700 RCA Grounding

mattoe

mattoe

Journeyman
Joined
Oct 2, 2016
Messages
68
Location
Hamilton Ont Canada
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Don't let any smoke out !
Just A dumb question , If followed to the letter Joe's star grounding scheme for the WOPL 700B would have *NO* continuity from the RCA
connector shield to the chassis ? That correct ?
 
so the original white wire off the copper strip that the rca jacks go thru is to be be tied to the gounding point on the left control board lug that comes off the copper buss ??
 
No wiring except for the signal and shields from the RCA's. Signal to the input of the driver PCB, shields to the respective input grounds of the driver PCB. For Joe's board that I believe is 1L/1R for signal, 2L/2R for shield ground. That's assuming you're running coax from the RCA's - With a twisted pair setup it's the same except no coax shields (one wire to each "hot" on the RCA, the other to each RCA's ground lug to terminate at the driver PCB).
 
So, The original PL700 had a connection or continuity to the chassis from the RCA's? ....... If I take my multimeter from the RCA shield / connector on the outside back of the amp to a bolt on the transformer on my WOPL I have continuity .... and a hum/ buzz oddly enough... That being the situation , is there still a connection or continuity somewhere on the driver board that would potentially give me this result ? Has anyone measured resistance from the RCA shield to case ground ? This should indicate or measure *open ckt* ???
 
Ahh.. that.. .. yes you will see "continuity" between the RCA grounds and the chassis because of the single ground run going between the cap/star ground and the chassis by way of the left upper screw and retaining sleeve. It just won't have more than one ground connection TO the chassis. At least it should NOT, which to me is the most important point here to convey. That is also why grounding the chassis via a 3 prong plug is not recommended, as for THAT you WILL have two separate chassis ground connections - and likely a ground loop as a result.
 
Get rid of the copper strip. Use Isolators (plastic shoulder washers or fiber) on both inside and outside of the RCA jacks.
 
WOPL Sniffer said:
It will read open or near it. Going to measure it right now.
Click to expand...

Nah.. it will read through the driver PCB, which is grounded by way of the star ground - which in turn is connected to the single point on the chassis.

Made the mistake ONCE of thinking I shouldn't have near or close to zero ohms RCA ground to chassis.. because the dang amp before I converted actually didn't have the connection from star ground to the chassis. I'm sure Phase Linear Fanatic here will attest to that one.
 
Yes Jer, you are correct. Grounded thorough the Control board.

Mattoe, there are hundreds of pics here in the wopl build section of how to wire it.


IMG_5995rs (2208 x 1656).jpg
 
Yup, 3 ohms is exactly what I measure.... Any hints on isolating the hum? .. With no RCA's connected got's the hum ..... Monster power conditioner, no better... flip the polarity of the power plug/ and or directly to the wall ..... no better.... switch house receptacles.. nope..... Turn off every other breaker in the house .. still no better
I Have a bone stock 400 that seems to be the quieter of the 2..... arg.....
 
Did you use fiber washers and heat shrink on the transformer bolts? Also, I have a pair of infinity speakers that hum when hooked up to the wopl but my other 2 pairs of GOOD speakers do not hum
 
[QUOTE .. With no RCA's connected got's the hum ...

Yep it will hum with no RCA's sometimes, how about with a pre hooked up?
 
Very minor to no audible difference with the RCA's connected or disconnected...
Actually, the buzz / hum seems more prevalent on the right channel, and more static
on the left....
 
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