Do warm amplifiers produce better sound?

[opelaez]

Newbie here seeking feedback on the sound coming from a cold vs warm headphone amplifier.

I noticed the sound from both Topping A90D and Topping L70 tends to become more "open", deeper and crisper after being powered-on for around 30 minutes to an hour, depending on room temperature. At first, I thought this was all my imagination, my ears getting used to the sound or just placebo effect. However, I noticed this did not seem to happen with my Drop+ THX 789. I noticed the 789 does not get warm whereas the Toppings do.

I went online and came across transistors/electronics take some time to get to an equilibrium state. I am not sure what to think about this.

What is really going on?

Thank you for your time.

I also want to thank Amir for his outstanding and brilliant work. I am absolutely dumbfounded by his unassuming personality while stacking up all the science facts and test evidence behind his words, in a simple way pretty much anyone can easily understand.

 

[VintageFlanker]

Welcome!

What is really going on?

You figured it out by yourself, already:

At first, I thought this was all my imagination, my ears getting used to the sound or just placebo effect.

 

[Keith_W]

Actually, the OP does raise an interesting question. I was told a very long time ago that the performance of electronic components changes according to temperature. Intuitively, it did seem correct. The impedance of voice coils goes up when it is heated and suffers from thermal compression. Changes in temperature affect the dielectric in capacitors and can change their capacitance. Resistors subject to heat increase in resistance. And the effects of temperature on electronics are observable in everyday life - mobile phones stop working when left in cars on a hot day, kitchen appliances with motors magically start working again when you let them cool down, and old LCD screens turn black when it is too hot. So the advice I was given was that my Class A amps were designed to perform at a certain temperature, and they would sound better after a period of warm-up. Is there any truth in this?

 

[Doodski]

Actually, the OP does raise an interesting question. I was told a very long time ago that the performance of electronic components changes according to temperature. Intuitively, it did seem correct. The impedance of voice coils goes up when it is heated and suffers from thermal compression. Changes in temperature affect the dielectric in capacitors and can change their capacitance. Resistors subject to heat increase in resistance. And the effects of temperature on electronics are observable in everyday life - mobile phones stop working when left in cars on a hot day, kitchen appliances with motors magically start working again when you let them cool down, and old LCD screens turn black when it is too hot. So the advice I was given was that my Class A amps were designed to perform at a certain temperature, and they would sound better after a period of warm-up. Is there any truth in this?

There is also the amp thermal tracking circuitry in amps that can change the parameters of the operation.

 

[Speedskater]

Skipping over loudspeakers and vacuum tube circuits. The warm-up changes in well designed solid state circuits are so small that it takes sensitive test equipment to measure them.

 

[dlaloum]

In some ways we are talking about the past - old designs, old components...

Modern designs can track the temperature and dynamically alter their operational parameters to compensate - simpler, older, amp designs, without monitoring and control circuits, have differing performance at different temperature levels - and are "rated " or specced to be run "warm".

Having said that - some currently made components use the older designs of yesteryear, which can sound very good, and there are advantages to simplicity!

 

[DVDdoug]

At first, I thought this was all my imagination, my ears getting used to the sound or just placebo effect.

Hopefully, it is your imagination...

If it had a defect the characteristics could audibly change with time or temperature.

...tends to become more "open", deeper and crisper after being powered-on for around 30 minutes to an hour, depending on room temperature.

Your description of the sound is a clue... With electronics there are only 3 sound-quality characteristics - Noise, distortion, and frequency response. If there's an issue it's usually noise but you would have told us if you were hearing hum or hiss or some other noise.

With "modern electronics" frequency response is usually flat (better than human hearing) and distortion is normally low (better than human hearing) unless you over-drive an amplifier into distortion.

There's no such thing as "10dB of openness", etc.

See Audiophoolery.

The way to eliminate the imagination factor is to do a blind ABX test. ...It's not practical to compare "cold" to "warm" blindly because you need the ability to switch quickly between A, B, and X. But, it would be possible to do a level-matched ABX test between the two Topping devices.

 

[jae]

Should not be an issue in competently designed (and even incompetently designed) modern electronics. A number of ASR reviews also show thermal stability measured over time and it is usually negligible.

 

[Zapper]

The A90 Discrete, or A90D, is an upgraded version of the groundbreaking A90. As its name suggests, the A90D uses fully discrete components in a complete redesign of the A90 NFCA module. Four discrete NFCA modules using 39 transistors each form the fully balanced amp architecture. The matched precision transistors ensure unparalleled distortion and noise performance.

So, they designed a discrete amp. Did they run thousands of simulations covering device, voltage, temperature variations to make sure the design was solid? Did they do thermomechanical modeling? Maybe not. There are a lot of ways to screw up the temperature stability of a discrete amp. It's not inconceivable that its electrical characteristics could drift an audible (and measurable) amount.

If so, it's a broken design.

 

[opelaez]

Your description of the sound is a clue... With electronics there are only 3 sound-quality characteristics - Noise, distortion, and frequency response. If there's an issue it's usually noise but you would have told us if you were hearing hum or hiss or some other noise.

I know I sound like a snake oil seller but I just wanted to give a description of the differences. There is no audible difference in noise, distortion or hum/hiss at all. IMO, it is not big deal but it is definitely undesirable.

The way to eliminate the imagination factor is to do a blind ABX test. ...It's not practical to compare "cold" to "warm" blindly because you need the ability to switch quickly between A, B, and X. But, it would be possible to do a level-matched ABX test between the two Topping devices.

I wish I had two chains with the same components to carry the test out.

 

[opelaez]

So, they designed a discrete amp. Did they run thousands of simulations covering device, voltage, temperature variations to make sure the design was solid? Did they do thermomechanical modeling? Maybe not. There are a lot of ways to screw up the temperature stability of a discrete amp. It's not inconceivable that its electrical characteristics could drift an audible (and measurable) amount.

If so, it's a broken design.

The A90D is the one I felt it was more affected with this issue out of the two Topping headphone amps I tried out. I also have the LA90, which shows a similar behavior, though this is a power amplifier.

Personally, I find interesting I have not experienced this with the THX 789 (even before realizing it runs cold to the touch all the time).
Also, I came across this video from Paul that might help out.

 

[SuicideSquid]

The A90D is the one I felt it was more affected with this issue out of the two Topping headphone amps I tried out. I also have the LA90, which shows a similar behavior, though this is a power amplifier.

Personally, I find interesting I have not experienced this with the THX 789 (even before realizing it runs cold to the touch all the time).
Also, I came across this video from Paul that might help out.

For an amp like that, this is almost certainly an imagined effect. The noise produced by that amplifier is already several orders of magnitude below the threshold of hearing - typically if there's a difference in performance as an amplifier warms up, it's on the scale of a couple of dB - for example, this recently measured Pyle amplifier showed more noticeable change in performance than average over time, and it's a super-budget product, and the difference was still only about 2dB - that's right at the threshold of hearing if you could a/b a hot amp and a cold amp, but there's no way you're able to perceive a gradual 2dB change in noise and distortion over ten minutes.

Also please take anything Paul from PS Audio says with a MASSIVE heaping of salt. The man is a notorious quack and snake oil salesman. As a general rule of thumb, anyone hocking power conditioners and USB cables that cost more than decent complete audio systems is someone who is more interested in separating you from your money than providing you with reliable information.

 

[JSmith]

cold vs warm

Amir sometimes does this test (in this case a tube amp);

Some DAC's have showed slight variations with temp... generally a non-issue as others have said and particularly from an audibility perspective.


JSmith

 

[egellings]

Skipping over loudspeakers and vacuum tube circuits. The warm-up changes in well designed solid state circuits are so small that it takes sensitive test equipment to measure them.

Agree!