[anthony a.]

okay, so i love my synthesis audio "the theater" tube monoblocks.  after years and years with ss amps and tube pre, i finally found the perfect combo of tube amp and ss pre.  but.... and there is always a BUT , i seem to have a bit of noise when standing 1-2 feet away from the speaker tweeter.  its kind of like a crackling sound, i know is the result of the tube as well as my stereovox hdse (unshielded) interconnects to my dac.  so im wondering what ways there are to help quiet this crackling noise.  and just to be thorough, all my front end is plugged into a balanced power conditioner (blue circle mr1200 music ring). 

[Tyson]

I'd recommend not putting your listening chair 2 feet in front of your speakers

[JakeJ]

OK, now for a serious answer.
 
Is the noise in both channels (assuming this is a two-channel system)?  If not try swapping tubes from the quiet amp to the noisy one until you can narrow it down to a specific tube.  If it is both channels then it's possible the input stage or driver driver tubes are inexpensive, low quality tubes that aren't up to the task.  It's also possible for the output tubes to be the problem.
 
I Googled the bejesus out of the company name and the model name and came up empty.  What is the tube compliment?  This may help us help you.

[kingdeezie]

okay, so i love my synthesis audio "the theater" tube monoblocks.  after years and years with ss amps and tube pre, i finally found the perfect combo of tube amp and ss pre.  but.... and there is always a BUT , i seem to have a bit of noise when standing 1-2 feet away from the speaker tweeter.  its kind of like a crackling sound, i know is the result of the tube as well as my stereovox hdse (unshielded) interconnects to my dac.  so im wondering what ways there are to help quiet this crackling noise.  and just to be thorough, all my front end is plugged into a balanced power conditioner (blue circle mr1200 music ring).

It could be simply your interconnects that are causing the problem.

I am running nonshielded interconnects as well and get a similar sound to what you describe along with a tiny amount of buzzing.

This was with SS amp as well as tubed amp.

Try a cheap pair of shielded ICS to see if the problem subsides. If you can't stand living with it you'll need to buy ICs that you like that are shielded.

I like the sound of my ICS so I live with it.

[jriggy]

I just had this 'crackling' issue in one channel myself...
 Tubed source, tubed pre, SS amp. Switched the signal tubes out in my source and the issue is gone.
 
 

[Niteshade]

Buzzing:

It can be caused by a few things:

1. Filament to cathode leakage
2. Diode ringing
3. The way the internal ground structure is set up (AKA: ground loops)
4. External ground loops

[anthony a.]

I Googled the bejesus out of the the company name and the model name and came up empty.  What is the tube compliment?  This may help us help you.

www. synthesis.co.it/wood.htm  (click on power amps, then on "the theater", then on details)

it uses 2 x 12au7 and 4 x el34 per amp.

[anthony a.]

PS  thanks to all for the helpful replies.  i am going to investigate further to see if its the tube or the interconnects causing the buzz.  i know the interconnects can cause it as they have in the past with my other system .. but they sound so good so it may be beyond my control.

[avta]

Do you have all of your equipment plugged into one power strip or conditioner ? I try to keep all of my stuff plugged into a single strip ( I use a Furman Conditioner/Strip ) to minimize ground loop problems at least that's what I've read.

[anthony a.]

yes, all mt front end components are on the same balanced power conditoner, except for the 2 amps which are on the same circuit but plugged straight into the wall.

after more investigation, it seems to be a bit tube related and a bit cable related.  as i knew already, the stereovox unshielded interconnects do pickup some noise but moving them around a bit helps diminish it.  im wondering what can be done here to eliminate some of this noise?  shakti stones maybe?

also, i found that one power tube was a culprit and seemed to start dying.  on powerup, i see that tube light up like a light bulb and then blow the fuse on the amp.  i thought it could be a coincidence so i put in a fresh new fuse, turn it on again, and then POP again.  so im thinking that tube's life is bye, bye and is causing the fuse out.  i swapped the other 4 tubes from the other amp and turned it on and it played fine.

this is the first time i have tube amps, so im wondering if this is normal when tubes start to go that they can blow the fuse and light up like that.  can any damage happen to the amp or is the fuse protecting the entire circuit for this type of stuff?

[JakeJ]

1)  You can shield the offending cable yourself with household tin foil.  Just wrap the length leaving the source end not touching the connector and do make sure it is touching the preamp end (this follows the "star" grounding concept).  To maintain good contact at the preamp end just zip tie it.

2) That output tube is shorted internally and you should not run your amp with it any more as it may cause catastrophic failure!  If it were me I would replace the entire quad with a fresh, matched set. then get the other three tested and see if they are worth keeping as backups.  Actually I would test all the output tubes in both amps just to see where they are in their lifespan and, if needed, replace the octet with a complete matched set.  If they are low in their lifespan then garbage 'em.  This all assumes you have access or own your own tube tester.  If not then hawk this circle and the Lab to see if another of us audiophools have a tester near you that would be willing to test them for you.  You can also avail a tube vendor that offers to test for a fee.  If these are not good options I may be able to test them for just the price of shipping both ways.

[Steve]

okay, so i love my synthesis audio "the theater" tube monoblocks.  after years and years with ss amps and tube pre, i finally found the perfect combo of tube amp and ss pre.  but.... and there is always a BUT , i seem to have a bit of noise when standing 1-2 feet away from the speaker tweeter.  its kind of like a crackling sound, i know is the result of the tube as well as my stereovox hdse (unshielded) interconnects to my dac.  so im wondering what ways there are to help quiet this crackling noise.  and just to be thorough, all my front end is plugged into a balanced power conditioner (blue circle mr1200 music ring).

Hopefully it is just a tube. If not, then it could be a poor connection, either poor solder or press fit (IC etc). It could also be a crackling/noisy resistor as well.

Good luck.

[Bugs]

You may also have a bad connetion with the tube socket.  Try lightly moving the offending channel tube in the socket while playing and listen for crackling.  If the socket is dirty or not making adequate connection with the tube pins you will hear moreof the crackling sound.  I've had this happen, a little deoxit helps clean things up, but make sure all is dry before you restart the amp.