FAQ
How long does it take to burn in my new icOn preamp?
If you ask me about the icOn’s burn (break) in time I would say: that for my icOn preamps there is no burn-in time. The copper wire and magnetic cores don’t change in short term (within a few years). But a lot of icOn customers stated that they have experienced improvement after approx. 100 hours of music listening. My understanding and experience are that this improvement happens in the listener’s brain and not inside the preamp. The autoformers produce quite a different sound than the resistive passive attenuators or active preamps. Our brain “learns” this new sound experience, and adapts to the complete lack of background noise and distortion, the higher transparency. Some audiophile calls this adaptation as the “burn-in”. I’m an engineer and music lover too but like to stick with the scientific and engineering facts. Maybe I’m wrong with the science, who knows? So as usually – YMMV … your mileage may vary 🙂
I did read a review where a different wall wart was used with the icOn and there was a slight improvement despite the passive sound path. Can I make my icOn even better with a LPS (linear power supply)?
Sorry, but a linear power supply doesn’t improve the sound of an icOn 4PRO. The icOn’s external wall wart power supply doesn’t have a direct connection with the signal path – because that is a passive circuit – and is galvanically separated from the icOn’s inner power supply circuits. The light of the display and the microprocessor’s operations can’t sense any difference between an smps and a linear power supply.
The problem with an smps in general in the audiophile community is the “generalisation”. Yes, 20-30 years ago it was absolutely true that in most cases the linear power supply was better. Today this is simply not true. Today there are amazing high-frequency switching devices, and new circuits which offer better result than a traditional 50-60Hz linear power supply. Audiophiles don’t have proper measuring equipment, A/B testing gears to hear and see the reality. And the “maybe I can hear a difference” bias is based on the outdated knowledge of “self-made experts” without any technical background.
Some facts which are never considered by the power supply “experts”:
1. If the switching frequency is 100 – 1000x higher, filtering and suppressing the noises is much much easier. (50kHz – 1MHz instead of 50 or 60Hz).
2. The noise and EMF from an smps are proportional to the current used. There is a huge difference between an smps of a power amp and the low current smps which I use.
3. Today’s digital audio electronics are full of small smps’, hidden from the audiophiles’ “critical eyes”, embedded on the pcb. They don’t know about them, they have no problem with them. But my “poor” wall wart is very obvious and immediately it is “suspicious”.
There are dozens of other factors which aren’t considered by audiophiles. My absolutely honest opinion: my smps solution isn’t worse than a pure linear power supply.
But I hear my audiophile friends, that some of them prefer something more “substantial” than a small wall wart ps. My new optional icOn power supply (expected around autumn 2022) will be a “hybrid” – like some other very popular audiophile power supplies – combining the best advantages of both the linear and switching power supplies.
What is the input and output impedances of the icOn 4PRO?
– the input impedance of icOn is depending on the power amp input impedance and the actual position of the volume, it’s different for every volume. Smaller the volume – higher the input impedance. For normal listening volumes it is higher than 1 MOhm. At 0 dB volume the input impedance of the icOn is equals with the input impedance of the power amps. For +1, +2, +3 dB it’s a bit smaller, than the power amp input impedance.
– the same is true for the output impedance, but with the opposite correlation. Smaller the volume – smaller the output impedance. With normal listening volumes (-20 dB) it’s only 1/100th of the output impedance of the source + the copper resistance of the Slagle autoformer, which is approx. 70 Ohm.
The good news is that the impedance matching is automatic with an AVC (or TVC) and they produce the best possible impedances both for the sources and the power amp. This is the huge difference comparing to the resistive stepped attenuators and the explanation why the autoformers are a much better choice.
Why does the icOn 4PRO use Autoformers for the volume control?
From 2016 till 2019 I used TVC transformers from SAC Thailand. http://www.sacthailand.com/Transformer_Attenuator.html They were good but not the best. Currently the best magnetic attenuators are the autoformers from Mr. Dave Slagle. They produce much better, more transparent sound and without any colouration. I use the customised Dave Slagle autoformers only. He builds these autoformers only for me based on my specification.