Hello,
I have assembled two K8060 amps in one casing. I used two toroid amps 120VA/2 x 25V from Amplimo. Everything works nicely but when no input is connected, i have a slight pink noise coming from the speakers. When input is connected, i have an little humming.
I have set the bias for both amps at exactly 10.1mV. I also fitted the K4700 speaker protection.
Should i set the bias a bit higher?
Could this be a ground problem? (I think it’s the input RCA making contact to casing, can that be?)
Can it be that both toroids are inverted? I mean, ph/N?
Hard to tell if it is normal or not, without exact figures.
The hum might be caused by a hum loop, check your wiring hookup.
Noise might be related to grounding of the chassis. Did you ground the chassis, if yes, how?
12VDC? We are sure you mean 12mV?
Class A output will be slightly higher but unit will run much hotter. Cannot say how much power will be delivered in class A before switching to AB, but it will not make much of a difference.
Yes I mean 12mVDC . But I didn’t change it…Left both at 10,1mVDC
I have solved the humming and pink noise.
There was no grounding whatsoever so that was not the problem…
I changed 4 things:
1: Ph/N of toroids were inverted. Changed this because the K4700 shorts the ground, so that can give some noise.
2: fitted bigger caps on the K8060’s(4700uF/63V)
3: Fitted a DC Trap in the mains with 2 x 10.000uF caps and 8 fast(30ms) diodes 6A/1000V. That improved the quality of sound singnificantly and it costs virtually nothing…(about 12 euro’s in parts, eliminates all DC current going in to toroids)
4: Re-fitted wiring so no mains and signal lines run next to eachother
. But I didn’t change it…Left both at 10,1mVDC
