Marantz AV 7701 with Crown XLS amp source levels - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 8 Old 12-31-2013, 09:16 PM - Thread Starter
Senior Member
 
blueskies758's Avatar
 
Join Date: Jan 2006
Posts: 223
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 10 Post(s)
Liked: 21
Just picked up a Marantz AV 7701 pre/pro and hooked it up to my new Crown XLS 1500 via unbalanced RCAs.

It sounds fantastic, but I wonder if I have the levels set correctly. I've been into home theater since I was old enough to save up and buy a Toshiba Cinema series tube in 1995, but I'm new to separates.

If I dial up the crowns gains to 60% or greater I detect a slight hum/buzz. Its only inaudible about 1-2 feet from the speakers.
The same buzz/hum is inaudible at a lower amp gain like 50% or so. I don't think its a ground loop, or if it is, it's among the quietest ground loop
I have heard.

I also feel like I should be getting more headroom on an amp that is 300W @ 8 ohms. The speakers are small 2 way Energy C-10s, until we buy a house next year and I can unpack the Paradigm Studio 60s. I am up near the mid 60s/100 volume on the Marantz with the amp set to the crowns gain of around 60%. I also have an inline Samson 7 band EQ with a gain knob which I have around 60% also.

Question is, how many of you dial up your pre/pro or AVR input level (in the menu HDMI 1, Blu ray, etc) to above "0" to compensate without inviting a higher noise floor? I could do that and/or dial up the R/L speaker levels again thru the Marantz menu as well.

Is that cheating?
blueskies758 is offline  
Sponsored Links
Advertisement
 
post #2 of 8 Old 12-31-2013, 10:18 PM
AVS Special Member
 
Knucklehead90's Avatar
 
Join Date: Nov 2008
Location: State of Confusion - 98823
Posts: 7,338
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked: 98
Why be concerned about anything that can't be heard from from your listening position when there is dead silence?

When all else fails - RTFM!

♫♫♫ Two Channel Rules! ♫♫♫

GO SEAHAWKS!!!
Knucklehead90 is offline  
post #3 of 8 Old 12-31-2013, 10:48 PM - Thread Starter
Senior Member
 
blueskies758's Avatar
 
Join Date: Jan 2006
Posts: 223
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 10 Post(s)
Liked: 21
Good question! I suppose for the same reason many of us are into this hobby. The pursuit of perfection or as close as can be achieved. And I like a lot of headroom in my sound I suppose.

Plus I wasn't sure if I should be able to set the gains on the amp to 70% or higher without introducing noise, then is there something wrong with my connections.

And again being new to separates I'm not quite sure as to what gains to adjust to reach my sweet spot without risking any damage to the gear.

As it stands I have

Crown gains
Marantz gains (internal to menu via speaker level and HDMI audio level)
In line Samson EQ 7 band gain

Its a lot more variables to tweak, but its fun for me..
blueskies758 is offline  
post #4 of 8 Old 01-01-2014, 06:58 AM
AVS Special Member
 
Selden Ball's Avatar
 
Join Date: Jan 2001
Location: upstate NY
Posts: 6,459
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 54 Post(s)
Liked: 327
Getting the gains set appropriately in the various parts of the signal chain is important in order to avoid distortion and clipping at higher signal levels and to minimize noise at lower signal levels.

With Marantz pre/pros, this concern has to include the trim levels on each of the inputs (which can be set individually), the trim levels on each of the speaker channels, and the setting of the master volume control.

If you can avoid it, you shouldn't try to compensate for low gain in a later stage of amplification by increasing the gain of a previous stage. When carried too far, this can cause the output of the earlier stage to overdrive the input of the later stage, which results in clipping. This can have audible results (a harsher sound) and, if the clipping happens in the final amplifier stage, it can cause damage to speakers (due to overheating by higher average currents through their electromagnets).

So....
I'm surprised that you can't run the Crown amps with a gain of 100% without audible noise. Are you hearing that with shorting stubs connected to the Crown amps' inputs? I.e. with an input signal guaranteed to be 0 volts with no noise? If so, I'd contact Crown, since the spec sheet for the 1500 claims that the noise is supposed to be 103dB down when driven at full power (i.e. with an input signal of 1.4v rms). That should translate to being completely inaudible when the input signal (and thus their output power) is at minimum (0v) unless you have your ears very close to the tweeters.

If you're only hearing noise when other equipment is attached to the inputs, then the noise probably is originating elsewhere, and not internal to the Crown amps. You should determine if the source is internal to the amps by putting shorting stubs on their inputs: if the amps are essentially silent with them attached, then the noise source is external. (Due to a "ground loop", in the 7701, or elsewhere.)

Are your Energy speakers actually RC-10s? I can't find a model C-10 on their site. If so, bear in mind that they have a maximum power capacity of only 175 Watts, so driving them at the maximum possible sound level (with the Crown amps outputting their full 300W) is likely to damage them.

WRT the volume setting on the 7701, don't forget that after Audyssey calibration, the 7701's volume settings are logarithmic. They tell the 7701 the sound level that you want to have at your primary listening position. Its volume settings tell you nothing whatsoever about what fraction of their maximum power your amps actually are producing. In particular, a value of 80 on the 7701's "absolute" volume scale would make your audio system attempt to produce movie reference sound levels, with peaks of 105dB. Energy RC-10 speakers aren't quite efficient enough to do that, and would be damaged if you tried. However, in most home listening environments, most people prefer to listen about 20dB below reference, with volume settings in the vicinity of 60.

Harman/Crown provides a calculator which tells you how much power is needed to produce a specific sound level using speakers of a given sensitivity at a particular listening position. It can be quite helpful in evaluating the kinds of equipment to get if you want to be able to listen at full movie reference levels. See http://www.crownaudio.com/elect-pwr-req.htm

I hope these comments help a little.

Selden
Selden Ball is offline  
post #5 of 8 Old 01-01-2014, 09:06 PM - Thread Starter
Senior Member
 
blueskies758's Avatar
 
Join Date: Jan 2006
Posts: 223
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 10 Post(s)
Liked: 21
Selden - your audio knowledge is something to behold. Thank you so much.

My current speakers are way way overpowered lol, as they are these little guys.

http://www.energy-speakers.com/products/connoisseur-series/?sku=CB-10

Not safe to unpack the Paradigm Studio 60s with our 1 year old around. When I have my dedicated room later this year (with a lock!) then I will bring out the bigger boys.

I read up on other crown amp owners experiences, and it seems that some report a slight hum/noise floor within a foot of the speakers, and some do not. Many have their gains around the 12 pm position, and I will dial mine back a bit and try your suggestion first.

ONE QUESTION - WHAT ARE SHORTING STUBS? Never heard of them. And I would insert them into the amps inputs ?
blueskies758 is offline  
post #6 of 8 Old 01-02-2014, 09:53 AM
AVS Special Member
 
Selden Ball's Avatar
 
Join Date: Jan 2001
Location: upstate NY
Posts: 6,459
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 54 Post(s)
Liked: 327
You're very welcome for what little help I've actually managed to provide. I've been involved in hifi audio for decades, since long before I joined AVS, and was trained in electronics repair in the military, which helps some, too smile.gif

Sorry I wasn't clearer about "shorting stubs". They often are stubs of RCA cables with the two wires shorted together. Sometimes they're available premade from places like Radio Shack as male RCA connectors with a wire soldered from the center pin to the shell.

In other words, they're a way to short the signal input (the center pin of the connector) to ground (the outer shell) so that you can guarantee that no noise is picked up on the amp's analog input. Sometimes with high-impedance inputs, if you leave the inputs "floating" they'll pick up noise radiated by other devices. The total picked-up noise can be fairly high if the wires (or circuit board traces) between the back-panel connectors and their associated input preamps are fairly long: all wires act as antennas. In most home environments, this kind of noise pickup really isn't a problem because most homes are very quiet electrically. Some aren't, though, especially if you live near a radio or TV transmission tower, or have an extensive electrical fence, etc.

Selden
Selden Ball is offline  
post #7 of 8 Old 01-02-2014, 06:29 PM - Thread Starter
Senior Member
 
blueskies758's Avatar
 
Join Date: Jan 2006
Posts: 223
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 10 Post(s)
Liked: 21
Selden each post I learn something from you. very cool.

Thanks for the heads up on shorting stubs, will look into them.

We are renters for now, so our AC could be dirty for lack of a better word. I do use an APC J15 so that helps I think some.
I will play around with the gains, perhaps cable swap, and remove the EQ for comparison purposes.
Other options I have are to attempt XLR connects, or put a ground loop gadget inline as well. So there are things I can do.

My volume is very satisfactory, and I very much like the amp.

Thanks again for all your help
blueskies758 is offline  
post #8 of 8 Old 01-02-2014, 06:42 PM
AVS Special Member
 
Selden Ball's Avatar
 
Join Date: Jan 2001
Location: upstate NY
Posts: 6,459
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 54 Post(s)
Liked: 327
You're very welcome.

From what you've written you're considering appropriate corrective actions.
Happy listening!

Selden
Selden Ball is offline  
Reply Receivers, Amps, and Processors

Tags
Marantz Av7701 Audio Video Preamp Processor , Crown Xls 1500 Power Amplifier 2 Channel 525w 4 Ohms Per Ch , Energy Esw C10 10 Inch 400 Watt Subwoofer Black
Gear in this thread

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off