Burn-in revisited

In my experience most of the burn-in is over after about 3-4 weeks but resistors (metal film - the type we use) can take up to 6 months, but that's going to be less noticeable.

http://www.analog.com/library/analogdialogue/archives/39-05/Web_Ch7_final_J.pdf

See page 7.13 (page 15 of 166)

The unit simply being switched on will do most of what's required as the DC voltages will be on the circuit. The signal (ac voltages) will in a way be there all the time also as all amplifiers produce what is termed as self-noise. Although this is only around -80dB on a Solo or -70dB on a phono stage it has some effect. Normal usage (which I would expect to be regular) in the meantime will apply the intended ac voltages. In the case of all of our designs, every electrolytic capacitor is always "biased on" with charge. Further reading on this subject can be found on the 'net authored by J L Hood who was an "authority" on the use of electrolytic capacitors in audio. Another "authority" on capacitors in audio, and much under-sung is Walt Jung who used to be an Analog Devices development engineer.

All our products are safe to power up without an output (or even an input) being connected. I once had an Amstrad IC2000 Mk.4 amplifier (circa 1972) on which the speakers had to be connected or the amp would burn-out. A friend had the receiver version and disconnected the speakers whilst switched on, which resulted in black smoke from the back of the unit. Obviously this was because of instability, and Mr Sugar is now in the House of Lords - God help us!

Came across the following snippet while pursuing other things - as one does 

http://www.acoustic-dimension.com/blackgate/techEcap.htm

The Idling Process If a Black Gate capacitor mounted on an electronic device is actuated, a signal current flows into it and the electrodes are gradually activated, reducing non-linear distortion and phase distortion substantially while improving the efficiency of power transfer efficiency. The time required for this process varies widely with the capacity, voltage and signal level a total of about 30 hours is the standard level. Once this process of idling is completed. The effect continues as long as the capacitor Is kept at the same place and the operating environment does not undergo a substantial change The effect of idling has been proved with all types of electronic equipment - analogue, digital, high-frequency and other devices. It must be noted that idling is different from ageing, which applies a direct current voltage without giving signals.

Goes some way to explaining the behaviour I have observed particularly with the Marantz CDPs I compared in another thread that both use a significant number of Blackgate caps, but also by extension to other electrolytics and explains, to me at least, why well burned in units such as a Solo or Reflex will take some days to arrive in full song after being powered off.

I have observed this behaviour in products from other manufacturers also and it suggests that passing a signal will speed the re-settling time to stable performance.

This was very useful information. A lot of stuff I had no knowledge about. I now also know why it´s good to keep the equipment powered on. Thanks.