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Pop Sound in my speakers when driven loud from studio recorded CD sources.

Hales Revelation 1 bookshelf speakers are what we're talking about.  Purchased in the mid 90's and had been in storage for about 15 years in climate controlled conditions.  Just started using them again.  I'm finding under most conditions they perform admirably all around.  When listening to certain studio recordings on CD where the sound is very dense or the recording has a compressed quality,  I am hearing a distinct "pop" (not part of the musical presentation) when, for instance, the drummer makes a strong slap on the snare drum or tom tom.  Low frequency bass response is still very agile and stable for these small speakers.  Is it possible my mid bass driver is stuttering under these circumstances?  These Hales are known to be power hungry speakers.  My amplifier is 85W per channel and I'm noticing this pop when I get the volume knob to about '12 o'clock' .  That's when it starts to sound loud in my listening room.  Other lesser sources like radio or streaming sources, don't seem to bring this on.  It's the up front, dense sound from a CD that does it.  

Any diagnostician out there that can tell what the disfunction is? ... what I can do about it, if anything?  Thanks!

chametzoo
almarg's avatar
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almarg
9,670 posts
 
Glad that the problem is finally solved.

It seems that what I had said in a post which I subsequently deleted (because it seemed inconsistent with the sensitivity of the problem to the setting of the volume control), but which I quoted in a subsequent post after you asked what I had said, was in fact applicable:

Given the 180 mv sensitivity of the Marantz receiver and the 2.1 volt maximum output level of the DacMagic+ unbalanced outputs, it seems very conceivable to me that the problem may be due to overdriving whatever circuitry in the Marantz precedes (i.e., is "upstream" of) its volume control.

As an experiment, and conceivably as a permanent solution, try enabling the DacMagic’s digital preamp function, reduce its volume control setting significantly, and increase the volume control setting of the Marantz to provide preferred volume levels. See if the problem still occurs.

I can’t explain, though, why putting a smaller signal level into the Marantz has helped, given that the problem had only occurred at higher settings of the volume control. Detailed knowledge of the Marantz' circuit design might be required to explain that.  As I indicated earlier sensitivity of the problem to volume control settings would seem to signify that the "pop" is being introduced "after" the volume control in the Marantz’ internal signal path, where signal levels are presumably about the same for a given perceived volume regardless of whether you are using the DAC’s preamp function or not.

Regards,
-- Al


chametzoo OP
25 posts
 
Wow... Thank you again Al.  I'll continue to monitor the situation and try various other CD's where I know the "pop" was happening before.
As you point out, the mystery may be within the Marantz's circuit design:
Detailed knowledge of the Marantz' circuit design might be required to explain that
At this URL, scroll down to the bottom, and there are links to PDF's for "schematic" and "diagram" for the Marantz 2270 I'm using:http://spacebullet.net/marantz-2270.html.  If you feel like it, take a look; my curiosity continues!  Best, Mike
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almarg
9,670 posts
 
Hi Mike,

Thanks for providing the link. I had previously found the service manual, including the schematic, at hifiengine.com, but the block diagram provided at your link is also helpful.

But after looking at these documents I’m still at a loss to explain the mystery. The circuitry between the line-level inputs (Aux, Tape In 1, Tape In 2) and the volume control looks pretty straightforward and conventional. With nothing I can see that would explain why the problem is apparently introduced in circuitry that is "ahead" of the volume control while also manifesting itself or not depending on the setting of the volume control, when the DAC’s preamp function is not used. As you said in one of your earlier posts:

Playing the same CD passages at lower volume does not produce any of the "pop" "fart" sounds. It only happens at higher volumes.

And as I indicated previously, signal levels in the circuitry that is "after" the volume control are presumably about the same for a given perceived volume regardless of whether you are using the DAC’s preamp function or not.

Best regards,
-- Al

chametzoo OP
25 posts
 
Hi Al... further experimentation with using the DAC in pre amp mode is proving that I can play at higher volume now, without inducing the "pops".  Thanks for your help!  I'll make any updates here.  If you have any further thoughts, post here.
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