Troubleshooting an humming WOPL : need help!

[Gepetto]

Ok, I think I have enough to do here : ) thanks a lot again for your very valuable advises.

Do you - by chance - know a little about PL 2000 pre-amp?
If so, I could come up with a couple of question later this week

I am sure we can muddle through on the PL2000 questions...

 

[Coldsmoke]

Me again guys,

I followed the whole process but the shhhhh is still here (I could'nt mesure anything with the scope but noise)

 

[Gepetto]

Me again guys,

I followed the whole process but the shhhhh is still here (I could'nt mesure anything with the scope but noise)

I thought your reported a 50Hz hum issue?

 

[Coldsmoke]

I thought your reported a 50Hz hum issue?

It was an issue a few mmonths back, but, having changed the grounding scheme as Laatsch (and now you) told me, I hadn't this problem anymore.
Despite this improvement, I could here a noise at a low amplitude but still audible : Laatsch proposed me then to get rid of the switching noise from the BR by installing the caps.
Unfortunately, I can still ear the shhh I mentionned a few months back :/

 

[Gepetto]

It was an issue a few mmonths back, but, having changed the grounding scheme as Laatsch (and now you) told me, I hadn't this problem anymore.
Despite this improvement, I could here a noise at a low amplitude but still audible : Laatsch proposed me then to get rid of the switching noise from the BR by installing the caps.
Unfortunately, I can still ear the shhh I mentionned a few months back :/

Both channels grounded to the input of the amp?

 

[orange]

You know, I had a humming amp once.

Turned out to be part of one side of Tubular Bells.

 

[Coldsmoke]

You know, I had a humming amp once.

Turned out to be part of one side of Tubular Bells.

ah ah, I'm not too much into Mike Oldfield, it has to come from somewhere else

 

[orange]

Well, if it made la la noises for 3 minutes, it would be the Bee Gees.

 

[Coldsmoke]

Both channels grounded to the input of the amp?

Yes, they are supposed to be, BUT : big improvement the noise alsmost disapears with no input plugged (just a 50Hz hum that I can ear from the left channel and a slight white noise from the right if I stick my ear to the speakers).

 

[Gepetto]

Yes, they are supposed to be, BUT : big improvement the noise alsmost disapears with no input plugged (just a 50Hz hum that I can ear from the left channel and a slight white noise from the right if I stick my ear to the speakers).

Sounds like time to work on your preamp

 

[Gepetto]

Yes, they are supposed to be, BUT : big improvement the noise alsmost disapears with no input plugged (just a 50Hz hum that I can ear from the left channel and a slight white noise from the right if I stick my ear to the speakers).

Your left channel hum is the vestigial pickup from the AC wiring running over to that thermo switch.

 

[gadget73]

So no hissing noise if you unhook the RCA input cables? If so, definitely agree that the preamp needs some work.

 

[Gepetto]

So no hissing noise if you unhook the RCA input cables? If so, definitely agree that the preamp needs some work.

Hiss usually is preamp in origin...

 

[Coldsmoke]

Your left channel hum is the vestigial pickup from the AC wiring running over to that thermo switch.

I am not sure to understand your point here? Is there something I could do?

 

[Gepetto]

I am not sure to understand your point here? Is there something I could do?

It means if you want your amp totally quiet, the recommendation is to re-route that AC wiring along the top edge of the chassis and a right hand dogleg turn down to the thermo switch.

Isolating the AC wiring from your audio signals is always a good thing to do to reduce noise.

Right now, that AC wiring runs smack dab through the center of the left channel wiring.

The left channel on Phase Linear amps is also noisier than the right channel because of proximity to the AC transformer and associated rectification circuitry.

 

[Gepetto]

I am not sure to understand your point here? Is there something I could do?

Look at some of Lee's build threads where he has documented the rerouting of AC wiring in the PL amps to optimize the clearance to the signal wiring. PL routed wiring that way for production efficiency, not because it was the optimum way to route it technically.

 

[Coldsmoke]

Look at some of Lee's build threads where he has documented the rerouting of AC wiring in the PL amps to optimize the clearance to the signal wiring. PL routed wiring that way for production efficiency, not because it was the optimum way to route it technically.

I guess Lee is Laatsch?

BTW, am I supposed to expect a totally 0 noise from the speakers at a certain point or is there some kind of noise floor that is not possible to pass...?

 

[laatsch55]

Yes. Lee is Lee Laatsch, AKA Laatsch55, AKA Sasquatch, AKA Wookie,

I have a very efficient set of Kornerhorns, since the introduction of Joe's driver boards and the improved grounding scheme and rewiring keeping the AC from the low level signals the noise floor is in the basement. I can not hear ANY noise with the ear up to the midhorns....

 

[Coldsmoke]

Yes. Lee is Lee Laatsch, AKA Laatsch55, AKA Sasquatch, AKA Wookie,

I have a very efficient set of Kornerhorns, since the introduction of Joe's driver boards and the improved grounding scheme and rewiring keeping the AC from the low level signals the noise floor is in the basement. I can not hear ANY noise with the ear up to the midhorns....

Lucky you Lee / Laatsch / Sasquatch / Wookie !

The only 91dB of my 4311 are allready too much at the moment :/

 

[laatsch55]

You should not hear anything out of those 4311's.

Have you shorted the inputs on the 400 to isolate pre-amp noise from amp noise?