Does anyone think amps sound better when they warm up. My A75 got a good burn in this past weekend. I listened to it for about 4 hrs while working in the garage. It got up close to 50 - 55 deg. C and stabilized there and really sounded good, really detailed and smooth. When I turn it on cold it doesn't seem to have the same liveliness. Is this explainable or is it my ears deceiving me?
Setting aside questions of bias settling in as the unit warms up, there's also the matter of electrolytics--particularly new ones or those which have been gathering dust--needing to get up to voltage.
I've heard of other possibilities, as well, but don't have the energy to start a ruckus this week. Perhaps next time around...
Grey
I've heard of other possibilities, as well, but don't have the energy to start a ruckus this week. Perhaps next time around...
Grey
Bleed resistors
I do use bleed resistors, especially when I'm still prototyping the design.
Why? Well, after discovering the 50,000uF caps on the +25V and -25V rails for my Aleph 30 monoblocks have easily enough instantaneous current capacity to spot-weld a stray wire to the ground plate, I decided to discharge those suckers with a 220R 5W resistor from each cap to ground.
With the mains power removed, the bias current drains the caps down to 3-4V or so, but then the output mosfets will turn off. A stray lead while I was modding the wiring and ZAP!
Come to think of it, I haven't removed the bleed resistors from the finished boxes. Perhaps I'll open the boxes up and take them out.
I do use bleed resistors, especially when I'm still prototyping the design.
Why? Well, after discovering the 50,000uF caps on the +25V and -25V rails for my Aleph 30 monoblocks have easily enough instantaneous current capacity to spot-weld a stray wire to the ground plate, I decided to discharge those suckers with a 220R 5W resistor from each cap to ground.
With the mains power removed, the bias current drains the caps down to 3-4V or so, but then the output mosfets will turn off. A stray lead while I was modding the wiring and ZAP!
Come to think of it, I haven't removed the bleed resistors from the finished boxes. Perhaps I'll open the boxes up and take them out.
Most of these parts, MOSFET and Bipolar, increase
their transconductance as they warm up a bit, and
their junction drop Vgs or Vbe alters with temperature,
so we always do our adjustments and evaluation after
they have warmed up for an hour. Over that period of
time you can measure very significant performance
changes, not to mention any subjective perceptions.
their transconductance as they warm up a bit, and
their junction drop Vgs or Vbe alters with temperature,
so we always do our adjustments and evaluation after
they have warmed up for an hour. Over that period of
time you can measure very significant performance
changes, not to mention any subjective perceptions.
PassFan said:Dave:
On average in central florida we can get upwards of 200 strikes + in a day. Somedays none, others it's coming down thicker than the rain. I've seen it do some crazy things and it loves ICs. I just don't take the chance.
WOW. I've occasionally seen storms like that on the prairies, and in one of those i'd be turnin' off the main hifi... i have some i'd be willing to chance
dave
PassFan said:Does anyone think amps sound better when they warm up.
My A75 got a good burn in this past weekend.
I listened to it for about 4 hrs while working in the garage.
It got up close to 50 - 55 deg. C and stabilized there and really sounded good, really detailed and smooth.
When I turn it on cold it doesn't seem to have the same liveliness.
Is this explainable or is it my ears deceiving me?
Hard to say.
Some amplifiers are more sensitive to temperature, than others.
My experience from my own Amplifiers,
is that
hot Class A Amplifiers need some hours 'to settle'.
Once there, they are not much sensitive to OUTSIDE ENVIRONMENT temperature, at all.
For those extreme temps you mention,
I think, this would effect most amplifiers in some ways.
Whether this effect does anything to 'harm the actual sound'
remains to be explored.
One thought pop up in my mind:
Are any LoudSpeakers effected by Temperatures ....
I mean most any material and even air, will change in quality with temperature.
... more or less ...
Regards, lineup
A75 warmup
My A75 dc offset at the output comes on just under 100mv when cold and it takes a while to settle back to 20mv but after an hour the heat sinks are hot and it sounds its best. I do have bleeder resistors but they are 22k, I could take them out but I have left them in for safety. I did take out the rail fuses since I have output fuses. I thought of putting in a speaker saver relay now that the amp is almost 15 years old but haven't gotten around to it. It still sounds good but perhaps not as good as the the new 160.5's--maybe NP will have an introductory sale!!!!!!!!!!!!
dave
My A75 dc offset at the output comes on just under 100mv when cold and it takes a while to settle back to 20mv but after an hour the heat sinks are hot and it sounds its best. I do have bleeder resistors but they are 22k, I could take them out but I have left them in for safety. I did take out the rail fuses since I have output fuses. I thought of putting in a speaker saver relay now that the amp is almost 15 years old but haven't gotten around to it. It still sounds good but perhaps not as good as the the new 160.5's--maybe NP will have an introductory sale!!!!!!!!!!!!
dave
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