[Kenneth Patchen]

A very loud hum is coming from the used AVA Fet Valve 550 Ultra I recently purchased here on AC. Other than that, it seems to be driving my HT2-TLs just fine. Will a humdinger remove the insidious hum? Is this hum  normal for a 550 Ultra or is this indicative of a more serious problem requiring maintenance? I have the 550 plugged directly into my hefty Torus power conditioner but the hum persists.

My thanks in advance,
KP

[ACHiPo]

Sounds like a ground loop.  A few suggestions:  1)  I'd contact the seller to make sure there aren't any peculiarities with the unit (i.e. make sure it didn't hum when he sold it, or if he had to do something to overcome a hum in his system).  2) Is the amp plugged into the same circuit as the rest of your gear? 3) Do you have a turntable and if so is the ground wire firmly attached.

[coke]

I have the same amp on a pair of HT2-TLs.  Should be silent.

[max190]

KP, A loud hum could be from a failed capacitor.
How old is the amp?

[avahifi]

First of all, shut down the amplifier, wait until it dies down really off, and then disconnect the RCA input cables at the back of the amplifier, so the amplifier is only connected to the speakers.

Turn the amp on again.  Does the hum go away?  If so the problem is not the amplifier, but the connections/cables ahead of the amplifier.

Is the hum coming from the chassis of the amplifier or from the speakers?  If it is from the chassis, a HumDinger may help.  It will not help if the hum is from the speakers only.

We have seen hum caused by use of exotic interconnect cables, such as those claiming to be unshielded or "one way" designs.  These often pick up excess hum or cause ground loop hum.  Try the amp with plain old cheap simple coax RCA cables.

If you still can't find the cause, please call me for help.  651-330-9871. 

The problem most likely is not a failed capacitor.  We have yet to have that happen on this series of amplifiers.

Frank Van Alstine

[ACHiPo]

First of all, shut down the amplifier, wait until it dies down really off, and then disconnect the RCA input cables at the back of the amplifier, so the amplifier is only connected to the speakers.

Turn the amp on again.  Does the hum go away?  If so the problem is not the amplifier, but the connections/cables ahead of the amplifier.

Is the hum coming from the chassis of the amplifier or from the speakers?  If it is from the chassis, a HumDinger may help.  It will not help if the hum is from the speakers only.

We have seen hum caused by use of exotic interconnect cables, such as those claiming to be unshielded or "one way" designs.  These often pick up excess hum or cause ground loop hum.  Try the amp with plain old cheap simple coax RCA cables.

If you still can't find the cause, please call me for help.  651-330-9871. 

The problem most likely is not a failed capacitor.  We have yet to have that happen on this series of amplifiers.

Frank Van Alstine

I'll defer to Frank's advice

[Kenneth Patchen]

First of all, shut down the amplifier, wait until it dies down really off, and then disconnect the RCA input cables at the back of the amplifier, so the amplifier is only connected to the speakers.

Turn the amp on again.  Does the hum go away?  If so the problem is not the amplifier, but the connections/cables ahead of the amplifier.

Is the hum coming from the chassis of the amplifier or from the speakers?  If it is from the chassis, a HumDinger may help.  It will not help if the hum is from the speakers only.

We have seen hum caused by use of exotic interconnect cables, such as those claiming to be unshielded or "one way" designs.  These often pick up excess hum or cause ground loop hum.  Try the amp with plain old cheap simple coax RCA cables.

If you still can't find the cause, please call me for help.  651-330-9871. 

The problem most likely is not a failed capacitor.  We have yet to have that happen on this series of amplifiers.

Frank Van Alstine

Well, that worked a treat! Terrific! Thanks Frank and everybody.

Pulled the ICs, still humming. Pulled the speaker wire, no hum! Replaced the bespoke ICs and speaker cable with plain vanilla generics, no hum! Thanks again Frank. I should have mentioned that our house is 106 yo with some of the original wiring still in place.

(Very nice amp that 550 Ultra. Really opened up the HT2-TLs.)

Cheers,
KP

[mocenigo]

Hi, I was wondering, how loud was your hum? Clearly audible from 1 meter, say during a silent night? 2 meters?

Also, what were the speaker cables you were using? If you do not want to say that explicitly you can DM me.

 Roberto

[orthobiz]

I had a tiny buzzing from my 550 that was cured with the Humdinger.

Paul