2. amps-preamps
  3. 1202697301

Belles 350a reference fireworks

I turned on my Belles 350A reference yesterday, and was greeted by a flash, then a wisp of smoke coming from the right hand side of the unit. White noise emanated from my SP Tech timepiece 3.0's. I turned the amp off immediately, but needless to say I'm worried--mostly about my speakers. My 350 does NOT have the soft-start, which I'm guessing is the problem. Now i'm torn: after reading a couple of other similar stories about the amps putting out DC and frying speakers (not to mention the amp itself), I'm unsure of whether I should send the amp back to Dave Belles for repair/soft-start upgrade, or just scrap the beast and go with something more user friendly/reliable. The sound I was getting from my Belles/Modwright pre, and the SP Tech (amazing speakers, btw), was great, but I've got a case of the jitters about the 350 now. Has anyone sent theirs in for the soft-start and have an opinion? I don't want to spend the money on repair/upgrade, if there will still be reliability issues...

thanks,

david
davidm1108
davidm1108 OP
17 posts
 
thanks guys--sleepysurf--i spoke to dan last year when i got the belles, and he had me send my modwright back in, so he could update it. i'll call to double-check and make sure...and yes, it would be hard to give up the belles, so here's to hping i get it sorted!
mitch2
3,717 posts
 
From the Soundstage review;
The 350A Reference is also AC coupled, while the 350A was DC coupled. The difference is essentially safety for your system. An AC-coupled amp will not pass DC to the loudspeakers, while a DC-coupled amp will if any is presented at the input. Under normal conditions, this should not be an issue, but, as we know, sometimes stuff happens. There are also sonic considerations here. AC coupling compromises the sound and may limit bass extension in the bottom octave because a capacitor has to be inserted in the signal path to block DC from passing through the amp to the outputs. Dave Belles managed to insert a capacitor that doesn’t limit the deep bass (detected by ear or by SPL meter using the DC-coupled 350A as a reference point). Thus, there’s no audible harm to the audio signal from the extra capacitor that I can detect.
davidm1108 OP
17 posts
 
thanks mitch--that makes me feel less worried about my speakers. this forum is a very cool place.
dwright
35 posts
 
Hi guys, this is Dan Wright from ModWright Intruments Inc. It has come to my attention that some people have had trouble with some of our earlier 9.0SE preamps and the Belles AC coupled amp. Our earliest units did allow for elevated DC levels right at power up due to a brief delay between when the mute circuit actuated the mute relay and when the B+ was energized.

This has been addressed in more current units and of course addressed with the tube-rectified supplies. If you have any questions, please don't hesitate to contact me via email at modwright@yahoo.com.

The proper and ideal way to power up and down any system is as follows:

1) Power up preamp.
2) Power up amp.

Powering Down:
1) Power down amp.
2) Power down preamp.

Thanks,

Dan W.
davidm1108 OP
17 posts
 
this is why modwright has the rep they do. class company.
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