It's a shame they don't give the poweramp (blue) distortion figures when it's in "strapped paralleled" mode also, this "could" give your problem.
Cheers George
Cheers George
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?
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?
Showing 6 responses by georgehifi
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.Read this above that you posted then this below from Eli. I see a similarity. "Very few amps work well, with simple paralleling. Unfortunately, heat and distortion are the typical result." As well I would have thought 2 separate channel negative feedback’s suddenly linked together via the transformer secondary tap could also be a problem, and maybe a source of this distortion. I could see if there was no global feedback as in some amps, then paralleling could work. But Luxman tube amps all use global feedback from the circuits of their’s I’ve seen. This is one that would be almost the same as yours, with the feedback highlighted. https://ibb.co/pRpGtPQ Just found the 88 circuit https://ibb.co/RhG8hJj Cheers George |
jsqt OP I believe Eli on diyaudio is quite clued up, from pass posts I’ve read, combining the feedback of both channels becomes an issue beside other things, here is what he says about paralleling tube amps. "Very few amps work well, with simple paralleling. Unfortunately, heat and distortion are the typical result." Cheers George |
So I don’t think tubes are the issue, but it’s the 3 ohmsThat 3ohms at 110hz with -50’ phase angle at 75hz to me is an issue, especially with SE tubes, this is where all the amps power is needed for bass repoduction. I find it hard to believe a speaker manufacturer would voice a speaker with this kind of load graph with "feeble" SE Border Patrol amps, that are probably good amps with the right speaker, easier loads than this.. Cheers George |
jsqt OP Bridging amps in solid state, Doubles the output impedance Halves the damping factor Increases the distortion Has have the current ability. Makes the amp less stable into lower impedance’s to what it was in stereo. So everything takes a hit, except you gain higher watts. I believe the same happens in tube amps also. https://www.stereophile.com/images/617Voltifig1.jpg If so where you may have had a amp that could "just" sort of drive the Volti Rivals 3ohm load at 100hz with 50 degrees of -phase shift in the bass. Now you have no chance bridged. Along will come the suggestion of autoformers, they are just a band-fix don’t get sucked into that. Solution go back to Stereo. You could vertically bi-amp the two stereo amps (one channel bass, the other mids and highs. (same for the other side) Change speakers or change amps. Cheers George |
@almarg Ooops sorry, just saw what he said in the first sentence. 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 In any case that phase/impedance load around 100hz is nothing that tube amps want to be seeing. https://www.stereophile.com/images/617Voltifig1.jpg Change the amps if you want to keep the speakers. or visa versa Cheers George |