Well, that's the wildcard here.It also says "Star ground (arbitrary placement for discussion)"
If we move the star and the IEC inlet right next to the signal connector and restrict the RF current flow to the outside surface of the chassis then we arrive at the preferred scheme that H.W.Ott and other EMC authorities recommend, both for RF immunity and emission.
OK the cycle home got enough oxygen into my caffeine stream to get what I wanted to say in my head. The large G&T I drank as the sun went down is however fighting for control. Happy solstice all BTW.
So If I understand correctly this is about loop areas. And we have to remember rule one of electron herding: If you give signals a choice of 2 or more paths then they will take all of them. In the normal case of an RCA bolted to the chassis with internal wiring via a twisted pair, then you have created two routes to the ground point and you have effectively maximised the loop area.
By not terminating the RCA at the chassis and using the screen as per the diagram then you have minimised the loop area, which is good. I could imagine you could make this look quite neat if you are good with semi-rigid.
Now clearly the way Neutrik does is with their EMC XLRs is a step up as you capacitively couple RF to the chassis and put enough inductance in the way of pin one to held herd things the way you want. But getting an RCA to do that is a challenge
Does any of this matter in the home? Probably not. But still interesting to think about.
So If I understand correctly this is about loop areas. And we have to remember rule one of electron herding: If you give signals a choice of 2 or more paths then they will take all of them. In the normal case of an RCA bolted to the chassis with internal wiring via a twisted pair, then you have created two routes to the ground point and you have effectively maximised the loop area.
By not terminating the RCA at the chassis and using the screen as per the diagram then you have minimised the loop area, which is good. I could imagine you could make this look quite neat if you are good with semi-rigid.
Now clearly the way Neutrik does is with their EMC XLRs is a step up as you capacitively couple RF to the chassis and put enough inductance in the way of pin one to held herd things the way you want. But getting an RCA to do that is a challenge
Does any of this matter in the home? Probably not. But still interesting to think about.
YouTube looks like the clergy oddly also have a sense of humour.
I hope all my left pondian friends have also watched 'Father Ted'?
No one can doubt that such extremely low levels of harmonic distortion is inaudible. Do I need to say that?
It is also known that there are many amps which are not that low. My comment applies to those. Many tube amps, SET amps, etc In the context of amps with high enough distortion, my comment applies.
So whats the deal with an RF bypass cap to chassis right at the rca/xlr connector? A long held common practice. With the wide band circuits we produce, HF-RF has potential to cause audible artifacts/interference.
HF/RFI is an issue whether it enters thru the ac cord/PS or coax cable. Either way, you have to filter it/bypass it before entering amplifier chassis.
THx-RNMarsh
Last edited:
How low? As is occasionally pointed out as a point of reference for extremely low level distortion some people can hear undithered 16-bit audio (note: all modern CDs are dithered, just a point of reference, that's all). There is no reason to be sure that would be the absolute limit, in fact the limit is probably at least a little bit lower. In the meantime, there there are probably those who may doubt whether an amplifier exists with distortion below the limit. Some people in this very thread have said Benchmark AHB2 has a sound despite it measuring < 0.0003 % THD+N at full output voltage, 20 Hz to 20 kHz (and I am not talking about me, either).
That's why I suggested you check out the Pass Labs group. Plenty of folks here building this stuff and loving it, metadata.
I'm thinking of adapting some for parts only old MOSFET amps to open loop class A operation (~.6% at 30W/8 Ohms). They even have +-65V power transformers so if I series two and flip one I should get +-25V rails and I can do the cheap power conditioner at the same time.
I have seen the data long ago. Its not for me. I am not into LIKE-able or not likeable issues. But for those who are trying only to find a Likeable amp, they hear differences between other likable possibilities .... and when thd rises with freq on those amps, it sounds brighter, harder and smeared. For them, IMO, they would Like an amp that has flat thd vs freq. Even if it is above threshold.... a more balanced sound.
I LIKE my car sound but I know it isn't accurate reproduction.
The Hafler XL 280 may be a good one for you to use IMO.
THx-Richard
Last edited:
And there are those of us that will remind you that the 16 bit dither thing isn't as clean of a measure that people are able to hear -96 dB as you'd like, as the truncation errors aren't just LSB (nor account for spot levels).
There's a happy medium, though, and I don't want to rehash this all nor get into unproductive arguments about where we suspect our limitations are. Much of this was clearly borne out when we discussed the truncate then dither versus dither then truncate -- the latter being the right operation, as they are NOT commutative.
I don't know. Better speakers - lower distortion speakers - will help better define the hearing threshold. I agree and why I don't try to put a number to the threshold. Just acknowledge there is a threshold for each of us. I think that Demir's amp is below that threshold at normal listening levels (mine). However, there are other factors that can cause audible differences besides THD or THD+N.
-RM
Last edited:
Is that to say that we cannot measure everything we can hear? Or, if we can then is that to say we can't correlate what we can measure with what we hear?
I'm just trying to understand the implications of where you seem to be going with that.
In the sense of the scientific method making changes to a circuit that effect more than one parameter (say THD and PSRR or maybe THD and noise) leads to ambiguity in what actually made the difference. You quoted one spec on the Benchmark, was the RF incursion or any other parameter measured connected with the rest of the system, or a different system/cables, different amplifier/cables/speakers?
Of course this experiment requires two, so the $20 budget is now $35. As it happens I just bought two 25VA Antek xformers, for the low, low price of $11 per. Shipping was an additional $45. Then you want an enclosure, fusing, capacitors, wire, connectors, IEC sockets, etc. How many $20 bills is this supposed to take?
It's still not expensive, but the $20 claim never made sense.
There really needs to be a Randi prize for audio.
Scott, any experience with non-profits? SY would come back from the dead for that one. ;-)
From what I gather it’s fact that no one here has been able to prove in any kind of controlled environment, A/B/X or otherwise that there’s any audible amplifier difference. (Besides Scott cheating in the HK room?)
If one could prove such a thing, they’d be Stereophile man (or woman) of the decade. It would be a nice payday for that individual. There’s a lot to be gained from evidence, so why not provide it?
I think it’s clear why Stereophile doesn’t publish yearly in-depth hearing tests for all their review staff. If you are saying you can hear better than everyone else, why not prove it?
Also, with all the measurement data thrown around here it’s pretty strange to see no one has provided any kind of measurement data for their own hearing?
I guess there’s a reason the measurements section gets tucked at the end of the articles.
Given the average age and gender of an audio engineer, reviewer, etc. I think hearing quality and hearing eccentricities aren’t taken remotely as seriously.
Even more critically, most hearing batteries don’t measure things like recruitment. It can tell you that you have some hearing loss, but it doesn’t accurately measure perceptive issues / imbalances which become more prevalent with age but can be present at all ages.
For those unfamiliar:
“Recruitment causes your perception of sound to be exaggerated. Even though there is only a small increase in the noise levels, sound may seem much louder and it can distort and cause discomfort. Someone with recruitment can have problems only with specific sounds and frequencies or may have problems with all sound in general.
The theory of recruitment is that as the hair cells in your cochlea become ineffective, they "recruit" their (still working) neighbor hair cells to "hear" the frequency the damaged hair cell was supposed to hear, in addition to the frequency the still working hair cell was supposed to hear. This increases the signal from the still working hair cells.
The sounds reaching our brains appear to be much louder that normal. This is because the recruited hair cells still function in their original critical bands and also in the adjacent one(s) they have been recruited into.”
———
I think this could explain a lot.
Who with vested audio financial interest wants to publish their latest hearing tests?
Any hands?
Either way I agree assessing a power amplifier in isolation, or a specific parameter in isolation is kind of like measuring an engine or transmission with no car attached to it. To have sound, or to serve it’s function, it by definition requires something else.
Otherwise this is just whack-a-mole meets Alice in Wonderland tea party rhetoric.
Scott, any experience with non-profits? SY would come back from the dead for that one. ;-)
From what I gather it’s fact that no one here has been able to prove in any kind of controlled environment, A/B/X or otherwise that there’s any audible amplifier difference. (Besides Scott cheating in the HK room?)
If one could prove such a thing, they’d be Stereophile man (or woman) of the decade. It would be a nice payday for that individual. There’s a lot to be gained from evidence, so why not provide it?
I think it’s clear why Stereophile doesn’t publish yearly in-depth hearing tests for all their review staff. If you are saying you can hear better than everyone else, why not prove it?
Also, with all the measurement data thrown around here it’s pretty strange to see no one has provided any kind of measurement data for their own hearing?
I guess there’s a reason the measurements section gets tucked at the end of the articles.
Given the average age and gender of an audio engineer, reviewer, etc. I think hearing quality and hearing eccentricities aren’t taken remotely as seriously.
Even more critically, most hearing batteries don’t measure things like recruitment. It can tell you that you have some hearing loss, but it doesn’t accurately measure perceptive issues / imbalances which become more prevalent with age but can be present at all ages.
For those unfamiliar:
“Recruitment causes your perception of sound to be exaggerated. Even though there is only a small increase in the noise levels, sound may seem much louder and it can distort and cause discomfort. Someone with recruitment can have problems only with specific sounds and frequencies or may have problems with all sound in general.
The theory of recruitment is that as the hair cells in your cochlea become ineffective, they "recruit" their (still working) neighbor hair cells to "hear" the frequency the damaged hair cell was supposed to hear, in addition to the frequency the still working hair cell was supposed to hear. This increases the signal from the still working hair cells.
The sounds reaching our brains appear to be much louder that normal. This is because the recruited hair cells still function in their original critical bands and also in the adjacent one(s) they have been recruited into.”
———
I think this could explain a lot.
Who with vested audio financial interest wants to publish their latest hearing tests?
Any hands?
Either way I agree assessing a power amplifier in isolation, or a specific parameter in isolation is kind of like measuring an engine or transmission with no car attached to it. To have sound, or to serve it’s function, it by definition requires something else.
Otherwise this is just whack-a-mole meets Alice in Wonderland tea party rhetoric.
Last edited:
Hi Scott,
-Chris
I think the question as posed, can't be answered. Too many variables, but then how would you nail the question down? I think that you would pretty much need to show distortion vs frequency and distortion vs power for various frequencies. Even then there are probably too many variables to nail the question down.
-Chris
I mentioned the AHB2 in the context of the discussion about Damir's power amplifier having audible distortion or being below some threshold, with Richard and Daniel going back and forth about limits. That context had nothing to do with plugging DAC-3 into a power conditioner last week. It didn't have anything at all to do with anything here where I am, I was talking about the discussion going on in the forum today, right?
Even going back to that unrelated time, it was DAC-3 that was directly changed, not AHB2, which only might have been affected indirectly. In any case I was not set up at the time to measure what changed, and I was not expecting any change.
Now, all of a sudden you said something about a fools errand trying to know a cause for what is being heard. I asked if you meant that trying to measure is a fools errand or where were you trying to go with that in the context of the discussion that was taking place here in the forum a few minutes ago about distortion numbers, power amplifier distortion audibility, and what Richard and Daniel were talking about?
- Status
- Not open for further replies.