2. amps-preamps
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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
9 responses Add your response
ladycharnet's avatar
ladycharnet
59 posts
 
I power up ARC pre-amps, on mute, power on head gear used, power on DAC, then power on the power amplifiers.

To shut down, I put the pre-amps in mute, power off the power amps, then power off the DAC, power of the head gear used, then power of the pre-amplifiers.
I think this is the correct method?
davidm1108 OP
17 posts
 
this is why modwright has the rep they do. class company.
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
 
thanks mitch--that makes me feel less worried about my speakers. this forum is a very cool place.
mitch2
4,007 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 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!
avguygeorge
2,300 posts
 
I was one of those owners of the 350 ref that did what yours did. It cost me 650 which included ship/both ways. Not one incident since---(10 months later).
sleepysurf
122 posts
 
I had a similar event last year, likewise with a Modwright Pre paired with a Belles 350A ref (WITH the soft-start circuitry). After LOTS of discussion, we suspect the problem originated with the Modwright Pre, as after checking with Dan Wright, I found my unit did NOT have the latest muting/protection circuitry to block DC surges. Turns out, David Belles uses VERY LITTLE protection circuitry in the 350A Ref, which is why it sounds so great! Dan upgraded my Pre to include the latest circuitry (as well as upgrading to the tube rectifier), and David Belles replaced my amp. Both have been singing sweetly ever since. David Belles (and Bruce Jacobs, marketing) are great to deal with and will certainly take care of you. I would also speak with Dan Wright, and have him cross-check your serial number to make sure it has the necessary protection. The power and finesse of the Belles makes it hard to give up, especially when the problem may have lied elsewhere.
rhyno's avatar
rhyno
649 posts
 
fwiw, i doubt the soft start would impact the cause of the failure; all the soft start does is keep the amp from tripping your circuit breaker at turn-on.

the service is now required, might as well get the soft start while its in.

sorry for your troubles mate; this too shall pass.
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