Re: Balanced pre-amps eliminating RF interference.
I think there is a common misconception that balanced audio circuits help
eliminate RF interference. Common mode rejection of typical balanced audio
input circuits quickly falls apart above a few hundred kHz. At typical
radio frequencies, the circuit looks more like a bunch of diodes, detecting
any RF that enters, whether common mode or not.
If there is any improvement, I think it is due to better design and RF
shielding of professional balanced devices, not common mode rejection at
MHz frequencies.
Ellis
On Thu, Jun 19, 2014 at 12:24 PM, Robert Cham <[log in to unmask]> wrote:
> Take a close look at the sine wave distortion of your UPS. Many are not
> sine waves at all. Computers may not care, but analog electronics do.
>
> Responding to another thread, back in the '80s, Straight Wire Audio made a
> balanced phono preamp. It required rewiring your tonearm, but it was a
> godsend for radio stations whose studios were in high RF environments.
>
> Think about it, there are two wires for each channel on a phono pickup.
> One channels low is generally grounded. that;s usually a strap that can
> be removed. Then you can feed it into a balanced mic preamp, and all you
> have to deal with is the RIAA curve.
>
> Bob Cham
>
>
>
> Do people ever use dual-conversion online UPS's for the purpose of
>> power-line isolation for audio equipment?
>>
>> The power is constantly going to the battery and running off the battery
>> being reconverted back to AC. Thus isolating the equipment from any
>> fluctuations from the power mains.
>>
>> It's what I use for my computer room servers, and so far (knock on
>> silicon) I haven't lost a power supply yet.
>>
>> Depending on the size they can produce some heat and noise (from the fans
>> cooling the rectifiers, etc) but if someone's considering rewiring an
>> entire house/studio perhaps an online UPS would work as well for less
>> investment, maybe in a nearby closet, etc.? Not an electrical engineer so
>> can't really compare the power they're outputting to the other options
>> mentioned, but seems like it could be a reasonable alternative if
>> power-line isolation is a serious concern.
>>
>> Arthur Gaer
>> [log in to unmask]
>>
>> Senior Systems Manager
>> Harvard University
>> Department of Mathematics
>> Science Center
>> 1 Oxford Street
>> Cambridge, MA 02138
>>
>>
>> On Jun 19, 2014, at 11:19 AM, Tom Fine <[log in to unmask]>
>> wrote:
>>
>> I'm with Lou about powerline hash. You guys with troubles might want to
>>> swap out some of the "high end" components and see if they are faulty
>>> designs at high prices. In the professional audio world (where good gear
>>> doesn't come all that cheap, as a matter of fact), proper shielding and
>>> grounding are a given and otherwise the gear acquires a bad reputation. A
>>> properly grounded and shielded piece of equipment should reject powerline
>>> and RFI noise completely. I also question whether some "high end" cables
>>> are the problem? I never noticed any technical tests with the "reviews" of
>>> the fancy wires, and manufacturer claims are mostly rooted in hooey rather
>>> than science, with any semblence of scientific proof rarely provided.
>>>
>>> Bottom line, a modern audio system shouldn't need a crazy dedicated
>>> power plant unless there are regular fluctuations in power line frequency
>>> and regular spikes and dips in voltage. I'm not underestimating the
>>> incompetence of power companies, these situations are definitely possible.
>>> It's also possible to have insurmountable hash, for instance in a space
>>> shared with an industrial welding company. But it's not a common problem.
>>>
>>> -- Tom Fine
>>>
>>> ----- Original Message ----- From: "Lou Judson" <[log in to unmask]>
>>> To: <[log in to unmask]>
>>> Sent: Thursday, June 19, 2014 10:10 AM
>>> Subject: Re: [ARSCLIST] Upgrading Audio Systems
>>>
>>>
>>> Ya know, when I sit in my van listening to music, I use the car
>>>> stereo, not the garage hifi. Besides, how can you use the garage stereo
>>>> when it is raining and the windows are up? And if it is raining in your
>>>> garage, close the washer lid.
>>>>
>>>>
>>>> But what would I know. My entire system including computers runs on a
>>>> single outlet, and never a noise I don't want.
>>>> <L>
>>>>
>>>> On Jun 19, 2014, at 7:11 AM, Shai Drori wrote:
>>>>
>>>> You guys are way off. You need to have your repair man make the spin
>>>>> cycle go only counter clock wise in the northern hemisphere. Gheez, do I
>>>>> have to teach you everything?
>>>>> Shai
>>>>> ·(tm)ý¯ÈÍ 19/06/14 1:05 PM, -ÈËÂË Carl Pultz:
>>>>>
>>>>> I've tried fabric softener to enhance liquidity, but I prefer the
>>>>>> real thing - EL-84s. Seriously, I have a home-brew tube amp for a system in
>>>>>> the garage. It's nice to have reference to old-school hifi sound while
>>>>>> having Benchmark/Bryston/Raal-Accuton modernity too. Reinforces what the
>>>>>> guys were saying on the Headroom thread.
>>>>>>
>>>>> >>>>
>>
>>> On 06/18/2014 10:21 PM, Frank Strauss wrote:
>>>>>>
>>>>>>> And with an extension cord snaked to the basement, the computer
>>>>>>>> reaches
>>>>>>>> another dedicated line. In the laundry room. I came to this in
>>>>>>>> stages,
>>>>>>>> having done the single circuit to minimize differences in chassis
>>>>>>>> potential
>>>>>>>> idea for ages. That may be the ticket for tube systems. On my SS
>>>>>>>> gear, this
>>>>>>>> sounds much better, particularly with the computer plug change.
>>>>>>>> Only
>>>>>>>> problem with that is the soundstage gets unstable during the
>>>>>>>> spin-cycle.
>>>>>>>>
>>>>>>>
>>>>>>> ÐHi Carl-Have you thought of trying different detergents?Ð I can't
>>>>>>> play an
>>>>>>> lp during the spin cycle. I'm trying to get my wife to take the
>>>>>>> clothes
>>>>>>> down to the stream and beat them with a rock.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>> --
>>>>> Cheers
>>>>> Shai Drori
>>>>> Timeless Recordings
>>>>> [log in to unmask]
>>>>> ··¯Î"¨
>>>>> ~ÈÝ"¯Â¯È
>>>>> ÓÂÓÁ"ÝÏ~ÈÓ¯ÝÂ"Ó¯"Ý~ÏÝýÂ"ÈÂÝÂÈ"ýÂÝÂÒ¯ËÈÌÝ8-35ÝÓÓÆ
>>>>>
>>>>
>>>>
>> !DSPAM:639,53a33245225291644332558!
>>
>
--
Ellis
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818-846-5525
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