XPost: rec.audio.pro, alt.audio.pro.live-sound
From: kludge@panix.com
liquidator wrote:
>"Phil Allison" wrote in message
>news:8150qeFrjeU1@mid.individual.net...
>>
>> "liquidator"
>>
>>> He's also wrong. all he needs to do is add transformers. Done it a
>>> hundred times.
>>
>> ** Really ?? Not with domestic amps like Technics.
>>
>> Such amps are never intended to drive 70 volt line ( step up) transformers
>> are very likely to be damaged by so doing.
>>
>> The issue is core saturation at low frequencies - hard to avoid
>> completely and deadly on anything but the most rugged amplifiers.
>
>Interesting. Have done it dozens of times. Tend not to use Technics, and do
>use quality transformers.
Wow. I had no idea Phil was still around! But yes, I have done it plenty
of times, even using some pretty shoddy amps based on STK modules (like
those Rane 1U power amps) and never had a problem. But I could see there
being an issue with undersized output transformers if you aren't filtering
the input of the amp.
I have generally designed 70v systems for high quality audio to have a
-3 dB point around 20 Hz, which requires pretty huge transformers. I
strongly recommend the Tannoy transformers (which are actually made by
some company in Canada for them) but the cheap Edcors aren't bad if you
buy their "extended low frequency" series. For background music systems
there's no need to have anything that extreme.
>What about a coupling capacitor or would that be a bad idea?
Bad idea if you put it after the amp, because the amp does not like driving
capacitive loads. But put a filter before the amp so the amp never puts
low frequencies into the system, and you'll be fine. Oh yes, and PLEASE
use a fuse on the input to the step-up. This will save you some day when
someone shorts out the wiring.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
|
