HK990 ELECTRICAL PROBLEM I Have purchased a new HK990 stereo amplifer. It sounds gr

[tiomiguel]

I Have purchased a new HK990 stereo amplifer. It sounds great, but I have a problem: When listening DIGITAL INPUTS, when SWITCHING ON/OFF any electric/electronic device at home, sound interrupts for a short time. So, I know when my refrigerator goes on and off, lights etc.

Electric installation in my house is new, and in perfect status.

I have proved everything. I have a HD990 and the problem is the same using HRS-LINK, coaxial or optical…

It is a pity, because HK990 is a outstanding machines but… My HK980 does not have any problem with the INPUTS.

HK990 is attached to a pair of TANNOY DC6T towers biwired. I have proved lots of variations: Perhaps interrupts could be a bad ground status. TANNOY have five connections; last is for groundig speaker chassis, so, I connected them to GROUND in amplifer, but did not solve the problem. For being sure to have OPTIMUM ground, I linked GROUND amp to GROUND in electrical installation (green wire in EU), but problem did not solve.

¿What should I have to do? Perhaps it is a bug of the amp, and a firmware update would correct this.

[DF96]

My guess is that the mains filter in the amp is faulty or has been omitted. The power supply is letting spikes through, and the DAC is temporarily losing lock on the digital data stream.

It seems to be surprisingly common for Chinese-made electronics to have the mains filter components simply omitted from the PCB for final production. That is, capacitors omitted and inductors replaced by wire links (thus proving that it is deliberate and not just a mistake).

Take it back and complain!

[tiomiguel]

I don not believe harman kardon has done this big mistake in his flagship amp, but, if this is true, there is anyway to avoid the lost lock. May be with external filtering, putting the amp behind a ups, filter... ¿any solution?

[DF96]

Why should H-K be any better than other big-name brands? They all have their stuff made in China, and I doubt if they check each item.

You could add an external mains filter, but this should not be necessary if the amp is well-designed and well-constructed.

[Leon08]

I had a similar problem with my DIY preamp.Some digital circuits react very strange if you switch on or off heavy loads such as transformers or electromotors.The problem is not the mains filter, but the grounding and layout.Mains filter can help also if there is no one.