John Curl's Blowtorch preamplifier part II

Status
Not open for further replies.
1/3 power pre-conditioning (in America, by the FTC) was also a reaction to an earlier era of inflated horsepower race claims, similar to auto sound these days. "Peak power output" and such. Everybody knew it was too stringent, but it brought law and order to the West. "Nothing like a noose around the neck to focus the mind."

It just very surprising that McIntosh, of all people, would have trouble with it. They used to eat that stuff for breakfast, with ground glass for garnish.

Speaking of McIntosh, and the proverbial 40 years ago, I remember visiting Mc's Binghamton fab 40 years ago and being stunned by the sight of a very very large room full of only women. They said that they had tried hiring men to do the (hand!) soldering, but none ever lasted more than a few days. Couldn't take it - only women could. There's a lesson there somewhere, but I'm afraid to know what it is.

Thanks,
Chris
 
John,
Snide remark aside, you were the one who made a comment about the 1/3 power test. I wanted to know which side of the argument you fell on and asked more than once for your comment. Are you for or against the test and why either way? I understand the need to make sure that the heat sinks are large enough to handle the toughest load that an amplifier may realistically be expected to see, that should go without saying for a competent design.
 
No that's not Bakelite. That's phenolic board, as explained by SY. Bakelite is a different material - I believe, for instance used in the past for light switches, kettle handles, that sort of thing.

Bakelite was a trade name that covered phenolic resin as well as a wide variety of things made using phenolic resin. So hitswire isn't really off base using the name more generically. It's no different than using Kleenex to refer to facial tissue, even if the facial tissue wasn't made by Kleenex.

se
 
Kindhornman, I made an 'exasperated' response to a 'snide' remark that you made about Stereophile and its test standards.
OK, let's come to understand what is happening. It just so happens that a Class B amp has MAXIMUM DISSIPATION at about 1/3 rated power. Therefore, you need the most heatsink IF you want to run continuously at about 1/3 power.
The page(s) that I inserted show the derivation of this 'heatsink' power dissipation with output power, through basic Calculus. And that may be beyond some here, but the graph on the following page should be clear to everyone.
It is not always necessary to make an amp for ALL applications or situations, and this MAC is a good example of this. Obviously this amp is heatsink light, or could use a fan.
Yet, most people would not notice it in 'normal' operation at home.
It is the FTC 'standard' to see if the amp can run at 1/3 power for a time.
It is a little like specifying an automobile to run continuously at 100mph. It is well possible that some American autos, 'might' overheat if driven continuously at 100mph, but people in the USA, usually cannot continuously drive at 100mph, for legal reasons, so it 'might' be possible that some auto manufacturer might make an engine with cooling system that overheats if continuous 100mph operation is attempted. Is this a bad thing? It would be a 'tradeoff' made by the automobile designers, yet most people would be unaware of it, IN THE USA. Take the same auto to Europe, and all bets are off. Just like, if you took THIS MAC into service as a PA amp, you 'might' have trouble. It is sort of the same thing.
 
Kindhornman, I made an 'exasperated' response to a 'snide' remark that you made about Stereophile and its test standards.
OK, let's come to understand what is happening. It just so happens that a Class B amp has MAXIMUM DISSIPATION at about 1/3 rated power. Therefore, you need the most heatsink IF you want to run continuously at about 1/3 power.
The page(s) that I inserted show the derivation of this 'heatsink' power dissipation with output power, through basic Calculus. And that may be beyond some here, but the graph on the following page should be clear to everyone.
It is not always necessary to make an amp for ALL applications or situations, and this MAC is a good example of this. Obviously this amp is heatsink light, or could use a fan.
Yet, most people would not notice it in 'normal' operation at home.
It is the FTC 'standard' to see if the amp can run at 1/3 power for a time.
It is a little like specifying an automobile to run continuously at 100mph. It is well possible that some American autos, 'might' overheat if driven continuously at 100mph, but people in the USA, usually cannot continuously drive at 100mph, for legal reasons, so it 'might' be possible that some auto manufacturer might make an engine with cooling system that overheats if continuous 100mph operation is attempted. Is this a bad thing? It would be a 'tradeoff' made by the automobile designers, yet most people would be unaware of it, IN THE USA. Take the same auto to Europe, and all bets are off. Just like, if you took THIS MAC into service as a PA amp, you 'might' have trouble. It is sort of the same thing.

You did noticed it shut itself down @30watts , so 50mph not 100 ...:rolleyes:
 
FTC test protects consumers , regardless of how absurd some think they are, the real absurdity was even at 6% of rated power, the Mac still failed. The next level of absurdity was from JA and stereophile for not sending that junk back to Mac...

Ohhh Phase Linears were junk too, hence the FTC ruling , yeah no revisionist history here mates ...:rolleyes:


Where's Peter Aczel .... :)
 
Last edited:
AX tech editor
Joined 2002
Paid Member
Bakelite was a trade name that covered phenolic resin as well as a wide variety of things made using phenolic resin. So hitswire isn't really off base using the name more generically. It's no different than using Kleenex to refer to facial tissue, even if the facial tissue wasn't made by Kleenex.

se

OK, thanks for the correction :)

Jan
 
Status
Not open for further replies.