Sound in/out during quiet scenes with external amp

[Whitey80]

Been having a problem with this since adding a pair of amplifiers to my setup.

(First off, I'll list the gear involved: Pioneer Elite VSX-92txh receiver, Crown ComTech 400 bridged running center channel, Crown ComTech 1610 running front L and R, hacked apart linelevel cables running signal to euroblock inputs of amps)

The problem is only occuring with the L and R channels, and only while running through the external amp.
Durning quieter scenes, it seems the amp cuts output and it clicks back in when it becomes louder, about a second after it begins. The amp has a power saving feature in the PIP card, but it's not to do with cutting signal or output, it should never cut when powered on, as I understand it.

I'm not positive what to check here, or possible routes of diagnosis at the point.


---Link to ComTech "10" series referrence manual http://www.crownaudio.com/media/pdf/legacy/101969.pdf

 

[highfigh]

How do you turn this amp on- power switch, or does it sense the incoming signal? If the latter, make sure the threshold voltage or time 'till shutdown are appropriate. If your receiver has a 12VDC trigger, use that- it only turns off when the receiver shuts down or if it goes to a different input, assuming the trigger is assignable.

 

[Seth=L]

If the PIP card doesn't detect enough voltage on the line input the amplifier will go into standby. I'd suggest making adjustments to the gain of each channel to say 3/4 or 1/2 of present output and compensate the rest of your equipment accordingly.

How long are your cable runs to the amplifier? Long cable lengths without amplification could also be the cause, or faulty cabling.

 

[Whitey80]

Highfigh:
I turn the amp on manually from the panel switch

Seth:
The cables are only 2' long, but quite bodged, so that could be a failure point.
I have tried running the amps gain low and increasing output from the pre-amp, to no effect. Will make some more proper cables, then possibly swap the PIP card from the 400 over and see how that goes.

 

[Whitey80]

Made new patch cables of much better quality today. Hooked suspect amp up to 2 channel system in another room, and no problems.
So my cables may have been the issue.....or, the preamp outputs from my receiver in theater (or processing) is the issue. Will find out when I place amp back into system in theater room.

 

[Seth=L]

Made new patch cables of much better quality today. Hooked suspect amp up to 2 channel system in another room, and no problems.
So my cables may have been the issue.....or, the preamp outputs from my receiver in theater (or processing) is the issue. Will find out when I place amp back into system in theater room.

Hopefully it was just the cabling and not a more serious problem. I think you can eliminate the amplifier as the origin of the problem, although it's possible that doing away with the PIP may get rid of the problem all together.

 

[highfigh]

Made new patch cables of much better quality today. Hooked suspect amp up to 2 channel system in another room, and no problems.
So my cables may have been the issue.....or, the preamp outputs from my receiver in theater (or processing) is the issue. Will find out when I place amp back into system in theater room.

Did you see the section about adjusting the input sensitivity in the manual? It's on page 28. The sensitivity control is inside of the PIP module cavity.

 

[Whitey80]

I did, it's not as useful as it sounds, it only has a couple of positions based on if you are using if for 8ohm or 70v systems

 

[highfigh]

I did, it's not as useful as it sounds, it only has a couple of positions based on if you are using if for 8ohm or 70v systems

IF this occurs again:

take an RCA Y-adapter that has an 1/8" stereo in and two RCA ends, connect it to the Crown's input jacks, turn it on and vary the level from your phone while it has music playing. Let it play for a few hours and vary the level repeatedly. If the problem can't be repeated, it's probably not the amp's fault. If you want a cheap piece of useful test equipment, find a Radio Shack (might be hard to do, now that they're closing 1800 stores) or some other store that sells electronic gadgets and buy an amplified speaker. If it has a short cable with 1/8" plug, buy the appropriate adapter and connect it to the Pioneer. Let it play for hours, varying the level from that piece.

I didn't see any mention of the speakers you're using. What are they? The manual mentions that if the speakers have an especially inductive load, a filter should be added.

 

[Whitey80]

Thanks for the thoughts on diagnosis, Highfigh.

Running Boston Acoustics VR950 mains and VR920 center.

 

[highfigh]

Thanks for the thoughts on diagnosis, Highfigh.

Running Boston Acoustics VR950 mains and VR920 center.

How hard are you driving these? If you're operating at extremely high SPL, the speakers may be suffering from over-excursion and that can cause problems for amplifiers with sensitive protection systems.

Out of curiosity, what made you choose these amplifiers? They're made for commercial/industrial installations.

 

[Whitey80]

The amps are overkill for the middling old speakers I'm currently using for certain. But I have a trio of quite nice, capable speakers that will require the power and actually make it to reference level in this room waiting in the wings to get in there once I switch to an AT screen that they can fit behind.

To your other question: Commercial amps I have used for other applications are absolute tanks.

Aside from being a little more difficult to integrate into consumer systems, they handle seriously difficult loads without a sweat (Switched from much more "refined" consumer mono amps to a big Crown to drive my nightmare Magnepans to great gain).
After trying so many different units over the years, there's not much of a comparrison between what you get from consumer level and pro level for the same price. And the flexibility ( I do use a 70v systems throughout the house and outdoors ).

 

[highfigh]

The amps are overkill for the middling old speakers I'm currently using for certain. But I have a trio of quite nice, capable speakers that will require the power and actually make it to reference level in this room waiting in the wings to get in there once I switch to an AT screen that they can fit behind.

To your other question: Commercial amps I have used for other applications are absolute tanks.

Aside from being a little more difficult to integrate into consumer systems, they handle seriously difficult loads without a sweat (Switched from much more "refined" consumer mono amps to a big Crown to drive my nightmare Magnepans to great gain).
After trying so many different units over the years, there's not much of a comparrison between what you get from consumer level and pro level for the same price. And the flexibility ( I do use a 70v systems throughout the house and outdoors ).

The bang for the buck is hard to beat but as you posted, some commercial amps are harder to integrate but there are some consumer amps that have the more common connections and are ready to receive the signal levels common in consumer gear. Plus, there's less chance of an impedance mis-match if you stick to consumer unless the pro/commercial piece has unbalanced inputs.

Not telling you to change amps, but you might want to look into the input impedance of the Crown vs the output impedance of the Pioneer.