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The problem with HOT idling SS amps as I see it.... [long post]

Posted by AbeCollins (A) on June 29, 2024 at 13:27:40

In Reply to: Hmm, now U inspired me to think about my PS Audio M1200... posted by jeffreybehr on June 27, 2024 at 17:31:17:

My theory based on facts:

HOT running Class A/AB amps run HOT for a reason. The power transistors are biased in an operating region for lowest distortion and best sonics constantly drawing lots of electricity and producing lots of wasted heat.... whether the music is playing or not.

For various reasons these solid state amps that idle and run HOT tend to sound best after being powered ON for a while. This is probably due to thermal mass (chunky aluminum heatsinks) and electronic circuitry that require time to stabilize to an optimum design temperature. In other words these amps with huge heat sinks start stone cold (ever feel a cold heat sink?) and can require an hour or more to fully 'heat up' and stabilize before sounding great.

I would argue that many of these solid-state amps require more power-ON warm-up time to sound good vs their vacuum tube counterparts - but that's another topic.

So what's a guy to do?

Here's the problem as I see it and have experienced for myself. When I listen to music I want to flip-ON the amp and start enjoying music. Not always, but I might listen for only 20 minutes then leave. I don't want to turn ON the amp, go make breakfast, shower and shave, read the paper, or perform other rituals to kill time. I don't want to accommodate the amp and its need for warm-up. I want the amp to fully accommodate my need, on demand, on my time, instantly sounding its best.

Before I retired I was more likely to sit down for listening sessions over the weekend. I would power ON my amp(s) on a Friday afternoon and leave them ON until Sunday night. Electric power consumption and heat be damned!

Can you imagine the electric cost of leaving these HOT SS amps ON 24/7 so they're always ready?*

Enter modern Class D amps:

Like you and others, I have auditioned and owned several Class D amps over the past 20+ years - along with various "traditional" Class A & AB amps. Class D has improved immensely over the years and I have fully embraced the benefits along with outstanding Class D sonics.

- Class D amps sound great within a minute or three of Power-ON. No long warm-up.

- Class D amps are very power efficient while idle or playing music meaning they consume very little average power overall and produce very little heat compared to "traditional" A/AB amps. Leave them OFF then turn them ON as needed, or just leave them ON 24/7 - doesn't matter as they are always ready to sound their best.

- - - - - - - - - -

* AC power electricity cost example:

Pass Labs XA100.8 monoblocks are "The middle sibling of the XA.8 series, the XA100.8's realize a muscular yet highly refined sonic profile."

Per Pass Labs the power consumption at idle is 500-Watts for each monoblock (1-kW for the pair). Assume a modest average of 20-cents per kWh of electricity in the US for 2024 (but as much as double that in parts of CA and Hawaii).

What is the cost of leaving these monoblocks powered ON 24/7 so they are always 'warmed-up' to sound their best?

1-kW X 0.20 dollars per kWh X 24 hours X 365 days = $1,752 per year (or $146 per month).

The Average Energy Prices in the USA

• Pass Labs XA100.8 tech specs   (Open in New Window)

Edits: 06/29/24 06/29/24 06/29/24 06/30/24 07/01/24 07/01/24

This post is made possible by the generous support of people like you and our sponsors:

Kimber Kable

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