PA 7-350 XLR gain differences & attenuation?

[Creature]

Hi,

I have a pair of Sherbourn PA 7-350's.  One purchased new and the second used from a member of this
board.  Both are working well and sound beautiful. 

I've recently completed a media room and have hooked both via balanced XLR to a Marantz AV8802A. 
For whatever reason, I chose to use the 7-350 purchased new to handle the left side of the room and the
used PA 7-350 to handle the right. 

After running the Audyssey, the level trim for all of the right is at -12 Db, which is apparently the Audyssey
limit.  The left trim results vary pretty much between -7 and -9 Db.  When running Audyssey setup, the right
is so loud I'm worried about damaging my towers.  The left channels all run through the chirps with authority
but I'd estimate the amplitude to be 6 Db or more quieter. 

Thanks for reading this far.  With no further ado, here are my questions. 

1. Other than the pre-production units, was there a change over the production runs in which the XLR
   balanced inputs had their gain level changed?  Mine seem to have something like a 5+ Db difference
   between the two amps. 
   
   
2. Should I order some 10 Db XLR line attenuators?  The description for many of these seem to be intended
   for use between microphones and pre-amps.  Though, I've read a number of posts where folks have put
   some of the same attenuators between the pre-amp/pro and their amplifiers.  Any gotchas, like having to
   carefully match impedence or anything?
   
   
3. Is there any way to get the AV8802A to reduce the amplitude of its XLR outputs during the Audyssey setup?
   After Audyssey setup completes, left and right sound pretty balanced.  However, I am afraid to run the
   Audyssey setup again for fear of damaging the speakers attached to the 7-350 with apparently higher gain.   
   I recognize that this third question may not be appropriate to this forum, my apologies. 
   

I'm grateful for any wisdom you're willing to share.  Thanks!

[Gary Cook]

Personally I'd call Emotiva support and ask question #1, first, before I did anything else.

Cheers
Gary

[Creature]

Hi Gary,

I took your advice and sent email to [e-mail].  I asked if there was a change of
gain levels during the various production batches.  Maybe the used PA 7-350 was from an
earlier production run.  The 7-350 purchased new was acquired in August 2013 and is likely
a late production example, and is the one apparently with lower gain. 

Oddly, neither has its serial number printed on the back of the amplifier chassis.  There's a
spot on the back for both the model number and serial number.  Both are missing the serial
number.  The serial number for the one purchased new in 2013 is printed on the cardboard
box in which it arrived, so is known.  The serial number for the used 7-350 is unknown by
me.  I wonder if the serial number is printed elsewhere on the chassis. 

I'll post an update upon receiving a response from the support folks.  Thanks!

[macromicroman]

All my Audyssey trim levels were -12db when I used the XLR outputs from my Marantz AV7005 into Emotiva XPA-5 Gen 1 amp. I have klipsch Reference speakers. I bought attenuators (10dB) and used them on the XLR outputs od the preamp. Everything then worked fine. Forgot where I got the attenuators (Parts Direct) I think.

[lynnmass603]

on the bottom of the unit

[xidane]

Hello
If any one selling sherbourn-pa-7-350 please email me at
[e-mail]
Really need one thanks
From canada

[Creature]

Hi,

I got an initial response from Support.  They thought I should check the XLR connections for having
been seated properly.  I explained that all were carefully seated and for each of the two PA 7-350
amplifiers, the apparent gain between all seven channels were quite uniform with one another.  It is
only when comparing from one amplifier to the next is there a significant difference.

One (the late production PA 7-350) powers six speakers on the left of the room and the other (the
older PA 7-350) powers the right six speakers plus the center channel speaker.  The right is all set by
the AV8802A to be at its indicated limit of -12 dB.  The left varies between -5.5 to -9 dB.  The three
towers on the left are within 1/2 dB of each other.  The -5.5 dB channel is a Monitor Audio CT380-IDC
that is further away and with higher impedence and lower efficiency.  The room is nearly symmetric
down its long axis, including attenuating and reflecting materials. 

The following links seam to suggest that early PA 7-350 amplifiers had a higher gain.  The Sound &
Vision and Audioholics lab tests both showed a gain of 34.7 dB.  Andrew's review stated 32 dB.  I'm
guessing both tests were measured using the unbalanced RCA inputs.  I've read that balanced XLR
inputs are generally about 6 dB below the RCA inputs on the same amplifier. 

www.soundandvision.com/content/sherbourn-pt-7030-surround-processor-pa-7-350-amplifier-ht-labs-measures
www.audioholics.com/amplifier-reviews/sherbourn-pa-7-350-seven-channel-amplifier-preview
www.andrew-robinson-online.com/review-sherbourn-pa-7-350-7-channel-power-amplifier/

I thought I read elsewhere, this board perhaps, were the PA 7-350 was stated to have a 29 dB gain,
which is the THX standard.  My guess (and question for Support) is that there was a specification change
during the span of production. 

Anyhow, not a big deal.  I have two pairs of XLR line attenuator cables on their way.  Two from Naiant
Studio and two from Audiogadgets.  I'll audition each.  If that seems to do the trick, I'll order several more
of the brand I like best.  I'll likely also rearrange the amplification channels, grouping similar efficencies
and impedences onto the better matching amp.  Thanks!
 

[highfihoney]

This might sound stupid but check your xlr cables to make sure they are proper xlr , ive ran into xlr's that have an odd configuration of the #3 pin being the hot pin vs the standard #2 pin hot configuration , i have zero idea why some manucacturers decided to reverse polarity on an imdustry cable scheme , ive also had some xlr turn out to be a 2 pin active scenario with the xlr ground missing so basically an rca posing as an xlr .

[Creature]

Hello again,

I'm replying with the intent to kind of wrap things up. I received some rather helpful and well considered
assistance from Emotiva. They acknowledged that early and late production PA 7-350s do have a different gain
level. I have an example of each.

Not knowing that the two amplifiers had different gain levels, I made an unfortunate decision to drive the
left with the lower gain amp and the right with the higher gain. Audyssey setup begins with the left front
speaker and pretty much works around the room clockwise. This meant that Audyssey chose its test tone level
based on the lower gain amp but then transitioned to the high gain amp. The result being a substantially
louder test tone down the right side of the room.

The advice was to deploy the amplifier channels differently. The key being two fold. 1) Have the left/right
speaker pairs driven by channels coming from the same amplifier. 2) Make certain that the channel used to
establish the test tone level (the left front in my case) is being driven by a channel from the higher gain
amplifier.

I did purchase a pair of -12 dB attenuator cables from Naiant Studio and will likely buy more. They are
very nicely crafted and at a most reasonable price. The reason I may use them is that Auyssey will only
display output channel attenuation in the +12 to -12 dB range. Pretty much all of the channels on the
high gain amplifier have hit the -12 dB mark. I think I'll use attenuators sparingly only for those
channels that would otherwise bump into that indicated -12 dB output level as set by Audyssey. Even if
used, I'll obey the maxims of the previous paragraph.

Thank you to those who replied here and to the kind folks at Emotiva.