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

Hi All... I’m dredging up this 1+ year old thread because I think I discovered the solution to the problem I brought up here (I’m the orginal poster).

I had complained of a pop or burp sound when I was playing CD’s and there was a brief spike in sound, like when the drummer slaps the snare drum. This would happen at fairly loud volume. So, it was preventing me from turning the volume up on my amp to a nice loud concert level. If you want to know more, see the original post at the top.
All of my digital sources are routed through a Cambridge Audio DAC Magic Plus. This DAC has a "pre amp mode" with a volume control knob that is activated when headphones are plugged into the DAC... or when it is purposely selected by the user for speaker listening. Until now, I have been using the DAC without that pre amp mode selected... and THAT is when I find that the amp’s volume knob tops out early and the popping/burping sound starts happening coincident with the brief spikes in sound.
Now, I am using the DAC in pre amp mode and putting the amp’s volume knob much higher and then adjusting the DAC volume knob to get the music to a good listenable loud concert level... and to my surprise, I no longer get those pops/burps in the same instances that I was before. I believe that one of the posts earlier in this thread hints at trying that very thing out. But it was not until now that I tried it.  I'm still working on the optimal ratio between the two volume knobs.

Of course, I’m happy about this, but what I would like to know from you all, is what might be happening within my system between the receiver (pre amp/amp) and DAC (with pre amp volume control activated). Now there’s actually 2 pre amps working simultaneously. I don’t really have the technical knowledge to know why it’s working better, but I’m sure curious. Thanks!

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

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

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

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.