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Old October 25th 19, 09:49 AM posted to
Phil Allison[_4_]
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Default overvoltage on audio circuits

gareth magennis wrote:


> I have here a batch of SSL channel strips rack mounted.
> The regulated PSU that came with them is marked +-18v but actually produces +- 21v with a 1A quick test load, with the adustment pots at minimum as they arrived, .
> (I suspect these are 24v based supplies - they are modular linear ones made in USA i think, 2 x "18v" and a 48v phantom)
> It seems the channel strips have been running with this supply at 21v for a long time now.
> What could be the possible detrimental effects?

** Very few, likely there is PCB level filtering of the DC supply via resistor and electros.

Many Soundcraft analogue desks had 68ohm resistors and 100uF caps fitted in each rail feed - so dropped a volt or two in order to remove residual noise from the external PSU.

Op-amps like the NE5532 are happier with 16 volt rails.

...... Phil

> I have only had a quick peek inside the first one of eight, and noticed a bulging capacitor on the SSL dynamics card.
> I would not power any of them up with this supply at present.
> Cheers,
> Gareth.