HiFi Subjectivist ¦ Audio Forum ¦ NVA User Group

Very strange. That a DAC can blow an amp when no P50 is there to limit the input voltage, I can follow. But the volume resistor ought to protect the power amps.

If it is one of the 2 digital sources, he could try unplugging one or the other from the DAC see if the problem is associated with a specific device.

I see that the Sotm uses only USB output - these connections are known to be electrically 'noisy'. He could try putting an Audioquest Jitterbug filter in the signal chain.

I don't see either how digital 'noise', even if if crossed into the analogue output signal, could blow an amp.

It is very possible for the DAC problem to bypass the preamp. The pre-amp protects if it is not volume dependent as seems to be happening, but the higher the volume goes the more open it becomes to pass something nasty, and this problem only happens with the volume up.

Dr Bunsen Honeydew wrote: ↑Sun Dec 02, 2018 11:14 pm The amps are working perfectly at low to medium volume, as soon as he gives it some welly the amps are going pop. Four times now and two different sets of amplifiers A100s and A80s.

Could the output voltage of his DAC be too high?

Fretless wrote: ↑Sun Dec 02, 2018 11:26 pm I don't see either how digital 'noise', even if if crossed into the analogue output signal, could blow an amp.

I can assure it has and does happen, but mostly as you said if the volume is a digital control in the DAC, those have given spurious signals or pulses that have taken out amps and not just NVA. It is why my recommendation is always use a pre-amp even if a simple pot passive, BUT there are many NVA systems out there working perfectly well with digital volume control outputs, it seems to only happen under a fault condition.

We expect only to get analogue signals out of a DAC, but faulty, even intermittent fault conditions can throw something nasty out, even a DC pulse, but mostly what resembles square waves.

CN211276 wrote: ↑Sun Dec 02, 2018 11:30 pm

Dr Bunsen Honeydew wrote: ↑Sun Dec 02, 2018 11:14 pm The amps are working perfectly at low to medium volume, as soon as he gives it some welly the amps are going pop. Four times now and two different sets of amplifiers A100s and A80s.

Could the output voltage of his DAC be too high?

The Onyx is fixed output - 2v.

Output impedance for the Onyx is 100 Ohm, voltage is fixed.

XLR output will be higher than RCA, I think.

The variable output Jade in the same series outputs up to 3V on RCA and 6V with XLR.

CN211276 wrote: ↑Sun Dec 02, 2018 11:30 pm

Dr Bunsen Honeydew wrote: ↑Sun Dec 02, 2018 11:14 pm The amps are working perfectly at low to medium volume, as soon as he gives it some welly the amps are going pop. Four times now and two different sets of amplifiers A100s and A80s.

Could the output voltage of his DAC be too high?

As said here others are using the Metrum with no problem.

Metrum's chief, Cees Ruijtenberg, is very 'hands on' and might be interested to help with this.

Metrum can be contacted at: info@metrumacoustics.com

I've found them to be very quick and friendly with queries.

The Metrum is being sent back for checking.