Sound Quality Vs. Measurements - Page 22 - diyAudio
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 27th December 2011, 04:11 PM   #211
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
Thanks for the great info chaps, sorry i could not get back here earlier. now to pull the discussion back to thermal stability:

Quote:
Originally Posted by john curl View Post
...real designers make sure that the THERMAL CAPACITANCE is very high by close mounting the output devices on good insulators (if necessary) properly torqued down and used with thermal grease on a substantial heatsink . This removes most of the short term gain changes due to temperature.
Yes John, that pretty much what I was trying to express. Since Class-A runs a such at high idle current and idle temperature, just how much will short term bursts of music change that point? I.E., if the dynamic peaks are only equal to the idle current, the change in current flow won't be high in relation to idle current. Temperature should not change much. Thorsten seems to say that it will, but I ask how much as compared to a low bias amp?

Tubes by their nature stay pretty warm, even in class AB. How much will the dynamic peaks of music change that temperature? And what differences will thermal stability make?
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 27th December 2011, 04:32 PM   #212
diyAudio Member
 
Join Date: Jan 2008
Location: Virginia
If the total measured THD of an audio chain (to the amplifier output posts) is below 0.05% there is no point in splitting the hair into odd-even harmonics. That level is low enough not to be a problem.
Limited bandwidth of a 44.1kHz sources is clearly audible on the sounds like in the original post. I found out that DSD or PCM 96kHz are needed for a "life-like" sound. Bandwidth and step/impuls response is clearly measurable.

Now, the speakers will never be in that range. I was amazed how much difference is between my speakers and a pair of decent headphones.
Measuring speaker's THD is a little more "delicate" to do because of their nature (pressure devices) and nelinear dependence of the actual level of electrical (input) signal.

As for thermal on tubes - anodes will heat up based on the current is flowing thru them (number of electrons hitting the anode). That will affect efficiency, noise...

Last edited by SoNic_real_one; 27th December 2011 at 04:35 PM.
  Reply With Quote
Old 27th December 2011, 04:38 PM   #213
a.wayne is offline a.wayne  United States
diyAudio Member
 
a.wayne's Avatar
 
Join Date: May 2008
Location: Front Row Center
Quote:
Originally Posted by Pano View Post
Thanks for the great info chaps, sorry i could not get back here earlier. now to pull the discussion back to thermal stability:


Yes John, that pretty much what I was trying to express. Since Class-A runs a such at high idle current and idle temperature, just how much will short term bursts of music change that point? I.E., if the dynamic peaks are only equal to the idle current, the change in current flow won't be high in relation to idle current. Temperature should not change much. Thorsten seems to say that it will, but I ask how much as compared to a low bias amp?

Tubes by their nature stay pretty warm, even in class AB. How much will the dynamic peaks of music change that temperature? And what differences will thermal stability make?

agree................ and my original point !!!

Quote:
Originally Posted by SoNic_real_one View Post
If the total measured THD of an audio chain (to the amplifier output posts) is below 0.05% there is no point in splitting the hair into odd-even harmonics. That level is low enough not to be a problem.
Limited bandwidth of a 44.1kHz sources is clearly audible on the sounds like in the original post. I found out that DSD or PCM 96kHz are needed for a "life-like" sound. Bandwidth and step/impuls response is clearly measurable.

Now, the speakers will never be in that range. I was amazed how much difference is between my speakers and a pair of decent headphones. Measuring speaker's THD is a little more "delicate" to do because of their nature (pressure devices) and nelinear dependence of the actual level of electrical (input) signal.

As for thermal on tubes - anodes will heat up based on the current is flowing thru them (number of electrons hitting the anode). That will affect efficiency, noise...
You should get better speakers, when correctly voiced they should sound pretty close to the headphones.
  Reply With Quote
Old 27th December 2011, 04:42 PM   #214
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Quote:
Originally Posted by Wavebourn View Post
Traditional means static measurements using sinewave generators, notch filters, AC voltmeters. However, spectrum analyzer is the way to observe dynamic behavior, but you can't name and calibrate all possible dynamic flaws of all possible topologies, to define a new tradition of measurements.
And even if you do, how many would agree with your new standards? At least, Stereophile always has own opinions, independent on engineers'.


Can't edit: I can use signal generator, DVM, oscilloscope, CD player, to observe behavior of the amp I design and to find potential flaws and directions where to go, but I would not call it traditional measurement. I would rather call it a specialized, topology - dependent test.
__________________
"Our youth [...] have bad manners, contempt for authority; they show disrespect for their elders, contradict their parents, [...] and tyrannize their teachers. -- Plato, 447-367 BCE
  Reply With Quote
Old 27th December 2011, 04:45 PM   #215
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by a.wayne View Post
could you elaborate more on your setup ..? what is an a typical PC setup.?
M-Audio 192 card in a cheap HP PC, which allows both balanced and unbalanced I/O as well as SPDIF I/O. Street price is ~$150. Bought it on Amazon. AudioTester, REW, Rightmark, HOLM, Soundeasy software. AT was about $40, the others were free.

Two interface boxes, one is Pete Millett's, the other is my own design (BUF03s, noisy but superbly low distortion and source Z). My box is set up to use standard (1x, 10x) scope probes.

I have conventional gear as well for backup and verification, but that seems to get used less and less. I'd love to have an AP2, but with a little elbow grease and one-off jigs, I can get just about all the measurements that an AP2 is capable of with the PCI card.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 27th December 2011, 04:46 PM   #216
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by Wavebourn View Post
Traditional means static measurements using sinewave generators, notch filters, AC voltmeters.
IOW, using your grandpa's gear.

A tacit point that you've made is that the ability to determine which measurement to make, what the error sources are, and how to interpret the measurement is thousands of times more important than the brand of equipment.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 27th December 2011, 04:47 PM   #217
diyAudio Member
 
Join Date: Dec 2011
Default Figure of Merit

John,
I am sure you balance steady state harmonics perfectly, given the topology and noise constraints.
What I pointed out was that given time series of "pink noise" will have a fourier transform; after amplification that fourier transform will be modified; against known human preception of that harmonic content of the transform S(w)amp/S(w)o there may be a measurable FOM that sorts ampifiers by their percieved quality.

In summary The point is pretty simple; why can't there be an accepted measurable quantity that can be used to gauge audible "fidelity"? If I look at THD and IMD S/N for:
a 1970's yamaha reciever
a 1970's kenwood 40WpC integrated amp
a 1960 HK Cit II
a Carver"the receiver"
a 1990's denon pre-amp
a pioneer super tuner car radio
A pair of PP monoblocks
Any modern amplifier "high" or "low" end
I can't "see" what I hear or have heard over the years . Further the feedback topology of the HK CITII suggests you can't "hear" the tubes, however I certainly know when the splitter pentode is aging, ( not sure if there is a measurable THD IMD with this though).
I also know a single ended triode preamp sound is recognizable, as this is DYI audio what I really want to know is ( so I clean up my preamp!):
a) why does a high NFB class A preamp sound "sterile" what measurement is sterile to musical?
b) what do I measure and minimize in the triode class A preamp to have my cake and eat it to?; that is a musical combination and no syrup colorations.
Do I move the B+ up? drop the 12AU7 stage? move the S.E. 12Ax7 final stage to SRPP? Do I take gain and feedback? How much? How do I know? What do I measure? What figure of Merit do I use?
What if I wanted to switch preamp? what FOM do I look for? That one I know: there is no published marketing info that tells me, not slew rate, not THD, not IMD. It is all word of mouth and audio trial and error.
c) Does a different topology change the sound/noise e.g. if I totem pole either the 12au7 or the 12ax7 stage will I "improve" the amplifier fidelity?
That is what I am looking for, a measurable way to gauge my amplifier mod or review known topologies and compare the fidelity of each.
Lou
  Reply With Quote
Old 27th December 2011, 04:49 PM   #218
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Quote:
Originally Posted by SY View Post
IOW, using your grandpa's gear.

A tacit point that you've made is that the ability to determine which measurement to make, what the error sources are, and how to interpret the measurement is thousands of times more important than the brand of equipment.
Exactly. But we still read here about THD and DF comparisons
__________________
"Our youth [...] have bad manners, contempt for authority; they show disrespect for their elders, contradict their parents, [...] and tyrannize their teachers. -- Plato, 447-367 BCE
  Reply With Quote
Old 27th December 2011, 05:00 PM   #219
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Only from people who believe that nothing has advanced since 1968.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 27th December 2011, 05:03 PM   #220
a.wayne is offline a.wayne  United States
diyAudio Member
 
a.wayne's Avatar
 
Join Date: May 2008
Location: Front Row Center
Quote:
Originally Posted by SY View Post
M-Audio 192 card in a cheap HP PC, which allows both balanced and unbalanced I/O as well as SPDIF I/O. Street price is ~$150. Bought it on Amazon. AudioTester, REW, Rightmark, HOLM, Soundeasy software. AT was about $40, the others were free.

Two interface boxes, one is Pete Millett's, the other is my own design (BUF03s, noisy but superbly low distortion and source Z). My box is set up to use standard (1x, 10x) scope probes.

I have conventional gear as well for backup and verification, but that seems to get used less and less. I'd love to have an AP2, but with a little elbow grease and one-off jigs, I can get just about all the measurements that an AP2 is capable of with the PCI card.
Thanks i have a spare PC , this has opened up some options ....

http://www.amazon.com/dp/B00064ABSG/...l_6zsc1krie4_b
  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
Quality Control differences = variations in sound quality? KT Class D 3 4th June 2014 12:02 AM
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
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 12:30 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