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?😕
no your ears probably aren't deceiving you.... as temperature changes so can bias, DC offset, and a number of other characteristics..... and they often change rather rapidly upon turn on until the amp reaches it's operating temperature.
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
Would it then be a good idea not to use bleeder resistors on the power supply caps ? Do they effect the charging of the cap in a negative way?
I don't use them, myself. Certainly not for a solid state piece, given the lower voltages. On a tube design, you could argue that it's a good idea...but I still don't. I'm jealous of each and every little electron. I want them to reach their destiny later on in the circuit.
Grey
Grey
I agree Grey, what with the usually horrendously low efficiency of the designs we commonly use, i want every little electron possible to get to where it can do some useful work.
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.
Warm Up
Solid State amps in particular seem to need to warm up -- i have found some stuff seems to get better over as long as 48 hours -- so i just never turn my hifi off. I like the music happening all the time anyway.
dave
Solid State amps in particular seem to need to warm up -- i have found some stuff seems to get better over as long as 48 hours -- so i just never turn my hifi off. I like the music happening all the time anyway.
dave
Keeping stuff on would be a disaster in Florida. Were the lightning capitol of the world. I am going to remove the bleeder resistors though.
lightning
The last major lighting storm we had was 6-7 years ago. A strike split a 40m red cedar in half & the ground surge took out 12 other trees, the power meter, and the modem port on my Mac. Hifi came thru fine...
dave
PassFan said:
The last major lighting storm we had was 6-7 years ago. A strike split a 40m red cedar in half & the ground surge took out 12 other trees, the power meter, and the modem port on my Mac. Hifi came thru fine...
dave
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.🙁
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.🙁
PassFan said:
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
talking about lightning strikes, if the stike occurs within a few hundred metres, then it wont matter if the device is plugged in or not, the EM Pulse will almost cirtainly fry it.
PassFan said:
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
Hi Dave,
Better get those relay soon (yes sometimes I am also lazy 😀 ), fuse distort considerably.
Cheers,
Hartono
Better get those relay soon (yes sometimes I am also lazy 😀 ), fuse distort considerably.
Cheers,
Hartono
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