Problem with Premier 140

[homey68]

I have the Premier 140 running ML Prodigy speakers. A couple months back, the power went off all of a sudden, and came back on immediately while the amp was playing. The amp was connected to a Shunyata Hydra 2 but that did not protect it. Both fuses on the rear were blown and I replaced. Upon turning the amp on again, I noticed a high pitched, squealing like noise coming from 1 speaker for about 20 seconds or so and then the noise was gone. The amp plays OK and I had to purchase some more tubes to weed out a bad tube.

So I switched out all the tubes and ruled that out. I then switched the speaker cables and the noise is still in the 1 channel. Anyone with any suggestions as to what this may be? Thanks in advance.

[admin]

Sorry to hear about the trouble. Can you confirm that it's the amp and not the preamp or the source? So it just lasts for 20 seconds, and then completely resolves?

Have you opened up the 140 to look for visible damage such as burn marks, discoloration of components, cap bulging, etc? We do have the schematics to the 140 in our database so you would be able to do a complete component check if needed. If we are 100% sure it's one channel, at least that narrows it down a bit.

[homey68]

Yes, I am sure it is the amp. I have switched speaker leads and interconnects, same problem. I have heard that same high pitched noise before in other equipment when it was a bad tube. That was my first instinct, but I have switched out all the tubes and tubes aren't the problem. I have it packed up and sending it in to have the pros check it out. This amp is too heavy for me to keep lugging it around.

[homey68]

Oh yes, I forgot to mention, I was listening to the amp last night and after the initial noise, I could still hear a constant noise at a very low volume.

[roberto]

Hola homey68 and welcome,

I am going to chime here a little bit. Do this: Turn your amp off and wait 1 minute. Disconnect the input cables to your Premier power amp, just leave the speaker's cable connected. No input cables now. Turn the power amp on, and have a listen. Do you still have that noise at the left channel?

if it is a yes, we have to track from where it is produced. If the answer is no, it is clean and no noise, then it is coming from the preamp, or a bad rca connector cable. Don't do many changes at the same time, just one by one. This way you can track better the culprit.

Happy listening!

[homey68]

I tried just about every scenario including eliminating the cables. I have owned a lot of tube equipment through the years and have had a few problems. This time, I feel that the surge of power that blew the fuses also damaged something else. Maybe a cap or resistor in the power supply? Just guessing. I used to fool around quite a bit with tube equipment, mods etc. I got out of audio for a bit and don't have any test equipment anymore. That is why I am sending it in for service. Just hoping it isn't going to be too expensive.

[roberto]

Hola homey68,

Can you describe the odd noise again? We know that it is coming from the left channel. Please do the test again, without any RCA connection to the amp. Only the speaker cables. We also know that the noise is independent of the volume of the preamplifier. This is the reason why I need you to do it again, if this do not bother to you. Sometimes, I get lucky with odd noise. I might help.

Thanks!
Roberto.

[homey68]

Roberto,
I checked the amp without the RCA connectors several times. That was the first thing that I checked. I thought my PS Audio DirectStream DAC had a problem. The noise was still there without the volume control in the loop. It is the amp. First time in years that I have had a problem with a modern day tube amp. I have owned many and never had problems. I have owned other CJ amps and they were pretty much glitch free.

[roberto]

Go it, Homey68, can you describe the odd noise please? Is it a hissing noise? Or it has low frequency content? The V1 is a 6922 shared for both channels. The 6922 is a double triode. The amp use one side for the left channel and the other for the right channel. The 6922 type of tube is known to produce odd noises, hissing, popping etc. Did you replaced it? The 6H30 also can produce this odd noise.

Just my 2 cents.

Happy listening!

[homey68]

Amp is on its way back from factory. Problem was bad power supplies driving the small tubes. Also some burnt resistors. Thanks for all the input.

[roberto]

Hola homey68,

Those are wonderful news that you are enjoying again your Premier 140. Yup, I was suspicious that you had the problem there, at the small tubes. Good idea to send the unit the CJ for repair.

Happy listening!

[homey68]

The amp seemed to be working fine, but last night, when my wife was doing laundry, the amp was picking up RF from the washing machine motor. I could hear it sitting about 10 feet away. I disconnected the amp from the Shunyata Hydra unit and plugged it straight in the wall. The noise was still there. I eliminated all the other components in the chain and the amp was the culprit. What was weird, was sitting near the amp, it sounded as if the tranformers were oscillating with the washing machine motor. Could a tube cause this? Never had this problem before I sent the amp in for repair. Any help appreciated.

[admin]

Not sure if this is technically a "problem with the unit." A high current electric motor is going to throw a lot of noise onto your electrical lines. You may be getting some significant voltage variation as well.

[roberto]

Hola homey68,

Your problem noise is an EMI (electromagnetic interference). Read about it here: https://www.westfloridacomponents.com/b ... affect-us/

To me, first of all, you should call an electrician and ask him to tight all your AC cables at the House Panel Control. All the cable breakers should be very tight, specially the ground cables and the neutral.

Your Sunyata is a very good device and I am guessing that it might have a problem. You should ask your dealer about it. You did pay good money to prevent this unwanted noise.

Reading how to cure this problem, I found this: The simplest way to reduce magnetically induced interference is to use twisted pair wires. This applies both for shielded and unshielded cables and for interference caused by shield currents or from other sources. Twisting the wires forces them close together, reducing the loop area and therefore the induced voltage.

Route your AC cables away from signal cables...this could help too.

Happy listening!

[roberto]

I forgot to mention that I have in my power amp a Shakti stone. I use it on top of my power amp where the power transformer is located. This stone is used in the airplanes to avoid this unwanted EMI. Here is the Shakti Stone information:
http://www.shakti-innovations.com/product/shakti-stone/

Happy listening

[homey68]

Roberto, thanks for the info. I will look into the Shatki stone. I heard about it in the past, never pursued it though. I did tighten the neutral and ground lugs in the panel. Some of them were kind of loose. I did have a power problem once before and it turned out to be one of the lugs at the meter was loose.

[roberto]

After that, I do know that your amp is getting fresher AC and there is now power! Please, have a listen and report your findings. I had that problem long time ago, and when I did the tighteen process, my system bass changed and also the dynamics. Clean sound after that!

Happy listening!