John Curl's Blowtorch preamplifier part II

Status
Not open for further replies.
Jump to Latest
3

31697B

Disabled Account
Joined 2012
many amps are dominated by noise at lower than full power levels. What one ought to be shooting for is a lack of 'curve' --- such as this quiet CFA power amp's distortion:

CFA-8.jpg


THx-RNMarsh
 
Last edited:
a.wayne

a.wayne

Member
Joined 2008
fas42 said:
Smartest thing to do, IMO. An audio amplifier is not a piece of industrial machinery, to do a "Look how big my bits are!!" are, on demand. In the ideal it should be continually self optimising, to achieve the highest sound quality - and wearing out the components by cooking them for extended periods is not the brightest thing ...
Click to expand...

Frank obvious you are into Fenky , try reading the bench report , the amp is well, Fenky , at 15k not acceptable , same as the brystons falling on their face below 8 ohm...

Ps: been there done that with both Bryston and Mac, Nothing special :snail:
 
a.wayne

a.wayne

Member
Joined 2008
Chris Hornbeck said:
Shuts off with standard preconditioning? Seems a long way from the days when Davey O'Brien would gleefully toss slightly weak Genalex KT88's into the trash to bring an old Mc amplifier brought to one of his clinics up to snuff (and for free.)

And your point about crossover distortion is not amiss: -93dB 3rd harmonic from a +25dBW output signal is -68dB ref 1 watt, a reasonably typical listening level with typical speakers of say 88dB SPL/1W/1M.

If they really cared about correlating measurements with sound, they would test the amplifiers at 0dBW or maybe +10dBW. But distortion of -68dB would look bad (cause it is.)

Thanks, as always,
Chris
Click to expand...


Yes they are longway from Mac of old ......

The system we listened to had a total of 6 meters going all at once , amp , pre-amp , et al , everything had a meter ....

:)
fas42 said:
The sound of the 2nd would be hugely coloured at anything like realistic sound levels ...
Click to expand...

Actually both curves would sound colored, guess which one would produce that SS GLARE most try to hide from ....

Yeah ..:)
 
Last edited:
fas42

fas42

Banned
Joined 2012
a.wayne said:
Actually both curves would sound colored, guess which one would produce that SS GLARE most try to hide from ....

Yeah ..:)
Click to expand...
Now we're starting to get somewhere ... that 'glare' is distortion due to system misbehaviour, somewhere - it is not due to the amplifier having quite excellent distortion measurements!! The amplifier with poor distortion figures is simply a workaround, to hide that the system has problems, gives the setup a 'Doris Day lens' (who knows that expression?, :)) - it's not solving the real problem!!


The amp with 'SS GLARE' is doing a great job of highlighting the system problems, and the latter is what has to be addressed - not changing the amp, and pretending the problem is not there!

So what's causing the SS GLARE, then? - that's the hard bit, this is where troubleshooting comes into it, one needs to work out precisely where the problem or problems are in the system - but this is how the real progress is made!

Just my 2 cents worth, :D ...
 
Kindhornman

Kindhornman

Member
Joined 2012
For once again I would have to agree with Frank that the distortion numbers on that Mac aren't bad before clipping and that is a bunch of power before you get there. So what is the problem with that amp, besides the shutdown under a partial load, which shouldn't happen in an amp that cost so much? Obviously they could use larger heat sinks but what is causing the poor sound quality?
 
fas42

fas42

Banned
Joined 2012
Kindhornman said:
So what is the problem with that amp, besides the shutdown under a partial load, which shouldn't happen in an amp that cost so much? Obviously they could use larger heat sinks but what is causing the poor sound quality?
Click to expand...
Apparently so weak technically that John Atkinson ended his measurements with:

I thought the McIntosh amplifiers sounded simply superb when I auditioned them in Paul Bolin's system in the spring. Nothing in the MC501's measured performance causes me to doubt what I heard
Click to expand...
... :rolleyes:

Bad sound is a system issue, not a component part issue ...
 
a.wayne

a.wayne

Member
Joined 2008
Kindhornman said:
For once again I would have to agree with Frank that the distortion numbers on that Mac aren't bad before clipping and that is a bunch of power before you get there. So what is the problem with that amp, besides the shutdown under a partial load, which shouldn't happen in an amp that cost so much? Obviously they could use larger heat sinks but what is causing the poor sound quality?
Click to expand...

Whats The problem? Chris voiced that well and Imo it has avg sonics , granted i have only spent 3 hrs in two different systems, listening and the sound was consistently The same , avg. Time for MAC to ditch that transformer and get on with it ...


Just saying ...:snail:
 
Status
Not open for further replies.
Top Bottom