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Post by Snoman on Dec 5, 2023 7:49:41 GMT -5
Good morning, was reviewing output impedance and unable to find any published specs.
Was hoping this data was simply overlooked when publishing the manuals and website;
PT1 PT2 TA1 TA2
XDA3 MC1 MR1 XMC-2 RMC-1L RMC-1
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Post by jpwoodbu on Dec 5, 2023 12:08:02 GMT -5
I believe you can calculate the output impedance for a given load, say 8Ω, by dividing the load by the reported damping factor of the amp. So looking at the first amp I pulled up, the BasX A1 Monoblock, the specs say it has a damping factor of >500, so I believe the output impedance would be 8Ω / 500 = 0.016Ω.
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KeithL
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Post by KeithL on Dec 5, 2023 13:24:49 GMT -5
Kind of... sort of... but not really. In theory you could do that... But the catch is that the numbers involved are incredibly difficult to measure accurately for power amps. And it gets even more difficult to calculate what they MEAN when you're talking about connecting speakers to that amplifier. Because, in terms of practical physical damping of the driver, at DFs over fifty or so, the voice coil impedance of the woofer dominates anyway... The bottom line is that, in real life, it's virtually impossible to accurately measure a DF over about 500... And, in real life, with actual speakers, the difference between a DF=4 and DF=8, which would be typical for tube amps, is clearly audible. And the difference between those and the DF=100 or so, which is the minimum for most "normal" solid state amps, is also clearly audible. And, since it's almost impossible to measure values above 500 or so, we simply rate our amps as ">500" ... But, above that, the actual values just plain don't matter... Just read that ">500" as "higher than could possibly matter for any practical purpose". (It would be sort of like asking how fast your car could go, in neutral, down a 60 degree downward incline.) Now, with things like preamps, and other line level sources, both the output impedance and the minimum load impedance do matter somewhat. But only in the context of whether they are sufficiently low compared to the load impedance of what you're connecting them to and the interconnects between them. And, on those sorts of device, if you really care, we can look it up for you... The reason we generally don't publish them is that they are apparently more likely to confuse people than to provide meaningful information. (For example, on a headphone amp, you might prefer a DF=10 over a DF=50, but it doesn't matter at all for the output of a preamp.) I believe you can calculate the output impedance for a given load, say 8Ω, by dividing the load by the reported damping factor of the amp. So looking at the first amp I pulled up, the BasX A1 Monoblock, the specs say it has a damping factor of >500, so I believe the output impedance would be 8Ω / 500 = 0.016Ω. |
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Post by ttocs on Dec 5, 2023 13:44:56 GMT -5
Now, with things like preamps, and other line level sources, both the output impedance and the minimum load impedance do matter somewhat. But only in the context of whether they are sufficiently low compared to the load impedance of what you're connecting them to and the interconnects between them. And, on those sorts of device, if you really care, we can look it up for you... The reason we generally don't publish them is that they are apparently more likely to confuse people than to provide meaningful information. Marantz doesn't publish output impedance. Nor do Denon or Monolith. But Krell does. (Disclaimer : I didn't lookup every model from the above manufacturers, just the top model in each line.) |
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Post by 405x5 on Dec 5, 2023 14:49:39 GMT -5
Good morning, was reviewing output impedance and unable to find any published specs.
Was hoping this data was simply overlooked when publishing the manuals and website;
PT1 PT2 TA1 TA2
XDA3 MC1 MR1 XMC-2 RMC-1L RMC-1
……NOT overlooked. In 55 years of messing around with this stuff as an amateur enthusiast I’ve never seen it published for the end user nor have I come across anyone looking for it. (Just sayin) |
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Post by AudioHTIT on Dec 5, 2023 15:11:05 GMT -5
… And, on those sorts of device, if you really care, we can look it up for you... The reason we generally don't publish them is that they are apparently more likely to confuse people than to provide meaningful information.(For example, on a headphone amp, you might prefer a DF=10 over a DF=50, but it doesn't matter at all for the output of a preamp.) … While in this situation that may be true — for some percentage of customers — this goes back to a discussion that’s not gotten a lot of traction, namely that Emotiva published specs — and more so published measurements — have diminished over the years. I would advocate that the more we know the better, and would even like to see additional things like ‘power consumption at idle’ published, others obviously want output impedance of both preamp/processors, and power amps. If we are confused, we know where to get answers, but to have to come here and ask about it, then send a request to get more detail is time consuming and tedious. Both of these examples are not far fetched, and (some) other venders do publish this information. |
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Post by PaulBe on Dec 5, 2023 15:22:35 GMT -5
… And, on those sorts of device, if you really care, we can look it up for you... The reason we generally don't publish them is that they are apparently more likely to confuse people than to provide meaningful information.(For example, on a headphone amp, you might prefer a DF=10 over a DF=50, but it doesn't matter at all for the output of a preamp.) … While in this situation that may be true — for some percentage of customers — this goes back to a discussion that’s not gotten a lot of traction, namely that Emotiva published specs — and more so published measurements — have diminished over the years. I would advocate that the more we know the better, and would even like to see additional things like ‘power consumption at idle’ published, others obviously want output impedance of both preamp/processors, and power amps. If we are confused, we know where to get answers, but to have to come here and ask about it, then send a request to get more detail is time consuming and tedious. Both of these examples are not far fetched, and (some) other venders do publish this information. ^^^^^ This |
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Post by Snoman on Dec 5, 2023 16:52:24 GMT -5
Could also simply be the data is no longer relevant with today's equipment. The McIntosh C8 tube pre-amp is 100 ohms/200 ohms (unbalanced/balanced) for example, while most dedicated amplifiers are at least 10k ohms. Plenty of well respected manufactures publicize the data, though as others have stated, most have moved towards this position of not providing it. Good morning, was reviewing output impedance and unable to find any published specs.
Was hoping this data was simply overlooked when publishing the manuals and website;
PT1 PT2 TA1 TA2
XDA3 MC1 MR1 XMC-2 RMC-1L RMC-1
……NOT overlooked. In 55 years of messing around with this stuff as an amateur enthusiast I’ve never seen it published for the end user nor have I come across anyone looking for it. (Just sayin) |
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Post by PaulBe on Dec 5, 2023 17:15:03 GMT -5
I'm confused as to why Emotiva won't publish meaningful information. Output impedance of a pre-amp is meaningful information. The more we know, the better. Perhaps the less we know the better it is for Emotiva.
It's better to be confused by data and seek answers to questions than to be confused by not having data.
We are not talking about simple table radios here.
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Post by 405x5 on Dec 5, 2023 17:57:15 GMT -5
I'm confused as to why Emotiva won't publish meaningful information. Output impedance of a pre-amp is meaningful information. The more we know, the better. Perhaps the less we know the better it is for Emotiva. It's better to be confused by data and seek answers to questions than to be confused by not having data. We are not talking about simple table radios here.
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KeithL
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Post by KeithL on Dec 6, 2023 11:06:21 GMT -5
We actually do publish what we consider to be the most meaningful and useful information. However not everyone always agrees about which information is the most useful... and there is far too much information to publish "all of it". For example... WITH AMPLIFIER OUTPUTS... - the difference between a DF=4 and a DF=8 would be extremely important and quite audible (those would both be somewhat typical for tube amps) - the difference between a DF=8 and a DF=100 would also be extremely important and quite audible (you might see that difference between a typical tube amp and a typical solid state amp) - the difference between a DF=100 and a DF=500 would probably be neither significant nor audible (so it would be more a matter of attempting to impress people with a big number) - the difference between a DF=500 and anything above that would be both unimportant and difficult to measure accurately (which is why most folks just say "greater than 500" ) Now... WITH PREAMP OUTPUTS... To start with there are two different "useful numbers". The first is the output impedance... And the second is minimum recommended load impedance... (Not only are these not the same but you cannot specifically determine one from the other.) Back in the days of tube gear it actually wasn't unusual to encounter situations where a certain preamp was not able to properly drive a certain power amp. This was especially likely to be the case if you were trying to drive a solid state power amp with a relatively simple tube preamp. Simple tube preamps tend to have a rather high output impedance... which works fine with the high input impedance on most vintage tube power amps. But, since most solid state power amps have a lower input impedance, many simple vintage tube preamp designs have trouble driving them. HOWEVER, and this is what counts, pretty much any modern solid state preamp or processor can drive the input of any normal power amp. (And, yes, that includes those vintage power amps.) And, in fact, most would have no trouble driving several amps if you add some passive splitters. So, unless you have some totally oddball situation, or need to run a few hundred feet of interconnect, it really doesn't matter. (A preamp with an output impedance of 01. Ohm isn't going to run your power amp any better than one with an output impedance of 1 kOhms.) So, to be quite blunt, if you really need to know, we can go look on the schematic for you... Otherwise we just don't see it as being worth mentioning... (And we try NOT to be "one of those companies who tries to impress you with long lists of impressive looking but meaningless numbers".) I'm confused as to why Emotiva won't publish meaningful information. Output impedance of a pre-amp is meaningful information. The more we know, the better. Perhaps the less we know the better it is for Emotiva. It's better to be confused by data and seek answers to questions than to be confused by not having data. We are not talking about simple table radios here. |
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Post by PaulBe on Dec 6, 2023 11:37:57 GMT -5
We actually do publish what we consider to be the most meaningful and useful information. However not everyone always agrees about which information is the most useful... and there is far too much information to publish "all of it". For example... WITH AMPLIFIER OUTPUTS... - the difference between a DF=4 and a DF=8 would be extremely important and quite audible (those would both be somewhat typical for tube amps) - the difference between a DF=8 and a DF=100 would also be extremely important and quite audible (you might see that difference between a typical tube amp and a typical solid state amp) - the difference between a DF=100 and a DF=500 would probably be neither significant nor audible (so it would be more a matter of attempting to impress people with a big number) - the difference between a DF=500 and anything above that would be both unimportant and difficult to measure accurately (which is why most folks just say "greater than 500" ) Now... WITH PREAMP OUTPUTS... To start with there are two different "useful numbers". The first is the output impedance... And the second is minimum recommended load impedance... (Not only are these not the same but you cannot specifically determine one from the other.) Back in the days of tube gear it actually wasn't unusual to encounter situations where a certain preamp was not able to properly drive a certain power amp. This was especially likely to be the case if you were trying to drive a solid state power amp with a relatively simple tube preamp. Simple tube preamps tend to have a rather high output impedance... which works fine with the high input impedance on most vintage tube power amps. But, since most solid state power amps have a lower input impedance, many simple vintage tube preamp designs have trouble driving them. HOWEVER, and this is what counts, pretty much any modern solid state preamp or processor can drive the input of any normal power amp. (And, yes, that includes those vintage power amps.) And, in fact, most would have no trouble driving several amps if you add some passive splitters. So, unless you have some totally oddball situation, or need to run a few hundred feet of interconnect, it really doesn't matter. (A preamp with an output impedance of 01. Ohm isn't going to run your power amp any better than one with an output impedance of 1 kOhms.) So, to be quite blunt, if you really need to know, we can go look on the schematic for you... Otherwise we just don't see it as being worth mentioning... (And we try NOT to be "one of those companies who tries to impress you with long lists of impressive looking but meaningless numbers".) I'm confused as to why Emotiva won't publish meaningful information. Output impedance of a pre-amp is meaningful information. The more we know, the better. Perhaps the less we know the better it is for Emotiva. It's better to be confused by data and seek answers to questions than to be confused by not having data. We are not talking about simple table radios here. We have been down this road before. I’m not impressed with lack of specs. We who have an Emotiva processor use a sophisticated device with a myriad ways to use it, applying complex internal FW, and complex outboard software. Yet, somehow, publishing ‘output impedance’ for a preamp would be ‘confusing’ to the user. Good grief. What does headphone amp and amplifier DF, and tube amp history, have to do with the OP’s original statement?: ~~~~~ “Good morning, was reviewing output impedance and unable to find any published specs. Was hoping this data was simply overlooked when publishing the manuals and website; PT1 PT2 TA1 TA2 XDA3 MC1 MR1 XMC-2 RMC-1L RMC-1” ~~~~~ You have spent a considerable amount of time and energy while refusing to answer simple questions. When I raised my children, I knew the simple concept that when they asked a question, they were ready for a real answer. All I had to do is answer within their ages, abilities, and maturity. I didn’t say I wouldn’t answer because ‘it wasn’t important to me’, or spend time blowing smoke. Perhaps you could publicly answer the simple questions from educated adults who are Emotiva's customer base or potential customers. |
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Post by 405x5 on Dec 6, 2023 11:57:04 GMT -5
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Post by PaulBe on Dec 6, 2023 12:02:34 GMT -5
No Answers For You!  |
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Post by leonski on Dec 6, 2023 20:20:56 GMT -5
Keith has it right with the difficulty of measurement of DF and associated.
That being said?
ONE additional approach might lead in the right direction without giving a 'rock solid' number.
Output devices have a parameter called RDON.......Resistance of the Device when ON......This can, I think, be directly related
to the limits of DF of the amp in which they are used.
Also? As a practical matter, speakers are connected to the amp with lengths of real WIRE. Longer / thinner raise resistant which lowers DF.
I use very short (about 30" or so, tops) of 10ga wire. But I suspect some of HT guys use lesser wire and in some cases, LOTS OF IT.....which
is bad for DF.....
Still and all? Do you really need a value over maybe 50 or even 100? I doubt it. And both can be gotten in real system.....
The KEY is 'meaningful informatiion'. Does the difference between a DF of 500 and 550 MEAN anything?
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Post by PaulBe on Dec 6, 2023 21:03:31 GMT -5
Keith has it right with the difficulty of measurement of DF and associated. That being said? ONE additional approach might lead in the right direction without giving a 'rock solid' number. Output devices have a parameter called RDON.......Resistance of the Device when ON......This can, I think, be directly related to the limits of DF of the amp in which they are used. Also? As a practical matter, speakers are connected to the amp with lengths of real WIRE. Longer / thinner raise resistant which lowers DF. I use very short (about 30" or so, tops) of 10ga wire. But I suspect some of HT guys use lesser wire and in some cases, LOTS OF IT.....which is bad for DF..... Still and all? Do you really need a value over maybe 50 or even 100? I doubt it. And both can be gotten in real system..... The KEY is 'meaningful informatiion'. Does the difference between a DF of 500 and 550 MEAN anything? Audio Myth - "Damping Factor Isn't Much of a Factor" benchmarkmedia.com/blogs/application_notes/audio-myth-damping-factor-isnt-much-of-a-factorDamping Factor Calculator with Frequency Response - spreadsheet at link above. Calculates for range of speaker impedance, wire length, and wire gauge. Spreadsheet can be downloaded. RDON is a small effect due to amplifier feedback. Feed forward techniques produce more consistent damping with frequency. DF is a side issue to the thread topic. But, we agree that a DF difference between 500 and 550 is meaningless. A system DF over 100 with real speaker cable lengths and gauges is hard enough to achieve. Don't forget the 1'-3' of cable that is inside the speaker box. And, the 100'-200' of inductor wire in series with most woofers. |
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Post by leonski on Dec 6, 2023 22:55:00 GMT -5
Right? I think? Doesn't this mean that DF is a red herring 'spec'? Those who 'chase' a high value are wasting time?
Some of those old-school 'big box' speakers needing little or NO amp damping at all sure sounded good....
RDON was a measureable of the devices we made. Lower better since less wasted power and heat.
It was measured at the wafer level and not, as far as I remember, part of any practical circuit. Maybe the
spec call-out WAS for a packaged device......?
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Post by PaulBe on Dec 6, 2023 23:23:31 GMT -5
Right? I think? Doesn't this mean that DF is a red herring 'spec'? Those who 'chase' a high value are wasting time? Some of those old-school 'big box' speakers needing little or NO amp damping at all sure sounded good.... RDON was a measureable of the devices we made. Lower better since less wasted power and heat. It was measured at the wafer level and not, as far as I remember, part of any practical circuit. Maybe the spec call-out WAS for a packaged device......? You are conflating a bunch of things. First - DF was not the OP's concern DF matters but needs to be examined with a sense of reason. The article I linked argues a DF limit of 300, at the amp outputs, is reasonable. Try to get there with any 10' length of speaker cable. Welding cable anyone? Old school big box speakers before 1973 were designed without T/S parameters. It was all majik and secret formulas. There was hardly any science in the process. Yes, some of them sounded good. An old 1930's console tube radio has a glorious sound. RDON is swamped by the value of output stage linearizing emitter or drain resistors, and has little DF impact on the output impedance of an amplifier using feedback . RDON is especially important in class D amps with limited heatsinking. |
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Post by leonski on Dec 7, 2023 1:26:48 GMT -5
RDON was one of our measureable. ON WAFER during probe. Manufacturers of OEM gear using our devices.....HEXFETs and such.....in N and P channel,
used this information....
DEvices or even entire lots could be 'failed' for this parameter.
And Yes, i see the OP was concerned with output impedance.
I'll hope he meant as a preamp.
I wouldn't worry about That, either. Most SS gear is fairly low in that regard and an amp of 10x that value input should be a good electrical match.
Speakers experienced a huge shift several decades ago. Big Box of usually fairly high sensitivity......to small box and the new acoustic suspension
with brands like the AR speakers. I dont' know who was first, but I heard and loved the AR3a and older AR2ax when I first heard them. What has happened
at the same time is less expensive watts and solid state. More to it than that, but just the general drift. Watts have fallen in cost, too, making low sensitivity speakers
easier to feed....and sensitivities of 85db not really the end of the world low.
TS revolutionized part of the design / test process.
I have the IR 'D' amp reference board over on the shelf. I need a +-50v PS to test it. I'm thinking it'll be ok for test with my panels......
And to repeat what I said earlier? DF of an amp is pretty much a red-herring spec. And for all the reasons you note and more.
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Post by leonski on Dec 7, 2023 1:42:11 GMT -5
Very interesting article.......
I'll stick with red herring for now. Most won't go thru the trouble of trying to work the spreadsheet and buy decent low-resistance speaker cables......
The Belden sold by blue jeans is just over 1 ohm per 1000 feet, so I suspect can safely be ignored in normal lengths....
And the article points out the total 'good' value......and it is nothing like what some claims I've seen.......
The speaker used...from the FOCAL line, appears to be a really good 'test case' for damping and amp-speaker interaction....
Happy Listening........
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