2. amps-preamps
  3. 1403055490

How quiet is your Rogue Sphinx?

I have a new Rogue sphinx, I don't recall the unit I demoed to be especially noisy but I do find my unit to have some noise despite other owners describing the model as 'dead quiet'.

In both 'standby' and 'on' there is a quiet though audible hum coming from the right hand half of the unit (maybe I can hear it through the vent on the top). You need to put your ears pretty close to the unit though.

There is also a similar hum to be heard through the mid/bass unit, audible about 2 feet away. This is aside from the more common 'hiss' that is also present. Oddly if I turn my balance control left all the way, the hum becomes much louder through the right speaker only and can be heard about 10 feet away. If I turn the balance to the right the original hum in the left speaker actually decreases in volume!

I am used to speakers having a hiss but the question I ask is do any other sphinx owners notice this extra layer of hum/buzz that varies with the balance control in this way? Is your actual amplifier unit dead quiet or does it have a faint hum also?

Just trying to figure out if my unit operates typically or otherwise.

Thanks in advance.
big_katydid

Showing 6 responses by lowrider57

lowrider57's avatar
lowrider57
5,418 posts
 
The hum coming from inside the amp is likely coming from the transformer. Noise or distortion on the AC line from light dimmers, small appliances, refrigerator can cause this. The only way to know in this case is to remove your amp from a shared AC line. Or it's possible that the factory transformer may be mounted in such a way that it produces noise; (a common occurrence). When playing your system, you don't hear the hum because the music is louder than the hum.

Transformer hum can not be heard thru the speakers. However, your balance control hum may be the same problem I experienced with my Perseus Magnum. After about a year of ownership, a hum developed thru the right speaker. When I panned the balance control left/right I could cause the hum to vary in volume.

I sent it to Rogue and it turned out to be a bad VC. It was replaced and no problems since then.
lowrider57's avatar
lowrider57
5,418 posts
 
Big_katydid; Transformer hum does happen with some amps and you should try to find a device like the PS Audio Humbuster (which I believe is discontinued).

As for the volume control related hum, I would send this unit to Rogue for warranty repair. This very similar hum on my preamp was the result of a faulty part. Rogue does not make the volume or balance pots, they buy a batch of ALPS pots. They may tell you to swap out the tubes and clean the contacts and other troubleshooting tips, but in the end, this is their problem.

They are a very reasonable group of guys and they want their customers to be happy with their products, so they should have no issue with servicing the unit. If it was me, I would tell them this hum was unacceptable.
lowrider57's avatar
lowrider57
5,418 posts
 
My final thoughts on the matter...the transformer hum seems to be in the design and it's not a deal breaker. You'll only hear it when the amp is idle and maybe not at all from your listening position.

However, no amp especially new and in spec should deliver hum thru the speakers. We know definitively that it is coming from the amp since you have repeated the problem when using the balance control. (I hope you have tested this by swapping cables).

I have read many threads regarding the Sphinx and nobody has ever mentioned hum and my suggestion is that instead of asking Rogue, you tell them you are sending it back for service. If you don't have the unit repaired, you will never in good faith be able to sell this amp if you decide to upgrade.
lowrider57's avatar
lowrider57
5,418 posts
 
Foster_9... "some noise from the balance is normal." Ridiculous statement, don't you think?

I've auditioned several preamps and an amp and the only noise I've ever heard was some hiss, and that came from the type of tubes being used.
lowrider57's avatar
lowrider57
5,418 posts
 
Mapman, no contest between the Pharaoh and the Sphinx. The Pharaoh measures up to Rogue's high-end gear. You won't hear any complaints about hum passing thru the balance control. lol.
lowrider57's avatar
lowrider57
5,418 posts
 
The Sphinx is an entry level model, so I wonder if Mark would do any mods to it. With the Magnum models he upgrades the caps, power supply and adds cardas wiring.
Food for thought.
More to discover