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Old 26th June 2012, 10:14 PM   #6471
DF96 is offline DF96  England
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I am not deaf. Please don't shout.

You now seem to be agreeing with me that 1% ripple on the supply rail does not necessarily mean -34dB ripple in the output? If so, my job is done.
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Old 26th June 2012, 10:50 PM   #6472
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Originally Posted by bcarso View Post
That someone was me, thanks very much for the attribution .
Sorry that was a bit rude . I was doing something else and being lazy . The half bridge is hype in so much as people say it like it has positive significance , doubtless Hypex didn't intend it as a mark of quality . As you say it can be driven differentially to overcome the " possible " weakness of half bridge . I can see how it relates to switch mode . A slightly unfortunate association I feel .

My pro audio friend John has great affection for his Class H amps . However increasingly they use D for the weight reduction . He did say D seems less reliable and can not be fixed as easily . New modules mostly . His class H amps usually loose one transistor and by then have shut down . A cheap and fairly instant repair .

My own feeling having been around this industry for years and knowing the big fish is to see class D as a cynical move to take all the business . In all fairness the chip makers publish PCB's so we can get it right . It is not the same as doing it ourselves . When photography came along many professional artists gave up . Impressionism flourished . I see Audio as being in a phase like this . I suspect many truly professional people will soon give up . Leaving the more eccentric people like myself to continue the seemingly old fashioned branch lines . A bit of a sad tale if I am right and I am fairly certain I am . Increasingly my work is of the impressionist type . I am doing that next week . I insisted on including a very low distortion option . The idea is to mimic a tape recorder in compression . Nothing original in it . Just a nice little job and useful to me for my own use . The device in question was common at the BBC but did not include optional compression . It has to drive 100 metres of cable without degradation . It has a slight resemblance to video transmission . I will give it 6 MHz bandwidth as it will do no harm . Then we can use it for other things if we choose .

Last edited by nigel pearson; 26th June 2012 at 11:03 PM.
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Old 27th June 2012, 12:36 AM   #6473
Pano is offline Pano  United States
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Is this forum's quote function so difficult to use that I have to fix it in 2 out of three posts?
Come on guys, it's not that hard. At least try to get it right. Thanks.
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Old 27th June 2012, 06:51 AM   #6474
dvv is offline dvv  Serbia
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Originally Posted by tvrgeek View Post
Yup. Blew up my dad's Kenwood on a pair of AR-2's. Funny, the Knight tube amp never had a problem. The 3 almost had a tweeter if I remember.
???

AR 3a was a three way speaker from its first day, using a 12" bass driver, a 38 mm dome midrange (or similar) and a 19 mm dome tweeter.

My own AR 5, the next model down the line, was the same, except it had a 10" bass driver, but was declared not as a 4 but as an 8 Ohm load.

Acoustic Research contributed to the world of audio with two inventions they had patents for - sealed ("acoustic suspension") type of enclosure and dome type drivers.

The golden age of AR were the 60ies, when everybody who was anybody in classical music owned AR speakers, from Herbert von Karajan all the way down the line. Undisputed king. During the 70ies, the competition got much tougher, and they decayed during the 80ies.

I believe my 94 was from the last series of quality speakers, but I am aware that in its "mk.2" form, it was a completely different speaker, with cheap and nasty drivers, in fact cashing in on the name. After that, they were gone.

Last edited by dvv; 27th June 2012 at 06:53 AM.
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Old 27th June 2012, 06:57 AM   #6475
dvv is offline dvv  Serbia
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Originally Posted by simon7000 View Post
Do really don't understand both issues?

If you have a 50 volt supply with .5 volts of ripple the ripple only is not passed to the next stage unless you are really trying something weird. If you just have a variable resistor powered through a fixed resistor you will have some loss of ripple along with the DC level. Now if you pass that to the next stage the ripple will decrease if it is an equal gain inverting stage. Only if by some not very common method you use a second non-inverting gain stage will the ripple increase.

HOWEVER ALL AMPLIFIERS THAT WOULD HAVE ANY RIPPLE PROBLEM USE ADDITIONAL POWER RAIL FILTERS ON THE INPUT STAGE! The question was about the main filter bank of capacitors and the effect on power output sags.

As to the second comment. the ear is not very sensitive to 50 or even 100 hz. signals. It is most sensitive to ones around 3,000 hz. What was said is that the intermodulation products up in the higher region sound really bad and are more easily detected than the hum. The hum would be masked by the music in actual use.
Simon, what happens to ripple if one uses fully electronically regulated power supplies?

Specifically, in my case, I plan to run everything but the output stage from fully regulated power supplies, only the output transistors will be fed "raw" DC from the caps.

Assuming I don't botch it up somewhere, as I see it, ripple should be of no concern to me - right?
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Old 27th June 2012, 10:49 AM   #6476
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Acoustic suspension was interesting . As a patent dodge I suspect it got renamed infinite baffle ? If I understood correctly the principle of acoustic suspension was to have the sealed box support the cone rather than have a stiff suspension ? A 10 to 1 ratio if I remember correctly of air to surround ( tightly sealed box ) ? I had a pair of AR'3 and loved them . The rolled off top said to be a reaction to early transistor amps ( I don't know if it's true ) . Later I had some Alison speakers which were similar , I think he was a development engineer for AR ? US speakers that I had . Dalquist DQ 10 , Dynaco A25 ( wonderful ) . Klipsche Forte , La Scala , Forte 2 ( love them ) . I was to meet Ed V , never did as my friend who was going to take me to see him died . Ed and I both lived in towns called Woodstock .

Dvv . I was thinking . You could run everything regulated up to the time loud music kicks in . It could be controlled by a simple thermostatic switch in fact ( the ones with 6.3 mm / 1/4 inch terminals ) . The switch / relay could kick in raw DC when you wanted to party . That would keep the capacitor layout optimum . You could then be posh for the regulated and bargain capacitors for the raw stuff . It would need a bit of thought . The raw ones could be charged ready to go .
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Old 27th June 2012, 12:27 PM   #6477
dvv is offline dvv  Serbia
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Quote:
Originally Posted by nigel pearson View Post
Acoustic suspension was interesting . As a patent dodge I suspect it got renamed infinite baffle ? If I understood correctly the principle of acoustic suspension was to have the sealed box support the cone rather than have a stiff suspension ? A 10 to 1 ratio if I remember correctly of air to surround ( tightly sealed box ) ? I had a pair of AR'3 and loved them . The rolled off top said to be a reaction to early transistor amps ( I don't know if it's true ) . Later I had some Alison speakers which were similar , I think he was a development engineer for AR ? US speakers that I had . Dalquist DQ 10 , Dynaco A25 ( wonderful ) . Klipsche Forte , La Scala , Forte 2 ( love them ) . I was to meet Ed V , never did as my friend who was going to take me to see him died . Ed and I both lived in towns called Woodstock .
Yes, Roy Allison did work for AR for a while, and then spinned oof his own company.

Yes, the basic principle was to use the air trapped inside the sealed box as a spring, rather than stiffer suspensions. The net result was a bass which rolled off earlier, but with a much more gentle slope and with a lot less phase funnies the bass reflex can't get rid of. Unfortunately, the acoustic suspension or infinite baffle or sealed speakers were also less efficient than their BR bretheren, and required bigger to much bigger enclosures for the same bass response, which eventually brought them to their present status, that of a dying breed.

Quote:
Dvv . I was thinking . You could run everything regulated up to the time loud music kicks in . It could be controlled by a simple thermostatic switch in fact ( the ones with 6.3 mm / 1/4 inch terminals ) . The switch / relay could kick in raw DC when you wanted to party . That would keep the capacitor layout optimum . You could then be posh for the regulated and bargain capacitors for the raw stuff . It would need a bit of thought . The raw ones could be charged ready to go .
Well, that's an idea. However, I will not use it just now, I'll do the amp under development as is, but I will try for it in the next project I have in mind. Quite simply, I'd like to have some time playing with any new idea before I rush in to implement it.

But it's well worth thinking about, methinks.
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Old 27th June 2012, 01:22 PM   #6478
gpapag is offline gpapag  Greece
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Quote:
Originally Posted by nigel pearson View Post
Acoustic suspension was interesting . As a patent dodge I suspect it got renamed infinite baffle ?
No. Two different implementations, which did not mixed their names.
Infinitive baffle, is the older (and more generic).
Acoustic suspension, around middle 1950 by Edgar Villhcur, implemented and marketed by Henry Kloss

Quote:
Originally Posted by nigel pearson View Post
If I understood correctly the principle of acoustic suspension was to have the sealed box support the cone rather than have a stiff suspension ?

Yes. The boxed air is to act like a spring to the cone (and cone is to be supported with a compliant suspension)

George
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Old 27th June 2012, 06:03 PM   #6479
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Quote:
Originally Posted by dvv View Post
Simon, what happens to ripple if one uses fully electronically regulated power supplies?

Specifically, in my case, I plan to run everything but the output stage from fully regulated power supplies, only the output transistors will be fed "raw" DC from the caps.

Assuming I don't botch it up somewhere, as I see it, ripple should be of no concern to me - right?
I would say "Bingo!" But as that may not translate properly, it means you win, you covered everything.

As long as your driver stages have the extra voltage to drive the outputs fully, you should get what you are looking for.

The downside is that when some designs done that way clip, they can have a nasty recovery and create messy noises which are easier to hear than a soft clip that is masked by harmonic distortion.

You should look at what happens to the stored charges during clipping, where they go and how things are restored. Most folks only analyze the linear behavior of their designs. If the amplifier is big enough and your source is only digital such as CD's then there is much less chance for clipping. If you play records then things such as record warp can actually cause the system to clip without you being aware of the source. Things just don't sound right.

There is also an issue with the initial attack of electronic music. As this is modulated by the inband musical energy you can again get LF clipping behavior.

Best of luck in your project.
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Old 27th June 2012, 07:23 PM   #6480
dvv is offline dvv  Serbia
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Quote:
Originally Posted by gpapag View Post
No. Two different implementations, which did not mixed their names.
Infinitive baffle, is the older (and more generic).
Acoustic suspension, around middle 1950 by Edgar Villhcur, implemented and marketed by Henry Kloss

Yes. The boxed air is to act like a spring to the cone (and cone is to be supported with a compliant suspension)

George
Please explain the difference between infinite baffle and acoustic suspension.

I ask because I am not aware of any, it was as Nigel said a matter of copyrights, but as far as I am aware, both use exactly the same principle and calculations.

Henry Kloss, who later started up KLH and eventually Advent, had no copyright problems simply because he was the co-owner of the original patent.
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