[ale] OT: One for the EE's, Amp noise?

[Robert L. Harris]

Nice description.  I'll find a set of RCA's I can cut open.


On Sat, Aug 10, 2013 at 5:54 PM, Alex Carver <agcarver+ale at acarver.net>wrote:

> No, no shorting, just disconnect the ground on each RCA from one side of
> the cable.  You want to keep the shield working but you don't want current
> to flow on the shield.  So choose only one side (could be the Yamaha or the
> Gemini but not both) and cut the shield on each audio wire (left/white and
> right/red) at that end.  Leave everything else intact.
>
> How about some good old fashioned ACII art? :)  I'm going to pick the
> Gemini side, but it works either way:
>
> Yamaha                                           Gemini
> RCA-Left Audio Center pin ----------------------- RCA-L Center pin
> RCA-Left Shield ----------------------------x x- RCA-L Shield
>
> RCA-Right Audio Center pin ---------------------- RCA-R Center pin
> RCA-Right Shield ----------------------------x x- RCA-R Shield
>
>
> Cut the shield (and only the shield) at the -x x- marks.  Verify that you
> have no electrical connection from the shield on one end of the cable to
> the other.  Leave everything else alone.  If the hum goes away you have a
> ground loop.
>
>
>
> On 8/10/2013 15:58, Robert L. Harris wrote:
>
>> So effectively short the 2 center pins to 1 (as if going mono) and then
>> cut
>> one of the grounds out completely?
>>
>>
>>
>>
>> On Sat, Aug 10, 2013 at 4:41 PM, Alex Carver <agcarver+ale at acarver.net>**
>> wrote:
>>
>>  On 8/10/2013 14:55, Robert L. Harris wrote:
>>>
>>>  So I have a Yamaha RX-A1010 receiver.  It's been great so far but not
>>>> enough volume when we want to have a party, etc.  So I picked up an
>>>> external Amp by Gemini.
>>>>
>>>> When I plug the pre-out from the Yamaha into the Gemini I get a low hum
>>>> that almost sounds like static.  If I plug my DVD player or Phone into
>>>> the
>>>> Gemini using an adapter ( 1/8th -> RCA ) the noise goes away, crisp
>>>> clear
>>>> sound.  If I use the Yamaha speaker out no noise either.  It seems to
>>>> only
>>>> be from the Yamaha to the Gemini.  I can use either of the pre-out (
>>>> front
>>>> or surrount ) or the headphone jack on the front and the sound persists.
>>>>
>>>> Any thoughts on how I can clear it up?  The yamaha is out of warranty (
>>>> 2.5yrs old) and a great unit but just too quiet on occasion.
>>>>
>>>>
>>> Without actually hearing the sound I'm inclined to believe you have a
>>> ground loop.  You can test for a ground loop issue by making an RCA patch
>>> cable that connects only the center pins together and leaves the ground
>>> on
>>> one end unconnected.  If the sound goes away it's a ground loop and you
>>> just either use that patch cable with the lifted ground or get a
>>> transformer-based ground loop isolator.
>>>
>>> It won't happen on your phone because the phone isn't grounded.  The DVD
>>> player may have isolation in it (or it may not be grounded at all,
>>> either,
>>> if it's got a two-prong plug).
>>>
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>>>
>>
>>
>>
>>
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Robert L. Harris

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