Hum from LF section in one of my Summit’s

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Wowfactor

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Hello. Just bought a nice set Summit’s in mint condition. Listened to them at the sellers place - sounds fine. Returning home I ran in to a strange error. When one of the Summits was connected to the mains only and without the jumpers it is humming. When I then mount the jumpers the hum is gone.
Any fellow members with same experience and a solution? I took out the back plate and checked for loose connectors. Seems fine to me. I would appreciate to get a copy of the service manual - anyone? I have also emailed ML support but take the chance here aswell for a quick fix.
Best regards
Mikael/Denmark
 

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Lightloopy

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Welcome. Beautiful system. Hums are usually a ground loop problem but will defer to others in the group. There is a process to work through. If the hum goes away once you are all ready to listen then great.
I have a MFA D75 amp that sends a hum through the 11A's when I turn it on standby then goes off when I flip the operate switch. Didn't do it with the SL3's. Could you share what other gear you are using? Looks sweet.
Good luck.
 

Wowfactor

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Hello Lightloopy. Thanks for your reply. I dont think it is a ground issue. With the speaker in standby or with music playing then pulling out one jumper the hum appears. I am in contact with ML. Next step for me is to try to isolate/narrow the problem. 1) check if both lf drivers hum. 2) remove one connector from internal amp to lf driver and observe. I will of course post my findings and hopefully what cause the hum. I have tried different amps (we import Linear Tube Audio exclusiv to Europe). Problem didn’t disappear. The last we tried different MHDT dacs, preamps and the Light tower” you see on the picture. Its from Audio Music, new model, 1x145 watt into 8 or 4 ohm single ended tube amp. Marvelous piece of work. The smaller one is a 1x50 watt version. Stay safe. Mik
 

spkrdctr

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Thanks for the equipment explanation. At first I thought your light tower was a fancy European coffee maker. I thought it looked good but I figured you must really drink a lot of coffee. But, now I know, it is just another fine looking tube amp. I hope you get your problem fixed. ML customer service is usually very good.
 

Wowfactor

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Thanks for the equipment explanation. At first I thought your light tower was a fancy European coffee maker. I thought it looked good but I figured you must really drink a lot of coffee. But, now I know, it is just another fine looking tube amp. I hope you get your problem fixed. ML customer service is usually very good.
I do drink a lot of coffee...........:) and the amps keep it warm...
 

ttocs

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I don't think Summits are designed to work without jumpers. The woofers are powered and need a connection to an amp providing the signal.

Let's try it this way, if you only connect the Woofers to the amp, no jumpers to the ESL, what happens? My bet is the hum goes away and there's no sound emanating from the ESL.

I believe the hum is simply a "no connection" or "partial connection" hum.
 

Wowfactor

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Nope ttocs. I have of course tried to run the other speaker with out jumpers and/or connection to the amp. No hum what so ever. My plan was to check the internal amps and see what happen if I disconnect first one driver, listen, plug it back and disconnect the other driver and listen. I suspect that one or both internal amps has a cold connection or is damaged and need replacements. Hope it is a cold connection/joint. Rgs Mik
 

ttocs

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I see.

If it were me, I would replace the humming speaker with the non-humming speaker, or vice versa. The only variable is the speaker, all else remains.

A little side story of hum. Just last weekend I connected a subwoofer for the Center Speaker to the same outlet as what the Center speaker and amp were plugged into, but that wasn't good enough - it hummed, so it had to be plugged into the same circuit as the preamp. Hum is funny that way.
 
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Wowfactor

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I have done all the standard error search before I post. So yes left speaker got signal from right mono amp and vice versa. Other amps are also tried. Make no difference.
 

18000rpm

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Summits can definitely run without jumpers since that's what you do when you bi-amp them.

To me it sounds like a ground loop, try using a cheater plug and see if the problem goes away. If it does, you can then try to narrow it down by disconnecting components in your chain.
 

ttocs

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This is in the Summit manual:
"Bi-Wire Connection
Bi-wiring the Summit is not necessary. The Summit is provided with a bi-wiring option to allow consumers who already own quality bi-wire cables to use their existing cables. This connection method replaces the jumper clips installed under the binding posts with individual runs of speaker wire from your amplifier. This doubles the signal carrying conductors from the amplifier to the speaker, thus direct-coupling each portion of the crossover to the amplifier.

Bi-Amplification
The Summit’s PoweredForceTM woofers are internally powered. Because of this, we do not recommend either active or passive bi-amplification."
 

Russr

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Howy Cwap, Batman... is that a tube-powered skateboard???!!!

:D
Awesome looking system... dig the wheels!
 
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