Some specifications about Cyber 30 (2A3 version, no specification for 300B yet)
CONTROL FUNCTIONS: Volume, Mode Switch(normal/headphone), Power On/Off
POWER OUTPUT: 3.5W x2 RMS 1kHz
TOTAL HARMONIC DISTORTION: less than 1%( 2 watt, 1kHz )
FREQUENCY RESPONSE: ( -3dB points at 2 watt ) 6Hz - 35kHz
INPUT SENSITIVITY: 600mV
INPUT IMPEDANCE: 100k ohms
OUTPUT IMPEDANCE: 4,8 ohms. User selectable.
SIGNAL/NOISE: 90dB
CONSUMPTION: 86 watt
INPUT INTERFACES: 1 group (RCA) - (on the rear panel )
INPUT INTERFACES: speaker terminals - ( on the rear panel ) and
headphone jack - ( on the front panel )
OVERALL NEGATIVE FEEDBACK: None
VACUUM TUBE: 2A3 x 2,ECC83 x1
DIMENSIONS: 320 ( L ) x 260 ( W ) x 150( H ) mm
WEIGHT:15kg ( packed )
> 1. Can the user switch between 2A3 and 300B configurations easily?
--- Just need to rewire heater and high voltage supply, change the cathode resistors. (templeboy: Very easy to do for DIYers)
> 2. Can you provide an internal parts list (caps, resistors, diodes, etc)?
--- RS Caps(U.K. brand, made in Italy), Dahongpao Military Resistors (Chinese made, used in aerospace project) , solid-state diodes.
> 3. Can the user specify upgraded internal parts?
--- I'm afraid not and we thought users prefer to do it themselves... (templeboy: again easy for DIYers)
> Could you provide me with information as to how the headphone circuit
is wired in the Cyber 30 (resistor based or transformer based),
--- I'm afraid it's a over-require and could not be published simply.
> what kind of headphone impedance it can drive and what kind of output power it can supply to the headphones?
From 10 ohm to 600 ohm, as well as Cyber-30.
For Cyber20, 1W for 10ohm and 200 ohm headphone , 0.1W(low) or 0.3W(high) for 100 ohm headphone, 0.8W for 300ohm phone and so on.
> Final question: What kind of warranty do the Cyber products carry?
---One year warranty except tubes, which is 90 days as tradition.
> And do warranty claims mean shipping the unit overseas?
Sure.