Go Back   Home > Forums > Member Areas > The Lounge

The Lounge A place to talk about almost anything but politics and religion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 29th November 2012, 12:01 PM   #7701
diyAudio Member
 
Join Date: Mar 2004
Location: At the output stage
Send a message via Yahoo to mr_push_pull
actually I'm all for Yuasa. it's a case where the hype is actually true, they're light years away compared to the cheap crap. if not abused they can last 10 years.
what matters with starter batteries is CCA (cold cranking amps) which have no direct relation with the rated Ah. batteries with the same Ah rating can have as much as 50% differences in CCA ratings.
so the car analogy (what would we do without them?) only goes so far. as long as you give the starter what it needs, you reach a point of diminishing returns. cheap or abused batteries (frequently reaching deep discharge state and/or not charged properly) simply can't provide the required CCA while maintaining the nominal voltage. that's why I advise everyone to first check the battery, no matter how good a state they think it's in, when having starting issues.
perfectly measurable, no magic. the same with speakers, a current starvation condition should be measurable.
__________________
we all love a good ol' stereotype until it's against us
  Reply With Quote
Old 29th November 2012, 02:03 PM   #7702
diyAudio Member
 
Join Date: Mar 2007
Location: Oxfordshire
This story might interest you . Mr friend John builds measuring equipment . One thing they test is magnetic fields . To tests field strengths some big coils need energizing . John thinks a big audio amplifier is called for . Why not make it very good and have the fruits of his work at home ? He even get loads of orders at $30 000 a piece . Months later he is still working on it . Stories of success and production always seem to be followed by stories of modifications . John is no fool and is surrounded by some very able people . It hasn't been a walk in the park . I asked if the problems came up in simulation , the reply is a long expressed yes .

Renault seem to use customers as a research dept and be happy for it to take 10 years + . A resistor in the airstream of the heating system with a wax type thermal fuse controls the fan speed ( fuse presumed to be open circuit ) . Plenty of complaints both in English and French on various forums . The device never in the same place twice it seems . Same model different layout . Bus-mans holiday trying to repair that . I was rather proud of getting the whole dashboard out in 30 minutes and back in similar time . Couldn't find the dam device . $600 + to have Renault fix it so not giving up yet . Things we do for friends ?
  Reply With Quote
Old 29th November 2012, 05:06 PM   #7703
dvv is offline dvv  Serbia
diyAudio Member
 
Join Date: Sep 2004
Location: Belgrade, Serbia
Nige, your reference to interface problems is a well made one. But also a hard one to solve satisfactorily.

It's true that a designer has no idea what will be connected to his amplification. For example, CD players have output impedances from as low as 47 Ohms (some exotic model, don't remember the moniker) to 2.7 kOhms (a Technics player).

Next, it seems very few manufacturers make them according to Red Book rules, these days nobody seems to have a 2V output, everybody has more, some have much more (3.7V for an Onkyo model some years back).

And God alone, if even He, knows what their output stages look like and what they would be happy with.

It seems to me that the only really safe way to go is to have active buffer input stages, with a variable gain, and posibly a small DIP switch selection of say three different impedances, say 47k, 75k and 100k. Having a good match is very important to having a satisfying musical experinece, but the perverse part is that by today, line sources have become like the phono RIAA inputs of yesterday, hard to match.

But, since this costs money, we are not likely to see it soon as standard equipment. On the other hand, some serious manufacturers, such as Meridian and Studer/reVox, have had buffers from the start.
__________________
Such is life, baby! Ета жизњ, бејби!
  Reply With Quote
Old 30th November 2012, 09:49 AM   #7704
diyAudio Member
 
Join Date: Mar 2007
Location: Oxfordshire
That I will drink to Dvv .

Last night at the pub John of magnetometer fame posed a question . On the big measuring apparatus John designed they have encountered small problems with the capacitance between the output transistors and heat sinks . John rather cheekily suggested we should listen to isolation washers for the best sounding ones . I said how many pf ? The answer was many nF ( I have measured it in the past and had forgotten ) . John and I said in unison Complimentary feedback pairs , FET's and Quasi complimentary will be slightly affected by this as the output is connected to ground or whatever . I did note some class D amp designers take this to be a problem . The usual Zobel circuit is 4R7 + 0.1 uF . I would have thought it more important ? As I said to John it probably is a good thing ?

John pointed out that many big amps isolate the heat- sinks from the chassis and keep them at rail voltage . All NPN on one heat sink , all PNP the other . The rail is about as good as ground for most things . This allows direct clamping of the transistor to the heat-sink . I would argue that machining the anodizing off the transistor interface might make it even better . Some heat transfer pads I saw were just heat transfer paste . Use once and no guarantee of electrical isolation . They have excellent transfer ability .
  Reply With Quote
Old 30th November 2012, 11:46 AM   #7705
diyAudio Member
 
Join Date: Mar 2007
Location: Oxfordshire
Slew rates .

I remember years ago the British press getting very snooty about slew rates and saying that bandwidth limiting might be preferable ( forgive them for putting it that way ) . It was implied that American designers were on a voyage of we do it because we can . I heard many high slew rate Japanese amps that made me very suspicious of any amplifier that claimed high slew rate . I almost took it to be a confirmation of bad design . In later life I started to do things which dictated I must use high slew rates , nothing to do with audio . I became comfortable with thinking it preferable . Recently have I started to question this . I can not think of any mechanism which would make high slew rates disadvantageous . Might I suggest high slew rates with some " unnecessary " bandwidth limiting might be advantageous ? Could be we just don't like reality ? I do find a poor source of sound is not made better by filtering . The effect I am thinking of is subtle . The analogy might be the 1A or 1B filter in photography that gives a slight pink tinge . It helps also with UV as the function is usually combined . The analogy holds some comparison with what is known about sound . It might also be that leaving an amp wide open might involve RFI intermodulation more than is realized ( UV ? ) ?

Denon did seem to do things on the Japan market versions that they did not do for export ( service manual ) . Could it be Denon were thinking the same ? I was told by Japanese engineers that they would not make hi fi they do if the home market dictated taste . Measure and be dammed was how they saw the world outside of Japan .
  Reply With Quote
Old 30th November 2012, 12:24 PM   #7706
diyAudio Member
 
Join Date: Mar 2004
Location: At the output stage
Send a message via Yahoo to mr_push_pull
Nigel,
in my experience, many of the common held beliefs that are part of the, let's call it "collective audiophile consciousness" started as partial or simply incorrect understandings of phenomena, which somehow propagated and have been assimilated, becoming audio fetishism cases (like the quest for jitter of the femtosecond order, to name an example).
I'm speculating that maybe it's a case of this, stemming from the belief that there are full-scale step-like signals in real music. even if it were so, that simply isn't possible with RedBook. so maybe there is nothing to gain from increasing SR past what is found in a full swing sine at 20kHz, which is pretty much the worst case. naively, no matter what superposition of individual band-limited harmonics might generate it will never exceed the slope of that full swing sine. so if it's ok with that absolutely unrealistic test signal it should be okay with music. and again, maybe, just maybe some think this is not the case.

don't get me wrong, I'm not saying that SR isn't beneficial, I'm just saying that it's possible that some audiophiles view it as necessary for the wrong reasons. as Mr. Curl put it, maybe it isn't as crucial as some might think with RedBook but there is something to gain from it with high-resolution formats?

if I were to come back to the abused car analogy, it may be something like the high octane fuel, a lot of people think it's canned power, which it isn't.
__________________
we all love a good ol' stereotype until it's against us

Last edited by mr_push_pull; 30th November 2012 at 12:31 PM.
  Reply With Quote
Old 30th November 2012, 03:06 PM   #7707
diyAudio Member
 
Join Date: Mar 2007
Location: Oxfordshire
That's right . The past and the present might mix to be even better , make it fast and make it how we like it . The world in not black and white , nor is it grey . It is in colour and complicated . To be frank if it was simple all of this would have stopped and a TDA 2030 chip would be hi fi , end of the story . In truth it probably is .

Thinking about special case slewing . Even though there will be supersonic output of MC pick-ups the 75 uS curve won't allow much output . SACD is virtually unknown amongst my friends . I doubt also SACD has high supersonic output , surely that is a dreadful defect if so ? No hi fi tweeter I know of will stand too much of that .

Before anyone runs away with the idea I dislike high slew rate . No . I dislike listening to frequencies which are not usually considered to be music . I would be the first to believe for almost mysterious reasons a bandwidth limited high slewing amp would sound better . My conjecture being it will have lower distortion . Even though it might mean showing respect for a budget product why not have normal and lab inputs as the NAD 3020 . Then we please everyone ? If a customer prefers something between we should be able to do that .
  Reply With Quote
Old 30th November 2012, 03:10 PM   #7708
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Nigel, you have not thought Rate of Change through. It does NOT take much high frequency energy to give a high dV/dT to an audio signal, JUST ALLOWED BANDWIDTH.
  Reply With Quote
Old 30th November 2012, 03:20 PM   #7709
a.wayne is offline a.wayne  United States
diyAudio Member
 
a.wayne's Avatar
 
Join Date: May 2008
Location: Front Row Center
The Great Audio Debate: Objective Measurements vs. Subjective Experience - Secrets of Home Theater and High Fidelity
  Reply With Quote
Old 30th November 2012, 03:47 PM   #7710
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
I think mr_P_P has made a good point. Certain parameters, such as slew rate, need to be good enough. Up to a certain point making them better improves the sound. Beyond that point the sound does not improve, but no direct harm will be done. The snag is that indirect harm may be done. All engineering is compromise so improving one thing may mean degrading something else. In some cases the designer will be aware of this and seek a good compromise/balance. In other cases he may not and in pursuit of one issue may damage something else. You can often see this 'overengineering' in newbie designs. I do it myself sometimes.

So to answer nigel, high slew rate is not bad in itself but if pursuit of this leads to other things being ignored then the net result may be worse than a more moderate, but still adequate, slew rate design.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Sound Card for Measurements Marik Solid State 2 2nd January 2012 08:59 PM
Sound Card Recommendations (For Audio Measurements) dchisholm Equipment & Tools 5 16th July 2011 09:40 AM
How to protect sound card during amp measurements? okapi Everything Else 13 2nd September 2008 03:06 PM
Quality Control differences = variations in sound quality? KT Class D 0 14th November 2004 06:51 AM
Sound cards - test and measurements jackinnj Everything Else 2 5th July 2003 03:02 PM


New To Site? Need Help?

All times are GMT. The time now is 09:56 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2