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API PSU clipping converters?
Old 21st July 2015
  #1
Gear Maniac
 

API PSU clipping converters?

So I have an API 500V (10 slot 500 series chassis), which is connected to my HEDD converters.

About half the time, whenever I turn on the API PSU for the chassis, the HEDD clips. It's just in one channel, but never the same one, and like I said, it doesn't happen every time. My monitors aren't on at this point, so I haven't heard anything, but the red LED is lit on the HEDD.

I'm using the official API PSU, and all the modules are in bypass when the chassis is turned on. This happens regardless of which modules are connected to the HEDD.

Is this a power issue? Is it normal?
Old 22nd July 2015
  #2
is it normal to have a power surge when you turn on gear? Yes. If you want to avoid it, install variacs.
Old 22nd July 2015
  #3
Gear Maniac
 

Got it. Does this surge risk damaging the equipment? I generally have fairly reliable power.
Old 22nd July 2015
  #4
Gear Maniac
 

Bump.
Old 22nd July 2015
  #5
no...short moments of insufficient power are no problem, most gear is designed to work within +-10% of its nominal voltage....but make sure there is some kind of protection against hv spikes
Old 23rd July 2015
  #6
Lives for gear
 
AllBread's Avatar
 

Turning gear on or off often causes a spike downstream which is why you always turn your monitors on last and off first as they are the only things that could be damaged.
Old 24th July 2015
  #7
Lives for gear
 

Hi
Practically all gear will produce an output 'thump' of some description when powered up (and down) unless the designers deliberately put 'mute' circuitry in, either a relay which disconnects the output or other devices that 'clamp' the surge.
OP amps and 'discrete' amplifier stages do not operate as amplifiers which are 'properly under control' until the supply voltage exceeds about 4 Volts. Once above this threshold they can then behave as amplifiers and would tend not to have any further 'issues' from 4 Volts up to their normal operating voltage.
Of course in normal use the supply goes from nothing (off) to 'on' within half a second or thereabouts so you just get a single 'blip' of noise during this phase.
You could consider this to be a single bass 'thump' of signal at full level which of course is not usually damaging to other gear in the chain except the speakers and your ears.
This activity goes on in ALL gear whether you are aware of it or not so don't worry excessively.
Using a Variac to try and overcome this 'noise' won't work reliably as different circuits would power up and transition from 'off' to 'linear' at different voltages depending on specific design details.
Matt S
Old 25th July 2015
  #8
So, in short, my response at post 2 was right? :-D
Quote:
Originally Posted by Matt Syson View Post
Hi
Practically all gear will produce an output 'thump' of some description when powered up (and down) unless the designers deliberately put 'mute' circuitry in, either a relay which disconnects the output or other devices that 'clamp' the surge.
OP amps and 'discrete' amplifier stages do not operate as amplifiers which are 'properly under control' until the supply voltage exceeds about 4 Volts. Once above this threshold they can then behave as amplifiers and would tend not to have any further 'issues' from 4 Volts up to their normal operating voltage.
Of course in normal use the supply goes from nothing (off) to 'on' within half a second or thereabouts so you just get a single 'blip' of noise during this phase.
You could consider this to be a single bass 'thump' of signal at full level which of course is not usually damaging to other gear in the chain except the speakers and your ears.
This activity goes on in ALL gear whether you are aware of it or not so don't worry excessively.
Using a Variac to try and overcome this 'noise' won't work reliably as different circuits would power up and transition from 'off' to 'linear' at different voltages depending on specific design details.
Matt S
Old 25th July 2015
  #9
Lives for gear
 

Hi
Yes it is normal, and no variacs won't help.
Matt S
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