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Discussion Starter #1
I am a newbie, as you can see. I am just a music listener and not an expert in any aspect of this hobby.

I purchased the HSU VTF-2 MK4 and MBM-12 MK2 around two months ago. I can hear the sub hums from 9 o'clock level and the MBM from 10 o'clock level, with or without the Mediabridge cables attached. I tried other outlets across the basement. I do not have TV services; I do have indoor antennae for my TVs. I have Verizon FIOS. I also have a subcompact Pinnacle sub and a Klipsch sub. They do not hum anywhere in the house. The HSU units hum either on the main floor or in the basement.

At 12 o'clock, the hums are very noticeable but of course cannot be heard if sounds, such as music or movie, exist. I am concerned because the sounds may be distorted but not always detectable. Our refrigerators, dishwasher, washing machine and dryer, central air-con, etc... made a lot of noises but I do not care. None of my audio gears, including my keyboards and synthesizer, and computer speakers, makes any noise. So that why I feel sad when my beloved bass units hum.

I spoke to HSU tech support few weeks ago and was told that that hum is normal. I spoke to an electronics engineer, who has worked with audio gears since the 70's, last night and he said that is not normal and bad capacitors might be the cause. This engineer built amps from big names', such as Pioneer, circuitry schemas, for fun and for a living. I sent another email to HSU this morning and will talk to tech support again tomorrow.

In the meantime, Please tell me what you think and any fix I should try. I appreciate your inputs! Many thanks!
 

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I am a newbie, as you can see. I am just a music listener and not an expert in any aspect of this hobby.

I purchased the HSU VTF-2 MK4 and MBM-12 MK2 around two months ago. I can hear the sub hums from 9 o'clock level and the MBM from 10 o'clock level, with or without the Mediabridge cables attached. I tried other outlets across the basement. I do not have TV services; I do have indoor antennae for my TVs. I have Verizon FIOS. I also have a subcompact Pinnacle sub and a Klipsch sub. They do not hum anywhere in the house. The HSU units hum either on the main floor or in the basement.

At 12 o'clock, the hums are very noticeable but of course cannot be heard if sounds, such as music or movie, exist. I am concerned because the sounds may be distorted but not always detectable. Our refrigerators, dishwasher, washing machine and dryer, central air-con, etc... made a lot of noises but I do not care. None of my audio gears, including my keyboards and synthesizer, and computer speakers, makes any noise. So that why I feel sad when my beloved bass units hum.

I spoke to HSU tech support few weeks ago and was told that that hum is normal. I spoke to an electronics engineer, who has worked with audio gears since the 70's, last night and he said that is not normal and bad capacitors might be the cause. This engineer built amps from big names', such as Pioneer, circuitry schemas, for fun and for a living. I sent another email to HSU this morning and will talk to tech support again tomorrow.

In the meantime, Please tell me what you think and any fix I should try. I appreciate your inputs! Many thanks!
Disconnect the cables to the units and attach a cheater plug to test. This is not a fix, though.
 

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I've had hum with bad interconnect cables, but you said you tried swapping out the cable to the amp right? Otherwise might be a mildly loose connection anywhere in the chain starting from the outside, the actually input which maybe you could tighten, to obviously inside the box within the amp, and the boys at HSU will take case of that. My VTF-2MK3 never hums even at 12 which I never have to crank it, because the gain is very touchy in our amps and the smallest increment in the knob makes a big difference.
 

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Discussion Starter #4
Disconnect the cables to the units and attach a cheater plug to test. This is not a fix, though.
Sorry I forgot to mention: the plugs are two-prong style. The HSU tech said cheater plug would not help.
 

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Discussion Starter #5
I've had hum with bad interconnect cables, but you said you tried swapping out the cable to the amp right?
I disconnected the RCA cables at the sub and MBM ends hopping the cables were the cause (!) because that would be an easy and cheaper fix. With the RCA cable attached but not connected to the AVR, the units hum. The tech said the cables acted like antennae. Without the cables, at the mentioned volume levels, they make noises, more like rumbling. I use all Mediabridge RCA. Not high-end but not cheap and quite good quality according to its users. Again, those RCA cables create no issue with other subs.

I have a Pinnacle sub and a Klipsch sub. I tried them with the RX-A1030 and they are silent just like they are with my Denon AVR-790. The HSU tech said the Pinnacle and Klipsch are lower gain units hence no hum. The electronics engineer said it's likely that bad capacitors leak A.C. hence the hum.
 

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Discussion Starter #6
A Nice Radio Station with Great Music. For Those That Like That Sort of Thing: RadioParadise.com
Thank you Sir. I must forward the link to the work e-mail.:D
 

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I envy you, I was thinking of getting an MBM and VTF-1 (both on sale), decided on the -2 instead. Super happy with its delivery of sub 30Hz content.
___________

Just as an anecdote, I bought my VTF-2 2 weeks ago or so. I turned off my avr, and turned its gain up to 12 o'clock, and hear a slight hum. Turned to 3 o'clock, and definitely hear a gentle hum. Turned off, disconnected the 15' Mediabridge coax cable ;) , turned back on, and hear almost nothing until gain at 3 0'clock, and hear a very quiet "wind noise."

I hear nothing at the recommended 9 o'clock gain position. Oh, I'm running EQ1, 1 port open, EQ about 0.4 or so. Cross over set OUT, of course.

The fact that both of your units have near identical hum suggests that there's not a manufacturing error in either one.

I have to ask, how close to you have to be to the VTF-2 to hear the hum? I was doing this standing right over it and peering at the rear control panel.
 

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Discussion Starter #8
Turned to 3 o'clock, and definitely hear a gentle hum. Turned off, disconnected the 15' Mediabridge coax cable , turned back on, and hear almost nothing until gain at 3 0'clock, and hear a very quiet "wind noise."
It appears your sub exhibits the same symptom. It could either be milder or our hearing sensitivity are different. It is very possible the subs are designed and manufactured like that. If that is the case, I do not like it. I believe if there is no signal input, there should be no sound output.
The fact that both of your units have near identical hum suggests that there's not a manufacturing error in either one.
I really hope so, but I cannot explain why they both hum. On the other hand, it is possible that both units have bad components. The chance is slim, but not impossible. Car companies recall their products all the time. I forgot to mention I tried a pair of NHT B-10ds. Like my other subs, there was no hum with the NHT subs. Now I regret I sent them back. I really like NHT's customer services.

I have to ask, how close to you have to be to the VTF-2 to hear the hum? I was doing this standing right over it and peering at the rear control panel.
I placed my ear right next to the amp panel. After 11 o'clock, I can hear the hum standing from a foot away. This can be why we hear the hum at different gain levels. The hums increase when the volumes increase. I run them both sealed.
 

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Thank you Sir. I must forward the link to the work e-mail.:D
Yep - enjoy.

Can you unplug and disconnect the Fios box? See if that helps.
 

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Well I love HSUs hope they'r eable to quiet it if its the capacitors, hearing it a foot away does not sound right to me even with our gainy amps. Best of luck with it man.
 

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Sounds like a possible ground loop hum. Try grounding the sub amp to the AVR chassis using a piece of wire.
 

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I suppose putting the Hsu sub on a UPS with conditioned power won't help? Mine is plugged right into a wall outlet.
 

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Thank you Sir. I must forward the link to the work e-mail.:D
It appears your sub exhibits the same symptom. It could either be milder or our hearing sensitivity are different. It is very possible the subs are designed and manufactured like that. If that is the case, I do not like it. I believe if there is no signal input, there should be no sound output.

I really hope so, but I cannot explain why they both hum. On the other hand, it is possible that both units have bad components. The chance is slim, but not impossible. Car companies recall their products all the time. I forgot to mention I tried a pair of NHT B-10ds. Like my other subs, there was no hum with the NHT subs. Now I regret I sent them back. I really like NHT's customer services.


I placed my ear right next to the amp panel. After 11 o'clock, I can hear the hum standing from a foot away. This can be why we hear the hum at different gain levels. The hums increase when the volumes increase. I run them both sealed.
It would be pretty remarkable if both new products exhibited a hum. My hunch is that it is probably ground loop related and introduced by the Fios box (see above). This should be tested.

Here's a recent post by Mark Seaton on proper ways to deal with ground loops:

http://www.avsforum.com/forum/113-s...seaton-sound-submersive1-99.html#post32794233
 
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Discussion Starter #14
Yep - enjoy.

Can you unplug and disconnect the Fios box? See if that helps.
I will do that during the weekend when the son is sleeping. To him, the Internet is sacred.
 

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Discussion Starter #15
Well I love HSUs hope they'r eable to quiet it if its the capacitors, hearing it a foot away does not sound right to me even with our gainy amps. Best of luck with it man.
I am still waiting for their response to my email. Thanks.
 

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Discussion Starter #16
Sounds like a possible ground loop hum. Try grounding the sub amp to the AVR chassis using a piece of wire.
I will try that too. It would be two long pieces of wire.
 

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I suppose putting the Hsu sub on a UPS with conditioned power won't help? Mine is plugged right into a wall outlet.
I am thinking about that too but I will try a power conditioner only. I do not think we need a UPS.
 

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It would be pretty remarkable if both new products exhibited a hum. My hunch is that it is probably ground loop related and introduced by the Fios box (see above). This should be tested.

Here's a recent post by Mark Seaton on proper ways to deal with ground loops:

http://www.avsforum.com/forum/113-s...seaton-sound-submersive1-99.html#post32794233
Thanks for the link. I have some Belkin. I am thinking of getting this Monoprice unit too.
However, I keep asking myself why the Pinnacle and Klipsch subs do not exhibit any hum.
 

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... Just as an anecdote, I bought my VTF-2 2 weeks ago or so. I turned off my avr, and turned its gain up to 12 o'clock, and hear a slight hum. Turned to 3 o'clock, and definitely hear a gentle hum. Turned off, disconnected the 15' Mediabridge coax cable ;) , turned back on, and hear almost nothing until gain at 3 0'clock, and hear a very quiet "wind noise."

I hear nothing at the recommended 9 o'clock gain position. Oh, I'm running EQ1, 1 port open, EQ about 0.4 or so. Cross over set OUT, of course....
It appears your sub exhibits the same symptom. It could either be milder or our hearing sensitivity are different. It is very possible the subs are designed and manufactured like that. If that is the case, I do not like it. I believe if there is no signal input, there should be no sound output.

I really hope so, but I cannot explain why they both hum. On the other hand, it is possible that both units have bad components. The chance is slim, but not impossible. Car companies recall their products all the time. I forgot to mention I tried a pair of NHT B-10ds. Like my other subs, there was no hum with the NHT subs. Now I regret I sent them back. I really like NHT's customer services.


I placed my ear right next to the amp panel. After 11 o'clock, I can hear the hum standing from a foot away. This can be why we hear the hum at different gain levels. The hums increase when the volumes increase. I run them both sealed.
I suppose putting the Hsu sub on a UPS with conditioned power won't help? Mine is plugged right into a wall outlet.
Well, since I really hadn't finalized my sub installation, I ran the power cord over to the UPS below my receiver (cord just reached!), and lo and behold -- no more hum with the coax connected to the sub.[1] Could be because the AVR and sub are now connected to the same conditioned power source, or simply that the sub is getting conditioned power versus raw AC from the wall.[2]

The coax and the power are zip-tied together, but with a shielded coax cable, this shouldn't be a factor? There's no hum at all.

[1] Same test as before, power connected, power set to AUTO or ON, coax connected to receiver, which is powered on. Turn gain all the way to 3 o'clock or so. Just hear a very mild "wind" noise heard out of the single open port.

[2] I sometimes wonder if I'm being a fetishist putting networking equipment, hi-fi and other electronics on a UPS, but this just convinced me. I'm surprised that the Hsu doesn't use 3-prong power, getting a ground from the building. (shrug)

Thanks for the link. I have some Belkin. I am thinking of getting this Monoprice unit too.
However, I keep asking myself why the Pinnacle and Klipsch subs do not exhibit any hum.
My two cents dropped with a heavy clunk:

If you're going to spend $20 or more on a butt-swankin' surge surpressor, spend $20 or so more for a UPS. Don't have to put the sub on the battery backup side (I put my AVR on battery, I just cringe at the idea AC being snatched from it while it's producing power out the other end), but the power on any UPS outlet should be clean and grounded. I'm skeptical of some companies' claims of their power conditioning on a glorified power strip....
 

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Discussion Starter #20
My two cents dropped with a heavy clunk:

If you're going to spend $20 or more on a butt-swankin' surge surpressor, spend $20 or so more for a UPS. Don't have to put the sub on the battery backup side (I put my AVR on battery, I just cringe at the idea AC being snatched from it while it's producing power out the other end), but the power on any UPS outlet should be clean and grounded. I'm skeptical of some companies' claims of their power conditioning on a glorified power strip....
So you use a UPS like a conditioner. Which one do you use?
I think Mark Seaton's post is to demonstrate how to eliminate ground loop using a surge protector.
Well, since I really hadn't finalized my sub installation, I ran the power cord over to the UPS below my receiver (cord just reached!), and lo and behold -- no more hum with the coax connected to the sub.[1] Could be because the AVR and sub are now connected to the same conditioned power source, or simply that the sub is getting conditioned power versus raw AC from the wall.[2]
Is COAX cable the RCA cable? It appears your UPS does the job.
 
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