Autocostuire Fenice 20a & hiss problems
Hi there,
I am using a T-amp driven by a regulated power supply and with a pair of Lowther Acousta's (EX3 drive units) with little or no noise (hiss or hum) from the speakers. These speakers are 96-97dB/w/m efficient so take little driving.
I've bought a Autocostuire Fenice 20a, boxed it, and connected it to the same power supply and Lowther's and used a 50kohm stepped attenuator I had lying around (from Ebay seller KYC111).
The Fenice has a 10u input capacitor, a 100Kohm resistor in parallel with an expected 100Kohm input pot then the standard 2uF input capacitor and R1/R2 gain resistors at 22Kohm each.
The problem I have is one of hiss from the speakers, considerable, obvious and loud at the listening position, it makes the unit un-listenable to.
I shorted the inputs to ground (pre input capacitor) with no effect of the volume of the hiss.
I've cranked the volume up and the hiss lessens very slightly with increase in volume but only slightly.
I've open circuited the inputs (removed the jumpers) and the unit quitens down acceptably.
I've checked the R1/R2 resistors and they are 22Kohm so the gain of the chip is "standard".
The first notch on the volume gives me a audible volume (at the listening position) with three steps or so in being "normal" listening levels.
Unfortunately with SMD components I can't reduce the gain so easily, does anyone have any experience or advice for me please?
Stoat
Hi there,
I am using a T-amp driven by a regulated power supply and with a pair of Lowther Acousta's (EX3 drive units) with little or no noise (hiss or hum) from the speakers. These speakers are 96-97dB/w/m efficient so take little driving.
I've bought a Autocostuire Fenice 20a, boxed it, and connected it to the same power supply and Lowther's and used a 50kohm stepped attenuator I had lying around (from Ebay seller KYC111).
The Fenice has a 10u input capacitor, a 100Kohm resistor in parallel with an expected 100Kohm input pot then the standard 2uF input capacitor and R1/R2 gain resistors at 22Kohm each.
The problem I have is one of hiss from the speakers, considerable, obvious and loud at the listening position, it makes the unit un-listenable to.
I shorted the inputs to ground (pre input capacitor) with no effect of the volume of the hiss.
I've cranked the volume up and the hiss lessens very slightly with increase in volume but only slightly.
I've open circuited the inputs (removed the jumpers) and the unit quitens down acceptably.
I've checked the R1/R2 resistors and they are 22Kohm so the gain of the chip is "standard".
The first notch on the volume gives me a audible volume (at the listening position) with three steps or so in being "normal" listening levels.
Unfortunately with SMD components I can't reduce the gain so easily, does anyone have any experience or advice for me please?
Stoat