[Amps] construct ferrite "line isolator"

[Jim Brown]

On 10/26/2010 10:58 PM, Jim Thomson wrote:
> Date: Tue, 26 Oct 2010 09:47:55 -0700
> From: Jim Brown<jim at 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