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  #21  
Old 06-11-2017, 10:10 PM
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djwhog djwhog is offline
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Is it the amp or the preamp, or is it an AC power issue?
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  #22  
Old 06-11-2017, 11:00 PM
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Is there any hiss at zero volume? If you turn the volume up (with no source coming
in), is there more hiss or stays the same for a while and eventually you hear more?
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  #23  
Old 06-12-2017, 01:33 AM
damacman damacman is offline
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Quote:
Originally Posted by MBlue72 View Post
One thing Matt and I have in common: our C52 preamps are driving pretty old amplifiers. Mine (MC7300) is over 25 years old. I'm not sure how or if that would cause the hiss while utilizing the equalizer. Maybe some of you have ideas whether older solid state amps can keep up newer preamps.

Just to reiterate ... my speakers are KHorns and typically rate at 104-105 db. I purchased them in 1990.

Also: I have never had my amp serviced but I "baby" my stereo equipment.

Thanks,

Dave
Dave, I also own an MC7300. This isn't the problem - the sensitivity of your speakers is so very high with Khorns, they make audible the noise floor of the components. This would be inaudible with speakers of typical sensitivity. As it's preamp noise you hear, the C52 is the source of the noise.

You could set the gains on your MC7300 at 12:00 (or lower even). This would eliminate hiss at the speakers while providing a greater usable range for your volume control with the Khorns. This is also possible with the MC7100 as it has gains on the rear. 12:00 is labeled at 2.5V - good starting point.

Last edited by damacman; 06-12-2017 at 01:37 AM.
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  #24  
Old 06-12-2017, 01:02 PM
MBlue72 MBlue72 is offline
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damacman:

Thanks so much. I think you have resolved (and explained well) the issue ... for me at least. Duh.

The "backstory" here is that for 24 years I had my c37 preamp driving my MC7300 amp. I intentionally turned the gain down on the MC7300 to about 40% because I felt the "throw" on the C37 preamp was so tight I couldn't get much control of the volume with the amp set at full gain -- a small movement of the volume knob would result in a huge swing in loudness. In April, 2016 I decided to upgrade and purchased my C52. When I installed the C52 into my system and began using it, I felt comfortable with the loudness control I had via my C52 with the MC7300 set to full gain.

It's odd that neither the tech at my local dealer nor at McIntosh thought to give me this suggestion/feedback. I provided them with the same information including the high efficiency ratings of my KHorns.

Thanks again,

Dave
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  #25  
Old 06-12-2017, 09:28 PM
eedork eedork is offline
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Hi damacman,

I had a similar thought regarding the input sensitivity of the amp, which in my case is an MC7100 (similar vintage to Dave's MC7300). I have had the gain controls on the 7100 set to 12:00, which is 2.5V for full power, since adding the C52. I experience hiss at this level but did try different levels and as expected the hiss does vary as the gain control are tweaked.

I'm waiting to hear back from my dealer. I've asked if they experience this same kind of hiss on any of their setups.

-Matt
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  #26  
Old 06-12-2017, 09:59 PM
damacman damacman is offline
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Dave - glad to hear. The MC7300 is a very fine amplifier. I have heard one powering Khorns w/ the Power Guard lamps flashing if you can believe that! Oh to be 25 again ... Mine is presently not in use at the moment but it's awaiting it's turn. I've always admired the styling and the full glass face. While the closed chassis isn't as visually appealing as the MC7270 it replaced, dusting is cake in comparison.

Matt - what speakers are you running? Sensitivity?
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  #27  
Old 06-13-2017, 02:59 PM
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Hi damacman -

I'm using Revel F32 speakers. Nominal impedance is 6.5 Ohms and the sensitivity is 86.5 - not super efficient like Khorns, but not too bad either.

-Matt
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  #28  
Old 06-13-2017, 04:01 PM
damacman damacman is offline
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Quote:
Originally Posted by eedork View Post
Hi damacman -

I'm using Revel F32 speakers. Nominal impedance is 6.5 Ohms and the sensitivity is 86.5 - not super efficient like Khorns, but not too bad either.

-Matt
You likely have a preamp problem if you can hear hiss through those speakers. The 18dB difference in sensitivity equates to a huge difference! 1W for Dave means about 75W for you to achieve the same loudness. You guys should swap amps!
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  #29  
Old 06-13-2017, 08:13 PM
MBlue72 MBlue72 is offline
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Quote:
Originally Posted by damacman View Post
You guys should swap amps!
Mmmm ... No, that's OK.

Dave
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  #30  
Old 06-14-2017, 04:07 PM
damacman damacman is offline
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Originally Posted by MBlue72 View Post
Mmmm ... No, that's OK.

Dave
Lol. I ran across a guy years ago that bought Khorns with an MC2600 new! Now that's crazy. I have two of those as well. I like this era of Mc amps.
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