[sdiy] A bit OT: mains conditioning.

[Buck Buchanan]

At 05:22 PM 3/1/2004 +0000, you wrote:

>My mains here is real poor, and im looking for a solution.  I dont know if
>its spikes or brownouts.  I used to get problems with things like my adsl
>router rebooting when the kettle is turned on, etc. but this has calmed down
>with a new 'wall wart' psu for the router, but my dac (hi fi style) is still
>suffering similarly.

>#Constant voltage transformer.
>harder for me to obtain.  looks like a good solution, but noisey?

For what it's worth....

The power where I live is real poor too with recorded voltages down to 98 
volts in the wintertime when I and my neighbors are running space heaters 
or whatever.  Some of my test gear was having problems with that. In 
researching, I found that 100V input seemed the bare minimum for many UPS 
jobs plus I was unsure if a UPS would introduce switching noise into my 
test gear.

So I got the Sola constant voltage transformer rig sold by C&H 
(1-800-325-9465) stock # STR9900 - brand new for only $225.00.  I'm sure it 
originally cost quite a bit more.  It's a a 500W model nicely enclosed 
rackmount thing with meters for voltage and current.  Now, regardless of 
what goes in, a relatively clean 122VAC comes out (~85V - 140V input 
voltage range).  I spent a decent amount of time testing it before I was 
willing to plug my gear into it but so far have been happy with it.

Some things to note:

Yes, it's acoustically noisy.  Much louder than a regular transformer.

It does NOT isolate your load.

It pulls an amp or so just sitting there with no load.

Its output waveform is cleaner when it's loaded to approx 30% or more of 
it's rated power but even unloaded, its output was closer to a sine than 
what was coming out of the wall (at my house at least).  Worst case 
(unloaded) it's harmonic spectrum was roughly comparable to what came out 
of the wall: a little better close in (<~500Hz), a tiny bit worse in the 
middle, and notably better further out (>~3KHz).  With load, all this improves.

Mine at least, did NOT like to see a surge suppressor on its output 
(Trip-Lite Isobar).  It gave it little ripples/ringing on the 
waveform.  Not sure what surge suppression inside your equipment does to 
it.  Not a big deal either way (I think) as I'm sure that's filtered by 
your gear's power supply.

Of most concern to me is that it does a quick spike or voltage overshoot 
when you initially turn it on.  Unloaded (worst case), mine peaked at 
~165VRMS for about 5 cycles before before settling down to ~120VAC.  The 
more load, the less overshoot and at full capacity (my 475W heat gun), 
there was no overshoot.   I don't know how serious a problem this is but I 
have been observing a power-up sequence to keep my gear from seeing 
this.  Any opinions out there on what danger a surge like this presents to 
test equipment/synth gear?

I'm hot sure how it would integrate into a system with UPS systems, 
isolation transformers, etc., but I wouldn't *assume* it works well in 
these conditions w/o testing it.  Unfortunately, I didn't test its 
load/no-load transient response but I don't get the impression it's all 
that good.  Running your blender off it while running audio gear probably 
isn't the best idea.

Don't know if that will help you any but there it is.

Buck