[kalido]

Hey guys,
First post ever. I'm a proud owner of a Candela preamp. Bought it used, but it was only around 5 months old when I purchased it.
Partnering amps are Consonance Cyber 800 monoblocks. First thing I noticed straight away after hooking it up is how well it presents the soundstage. Wide and open.

But I'm experiencing annoying hum from the speakers with the preamp in chain. Don't think it's ground loop as they're all on the same power strip and I've never had any ground loop issues in the setup in the past.

The previous owner informs me that he had the same hum in his setup but he's quite confident it's just normal operation of the candela. The hum is not too loud though but certainly audible during late night listening or when it's really quiet.

My question : is this hum really normal ?


thanks guys

[JCarney]

Hi kalido, and welcome to AC. I had a Candela way back when it first came out, and had the same issue. I sent it in to get a check up, and was informed everything was alright, except the bias was just slightly off. Adjusted and returned. Hooked it up, and the noise was still there. So I worked a deal with Klaus to return it, and sent in my Extreme mono's for the Glass ceiling upgrade. Probably not what you want to hear, but it's honest. Klaus and company are well known for customer service. Contact him to see what he has to say, he will take care of you. Klaus is a top notch guy, he wants you to be happy.

Hope this is helpful,
JCarney

[geowak]

This is the very reason that I got rid of the Stratos, the Tempest and the Candela. Hum issues in all three. I isolated the problem and could not get rid of hum amd other spurious noise issues.... I hope you have better luck than I did.

[richidoo]

Why did the preamp hum? Because it forgot the words.      booo

Welcome to AC kalido!

If your system includes TV, then disconnect the cable TV or Satellite TV signal coax wire. If that stops the hum, get a Jensen coax isolation filter.  There is no other way to fix this, and it is common. It happened to me with ground loop coming in from my FM antenna, but the coax filter fixed it. The cheap filter from PE is junk.
http://www.audioholics.com/home-theater-connection/ground-loops-eliminating-system-hum-and-buzz

To rule out your home wiring being cause of the ground loop, simplify the system down to just preamp, amp and speakers. Plug amp and preamp into the same outlet with no power strips or conditioners. If the hum is less than before then you need to improve the quality of ground in your outlets. Loose wirenuts, back stab outlet connections, loose outlet screws, different length circuits, shared circuits with bad connections, power strips. Also check the polarity with an outlet tester.

There are more things you can do to isolate the cause of the loop, but I can't print them in public for safety reasons. Get advice from Klaus.

There are devices that can remove ground loop voltage from the power inlet and the signal inlets, but they can be expensive so it's better to eliminate any technical problems first before resorting to workaround. Jensen makes RCA signal isolation transformers that are very good, but expensive. Checking the chassis ground  bolt is tight and clean, and signal ground circuit for problems is another step, but don't go inside if you don't know what you're doing. You want the connection between the chassis and the service panel to be as low impedance as possible, same with connection between RCA jack ground and the chassis ground bolt. Measuring with a voltmeter can be helpful if you know where to check and understand the risks inside a tube amp. Otherwise, leave it to a pro.
Good luck!
Rich

[klaus@odyssey]

Hey Kalido,

Definitely call me,  Alex and I will take care of it. 
Now, as for guidance, richidoo is 100  % on the money...definitely try these things first,  especially with making sure that the RCA connectors don't touch the chassis....we found that 90 % of the time this was a problem.  Also,  if this is an older unit, then we can certainly rectify some issues just by bringing it up to current specs.

We have had some hum issues in the past, albeit in very small percentages, pretty much just like other manufacturers too.  And yes, there were times when our gear was the culprit in  specific situations, and then there were the results of owner mistakes as well as other components acting up.....  As every circumstance is unique, it's hard most of the time to duplicate certain problems,  but obviously,  we have also learned quite a bit over the years.  Now,  there are indeed 2 different hum issues at work, inter - system related and AC grounding...and then there is the tube issue.....as I said,  call me and we'll guide you through this.
Either way, it is not normal to hear any noise whatsoever.........

Late,
Klaus

[kalido]

hey guys,
thanks for all the replies. I'll try to do some of the suggested tests and report back. Don't think it's a tube issue as I've tried the stock and a pair of RCA 5814. Hummed with both. Klaus, thanks for your response as well and I'll be in touch via pm to get some thoughts.

cheers

[Phil A]

No issues with mine. Have had it in the secondary basement system for about a month. I put Synergy HiFi tubes in mine.

[lazydays]

If the preamp hums as you said it does (I'm sure it does), it's mostly likely cause by something outside of it. A good way to start is to have somebody moving the interconnects around while your listening with an ear very close to the speaker. Still there? Now clean all the connections. You may hear a difference, and possibly a sound improvement. Still there? now with the system up, disconnect each interconnect from the source to the preamp (at the preamp end of course). Do this one set at a time. Still there, then shut the amps down and clean the interconnect points. Lastly unplug the turn table and phono stage (even though the cables have been removed). If your using a power conditioner, try swapping the power cords around. Also make sure your interconnects and cables are not crossing over each other. This is a common problem.

Still no luck?? Then put the system back together again, and look elsewhere. I'd start out by swapping power cables one source and amp at a time. Look around for a dimmer switch close by. The new energy saving light bulbs will wreak havoc in a system. I would next turn the power off to the outlets, and inspect the outlets and the circuit breakers as well. (may want an electrician to do this part). Now is a good time to replace the outlet with a hospital grade one, and a new circuit breaker. Also before I forget, are your speakers very close to the television?
gary

[hpc]

I'd advise against moving interconnects about on a preamp that is powered on - or any component for that matter.  Most gear is not
designed for hot swapping of interconnects/cables.   But, I'll defer to Klaus and Alex as they know their gear.

But, I also dislike having to power-cycle equipment a lot over a short period of time.

Agree with the check the cable/TV cable/coax/interconnect before all else.  Cable TV has a different ground than the house - causing ground
loops (hum).

[kalido]

I haven't completed full troubleshooting yet but lookin at doin it this weekend.
FWIW, I had my tube power amps directly off my NAD M51 DAC/Preamp and it was perfect, no hum whatsoever. So where ever its coming from, it's being triggered by either the candela itself or, like u guys said grounding or connectors. I did do a complete connectors cleanup last week with CAIG DeoxIT cleaner and protector.That did not change anything but things just sounded a lil more transparent after that ( could be placebo though )
Are you guys able to derive more possibilities/conclusions based on these facts ?

[AlexG]

Hi kalido, Welcome to AC and Odyssey.

You should have no "hum" or "buzz" coming out from the speakers in a normal two channel setup. You should only hear a slight "tube rush" (small hiss) at ear level from the speakers, and this is normal on tube based preamps. This tube rush/hiss is very dependent on tube type (brand) used and varies from manufacturers. Unfortunate, there are other variables that come in play while setting up audio equipment!

Please PM me your phone number and best time to call you so we can trouble shoot your problem.

Thank you.
Alex

[kalido]

hi Klaus and Alex. Thanks heaps for the super fast response. PM sent with the latest findings.