Sunfire True Sub MKII

I was wondering if anyone has remedied the annoying hum that seems to be a common problem with these subs (based on a internet search)

I sent mine out to Rita's and just got it back. My hum would come and go, get loud after hard bass hits etc. I connected it after service and the hum is louder than before, constant at all times, and playing with the volume knob does not make it change in intensity (it goes louder/softer, but previously I could make it go away at times by playing with the pot)

I have temporarily remedied it by inserting a ground loop isolater in the RCA line but this is not a proper fix. I realize that there may be issue with ground connections in my home, but none of my other equipment, including the Velodyne sub I used in the Sunfires place while out for service had this hum.

Has anyone come up with a fix or am I stuck leaving the isolater in the line until I find something that sounds as dramatic as this sub?

Any suggestions are appreciated.

Welcome TurboJim.

If you've had it serviced by Rita, and it is functioning well otherwise, then I would say the hum probably IS a ground loop issue, and inserting a grould loop isolator probably IS a proper solution. I have an older Velodyne sub (F-1500b) and it works wonderfully, UNLESS it's plugged into the same outlet (or power strip) as my Cable box, or ANYTHING that is connected to my cable (like th receiver or TV). Cable TV cable systems are NOTORIOUS for having wonky grounds, and sometimes they can cause very difficult to cure ground loop issues. The only way I got rid of the hum in my old setup was to 1) connect the cable box to the receiver with a TOSLINK cable (so there was no electrical connection, only fiber optic cable), AND 2) connect the sub to the receiver with a GLI box inserted between the cable and the sub, AND 3) to put the sub on it's own power strip, on a completely separate outlet (which was on a different breaker).

In my current system, the cable system doesn't seem to induce hum, but I've still got the sub on a different outlet (because of where the sub is located, relative to the rest of the components). But now, I've got a completely different problem with the Velodyne. My interconnect between the sub and the reciever is about 4 meters long, and now, any time my sweety and I are sitting on the couch, and have our cell phones sitting near the sub (both are "smart phones"--a 3G iPhone and a 2nd gen BlackJack) and one of our phones receives a call, about 5 seconds before the phone rings, the sub will "chirp" with a high-frequency digital "twitter". It's so quiet that if we're watching a movie with the 5.1 system playing, we don't hear it, but if the receiver is off, and we're just watching TV using the built-in speakers, this digital phone "twitter" coming from the sub is REALLY annoying. It took me about a week to figure which speaker the noise was coming from, and now that I know, I STILL haven't figured out how to remedy THAT little issue...

Anyway, it has been my experience that about 95% of the "hum" issues with a subwoofer in a multi-channel surround rig are due to ground loop issues, and about 50% of those issues are DIRECTLY attributable to the wonky grounding protocols of the cable system...

Ground-loop hums are a HUGE pain in the butt, and can be REALLY tricky to track down and kill. GL hum is like a ghost--it can come and go, and just when you think you've got it fixed, it can come back at the oddest moment, without reason or warning.

Good luck figuring this out, and welcome to the Carver Forum!

--Richard

If you've had it serviced by Rita, and it is functioning well otherwise, then I would say the hum probably IS a ground loop issue, and inserting a grould loop isolator probably IS a proper solution. I have an older Velodyne sub (F-1500b) and it works wonderfully, UNLESS it's plugged into the same outlet (or power strip) as my Cable box, or ANYTHING that is connected to my cable (like th receiver or TV). Cable TV cable systems are NOTORIOUS for having wonky grounds, and sometimes they can cause very difficult to cure ground loop issues. The only way I got rid of the hum in my old setup was to 1) connect the cable box to the receiver with a TOSLINK cable (so there was no electrical connection, only fiber optic cable), AND 2) connect the sub to the receiver with a GLI box inserted between the cable and the sub, AND 3) to put the sub on it's own power strip, on a completely separate outlet (which was on a different breaker).

Thanks for the reply Dreamer. I didnt mean to imply Rita and crew introduced a problem, but rather the intermittent nature of my hum may have been intermittent due to the fact I has a problem with my unit and now that its fixed, remains constant. I just feel that the circuitry in this sub is more sensitive to grounding issues than my other equipment may be. Although I dont really understand why since this unit would be used in rooms of questionable wiring and you'd think Sunfire/Carver would engineer their products for use in any situation like most other manufacturers do.

In my current system, the cable system doesn't seem to induce hum, but I've still got the sub on a different outlet (because of where the sub is located, relative to the rest of the components). But now, I've got a completely different problem with the Velodyne. My interconnect between the sub and the reciever is about 4 meters long, and now, any time my sweety and I are sitting on the couch, and have our cell phones sitting near the sub (both are "smart phones"--a 3G iPhone and a 2nd gen BlackJack) and one of our phones receives a call, about 5 seconds before the phone rings, the sub will "chirp" with a high-frequency digital "twitter". It's so quiet that if we're watching a movie with the 5.1 system playing, we don't hear it, but if the receiver is off, and we're just watching TV using the built-in speakers, this digital phone "twitter" coming from the sub is REALLY annoying. It took me about a week to figure which speaker the noise was coming from, and now that I know, I STILL haven't figured out how to remedy THAT little issue...

My Velodyne and Polk are dead silent using the same outlet and RCA so there must be circuitry to break the ground in these units already?

As far as your cellphone noise, thats normal and common. The radio/CD player in my vehicles both suffer from this anomaly, as does my PC. I think its a shielding issue. I remember on Youtube or something a group of kids showing a popcorn kernel popping from the RF/Microwaves generated by a cellphone. Kinda scary that we keep these things on our person and near our brain isnt it? FWIW, I always know when my phone is about to ring or recieve a text msg as my PC will make that cellphone "noise" just before it rings if the phone is on the desk near it.

Anyway, it has been my experience that about 95% of the "hum" issues with a subwoofer in a multi-channel surround rig are due to ground loop issues, and about 50% of those issues are DIRECTLY attributable to the wonky grounding protocols of the cable system...

Ground-loop hums are a HUGE pain in the butt, and can be REALLY tricky to track down and kill. GL hum is like a ghost--it can come and go, and just when you think you've got it fixed, it can come back at the oddest moment, without reason or warning.

Good luck figuring this out, and welcome to the Carver Forum!

--Richard

I agree on all accounts and this hum can make my movie watching unpleasant and my system unlistenable. I may not be an audiophile by most standards, but my system is well above average and I know what sounds good. Hum does not

BTW: What did you use for a GLI? I am using one of those chokes with RCA's on each end made for car audio, but the cabling is kinda chincy. I'd like to have something of a little higher quality.

Digital amps are notorious for doing this. It's not the sub, it's your ground loop issue. Using the cheater plug would, in this case be the proper fix. The only other way around it would be to put an isolation transformer in line with some of the IC's or you could use a separate isolation transformer on the sub itself but that's not recommended. Either way, you have a ground loop issue but rest assured it's not the sub.

A quick test would be to turn off the power to the sub and unhook everything. Take the sub and just plug it in to a separate circuit altogether than what your rig is on. Make sure that you don't have any SS variable light dimmer switches or fluorescent lights on that circuit. Is the hum gone?

Digital amps are notorious for doing this. It's not the sub, it's your ground loop issue. Using the cheater plug would, in this case be the proper fix. The only other way around it would be to put an isolation transformer in line with some of the IC's or you could use a separate isolation transformer on the sub itself but that's not recommended. Either way, you have a ground loop issue but rest assured it's not the sub.

A quick test would be to turn off the power to the sub and unhook everything. Take the sub and just plug it in to a separate circuit altogether than what your rig is on. Make sure that you don't have any SS variable light dimmer switches or fluorescent lights on that circuit. Is the hum gone?

Tom, I have a digital Klipsch sub and it's always been dead silent...so I don't know where that info came from.

HOWEVER, the Sunfire subs DO have a lot of hum issues. I'd call Rita & ask about this since you just had it serviced. BillD had an issue with a Sunfire sub; he traced it down to a loose ground nut somewhere inside the sub.

Mr. Rabbit, I said digital amps are notorious for doing this.....not all digital amps. Hell, for all we know it could be the PC picking up noise? Just trying to locate the source of the issue here...

Well, I have the exact same sub that HAD the exact same problem. It would be mostly silent until a big bass note hit and then it would start humming. I could get it to stop humming by turning the volume control all the way up and it would go "bump" and back to being relatively quiet until the next time. Cheater plug (to reverse polarity on the polarized plug) didn't help. What did was tightening down the nuts on the pots on the back. It seems that if the pots lose contact with the plate amp, it hums. With all that shaking going on, the run themselves loose.

This may help you if we haven't nailed it yet.......

http://www.epanorama.net/documents/groundloop/

http://www.audioholics.com/tweaks/co...m-hum-and-buzz