John Curl's Blowtorch preamplifier part II - Page 4251 - 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 20th August 2013, 03:08 AM   #42501
fas42 is offline fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 11
Yes, since we have been talking about digital audio I thought the context would have been fairly clear ...
__________________
Frank the truth is, I just like a bit of ASMR ...
  Reply With Quote
Old 20th August 2013, 09:06 AM   #42502
marce is offline marce  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
Location: Blackburn, Lancs
Woops
  Reply With Quote
Old 20th August 2013, 09:28 AM   #42503
marce is offline marce  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
Location: Blackburn, Lancs
Curious as to what you do consider is a perfect square wave?
Perfectly square edges are never going to be reproducible through any electronics.
I am at a bit of a loss here at what you are trying to achieve?
Enlighten me please Frank
  Reply With Quote
Old 20th August 2013, 10:09 AM   #42504
fas42 is offline fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 11
The square wave, expressed in digital form, will never be truly thus, there must alway be at least one sample period between successive samples, from -ve max to +ve max - which obviously then determines what the corresponding analogue slew rate will need to be, to be a correct reconstruction. As you say, in the analogue world the rise time will always be some value greater than zero, so 'perfection' can never be achieved there either.

The confusion has arisen because I used the word "perfect" to describe the trivial exercise it is for software to generate an audio track which at first glance looks to be, exactly a square wave. Which it is not, of course - just passing it through software equalisation with flat response immediately exposes the intrinsic ripple component, that is 'hidden' at the initial software creation of the waveform.
__________________
Frank the truth is, I just like a bit of ASMR ...
  Reply With Quote
Old 20th August 2013, 10:14 AM   #42505
marce is offline marce  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
Location: Blackburn, Lancs
Cheers Frank
  Reply With Quote
Old 20th August 2013, 10:30 AM   #42506
fas42 is offline fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 11
__________________
Frank the truth is, I just like a bit of ASMR ...
  Reply With Quote
Old 20th August 2013, 03:02 PM   #42507
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by simon7000 View Post
Scott,

In looking back on this thread there was an issue that we didn't quite settle on.

Attached is the picture of the setup. A current source of 1 amp was used and the voltage across the resistors was 7.32 and 7.31 volts. Both pieces are .125" 5052 aluminum 3' x 6" with the hole .125" centered. The finish was mill finish cleaned with a lye bath. Paint is Rustoleum Flat Black spray paint both sides. Temperatures measured using a bead thermistor in direct contact at the heatsink back just under the mounting bolt were 39 & 42 C.
Not a lot of difference IMO. I don't see 10-15% difference changing things enough considering a resonable overdesign margin.
__________________
"Greetings from The Humungus! The Lord Humungus! The Warrior of the Wasteland! The Ayatollah of Rock and Rolla!" aka the Wizard of Wrestling.
  Reply With Quote
Old 20th August 2013, 03:15 PM   #42508
diyAudio Member
 
Join Date: Nov 2008
Location: Oakmont PA
Quote:
Originally Posted by scott wurcer View Post
Not a lot of difference IMO. I don't see 10-15% difference changing things enough considering a resonable overdesign margin.
Let us look at the costs! One square inch of .125" aluminum costs me about $.04. The cost to anodize it black is around $.02. So for heatsinks running under about 50 C the advantage is clear. For those running above that the advantage goes to a fan. But if a fan is not acceptable for either noise or MTBF then the advantage goes dark.
  Reply With Quote
Old 20th August 2013, 03:23 PM   #42509
diyAudio Member
 
Kindhornman's Avatar
 
Join Date: Aug 2012
Location: Los Angeles, California
Simon,
If I am reading this correctly and not doing the math here it would appear that a small increase in surface area would be cheaper than the black coating for the small 10% differential you would get with the black. If space is at a premium then the black coating may be required but if not simply sizing the aluminum a bit large would make a greater differential. That does not mean we shouldn't use the black coating, just that surface area would seem to be the driving force here. Correct me if I am wrong, I could just do the math and answer my own question.
  Reply With Quote
Old 20th August 2013, 03:30 PM   #42510
diyAudio Member
 
Join Date: Nov 2008
Location: Oakmont PA
Quote:
Originally Posted by Kindhornman View Post
Simon,
If I am reading this correctly and not doing the math here it would appear that a small increase in surface area would be cheaper than the black coating for the small 10% differential you would get with the black. If space is at a premium then the black coating may be required but if not simply sizing the aluminum a bit large would make a greater differential. That does not mean we shouldn't use the black coating, just that surface area would seem to be the driving force here. Correct me if I am wrong, I could just do the math and answer my own question.
Metal cost $.04 To get 10% better $.044
Anodized cost $.06

However anodized radiates better as temperature goes up. So as a heatsink gets to temperatures that one should avoid any human contact anodized becomes price effective. But a fan will keep such a heatsink cool enough to be safe.

So when a heatsink size is limited and you cannot use a fan then anodized is a solution. The other reason to anodize is that it looks good.

Shown is my Class A "Butterfly" amplifier.
Attached Images
File Type: jpg P9230004.jpg (104.2 KB, 153 views)
  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



New To Site? Need Help?

All times are GMT. The time now is 05:53 AM.


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