Amplifier Warm Up

[Joesax]

I have a Quad 909 Amp. When first turned on it sounds fine but a little lacking in overall smoothness. Sounds a bit bright. However after about 30-40 minutes it transforms into a smooth warm delightful amp. So my choices are

Leave on
Turn it on an hour before I listen

As it is 13 yrs old I don’t want to leave it on.
I’ve been turning it on at least 30 minutes before listening for years.

My question.

Are there any new amps that sound their best upon turning on and do not require a warm up period? Or is this just an accepted fact?

Joe

 

[Willem]

I think you are probably imagining things: I feel the same in a live concert of classical music.
I have a Quad 606-2 which is basically the same and it is just fine. Peter Walker knew what he was doing.

 

[digitalfrost]

Some amps just take a lot of time to reach their temperature. My old Sony needed 2-3hrs to be equally hot everywhere. The thing is, you typically set the bias voltage after X amount of time with the unit on, let's say 5 minutes. You could measure bias voltage later and see how it changes. I do believe some amps need warm up to sound their best, but without measurements, I could well be imagining things.

 

[MRC01]

When I turn on my Adcom 5800 (original owner!) without playing any music, the cooling fans engage after about 5-10 mins. I've never been able to tell any difference in sound if I play music right after turning it on, or after it's been on for several hours. The DC offset measured across the output doesn't change either, but is always around 2-5 mV. I usually wait about a minute just to let the voltages & currents stabilize before playing music.

 

[Soniclife]

As it is 13 yrs old I don’t want to leave it on.
I’ve been turning it on at least 30 minutes before listening for years.

Has it always behaved like this?

 

[Joesax]

To my ears, yes it has always behaved this way. I listen to a lot of Classical and string tone seems smoother and the overall sound is a touch warmer after warm up. I use this amp in my studio and my piano VST sounds better after warm up as well. Maybe I'm imagine it but I notice it every time and have for years.

 

[amirm]

I have tested a number of new amps and there is difference of note in their performance after warming up.

 

[Willem]

Time then to test this classic amplifier design. However, I would still be surprised if it shows a different sound once warmed up. It is extremely stable and there is no bias to set.

 

[DonH56]

A lot of amplifiers (or just audio components in general) do not have terribly stable bias circuits and may change a bit during a (usually brief) warm-up period. This is not the same as "burn-in" which implies a long-term issue (to me). I have noticed in the past it was more prevalent among power amplifiers, probably due to their higher bias and generally simpler circuitry compared to line-level components. A notable exception being tube gear in general; my old ARC preamp (SP3a1) needed at least 5 minutes before the output was decently stable and 20~30 minutes before measurements were stable, and my amplifier (D-79) was similar despite having a regulated B+ rail.

IME/IMO - Don

 

[Joesax]

Time then to test this classic amplifier design. However, I would still be surprised if it shows a different sound once warmed up. It is extremely stable and there is no bias to set.

Willem

Listen to orchestral strings and/or the upper register of solo piano and full symphony orchestra with cymbals and percussion. You probably won’t notice anything on pop, rock or jazz recordings in my experience.

 

[Wombat]

Here is the solution to the problem. Put one of these under each piece of gear, arranged via timer or thermostat, to switch off at the item warm up time.

Reset heaters when item/s is/are turned off.

Pads

 

[Willem]

I mostly listen to classical music. As a pre amplifier I use an ADI-2 with inline attenuators at the power amp to match voltages. Before I had the ADI I still used a Quad 33 preamp and that was less than perfect.
Speakers are Quad 2805s so pretty revealing.

 

[VintageFlanker]

Listen to orchestral strings and/or the upper register of solo piano and full symphony orchestra with cymbals and percussion. You probably won’t notice anything on pop, rock or jazz recordings in my experience.

No...not here, please...

 

[Sal1950]

I have a Quad 909 Amp. When first turned on it sounds fine but a little lacking in overall smoothness. Sounds a bit bright. However after about 30-40 minutes it transforms into a smooth warm delightful amp. So my choices are

Leave on
Turn it on an hour before I listen

As it is 13 yrs old I don’t want to leave it on.
I’ve been turning it on at least 30 minutes before listening for years.

My question.

Are there any new amps that sound their best upon turning on and do not require a warm up period? Or is this just an accepted fact?

Joe

Put a heating blanket under it. Makes me work better in my old age too.

 

[solderdude]

The 909 is current dumping amp so it should not be bothered by class-AB stages needing to set itself to the correct idle current.
It has a class-A and class-B output stage combined in the bridge circuit.

 

[Hipper]

I have tested a number of new amps and there is difference of note in their performance after warming up.

Have you found this with latest class D amps you've been testing?

 

[maty]

It will depend on the design of the amplifier and how much bias used.

My modded AV Marantz SR4500 (class AB) sounds better when it is warm, without any doubt. Of course, I listen to very good recordings with high / very high DR, with acoustic or electrified instruments.

With complex music like orchestral the difference is very evident to me.

If you listen to bad recordings (as well as more than 90% of the population) you can not appreciate many differences in almost nothing, all decent amplifiers will sound the same to you, cold or hot, MP3 or FLAC, 16/44 or 24/96... hence it is not logical to spend a lot of money on the stereo.

 

[solderdude]

Maty, the amp in question doesn't have a class-AB output stage.
It is a current dumping amp so has class-A and class-B output stages.
The class-A part of course is what is warming up the amp slowly here.

 

[DonH56]

The 909 is current dumping amp so it should not be bothered by class-AB stages needing to set itself to the correct idle current.
It has a class-A and class-B output stage combined in the bridge circuit.

Did not know (just to hide the fact that I forgot) that. So the class A stage may need a little time to stabilize (if anything).

Edit: As you just said...

 

[Willem]

It is said that one of the advantages of the design is precisely its insensitivity to temperature changes.