different audio forum

[AllenB]

Lol, goodnight KaffiMann.

I regret the misunderstanding. Please don't assume that when a person is working with analogue that the result is approximate, when I say I fix the response of a resonance I mean it. DSP is no different there.

 

[Pharos]

Clarke's third law - Any sufficiently advanced technology is indistinguishable from magic.

That is like saying that we can increase the quality of a design to the point at which it cannot be perceptively faulted, which of course is what in essence this pursuit is attempting to do.

I disagree even with the view that it can be done for one spot. Equalising to response doesn't account for that response being the result of signals that also have direction and timing differences. A resonance can sound wrong no matter where you set the dial.

Yes, that (mine), was just a superficial criticism, we don't know what reflections have contributed to the equalisation, possibly numerous additive reflections which will be very disturbing to the ear.

 

[Pharos]

Edit:

Sigh, people are so judgemental these days, be a bit and a half over 100kg, walk barefoot in the forest looking for berries and mushrooms, have a secret hoard of alcoholic beverages and all of a sudden you get the troll stamp.
Perhaps I can be a bit direct sometimes, but that falls under the "people are different" thing, right?

Anyways, have a good night people, the missus is shouting at me from the bedroom.

As we have, I suppose because of the pressures of modern life, seen so much dyfunctionality in the form of excesses, so the tendency to be super-critical of even slight divergence from a supposed norm are severely criticised, and often extremely irately.

 

[Fast Eddie D]

And so to everyone .......... Good bye. Jim

I hope you don't leave. Just because you don't have the knowledge that some members have doesn't mean you can't participate.

You ask questions that some people may think are stupid, but we've all been there at one point in time. Nobody is born knowing this stuff.

I realize that some of this stuff may seem opaque if you don't have the education and experience. Some of the stuff that vexed me in high school is crystal clear to me now. Stuff like Nyquist stability criteria more was like voodoo to me when I was 14 or so. I understood it barely enough to punt.

I see you trying to understand and learn. I'm always happy to try and help someone that's applying themselves and making progress.

 

[KaffiMann]

Hah!
I guess you can say that
But what *is* the norm? Start to really look hard and deep at people you know well, I think you'd be hard pressed to try and fit all of them into the category A - Average person.
That can only be true if you do extremely general sweeps and assumptions and use averaging on a large number of people, most people are not average.

...

At any rate, time to resurrect my mushroom thread.

 

[Fast Eddie D]

Brute force max flatness is just horrible, less is more.

This is very true in my limited experience. Tweaking a passive crossover made me realize that completely eliminating a resonance (with a notch filter) or trying to flatten the impedance of a woofer too much absolutely smothers the sound. Less is more; even a few decibels of correction can make a huge difference.

I haven't used DSPs but I've built active analog correction filters. Members here were quick to point out that the filter didn't do what I thought it did. But if I would have gone for full correction then I would have more than doubled my power requirements and reduced my practical max SPL by a few decibels. In practical applications, it can be a juggling act.

 

[KaffiMann]

My previous post was a reply to Pharos btw.

But yes, no matter how you correct stuff it's a delicate balance act.

 

[Pharos]

We get the idea of norms mooted form the media, and women must suffer enormously with pressure to conform to these supposed norms, and which are really touted figments of construction.

 

[AllenB]

* We should stay on topic and remember this is jimmyjoe's thread.

That is like saying

To be frank, when DSP began to gain popularity many were keen to talk about all that it could do.. However, people who were previously not into circuit building now had access to filters. Those who were into circuits simply said OK, here's yet another way to do what we've always been doing.

 

[Pharos]

Yes I apologise, this thread has moved a long way from the OP.

I only responded because of a mail, and didn't look back very far, and so responded to the drift posts.

 

[KaffiMann]

To be frank, when DSP began to gain popularity many were keen to talk about all that it could do.. However, people who were previously not into circuit building now had access to filters. Those who were into circuits simply said OK, here's yet another way to do what we've always been doing.

Yes!
But the advantage is that you can do all that stuff, without etching PCB's, planning and filling out BOM's, soldering, quality control +++ And you can even take the DSP unit of choice away, and use it on another project should you wish to do so. And if you want to make changes you do not have to do the manufacturing process all over again
Using it "right" does take a bit of effort and understanding, but then you are rewarded with far less labour (and waste), it's also easier to adjust for differences between individual speaker units, placements etc.

Not to mention that passive filters swamp power, and the component values frequently drift with temperature change.
A passive filter can also be absolute crap if it's not adapted well enough for the application.

 

[AllenB]

If you'd like me to respond to that, start a separate thread.

 

[jimmyjoe]

Well, I'm back with another question. I guess I like you people so much that I just had to return ...... or not.
This question has to do with amplifiers. Let's say that there are three amplifiers; the first has a maximum distortion rating of .7%, the second a rating of .07%, and the third .007%. If all three levels of distortion are below the threshold of audibility (are they?) then why do so many people declare that the third is better than the second and the second is better than the first?
In other words, if something is inaudible, why should I care?

Thank you for your help ...... as always. jj

 

[rayma]

You shouldn't care, though 0.7% is probably audible.

 

[Galu]

Allow me to put the topic of distortion into perspective.

1. In 1945, H.J. Leak & Co produced their first domestic hi-fi amplifier, the Point One Type 15, and claimed it was "the first in the world" to produce just 0.1% distortion. This was at the time when 5% was the norm and 2% the laboratory standard. In my opinion, anything less than 0.1% at the rated power output is the icing on the cake!

2. We don't often mention the distortion caused by the loudspeaker that the amplifier is driving. I have bookshelf speakers that produce 1% second harmonic distortion at 96dB sound level, dropping to 0.3% over most of the frequency range at 86dB. Obviously we want the amplifier to supply as clean as possible a signal to the loudspeaker, but ultimately the loudspeaker will make the greatest contribution to the distortion we hear in a modern sound reproduction system. In comparative terms, I would be comfortable with your 0.07% amplifier distortion figure, but obviously not with 0.7%.

 

[jimmyjoe]

Very good point .... as usual. It seems, now that you mention it, that I might be referencing two different things here; one would be the audibility of distortion, any distortion, anywhere in the chain, and the other would be the relative importance of several different levels of distortion that are very low compared to the greater levels of distortion injected by speakers.
I couldn't hear any difference in the distortion levels offered by different amplifiers. So I thought that possibly that moderately low levels of distortion vs. extremely low levels of distortion was an issue that was irrelevant. And I think I was correct; it IS irrelevant, but only in the sense of the larger picture. The loudspeaker (ESPECIALLY a moderately priced loudspeaker) produces enough distortion to mask the characteristics of any decent amplifier. (No, not a junk amplifier; I said any decent amplifier)
I think my search for audio equipment just got both easier and more difficult; easier in respect to electronics, and more difficult in regards to speakers.

Thanks. jj

 

[benb]

I have the usual rant about THD, but here' older threads.
THD
Are distortion ratings accurate for most amps?

 

[Galu]

I have an old Yamaha CD Receiver which I use mainly for listening to DAB and FM radio. It uses Class A/B amplification and is rated at 25W RMS per channel into 6 ohm with 0.1% THD at 1khz.

Its current Yamaha CD Receiver equivalent uses Class D amplification and is rated at 22W per channel into 6 ohm with 10% (yes 10%!) THD at 1 kHz.

I guess that's the price you have to pay for the Wi-Fi and Bluetooth capability that my model lacks!

Moral: Always read the small print!

 

[jimmyjoe]

" .... Moral: Always read the small print! ...."

At my age, I can't read the small print!
(p.s. - thank you for knowing that "it's" is a contraction and "its" is the possessive.)

jj

 

[jimmyjoe]

Back again.
This time the question has two parts.
1) if a tube preamplifier has an output impedance of 800 ohms, what is the minimum input impedance of the solid state amplifier that it is driving so as to insure stability?
2) If (and I emphasize IF) the input impedance of the solid state amplifier is too low, is there some sort of buffer that would match them up? I am, of course, speaking of a low-cost item. I'm cheap. ;D Thank you. jj