Frequently asked questions

USB

Why are there 4 USB ports on the ISO-HUB & how can they be used?


As can be seen from the picture there are 4 isolated USB ports on the ISO-HUB. These USB ports provide isolated & reformatted USB signals. Any USB audio device can be connected into any of the ports. Other USB devices may be USB devices holding music files, USB sticks or USB SSDs or HDDs. Playing back audio files from these storage devices plugged into the isolated & cleaned USB ports provides better sound quality than the same files on computer HDD, SSD or USB sticks. For any plugged in USB devices that require 5V USB power this power can be injected into the rightmost USB port. See FAQ question "Is 5V power on the USB ports?"




Why is USB isolation needed - is battery/supercap power not low noise?


I once thought that battery power isolated my Ciunas audio devices from any electrical noise intrusion. I was wrong. When I tried the Uptone Intona Regen, the first USB high speed isolator, I could hear a definite audible improvement. It turns out that the USB connection is another conduit for electrical noise intrusion.

Battery power breaks the ground loop pathway that often exists between computer & attached audio device which can be a conduit for electrical noise that affects sensitive audio devices.

The USB data lines are more important to clean/regenerate for best audio quality.




Why is USB reforming needed after USB isolation ?


All isolation devices add timing variations in the signals being blocked - this is called jitter. USB jitter seems to be audible & reforming/regeneration of the USB signal results in better sound.




What is the benefit of battery/supercapacitor power


Low noise & highly stable power is supplied by batteries/supercapacitors which is exactly what is required for optimal performance of all audio devices. High capacity super capacitors, which I now use in all my audio devices, are slightly faster at current delivery than LiFePO4 batteries that I previously used. This seems to translate into a sound with more bite.





Power

Is 5V power available on the 4 USB ports?


5V power can be injected into the rightmost USB port which then becomes available on the 3 other USB ports. This allows the user to control the quality & current capability of this power, 500mA, 1Amp, 2Amps, etc. A USB cable for this power injection like this is needed: Available here or here A suitable 5V PS with 2.1mm plug can be inserted into this socket thus providing 5V power via the USB plug. Does this power injection introduce a 'dirty' ground into the output? I have found that the major noise contributor affecting audio is the noise on the USB signal lines themselves, not the USB 5V or ground.




What are the advantages of battery (now supercapacitor) power?


  • Batteries/supercaps are a stable, low noise source of power and aren’t sources of leakage currents or suffer from ground loops as mains rectified power can. This cuts out one source of electrical noise that can plague audio systems.
  • Some people state that batteries are noisy under load but this criticism is based on older sealed lead acid (SLA) battery technology where the chemical reaction needed to produce current is noisy. Modern battery technology, such as LiFePO4, which are used in all my products, is ultra silent under load.
  • The advantage that DIRECT battery/supercao power has over voltage regulated power is it's noise stability. Almost all voltage regulators use feedback to maintain constant voltage output. Feedback systems are prone to noise generation when current requirements vary, particularly if they vary rapidly as is the case with current demands of digital devices integrated circuits.
  • Direct battery/suprcap power is optimal when low impedance is employed. This ensures low & stable noise throughout a wide frequency range - from very low frequency to very high frequencies




What about the problem of battery charging?


The charging scheme uses isolated chargers which continually trickle charge the batteries. This allows the user to experience all the sonic benefits of batteries without any of the concerns about charging - it is plug & forget. There is no audible downside from this charging arrangement.




Are these batteries safe?


Unlike other Lithium Ion batteries these batteries use a different, stable formulation (Lithium Ferrous Phosphate, LiFePO4) which doesn't go on fire due to overcharging or shorting.




How do batteries compare to supercapacitors?


Supercapacitors are capable of delivering very high currents at low noise but they have some drawbacks. The main one is that they are found mostly in 2.5 voltage versions. To output 3.3V, two supercapacitors in series are required plus balancing circuitry & usually a voltage regulator is used on the output. Our experience is that balancing circuits & voltage regulators are inferior sounding compared to direct power so we avoid using voltage regulators on the output of the supercaps & sorted the balancing issue.




What about the chemical noise of batteries?


Modrn battery chemistry is far superior to lead acid (SLA) batteries where chemical reaction noise was an issue when a significant current was being drawn by the load. The design of these liFePo4 batteries use nano particles as anode which means that their reactive surface area is far greater than a lead plate in an SLA. This results in an internal impedance of 6mOhm (lower than almost all capacitors) which means an ability to deliver instant current of 120Amps pulse for 10 secs & 50Amp continuous output. When supplying 3.3V at very low currents the load on the battery is minimal & one can safely say that there is immeasureable battery noise. Old NIST paper (1995) on battery chemical noise - before LiFePO4 batteries were available & Ni-Cd is -205dB @ 10KHz http://tf.boulder.nist.gov/general/pdf/1133.pdf





Noise

What noise is USB isolation blocking?


  • There are a number of different sources of noise on the USB connection - the 5V wire, the ground wire & both USB data wires

  • The 5V USB power should never be used for powering sensitive audio devices - it just hasn’t got the stability or low noise requirements for this role - it’s has the opposite characteristics - variable quality, instability & noisy

  • The ground wire has similar variable quality & noise issues dependent on the source

  • Once the above two areas of noise have been dealt with (using battery/supercap power, for instance), the USB data wires are the main source of noise intrusion. This is usually l common mode noise which the differential USB circuitry does not deal with.




What does this noise sound like?


It doesn’t sound of itself - it’s only it’s removal that is noticeable as greater dynamics, better insight into the interplay of the music - in two words more musicality & realism