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Mark Levinson 433 Pop sound

Hi,

I hope somebody can help me on this.

Just get a ML 433 and I noticed a pop sound when I turn on and off the unit (from standby to on). Pretty loud pop from all channels.

If I disconnect all the RCA inputs (with speakers connected), the pop sound disappears.

I did try two pre-amp and still have the same issue. Both of them are un-balanced preamp (Marantz and Conrad Johnson)

A couple questions with this:

1. Would using a balance Pre-amp and XLR connection solve this/minimize the pop sound?

2. How critical the xlr shorting pins to the pop sound?

3. Do you think there is something wrong with the 433?

This is actually the second units, the first unit did the same pop sounds. But it was also have humming/ground loop issues. It finally stop working after about a month of use. I'm just worry if the second unit have the same issue as the first, and would stop working as well.

Thanks
caweran
lowrider57's avatar
lowrider57
5,417 posts
 
Nothing wrong with the ML 433. It's cause the amp is hooked up to a preamp (most likely tubes?)
Do what ZD suggests and try a different turn on/off sequence.

Turn the preamp ON first, (volume down, source Off). Wait a minute; there may be some clicking in preamp during startup. Then turn ON amp.
-to power off, turn down volume, Amp OFF, Preamp Off last.

(Amp ON last/ Amp Off 1st)
caweran OP
12 posts
 
I still get popping sound from all channels no matter which sequences I used.

Do you know any method to minimized this? Worried that it might damage the tweeters.

Mark levinson tech told me that this might be because I use unbalanced connection to the pre-amp. He mentioned that this issue should be fix going to full balance system. It this true? He mentioned about DC offset/discharge going to the speaker output instead.
lowrider57's avatar
lowrider57
5,417 posts
 
Try using some inexpensive balanced cables as recommended. However, the cables must be truly balanced and not just cables with XLR connectors.

Radio Shack carries what they call XLR cables; they don't mention if they are balanced. Look for these...
http://www.bluejeanscable.com/store/balancedaudio/index.htm

You may also try to have all the unused preamp inputs connected using jumpers.
zd542
5,339 posts
 
He's right. You definitely want to make sure really balanced, and not just SE with xlr connectors. If you live near a music store, you could try those Mogami balanced cables everyone is always talking about. They're not expensive. If you live near a Guitar Center, you can return the cables if they don't fix the problem.
caweran OP
12 posts
 
I tried the shorting straps last night, and it helps. No popping sound when going from standby to on.

Still have the popping sound when going to standby.

Next I will try to use xlr, but first I have to get a balance preamp...
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