Poping sound when LS100 unmutes itself on start up - is it harmless?

danvu · « **on:** 21 Apr 2012, 06:18 pm »

I'm using the LS100's trigger output to turn on/off my monoblocks together with the preamp. As you know, the preamp is muted when turned on and unmutes itself after 45 secs and whenever it does that, it produces a moderate poping sound thru my speakers. I read somewhere online that this is caused by the preamp generating a large pulse and it can potentially damage the amp's output stage and the speakers. Can someone please confirm if this is true or it's not the case in the LS100 unmuting? I hope it is not the case for the LS100 since I really want to use the trigger output to turn on/off both preamp/amps from the remote control; otherwise, the trigger output feature is kinda useless for me. If it's harmless, I can live with the poping sounds though it's a bit annoying.

Thank you for your help.

PS: Forgot to mention that the pop only happens when the preamp unmutes itself on initial start up. After it warms up, there's no problem to mute/unmute

mraudio · « **Reply #1 on:** 22 Apr 2012, 06:04 pm »

I have "kind of" the same problem. I'm not using the 12V trigger, however my LS100 unmutes after initial turn on, in 15 seconds, not 45. This creates a moderate "pop" or "click" through my speakers, (I keep my Sanders ESL amp on 24/7). If I remute it right away, I get a very LOUD "pop" through the speakers

. If I wait to remute it for 45-60 seconds, it's completely quiet.

After this sequence, the LS100 is perfect. Never another problem. Just that first initial turn-on/mute situation. I assume there is a timer or whatever that controls the amount of time for unmuting. Mine either needs adjustment or replacement.

dminches · « **Reply #2 on:** 22 Apr 2012, 07:01 pm »

mraudio, 15 seconds is very short. Mine takes 45 seconds also. I don't get the pop though.

nnck · « **Reply #3 on:** 22 Apr 2012, 07:16 pm »

FWIW, I always thought my LS100 unmuted itself rather quickly as well. Just timed mine and it took 15 seconds, like mraudio's.

mraudio- I'm curious whether your LS100 has always unmuted in 15 seconds? Or did it originally take longer to unmute, but then somehow changed?

As far as the 'pop', I cant really add much- I dont use the trigger function, and my KWA100SE amp takes longer to turn on than the LS100. Usually, I just click both power switches on at the same time. The LS100 will unmute itself first after 15 seconds, and then about 30 seconds later, the KWA100SE will switch on and be ready to go.

The few times I have powered on the KWA100SE amp prior to the LS100 has caused the amp to shut itself off when the pre unmutes. It seems some safety mechanism inside the amp doesnt like when the LS100 unmutes and it just immediately shuts down. It requires that I unplug and replug the power cord from the back of the amp and then switch it back on for it to function again. Anyone else noticed this?

mraudio · « **Reply #4 on:** 22 Apr 2012, 07:50 pm »

Quote from: nnck on 22 Apr 2012, 07:16 pm

mraudio- I'm curious whether your LS100 has always unmuted in 15 seconds? Or did it originally take longer to unmute, but then somehow changed?

Mine has always had the initial 15 second unmute. I said above that when it unmutes I hear a "moderate" pop or click. To be honest it's really a "softer" click sound more than anything else. I'm sure it's not causing any problems. The only frightening sound comes if I remute it right away. Now that's a really LOUD POP through the speakers.

I'm used to just waiting an additional 45-60 seconds to remute it now, so it's not a huge problem, but I'm also sure if the timer took the specified 45 seconds to unmute, it would solve the problem.

dminches · « **Reply #5 on:** 22 Apr 2012, 11:09 pm »

nnck, that is the amp's protection circuit sensing a DC overload, thus shutting the amp down. I have the same thing happen with my KWA-150 SE.

danvu · « **Reply #6 on:** 23 Apr 2012, 12:41 am »

Hmm, interesting. Looks like some of us have that problem but it's minor so no one brought it up before. Since you guys mentioned about the short mute time, I actually did the counting (in my first post, I just used the 45 secs stated in the manual) and mine is short too, somewhere between 15-20 secs. See if Dan Wright has anything to say about this.

I also did a little experiment. Using the trigger output, I turned on the pre/amp together, played some music so they warmed up and turned off both. Then after about a minute, I turned on the pre/amp and the pre unmuted itself (15 secs later) without the pop as it's still warm. But if I let it cool down for like an hour and turned on again, then the pop happened.

So to stay on the safe side, I will stop using the trigger output and wait for the LS100 to unmute itself first before turning on the amps to avoid the pop though I dont know if this sequence is recommended. Anyone? The trigger is now useless. Bummer.

AB · « **Reply #7 on:** 23 Apr 2012, 01:08 am »

I know this is no answer to this issue and some of you keep your amps on 24/7 but you really shouldn't turn your amp on before you turn your preamp and source on. If anything goes wrong with your pre or your source, the amp is going to amplify the problem and send it straight into your speakers.

It's been my habit to turn on my gear in sequence - source, pre then amp with a minute or two between each - just in case.

I am sure Dan will arrive here any minute and sort this out as it really sounds like your mute circuits are not working properly. The mute should be giving your preamps more than 15 seconds to warm up and stabilize before passing a signal.

I am not sure what failures are required (beside the tube warm up pulse)for a preamp to pass too much DC but I know it does happen - and thus these DC offset protection circuits in the power amps we buy.

It's good to remember that there's a crap load of DC in these boxes and the only thing keeping it under control are the circuits needed to turn it into music - if those circuits fail...

...the fuses blow.

vintagebob · « **Reply #8 on:** 23 Apr 2012, 05:24 am »

That "pop" blows the fuses in my McCormack DNA-250. I wait for the LS100 to completely cycle on before I turn on my amp.

After everything warms up though, I sure get to listen to some great sound!

danvu · « **Reply #9 on:** 23 Apr 2012, 09:27 pm »

FYI everyone, Dan's responded to my email regarding the short muting time:

Quote

I apologize, I believe that we mistakenly programmed a few PICs with turn on delays that were too short. I would recommend turning on the preamp first, with amp off, wait another 30 seconds, and then power on your amplifier.

I will also program another PIC for you, with proper delay time. I will do the same for ANYONE having this problem! I will send a diagram, indicating which of the two socketed IC's is to be replaced.

Thank you for bringing this to my attention.

Sincerely,

Dan W.

Quick turn around and excellent customer service. So I guess anyone with this problem will be contacted by Dan or you can let him know and he'll take care of it. Hope this fix would also fix the 'pop'. Good luck to all!

mraudio · « **Reply #10 on:** 24 Apr 2012, 02:50 am »

Quote from: danvu on 23 Apr 2012, 09:27 pm

FYI everyone, Dan's responded to my email regarding the short muting time:
Quick turn around and excellent customer service. So I guess anyone with this problem will be contacted by Dan or you can let him know and he'll take care of it. Hope this fix would also fix the 'pop'. Good luck to all!

Danvu,
Thanks for following up with Dan Wright. I'll send him an e-mail. Thanks again.

danvu · « **Reply #11 on:** 24 Apr 2012, 04:53 am »

You're welcome, mraudio

mraudio · « **Reply #12 on:** 26 Apr 2012, 10:48 pm »

I e-mailed Dan and mentioned this problem. He has already shipped the new PIC with instructions to me. If anyone else has this problem, please get a hold of Dan. He will take care of it immediately. Dan's the man!

danvu · « **Reply #13 on:** 2 May 2012, 01:31 am »

I got the PIC and installed it. With the longer mute time, the popping sound is now gone when the preamp unmutes. That's great as we now know the cause of the pop. However, there's another problem coming with the new chip. The preamp cannot turn on/off the amps via the trigger output. Only the trigger button on the remote control works. Pretty sure I didn't touch anything else inside the preamp beside using a duster to blow any dust.

Mraudio, did you get yours and replace it yet? Can you test your trigger output to see if it's still working? Still waiting for Dan's response on this.

mraudio · « **Reply #14 on:** 2 May 2012, 06:42 pm »

Danvu,

I got my new PIC and it works great. Sorry, but I do not have any 12 volt trigger gear, so I can't test it out. I have never used a 12 volt trigger on anything.

Let us know what Dan says. Maybe he forgot to program the trigger on the new PIC or...who knows?

danvu · « **Reply #15 on:** 3 May 2012, 09:38 pm »

The trigger output is working now. I dont know what happened but I put back the old PIC to confirm my finding and switched again to the new PIC and it worked all the sudden. Maybe something was loose the first time, either the trigger jack (since the trigger female connector is kinda flimsy) or the PIC.

mraudio · « **Reply #16 on:** 4 May 2012, 05:16 pm »

Glad you got it working!

nnck · « **Reply #17 on:** 9 May 2012, 11:23 pm »

I installed my new PIC with success as well. Now the preamp mutes after about 60 seconds instead of 15.

This was a very quick fix, thanks to Dan, and a very simple install.

While I dont in practice turn the amp on prior to the preamp, I went ahead and tried it just one time. The new PIC alleviated the problem I referred to in my earlier post where the amp would turn itself off via a safety mechanism when it was inadvertently turned on prior to the preamp. The added warm up time on the preamp now eliminates this from occurring.

modwright · « **Reply #18 on:** 11 May 2012, 05:30 pm »

Thanks guys and sorry for the hassle. Not sure how the code go changed to shorten the mute time or how I missed it, but am glad that those who have this issue are finding the PIC replacement an easy solution.

Sincerely,

Dan

mraudio · « **Reply #19 on:** 11 May 2012, 07:13 pm »

Dan,

Thank you for the quick response and solution! My LS100 works perfect now. Nice to have a designer/manufacturer take great pride in their product and customers.