[nightfury]

Hey guys,

I've run into a problem with my amp unit and wanted to see if anyone here could perhaps help me solve it. I've owned a wa3 with dt990 combo for over a year now. It sounds great, but two issues have arisen with the unit since I've acquired it. I've toughed through them with my busy life, but enough is enough and I'm now ready to try to tackle the problem.

The first issue is that when the amp is plugged into the outlet using the power cable I bought from monoprice, and I run a like borderlands 2 for example, there is an audible buzz coming from the unit, as if someone is shaving. This buzz changes as things are changing on the screen. Outside the game you can "hear" your mouse moving across the screen. The support guys at woo are convinced that it is due to a dirty outlet line. However, I've moved since then and it is not different. The only thing that has fixed this is by using a 3 prong to 2 prong adapter at the end of the power cord. No noise is heard, or is so reduced that is not audible. I don't understand why this works, but removing the ground pin had something to do with the "dirty outlet line" theory? Enlighten me if you know otherwise. This solution doesn't make me feel any better as I don't consider it a real solution, rather a cover up. I've had to accept it as I had no time to figure out a better one.

The second issue remains unto today. After about 15 min of continuous use I begin to hear a different kind of noise that is independent of the content I am viewing. If sounds like a high pitch whine, such as from a TV unit or a power supply brick. It starts small and then picks up in intensity. It can easily be ignored due to how our brains get used to the background noise in general, but it also means there is no silence and when nothing is playing, I can't keep the headphones on. It's annoying. The oddest part is the solution, if I hit the unit (amp) with my finger or a pen, the buzz immediately stops. Then it starts up again after a while. Even more odd, is that if I elevate the front of the unit so that it is tilted 30 degrees (I prop it up with foam blocks) the noise severity is lessened and I don't need to tap the unit as much. However, it does not disappear.

Would someone with knowledge of the inner workings of the wa3 unit help me figure out why I'm having these problems. I truly love how it all sounds and have invested lots of money to make it happen. It terrible that I have to endure this annoyance. I would not wish it upon anyone else.

Sry for any typos, this was written on a phone. Thank you for your assistance.

 

[Edmond40]

I have the same problem as you, the problem may come from the tube or the resistor. I did I try to change the tube the problem has been improved so I think OTL amp the tube quality is very important, all the tube sound will direct to the headphone.[/B]. I just bought this amp last month so I don't think the resistor is an issue.

 

[hodgjy]

I have the second problem with my WA3.  It might be a design issue or a tube issue.  Other tubes make the sound more or less intense, but it never fully goes away.
 
The first issue is likely caused by the computer.  Isolate your computer from the amp by connecting via other means to rid yourself the interference. 

 

[Edmond40]

If the signal tube getting weak the noise can be happen. It is easy to know which signal tube is the problem, try to use a pencil light rubbing the tube you can hear the noise in the headphone.

 

[GrindingThud]

The whistle you hear is microphonics. It can be from the drivers or the output tube, but usually the drivers. Tapping them can make it stop, as can tipping the amp. New tubes will fix this. Or, if they are cheap tubes or well worn out, you can rap them with a pencil pretty sharply and sometimes they shake into a position that stops ringing. The 1st noise sounds like a ground loop with your source. Make sure everything is plugged into the same outlet and if on a strip, use adjacent sockets. If one of the plugs is two pronged and symmetric, you can try flipping it. Using a cheater plug breaks the ground loop, but also floats the system, leaving it unprotected in the unlikely event of a short....well not completely unprotected, as it's getting ground through the RCA jack to the system it's connected to.

What impedance DT990 do you have?

 

[Frank I]

Another solution for microphonic tube is to use use a tube damper sold at various online dealers. The dampers will help some.  Here is a good dealerhttps://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CC0QFjAA&url=http%3A%2F%2Fherbiesaudiolab.net%2Ftube.htm&ei=WHHdUqugOfLksATprYG4DQ&usg=AFQjCNE3Fb8bJe33XdiXJ4rHxqu97e-qWw&sig2=-Ze7LUN9CF5Kd7b1c5cYuQ&bvm=bv.59568121,d.cWc

 

[nightfury]

Thanks all for your input regarding this.
 
Quote:

 
The first issue is likely caused by the computer.  Isolate your computer from the amp by connecting via other means to rid yourself the interference. 

 
Could you clarify what you mean by "other means"?
 

  Another solution for microphonic tube is to use use a tube damper sold at various online dealers. The dampers will help some.  Here is a good dealerhttps://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CC0QFjAA&url=http%3A%2F%2Fherbiesaudiolab.net%2Ftube.htm&ei=WHHdUqugOfLksATprYG4DQ&usg=AFQjCNE3Fb8bJe33XdiXJ4rHxqu97e-qWw&sig2=-Ze7LUN9CF5Kd7b1c5cYuQ&bvm=bv.59568121,d.cWc

 
I will have to try these out i guess. thanks. Have you used them and do they work for you? They are quite expensive.
 

If the signal tube getting weak the noise can be happen. It is easy to know which signal tube is the problem, try to use a pencil light rubbing the tube you can hear the noise in the headphone.

 
It sounds like the larger tube is more susceptible to the pencil test. I have replaced the stock tube that came with the unit with a 2399 Chatham. The effect was present with both tubes. It does seem like tapping the bigger tube gets rid of the noise faster, however I've resorted to tapping the metal casing of the unit, since I don't want to smash the glass tube out of anger/frustration.
 

The whistle you hear is microphonics. It can be from the drivers or the output tube, but usually the drivers. Tapping them can make it stop, as can tipping the amp. New tubes will fix this. Or, if they are cheap tubes or well worn out, you can rap them with a pencil pretty sharply and sometimes they shake into a position that stops ringing. The 1st noise sounds like a ground loop with your source. Make sure everything is plugged into the same outlet and if on a strip, use adjacent sockets. If one of the plugs is two pronged and symmetric, you can try flipping it. Using a cheater plug breaks the ground loop, but also floats the system, leaving it unprotected in the unlikely event of a short....well not completely unprotected, as it's getting ground through the RCA jack to the system it's connected to.

What impedance DT990 do you have?

 
I have 600 Ohm 990s. Is there anything that can be fixed on the inside of the unit to get rid of the microphonics? Or is solely because of the tubes on the outside?

 

[Edmond40]

The noise come from the poor tube , Change the good tube with low noise can be improved. Don't use damper if the tube is getting weak. It doesn't help.

 

[hodgjy]

By "other means" I mean try connecting your computer to an external DAC and then the amp the DAC.  That eliminates a lot of noise. 

 

[GrindingThud]

For noisy tubes, no, there is no mod or fix to be made to the amp. Dampers may help some, but not always. These tubes are 50 years old in some cases...and the cheaper ones used up. Your best bet is new old stock tubes from a vendor that guarantees them. Many tubes will work in the WA3 driver section, many being very inexpensive. The 6N1P-EV is a very quiet Russian military tube that sounds nice and is easy to find cheap. Another good one I'd look at is the 6BZ7. The GE 6BZ7 is plentiful and just a few $ a tube.

I have 600 Ohm 990s. Is there anything that can be fixed on the inside of the unit to get rid of the microphonics? Or is solely because of the tubes on the outside?

 

[jackwess]

Tubes wear our gradually, and they start showing some unwanted distortion. As for the second issue, you may have something loose in your amp or probably your energy socket is causing a ground loop? 

 

[Edmond40]

For noisy tubes, no, there is no mod or fix to be made to the amp. Dampers may help some, but not always. These tubes are 50 years old in some cases...and the cheaper ones used up. Your best bet is new old stock tubes from a vendor that guarantees them. Many tubes will work in the WA3 driver section, many being very inexpensive. The 6N1P-EV is a very quiet Russian military tube that sounds nice and is easy to find cheap. Another good one I'd look at is the 6BZ7. The GE 6BZ7 is plentiful and just a few $ a tube.

Thank you your suggestion of the driver tube, would you pls. Recommend the low noise power tube. I am using sovtek 6as7g, could you pls. Commend!

 

[GrindingThud]

The military version of the Sovtek 6AS7G, the 6n13s (6H13C), tends to be a pretty quiet tube and don't cost too much. A little harder to find, and one of my favorite for being quiet, is the TungSol 6080WA with the metal mica supports that look like this:

Thank you your suggestion of the driver tube, would you pls. Recommend the low noise power tube. I am using sovtek 6as7g, could you pls. Commend!