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What does an impedance-matching issue "sound" like?

I recently added a 2nd Luxman MQ-88uSE to my 2 channel system, bridged to mono so I am running a Luxman to each of my 6ohm Volti Rivals.

The SE version of this Luxman amp only has single speaker taps which output 25Wpc to 6 ohms, and 20Wpc to 4 ohms and 8 ohms (from the manual). I used a jumper between each of the "positive" taps so I am not sure what the bridged output is to the 6 ohm Rivals.

Now what I am hearing is definitely more power and presence in the sound, better bass, as well as improved separation. BUT occasionally I am hearing what sounds like a bit of breakup deep in the mix of some songs. Like the whole channel isn’t breaking up, but suddenly a rhythm guitar part sounds noisy like it’s being played through an AM radio or something. On some songs, the entire mix may sound reduced in scale and less dynamic.

I am not sure if my ears are playing tricks on me, or if I’m crazy, or if there could be something happening in the pairing of these amps and speakers that is bad for the equipment and sound. I realize this is a complicated issue because one amp is brand new and the other is broken in, and they are both tube amps., So chasing down the culprit could get messy.

Is it possible there are impedance issues at play here? What would that sound like?



128x128jsqt
erik_squires
16,021 posts
 
If you are attempting passive bi-amping:


Amp L ( + ) ------ Speaker HF (+)
Amp L (-) .-------> Speaker HF (-) 

Amp R ( + ) ------ Speaker Low F (+)
Amp R (-) .-------> Speaker Low F (-)


In neither case should the (+) amp terminals touch each other, even from matched amps. The slightest (0.001V) variation in output can induce significant current as the sides fight for the right value. 


Best,


E
erik_squires
16,021 posts
 
Sorry, if you are using different output amps, your set up would look more like this:

Amp 1 - L  ( + ) ------> L Speaker HF (+)
Amp 1 - L (-) .------->  L Speaker HF (-)

Amp 1 - R ( + ) ------>  R Speaker HF (+)
Amp 1 - R (-) .------->  R Speaker HF (-)
jsqt's avatar
jsqt OP
117 posts
 
Thanks guys this helps a bit.

I may be confusing bridging and parallel, depending on how it was described to me. 

The setup is basically diagrammed here, aside from the multiple speaker taps and the fact it is a MQ300 and not an MQ-88uSE (but they should be set up the same way)

https://onahighernote.com/blog/productfaq/connect-luxman-mq-300-mono-block/

As Al mentioned, there could be a number of factors contributing to what I'm hearing. I'll continue to run in the new amp and see how things settle down over the next couple of weeks.

jsqt's avatar
jsqt OP
117 posts
 
Also, I confirmed before purchasing the second amp from Luxman that they could be run in mono configuration using the above setup so I am confident it is setup properly. 
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