On 10/26/2010 10:58 PM, Jim Thomson wrote:
> Date: Tue, 26 Oct 2010 09:47:55 -0700
> From: Jim Brown<jim@audiosystemsgroup.com>
> Subject: Re: [Amps] construct ferrite "line isolator"
>
> On 10/26/2010 8:22 AM, Jim Thomson wrote:
>> None of my audio rack gear has any Pin 1 problems. It has to be some pretty
>> old audio rack gear to have Pin 1 problems.
> Nope. Most consumer and semi-pro audio and video products, and
> virtually ALL ham and computer products have pin 1 problems at every
> audio input and output. The good news is that most PRO audio mfrs have
> gotten the word, and do not have pin 1 problems.
>
> 73, Jim K9YC
>
> ## By 'audio rack gear' I meant semi pro and pro audio, 19" wide, rack
> mount audio gear.
> You can see all 14 x pieces of audio gear, split between 2 x Hammond steel
> cab's, on the 1st of 4 x pix
> on my qrz.com page. I use another 3 x pieces of 19" gear for the tv / stereo
> upstairs. None of it has Pin 1
> problems.
There is nothing magic about rack mounted gear that makes it more
professional, nor makes if free of pin 1 problems. When Neil Muncy
published his landmark paper exposing the Pin 1 Problem in 1994,
virtually every piece of RACK MOUNTED GEAR in the exhibit hall at that
convention had Pin 1 Problems. Now, 16 years later, it's more like 50%
of that gear. The next AES Convention will be held in San Francisco
next weekend. If you have time, we can walk the show floor together and
I can show you some Pin 1 Problems. :)
> I wouldn't buy any Pro-audio gear with Pin-1 problems. I also made up all my
> own cables..using
> shielded [braided] cables..and neutrik XLR connectors. There is enough room
> inside a XLR connector to install
> 500 pf @ 25V , ceramic bypass caps. Tip to grnd..and ring to grnd...and both
> ends of each cable. I matched
> em all up with my LCR meter before installing. No ferrite used anywhere,
> Zero RFI problems.
RF suppression and Pin 1 Problems are DIFFERENT. You can put RF
bypassing on inputs and outputs, but if they have Pin 1 Problems, they
will detect RF and amplify it.
> The
> XLR inputs of all the rack gear have built in RFI suppression anyway. All
> the Aphex gear also has RFI
> suppression on the 120 vac inputs.
I can show you Aphex products with SCREAMING Pin 1 Problems -- I own
some, and they are rack mounted! Their line level inputs hit the
threshold of limiting on detected RF from about 10 MHz to above 70
MHz. I love some Aphex products, including their Compellor and their
superb peak limiter, and I've both sold and specified a lot of them. But
some Aphex products DO have Pin 1 Problems.
> All the gear plugs into the same 120 vac, rack mounted power strips,the
> power strips are rack mounted to the rear of the 2 x cabinets, daisy chained
> together. That power bar mess
> all plugs into one big PI filter, then into the 120 vac.
That's nice, but it does not solve Pin 1 Problems.
73, Jim Brown K9YC
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