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Sam
Reply with quote  #1 

Hi All,

Recently put a Masterpiece and up until recently it has worked fine. Now however there's a periodic (about 180hz) popping sound from the right channel (of course I have tried switching out the tubes). Also, I recently purchased 100dB sensitive speakers and the background noise is very noticeable. 

None of the above occurs when listening with headphones.

Suggestions would be appreciated!

Cheers,

Sam

Tubemon
Reply with quote  #2 
Hi Sam
If you are not getting the same noise from your headphones. Did you check your amps?
Robbert
Reply with quote  #3 
Problems like that should be searched systematic.

First lets change the inputs of your power left goes to right and right goes to left.  Did the problem moved to the other channel?

NO. Problem is in your power amp. Do not know what power amp you have you did not tell yet.

YES. problem in the master piece.

Lets first look at a bad solder connection. tug all connections. Re-solder bad / dull looking ones.

Then lets take a look at the schematic. The only thing not shared between  the headphones and the RCA out put are the caps , 5.1 K resistor and the RCA connectors them self. Take a good look there.

Is the 3.3uF cap all OK? is the resistor of 5.1 K looking good, did it got over heated when soldering?

Perhaps you can rewire the system that the power amp is connected to the headphone connector.

Is the ground to the RCA good?

O yes I almost forgot the relay in the master piece is also in the signal path. Problems there?

I bypassed the relay. The only thing I needed to do now is switch on the amplifiers in sequence. switching on, first master piece and 30 second later the power amp. Switching off first the power amp and after 30 seconds the master piece.

Lets start here and see what you find

Greetz

Robbert
mjhardyman
Reply with quote  #4 
My initial impressions of the Masterpiece were very favorable.  Slowly that faded as one channel was generating additional noise like that of rubbing cloth together.  No pure tone or total dropouts at all.  I finally isolated it to the Masterpiece by swapping tubes, changing amps and eliminating everything else.

I bit the bullet this morning and did surgery by cutting the relay out of the signal path.  I"m very careful about turning equipment on and in what order so excising the relay was not a problem.  The unit has been on for a number hours and not one sign of the noise has crept up. 

In looking at the stats for that particular relay, I've found that is not really designed for audio but it does pass current.  I'd expect to see its kind controlling all kinds of things.
Robbert
Reply with quote  #5 
Thanks for the build mjhardyman.

Glad your masterpiece sounds as intended again.
Achim
Reply with quote  #6 
Hi folks,

am i seeing this incorrectly, as I think the relay is not in the signal path proper, but merely grounds the outputs as long as it has not switched on - after that moment, it is only an open appendix to the signal path.

Therefore no surgery is needed, strictly speaking. I simply pulled it, everything works fine and - surprise, surprise, I don't know why - me also thinks that the sound is improved. Might imagine this, though.

Nevertheless, anyone can test this without much ado.

Interestingly, without the relay there is no more power-off plop that was there before.

Achim
Robbert
Reply with quote  #7 
Yes Achim you are absolutely right. the relay contacts short too the ground.

Relay and the wires to it can become an antenna when not shortened.

My thoughts: perhaps the "antenna" gives some sound degradation. We do not hear the radio signal but the tubes can handle it and could perhaps even over load, close to a person with CB? or a GSM phone very close?

When you first put the masterpiece on, wait 20 seconds and put the rest on you will have no plop.

Having build many pre amps, with the obvios ECC82,  single ended with tube 26, push pull configuration, name it. The masterpiece is my most musical one.

Bruce has a design philosophy which pulls the best out of regular parts. Yes boutique parts brings it a notch up. but already with base parts is sounds pretty impressive or should I just say musical.

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