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#1
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Microphone attenuators
The signal I get on certain close-miced drums is too hot for my mixer, which
doesn't have any built-in attenuation. Do I need to buy an attenuator from a supplier or can I just build my own with resistors? If I need 10-20dB of attenuation, what values should I use, and what about impedance issues? Is there any significant difference in sound quality between using different components (resistors, wires, solder etc), or just a difference in accuracy of level reduction? Thanks, -- tj hertz tjhertz at gmail dot com |
#2
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"sycochkn" wrote in message
ink.net... So what is the impedence of the microphone? What does it like to see. 300 ohm 50k ohm? Single ended balanced? Would you use a different attenuator for every mic in your collection? The mics in question are an SM57 and D112 or D6. I understand basic electronics but I'm not really up to speed on impedences. Thanks -- tj hertz |
#3
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"Scott Dorsey" But there was a recent thread here in which Phil insisted everyone was wrong about attenuator resistor values, ** You are a stinking liar, Scott Dorsey. .......... Phil |
#4
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TJ Hertz wrote:
"sycochkn" wrote in message link.net... So what is the impedence of the microphone? What does it like to see. 300 ohm 50k ohm? Single ended balanced? Would you use a different attenuator for every mic in your collection? Probably not. The mics in question are an SM57 and D112 or D6. A single design will serve these quite nicely. I understand basic electronics but I'm not really up to speed on impedences. For the purposes of a mic attenuator you can simply think of the impedances as resistances. I found a page that describes a design approach at http://www.isce.org.uk/engnotes/ENote3.pdf I agree with Scott, though. You should buy the Shure A15AS. It's pre- engineered, can be set to three different levels of attenuation, can usually be purchased for less than it will cost you for the equivalent parts, and will probably be more rugged and reliable than homebrew. -- ================================================== ====================== Michael Kesti | "And like, one and one don't make | two, one and one make one." | - The Who, Bargain |
#5
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"TJ Hertz" wrote in message k... "sycochkn" wrote in message ink.net... So what is the impedence of the microphone? What does it like to see. 300 ohm 50k ohm? Single ended balanced? Would you use a different attenuator for every mic in your collection? The mics in question are an SM57 and D112 or D6. I understand basic electronics but I'm not really up to speed on impedences. Thanks -- tj hertz most modern mixer inputs are what you would consider to be high impedance, therefore a high Z pad would seem to be the way to go to me but then most of the mixers i run across lately don't need the pad as the input can be trimed enough to keep from clipping. which unit are you working with? |
#6
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#7
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"dan lavry" Also, I would not go through all the trouble with 5% resistors. Go fro some good resistors with nice tolerance; say 0.1%, for the pair of the series resistors. The single load resistor tolerance is not important, but the series resistors tolerance matters a hack of a lot for common mode rejection!!! Remember that 1% mismatch is only -40dB, and even 0.1% mismatch is -60dB rejection. ** Because the network has no connection to ground, resistor tolerance does not impact CMRR as badly as it otherwise would. I did a few tests as follows. With values of 560, 470 and 100 ohms ( ie an error of 20% in the series resistors) the CMRR was 50 dB. With values of 493, 470 and 100 ohms ( ie an error of 5% in the series resistors) the CMRR was 54 dB. With values of 470, 470 and 100 ohms ( all 1% types chosen at random ) the CMRR was 79 dB. With the inputs shorted together the CMRR was 80 dB. .............. Phil |
#8
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#9
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"Mike Rivers" Dan Lavry Phil Allison Also, I would not go through all the trouble with 5% resistors. Go fro some good resistors with nice tolerance; say 0.1%, for the pair of the series resistors. The single load resistor tolerance is not important, but the series resistors tolerance matters a hack of a lot for common mode rejection!!! Remember that 1% mismatch is only -40dB, and even 0.1% mismatch is -60dB rejection. ** Because the network has no connection to ground, resistor tolerance does not impact CMRR as badly as it otherwise would. I did a few tests as follows. With values of 560, 470 and 100 ohms ( ie an error of 20% in the series resistors) the CMRR was 50 dB. With values of 493, 470 and 100 ohms ( ie an error of 5% in the series resistors) the CMRR was 54 dB. With values of 470, 470 and 100 ohms ( all 1% types chosen at random ) the CMRR was 79 dB. With the inputs shorted together the CMRR was 80 dB. I'm surprised that someone as dedicated to specifications and number as you would find the difference between 50 dB CMRR (with 20% imbalance) or 54 dB (with 5% imbalance) and 79 dB (with 1% imbalance) to be a small impact. What is your criteria if not a loss of 25 dB or more of CMRR? ** The total ****wit, incontinent, smelly parrot has not read my words in context - as per bloody usual I am suggesting that cheap, readily available *** 1 % *** resistors are adequate - that is what the numbers say. No need to go for exotic 0.1 % ones as Dan Lavry assumed. .............. Phil |
#11
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"Phil Allison" wrote in message ** Because the I'm surprised that someone as dedicated to specifications and number
as you would find the difference between 50 dB CMRR (with 20% imbalance) or 54 dB (with 5% imbalance) and 79 dB (with 1% imbalance) to be a small impact. What is your criteria if not a loss of 25 dB or more of CMRR? ** The total ****wit, incontinent, smelly parrot has not read my words in context - as per bloody usual I am suggesting that cheap, readily available *** 1 % *** resistors are adequate - that is what the numbers say. No need to go for exotic 0.1 % ones as Dan Lavry assumed. ............. Phil I did not assume a thing. It is not about assumptions, and certainly about foul language. Well, I did not want to assume that there is no ground path, it was not a given. You are stating it is so, but it is someone elses gear. But the point is simple: One is going to invest say 1 hour of their time in building a simple resistor network. It sounded like someone that needs to buy the resistors anyway. Only factories labs and alike have a large selection of parts on hand. So you call Digikey or Mouser, and find that you can do it with 5% resistors that will cost you a couple of cents, or 1% resistors that will still only cost a couple of cents, or you can go for 0.1% and pay a whole couple of dollars for a pair, keep that RO at 1% or whatever. Now you add shipping costs, and the materials are NEAR NEGLEGABLE! It is not like I am sugesting someone to spend $1000 on matetrials. I stand by my sugestion to go for .1%, even if it only buys you a couple of dB. It will probably do better than that. So instead of swearing a lot, listen to what I said - and I am telling you that computing is a must, not just measuring, unless you want to specify exactly the value of the resistors used in the circuit you tested, which is a real waste of time... My advice: just go for .1% at 25ppm/C or similar and pay a couple of bucks. You could in the future use that attenuator with gear that does not have great isolation. I am not yet sure the mixer we are talking about does. BR Dan Lavry |
#12
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"dan lavry" wrote in message
m... My advice: just go for .1% at 25ppm/C or similar and pay a couple of bucks. Or... Digi-Key sells its 1% resistors in packets of five. Within a batch, my experience is that the spread is less than 1%; if you buy two packets, you're likely to get at least two pairs that match within 0.1%. If you have a digital multimeter, the job of matching's easy. (And if you don't, you probably ought to have one anyway. Radio Shack sells 'em at very reasonable prices.) Peace, Paul |
#13
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#14
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"Mike Rivers" Paul Stramler Digi-Key sells its 1% resistors in packets of five. Within a batch, my experience is that the spread is less than 1%; if you buy two packets, you're likely to get at least two pairs that match within 0.1%. If you have a digital multimeter, the job of matching's easy. How do you think they make 0.1% resistors? g ** Nothing a demented, incontinent, squawking Parrot would ever know - that is for sure. What you aren't likely to find are two that are within 0.1% of the marked value, because those get branded as 0.1% and sold for more money ** Squawk ... squawk .... squawk ..... squawk .......... The parrot has got a bad dose of avian diarrhoea !!! because there are fewer of them than those within 1% of the marked value. But for this application, the absolute value isn't critical. ** Oh my god - now the featherless abomination is parroting my words !! ............. Phil |
#16
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"Phil Allison" wrote in message ...
"Mike Rivers" Paul Stramler ** Nothing a demented, incontinent, squawking Parrot would ever know - that is for sure. ** Squawk ... squawk .... squawk ..... squawk .......... The parrot has got a bad dose of avian diarrhoea !!! ** Oh my god - now the featherless abomination is parroting my words ............ Phil Phil, you win, I am out of here. I do not like your style. You probably think it is cool or cute. It may be so for some, but the internet has all sorts of people, from various cultures and walk of life. I, for one, at nearly 60 years old, find your comments do not fit my style. I'll say that much: all that hoopla with parrot and diarrhhoa is very un inviting to have a dialog. It is a distruction, making people less willing to have a dialog. Of course you are right, I must be an old fart and a nurd for saying so. Good luck Dan Lavry |
#17
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Phil, you win, I am out of here. I do not like your style. You
probably think it is cool or cute. It may be so for some, but the internet has all sorts of people, from various cultures and walk of life. I, for one, at nearly 60 years old, find your comments do not fit my style. I'll say that much: all that hoopla with parrot and diarrhhoa is very un inviting to have a dialog. It is a distruction, making people less willing to have a dialog. Of course you are right, I must be an old fart and a nurd for saying so. Good luck Dan Lavry Well, I'm 64 and I don't care for it either. Killfile coming up. --Wayne -"sounded good to me"- |
#18
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On or about Thu, 2 Sep 2004 00:20:11 +1000, Phil Allison allegedly wrote:
** Nothing a demented, incontinent, squawking Parrot would ever know - that is for sure. ** Squawk ... squawk .... squawk ..... squawk .......... The parrot has got a bad dose of avian diarrhoea !!! ** Oh my god - now the featherless abomination is parroting my words I think you must've been hanging out too much with Rod Speed, Phil. Noel Bachelor noelbachelorAT(From:_domain) Language Recordings Inc (Darwin Australia) |
#20
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"Tony" My 0.1% resistors have much tighter specified tempcos than my 1% resistors. ** Naturally - since they are made with different and better materials and a different process. The aging characteristics are an order of magnitude better as well. Are you suggesting that they select the tempcos as well? or that it always just happens that if a resistor is very close to its design value, it automatically has a tighter tempco? Or that the makers lie about the specs? Or have you just managed to find 0.1% resistors with bad tempcos? ** How you are enjoying sticking the boot into that Septic featherless, squawking parrot ?? .............. Phil |
#21
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#22
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Mike Rivers wrote:
In article writes: Digi-Key sells its 1% resistors in packets of five. Within a batch, my experience is that the spread is less than 1%; if you buy two packets, you're likely to get at least two pairs that match within 0.1%. If you have a digital multimeter, the job of matching's easy. How do you think they make 0.1% resistors? g What you aren't likely to find are two that are within 0.1% of the marked value, because those get branded as 0.1% and sold for more money because there are fewer of them than those within 1% of the marked value. But for this application, the absolute value isn't critical. Actually my experience is different. Commercial 1% resistors measure *far* better than 1% in practice. I suspect that 0.1% resistors are generally manufactured on a special line. They are a specilaised high cost item. In any event, the demand for them is inadequate to exhaust those 1% types that would be 0.1%. Graham |
#23
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"Mike Rivers" Tony Are you suggesting that they select the tempcos as well? or that it always just happens that if a resistor is very close to its design value, it automatically has a tighter tempco? Or that the makers lie about the specs? Or have you just managed to find 0.1% resistors with bad tempcos? I have never been concerned with "tempcos" (I assume that's Australian for temperature coefficient) for a device that will always be used at room temperature. ** Resistors get very hot due to dissipation - you tenth witted, demented parrot. The term "tempco" is actually an Americanism. Shame that does not extend to featherless poop droppers. Isn't the temperature coefficient primarily a function of the material the resitor is made of? ** Yep - and 0.1% types are not made from the same material as 1% types. Educate me here, don't just challange my statement. ** No one can educate a ****wit parrot who thinks it already knows. Squawk...squawk ....squawk ..... And explain, don't just point me to a web site. ** ROTFLMAO !!!!!!! That way I'll be confident that you know what you're saying. ** THAT has to be the dumbest post of the year !!!! ROTFLMFAO !!! ....... Phil |
#24
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Phil Allison wrote: ** THAT has to be the dumbest post of the year !!!! I don't know, Phil. You have provided an awful lot of competition. |
#25
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"Mike Rivers" wrote in message
news:znr1094259452k@trad In article writes: Are you suggesting that they select the tempcos as well? or that it always just happens that if a resistor is very close to its design value, it automatically has a tighter tempco? Or that the makers lie about the specs? Or have you just managed to find 0.1% resistors with bad tempcos? I have never been concerned with "tempcos" (I assume that's Australian for temperature coefficient) for a device that will always be used at room temperature. Not to mention the fact that if the components of an attenuator are kept in reasonbly close thermal contact with each other, their ratio, which sets the attenuation, will remain the same, even if their values change with temperature. |
#26
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"Mike Rivers" wrote in message
news:znr1094259452k@trad In article writes: Are you suggesting that they select the tempcos as well? or that it always just happens that if a resistor is very close to its design value, it automatically has a tighter tempco? Or that the makers lie about the specs? Or have you just managed to find 0.1% resistors with bad tempcos? I have never been concerned with "tempcos" (I assume that's Australian for temperature coefficient) for a device that will always be used at room temperature. Not to mention the fact that if the components of an attenuator are kept in reasonbly close thermal contact with each other, their ratio, which sets the attenuation, will remain the same, even if their values change with temperature. |
#27
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#28
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#29
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Pooh Bear wrote in message
I suspect that 0.1% resistors are generally manufactured on a special line. They are a specilaised high cost item. In any event, the demand for them is inadequate to exhaust those 1% types that would be 0.1%. Graham When I brought that issue about .1% being tighter tolerance for better common mode rejection, I did mention the tempco which is temperature coefficient, and I pointed at 25ppm .1% as a "reasonable" way to go. Why? Because you can get those for a buck each, and given that one is considering going through all the trouble of buliding a rig, this is a worth while thing to do. But since people are asking questions, I would answer some and add a point or two: First, it is about materials, of course it is, and that is one of the major factors for the resistor manufacturers to figure the proper mic of materials to meet some given specifications. That does include both abolute value, and temperature drift, and by the way, the aging is already included in the tolerance, at least for the resistors I use. Let me point out that I my sugestion to invest the couple of bucks was reasonable, and I even pointed out you could buy them at Mouser or Digikey. Those outlets will deal in small quantities, while the big part houses will mostly not. I could have "gone crazy" to sugest some really expansive parts, such as bulk metal foil, and I have seen those go for $60 each at small quantity. What do you get? .01% tolerance with 1ppm/degree tempco! I did not sugest that, because I am a parctical design engineer, not just someone wasting your time. But the internet always seem to encourage one more guy to say one more thing. I wish it were not so... There is also another way to go, which may be just a bit more costly, perhapse a couple of bucks more, and makes a lot of sense: The idea is to have good matching, so the initial tolerance is importent. But when it comes to drift due to temperature or againg, an alternet way to go is to use 2 resistors made out of the exact same material and to be sure that they are at the same temperature and humidity. Who do you do that? You buy a resistor network (2 or more resistors on the same substrate). It often looks like an IC (dual in line - 2 rows, 8 pins, 14 pins, 16 pins...) or some are a SIP (single in line package). All the resistors are made on the same substarte. Often you deposite some material (they call it film), and then isolate the areas to yield the desired resistance. Now, thick film is the cheaper process. Thin film is the one to look for, it comes in veriety of specs but tends to be good on tolerance and temperature. If one wants to go that route, the initial tolerance is importent, but the better spec is initial matching (for this attenuator case we are discussing). Also, it is not the TC (temperature coefficient) that is key. The TCT (temperature coefficient tracking) is the key. Why? Because you really are not that interested the exact value. You want to be dran shure that the pair will have the same value, out of the box, and at different temperature and aging. So you want initialy good match, than the variation to be the same on both parts (tracking). I have not look and will not look for a specific part for this case, but with 30 years analog design, I bet you get what you want for less than $3 for the pair. Those that understood my comments about initial matching and tracking of materials on the same substrate can now understand how resistor based DAC's are designed. It is the same thing - good initial matching (often done with laser triming of the material), and than all the resistors are made of the same material, and all in a very small space, thus same temperature and other conditions... BR Dan Lavry |
#30
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Pooh Bear wrote in message
I suspect that 0.1% resistors are generally manufactured on a special line. They are a specilaised high cost item. In any event, the demand for them is inadequate to exhaust those 1% types that would be 0.1%. Graham When I brought that issue about .1% being tighter tolerance for better common mode rejection, I did mention the tempco which is temperature coefficient, and I pointed at 25ppm .1% as a "reasonable" way to go. Why? Because you can get those for a buck each, and given that one is considering going through all the trouble of buliding a rig, this is a worth while thing to do. But since people are asking questions, I would answer some and add a point or two: First, it is about materials, of course it is, and that is one of the major factors for the resistor manufacturers to figure the proper mic of materials to meet some given specifications. That does include both abolute value, and temperature drift, and by the way, the aging is already included in the tolerance, at least for the resistors I use. Let me point out that I my sugestion to invest the couple of bucks was reasonable, and I even pointed out you could buy them at Mouser or Digikey. Those outlets will deal in small quantities, while the big part houses will mostly not. I could have "gone crazy" to sugest some really expansive parts, such as bulk metal foil, and I have seen those go for $60 each at small quantity. What do you get? .01% tolerance with 1ppm/degree tempco! I did not sugest that, because I am a parctical design engineer, not just someone wasting your time. But the internet always seem to encourage one more guy to say one more thing. I wish it were not so... There is also another way to go, which may be just a bit more costly, perhapse a couple of bucks more, and makes a lot of sense: The idea is to have good matching, so the initial tolerance is importent. But when it comes to drift due to temperature or againg, an alternet way to go is to use 2 resistors made out of the exact same material and to be sure that they are at the same temperature and humidity. Who do you do that? You buy a resistor network (2 or more resistors on the same substrate). It often looks like an IC (dual in line - 2 rows, 8 pins, 14 pins, 16 pins...) or some are a SIP (single in line package). All the resistors are made on the same substarte. Often you deposite some material (they call it film), and then isolate the areas to yield the desired resistance. Now, thick film is the cheaper process. Thin film is the one to look for, it comes in veriety of specs but tends to be good on tolerance and temperature. If one wants to go that route, the initial tolerance is importent, but the better spec is initial matching (for this attenuator case we are discussing). Also, it is not the TC (temperature coefficient) that is key. The TCT (temperature coefficient tracking) is the key. Why? Because you really are not that interested the exact value. You want to be dran shure that the pair will have the same value, out of the box, and at different temperature and aging. So you want initialy good match, than the variation to be the same on both parts (tracking). I have not look and will not look for a specific part for this case, but with 30 years analog design, I bet you get what you want for less than $3 for the pair. Those that understood my comments about initial matching and tracking of materials on the same substrate can now understand how resistor based DAC's are designed. It is the same thing - good initial matching (often done with laser triming of the material), and than all the resistors are made of the same material, and all in a very small space, thus same temperature and other conditions... BR Dan Lavry |
#31
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"Mike Rivers" Phil Allison I have never been concerned with "tempcos" (I assume that's Australian for temperature coefficient) for a device that will always be used at room temperature. ** Resistors get very hot due to dissipation - you tenth witted, demented parrot. Mister-theory-practice-be-damned speaks wisely. ** The lying, ****wit parrot has snipped and shifted the context again !!!!!!!!! Any resistor claimed to be of 0.1% precision by its **maker** must have commensurate tempco and long term stability figures as well. Selecting 0.1% tolerance examples from 1% stock will NOT give you that. The ****wit parrot's ****wit notion is just as putrid ad ever. ............ Phil |
#32
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"Mike Rivers" Phil Allison I have never been concerned with "tempcos" (I assume that's Australian for temperature coefficient) for a device that will always be used at room temperature. ** Resistors get very hot due to dissipation - you tenth witted, demented parrot. Mister-theory-practice-be-damned speaks wisely. ** The lying, ****wit parrot has snipped and shifted the context again !!!!!!!!! Any resistor claimed to be of 0.1% precision by its **maker** must have commensurate tempco and long term stability figures as well. Selecting 0.1% tolerance examples from 1% stock will NOT give you that. The ****wit parrot's ****wit notion is just as putrid ad ever. ............ Phil |
#33
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"dan lavry" Pooh Bear I suspect that 0.1% resistors are generally manufactured on a special line. They are a specilaised high cost item. In any event, the demand for them is inadequate to exhaust those 1% types that would be 0.1%. When I brought that issue about .1% being tighter tolerance for better common mode rejection, ** Which, as I demonstrated with real tests, is a total fallacy. I did mention the tempco which is temperature coefficient, and I pointed at 25ppm .1% as a "reasonable" way to go. ** It is a pedantic fool's idea. Let me point out that I my sugestion to invest the couple of bucks was reasonable, ** It is a pedantic fool's idea. I could have "gone crazy" to sugest some really expansive parts ** That would be a pedantic ****wit's idea. Those that understood my comments about initial matching and tracking of materials on the same substrate can now understand how resistor based DAC's are designed. It is the same thing - good initial matching (often done with laser triming of the material), and than all the resistors are made of the same material, and all in a very small space, thus same temperature and other conditions... ** Massive red herring. ........... Phil |
#34
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"dan lavry" Pooh Bear I suspect that 0.1% resistors are generally manufactured on a special line. They are a specilaised high cost item. In any event, the demand for them is inadequate to exhaust those 1% types that would be 0.1%. When I brought that issue about .1% being tighter tolerance for better common mode rejection, ** Which, as I demonstrated with real tests, is a total fallacy. I did mention the tempco which is temperature coefficient, and I pointed at 25ppm .1% as a "reasonable" way to go. ** It is a pedantic fool's idea. Let me point out that I my sugestion to invest the couple of bucks was reasonable, ** It is a pedantic fool's idea. I could have "gone crazy" to sugest some really expansive parts ** That would be a pedantic ****wit's idea. Those that understood my comments about initial matching and tracking of materials on the same substrate can now understand how resistor based DAC's are designed. It is the same thing - good initial matching (often done with laser triming of the material), and than all the resistors are made of the same material, and all in a very small space, thus same temperature and other conditions... ** Massive red herring. ........... Phil |
#35
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On Sat, 4 Sep 2004 14:35:48 -0400, "Arny Krueger"
wrote: "Mike Rivers" wrote in message news:znr1094259452k@trad In article writes: Are you suggesting that they select the tempcos as well? or that it always just happens that if a resistor is very close to its design value, it automatically has a tighter tempco? Or that the makers lie about the specs? Or have you just managed to find 0.1% resistors with bad tempcos? I have never been concerned with "tempcos" (I assume that's Australian for temperature coefficient) for a device that will always be used at room temperature. Not to mention the fact that if the components of an attenuator are kept in reasonbly close thermal contact with each other, their ratio, which sets the attenuation, will remain the same, even if their values change with temperature. That's very true, and certainly for the mic attenuator and many other applications, tempcos would not be an issue. But my comment was directed at Mike's assertion that 0.1% resistors were simply selected from 1% production, which I still don't believe to be true. Tony (remove the "_" to reply by email) |
#36
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On Sat, 4 Sep 2004 14:35:48 -0400, "Arny Krueger"
wrote: "Mike Rivers" wrote in message news:znr1094259452k@trad In article writes: Are you suggesting that they select the tempcos as well? or that it always just happens that if a resistor is very close to its design value, it automatically has a tighter tempco? Or that the makers lie about the specs? Or have you just managed to find 0.1% resistors with bad tempcos? I have never been concerned with "tempcos" (I assume that's Australian for temperature coefficient) for a device that will always be used at room temperature. Not to mention the fact that if the components of an attenuator are kept in reasonbly close thermal contact with each other, their ratio, which sets the attenuation, will remain the same, even if their values change with temperature. That's very true, and certainly for the mic attenuator and many other applications, tempcos would not be an issue. But my comment was directed at Mike's assertion that 0.1% resistors were simply selected from 1% production, which I still don't believe to be true. Tony (remove the "_" to reply by email) |
#37
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On 4 Sep 2004 07:11:59 -0400, (Mike Rivers) wrote:
In article writes: Are you suggesting that they select the tempcos as well? or that it always just happens that if a resistor is very close to its design value, it automatically has a tighter tempco? Or that the makers lie about the specs? Or have you just managed to find 0.1% resistors with bad tempcos? I have never been concerned with "tempcos" (I assume that's Australian for temperature coefficient) for a device that will always be used at room temperature. Yes, it's short for temperature coefficient, but not just Australian, and yes, if you are only ever going to use a device at room temperature, and you can select devices at the same "room temperature", you don't need to be concerned with tempco. If you've never considered tempcos, I guess I can see how you might think that makers might select the "good" ones and rate them at 0.1%. But when you think about the other "stability" ratings, that's just impractical. One other subtle point- some metal film resistors might have +/-25ppm/K, others might have +150ppm/K nominal tempco, which doesn't necessarily make them "bad", in fact it can be quite good in a tuned circuit with a cap whose tempco - -150ppm/K. Isn't the temperature coefficient primarily a function of the material the resitor is made of? Unless (for example) there are no 0.1% metal film resistors because the temperature coefficient can't support that tolerance. The material, the recipe tolerances, the precision of its preparation, the precision of the control of thermal profiles, the care taken in trimming, the lead attachment method, any annealing processes used, etc, etc. As in everything, you can always find ways to do essentially the same thing a little faster and/or cheaper, but you often pay for it in some other way. If you want to rate a resistor as 0.1% with similarly tighter tolerances for tempco, long-term drift, stability under load and other drifts, you don't get to take so many short cuts. Educate me here, don't just challange my statement. And explain, don't just point me to a web site. That way I'll be confident that you know what you're saying. This IS only a public forum, in which no-one is really obliged to always be an expert, or to not make mistakes, or even the occasional major faux pas. We all just express our opinions. And occasionally some of us may become a little too caught up in the debate. I'd like to be able to expound the virtues of every resistor manufacturing process used around the world, but I can't do that, or even suggest a web site. But I CAN tell you that when ever I need to compare two similar but different components, the data sheets usually have everything I really need to know. Even the lowly resistor has quite a story to tell; and don't get me started on capacitors... Tony (remove the "_" to reply by email) |
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On 4 Sep 2004 07:11:59 -0400, (Mike Rivers) wrote:
In article writes: Are you suggesting that they select the tempcos as well? or that it always just happens that if a resistor is very close to its design value, it automatically has a tighter tempco? Or that the makers lie about the specs? Or have you just managed to find 0.1% resistors with bad tempcos? I have never been concerned with "tempcos" (I assume that's Australian for temperature coefficient) for a device that will always be used at room temperature. Yes, it's short for temperature coefficient, but not just Australian, and yes, if you are only ever going to use a device at room temperature, and you can select devices at the same "room temperature", you don't need to be concerned with tempco. If you've never considered tempcos, I guess I can see how you might think that makers might select the "good" ones and rate them at 0.1%. But when you think about the other "stability" ratings, that's just impractical. One other subtle point- some metal film resistors might have +/-25ppm/K, others might have +150ppm/K nominal tempco, which doesn't necessarily make them "bad", in fact it can be quite good in a tuned circuit with a cap whose tempco - -150ppm/K. Isn't the temperature coefficient primarily a function of the material the resitor is made of? Unless (for example) there are no 0.1% metal film resistors because the temperature coefficient can't support that tolerance. The material, the recipe tolerances, the precision of its preparation, the precision of the control of thermal profiles, the care taken in trimming, the lead attachment method, any annealing processes used, etc, etc. As in everything, you can always find ways to do essentially the same thing a little faster and/or cheaper, but you often pay for it in some other way. If you want to rate a resistor as 0.1% with similarly tighter tolerances for tempco, long-term drift, stability under load and other drifts, you don't get to take so many short cuts. Educate me here, don't just challange my statement. And explain, don't just point me to a web site. That way I'll be confident that you know what you're saying. This IS only a public forum, in which no-one is really obliged to always be an expert, or to not make mistakes, or even the occasional major faux pas. We all just express our opinions. And occasionally some of us may become a little too caught up in the debate. I'd like to be able to expound the virtues of every resistor manufacturing process used around the world, but I can't do that, or even suggest a web site. But I CAN tell you that when ever I need to compare two similar but different components, the data sheets usually have everything I really need to know. Even the lowly resistor has quite a story to tell; and don't get me started on capacitors... Tony (remove the "_" to reply by email) |
#39
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On Sun, 05 Sep 2004 15:49:31 +1000, Tony wrote:
On Sat, 4 Sep 2004 14:35:48 -0400, "Arny Krueger" wrote: "Mike Rivers" wrote in message news:znr1094259452k@trad In article writes: Are you suggesting that they select the tempcos as well? or that it always just happens that if a resistor is very close to its design value, it automatically has a tighter tempco? Or that the makers lie about the specs? Or have you just managed to find 0.1% resistors with bad tempcos? I have never been concerned with "tempcos" (I assume that's Australian for temperature coefficient) for a device that will always be used at room temperature. Not to mention the fact that if the components of an attenuator are kept in reasonbly close thermal contact with each other, their ratio, which sets the attenuation, will remain the same, even if their values change with temperature. That's very true, and certainly for the mic attenuator and many other applications, tempcos would not be an issue. But my comment was directed at Mike's assertion that 0.1% resistors were simply selected from 1% production, which I still don't believe to be true. Tony (remove the "_" to reply by email) You are right - it certainly isn't true. If it were, all resistors other than the very best would have a bimodal distribution - a hole in the middle where the best ones had been removed. They don't. Typically resistor tolerance describes the width of the three-sigma level of distribution, and that distribution tends to be normal. In other words, resistors are "made" to the appropriate tolerance. d Pearce Consulting http://www.pearce.uk.com |
#40
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On Sun, 05 Sep 2004 15:49:31 +1000, Tony wrote:
On Sat, 4 Sep 2004 14:35:48 -0400, "Arny Krueger" wrote: "Mike Rivers" wrote in message news:znr1094259452k@trad In article writes: Are you suggesting that they select the tempcos as well? or that it always just happens that if a resistor is very close to its design value, it automatically has a tighter tempco? Or that the makers lie about the specs? Or have you just managed to find 0.1% resistors with bad tempcos? I have never been concerned with "tempcos" (I assume that's Australian for temperature coefficient) for a device that will always be used at room temperature. Not to mention the fact that if the components of an attenuator are kept in reasonbly close thermal contact with each other, their ratio, which sets the attenuation, will remain the same, even if their values change with temperature. That's very true, and certainly for the mic attenuator and many other applications, tempcos would not be an issue. But my comment was directed at Mike's assertion that 0.1% resistors were simply selected from 1% production, which I still don't believe to be true. Tony (remove the "_" to reply by email) You are right - it certainly isn't true. If it were, all resistors other than the very best would have a bimodal distribution - a hole in the middle where the best ones had been removed. They don't. Typically resistor tolerance describes the width of the three-sigma level of distribution, and that distribution tends to be normal. In other words, resistors are "made" to the appropriate tolerance. d Pearce Consulting http://www.pearce.uk.com |
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