2. amps-preamps
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Mystery 30 Minute Sound Degradation

I come to you experts with a recent mystery. For the first 30 minutes after I turn on my system, and whether I am using my tuner or Bryston BDP-1 through my W4S DAC2, the first 30 minutes or so of playing the music is thin and shrill, and I have to turn up the volume about 50% more than usual to get the same sound level as I used to get.

Possible contributing factors, though I lack the technical knowledge to know why or if:

1. Upgrade to Solen teflon cpacitors in my pre -- Wyetech Opal about 2 weeks ago;

2. Insertion of HiFi Supreme Tuning Fuse in pre a few days ago. I am virtually certain (but will check again) it is the right size and amperage and that it is inserted in the right direction.

The condition was sporadic before fuse replacement but now it consistent every day.

After about 30 minutes, the sound quality and volume returns to what was its normal wondefrul state.

Any thoughts? Thank you.

Neal
nglazer
7 responses Add your response
nickjn
111 posts
 
Glad to hear that Neal. Keep us posted,

Nick.
nglazer OP
842 posts
 
Thanks, Nickjn. I have been leaving the pre on all day fed by Verizon FIOS jazz station, to burn in caps. Also, I think the problem was the new HiFi Supreme Tuning Fuse I installed. It is directional and although I swore I inserted it correctly, it turned out to be backwards. Now, the problem I described has disappeared.

Nice sound improvement from the fuse; still waiting on caps.

Thanks again.

Neal
hifigeek1
770 posts
 
Teflon caps are notorious for taking forever to break in. I would suggest you wait till you have at least 100hrs. break in on the caps before you start changing anything in your system. I'm guessing it's just the coupling caps acting weird.
nickjn
111 posts
 
I have replaced caps on my equipment, Initially they sounded shrill and i thought it was a mistake to replace them.

After some hours they are getting better..

Probably the new caps need burn in? give em' some time.
nglazer OP
842 posts
 
Almarg,

Thanks for reply. The change to "normal" is abrupt. I know the capacitors were of the right values as I checked them before installation.

Sgr,

It may be a warmup issue peculiar to these capacitors although I don't know why that might be. I suspect the new fuse has something to do with it because it happens whether I use the tuner or DAC/BDP-1, so it is likely the change to the pre. I reversed the fuse so let's see what happens.

Thanks for replies.

Neal
almarg's avatar
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almarg
9,670 posts
 
Just a completely wild guess, but I see that the literature on your preamp indicates that following turn-on "about 10 seconds after the filaments light up the DC rails are slowly brought up to full voltage of 200 Volts over a period of 60 seconds. At the end of 90 seconds the auto-mute is disengaged completing the turn on sequence."

Perhaps something was done wrong in the capacitor upgrade, perhaps even replacement of a capacitor with an incorrect value, that is causing the 60 second rise of the 200 volt supply to take 30 minutes instead.

After the 30 minutes, do the sound quality and volume abruptly jump up to normal, or is there a gradual improvement during part or all of the 30 minutes?

Regards,
-- Al
sgr's avatar
sgr
689 posts
 
The fuses do take some time to burn in and can sound strange for a while. Do you leave your electronics on all the time? You could be experiencing warm up. I leave all my solid state electronics on all the time. It might be considered wasteful, but this will be better or your electronics rather than the stress of turning them off and on plus they will always sound their best. Front end electronics such as preamps and digital really thrive in this environment. You will still have to wait for your amp to warm up though.
I'd simply leave it on all the time.
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