Cubasis software they threw in which didn't work well with my XP machine. Fortunately, my old SoundForge Studio 6.0 worked very well with it. Then, to get the full 24 bits I bought n-Track Studio which is working quite well so far. Sooooooo for $275 it's a good deal IMO. Joe |
#53
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#54
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On 2004-12-05, Mike Rivers wrote:
Hey, they put something in the package that let a ground-zero beginner do something with the US-122 without buying anything else, and that's better than nothing. These days you can get a copy of Traction for free (there's a thread or two about it here) Free-ish. But it looks like the arrangement is still licensed to a single hardware configuration, which means the life expectancy of this free version of tracktion will be that of whatever machine you install it on, and beyond that you will be out of luck. Opinions vary on the relevance of this point, but I consider that to be toxic. Mackie would indirectly be exerting some control of my art, by arbitrarily limiting my access to what I create. Totally unacceptable... I won't bestow the appellation "free" onto anything that seeks to limit my use of it in any way, whatsoever. Others may restrict their definition of the word "free" merely to "available at no monetary cost." But when someone exerts control of my art, the cost is a part of my soul. I'm totally serious about this. |
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