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  1. #1

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    Default Parasound 2250 hum

    My Parasound 2250 has a slight hum/buzz, which is audible when my ear is within a couple of feet of the amp and the room is quiet. It has a ground loop switch, which I tried but the hum remains. Is this normal or should I be concerned? Any potentially easy fixes I could try like moving cables and power cords around. I already did that a little but my set-up does not really allow for allowing wires to not cross.

    Any advice or suggestions would be appreciated!

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    If the buzz is coming from the amp itself, not the speakers, you could check to make sure the transformer is tight. You could also loosen it up a little and slightly re-position it, then tighten back down.

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    William,
    Thanks for the suggestion. Since it is still under warranty, I'm afraid to open it up for fear of invalidating the warranty. At the very least I should probaby contact them. I take it that a slight hum/buzz is not normal in your opinion/experience.
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    Some amps will have a slight buzz or hum, and it is normal. If you can't hear it from your normal listening position, it's probably not an issue. I was just pointing out a couple of ways to reduce it.

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    Quote Originally Posted by NewHTguy View Post
    William,
    Thanks for the suggestion. Since it is still under warranty, I'm afraid to open it up for fear of invalidating the warranty. At the very least I should probaby contact them. I take it that a slight hum/buzz is not normal in your opinion/experience.
    If it's under warranty, just call Parasound and send it to the authorized repair center to have it checked. Parasound amps should not produce any kind of hum/buzz when used with 8 or 4 ohms speakers (I have several parasound amps and used with RTi and LSi speakers). If it's hums, something inside is wrong. HCA-2250 is Dead Quiet Amp unless something is wrong. Like the other member has suggested, the bolts that holds transformer might need to be tightened but if you are hearing it constantly at any kind of volume, it might be the filter caps that needs replacing. As long as under warranty, any issue should be handled by Parasound.
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    Mega,
    Thanks. I didn't know whether I was just being a worry wort. Sounds like it is worth investigating. The manual does suggest moving wires etc but that makes more sense when things are one. I'm hearing the hum/buzz when the equipment is plugged in and everything else is off.
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    Fyi, I disconnected the amp and plugged it in different outlet that had no other electrical devices. The hum/buzz was still there. So I called Parasound. While the tech people were gone for the day the phone person said I have a "mechanical hum" because the sound is not coming from the speakers. He also said the likely culprit was a loose transformer. What William said. I'll keep you guys posted in case anyone else has this problem.
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    Make sure it's not coming from the speakers. Unhook them and turn the amp on. If you still get the hum it is your amp. If not, go out & get a 3 prong to 2 prong plug. Plug the amp plug into the cheater plug & plug that into the wall.

    The hum should disappear.
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    If it's mechanical hum, you can check to see it's it's coming from the inside of the amplifier.

    Turn off the amp first.

    Totally Disconnect all the speaker wires and the RCA inputs to the amp.

    Then turn the amp on and listen closely from the top of the amp. You'll likely hear a small hum or buzz from inside of the amp. In most cases it means the transformer is making mechanical noise or something such as screws or washers inside is vibrating.

    There are seldom transformer noise that can't be detected by listening closeup to the amp with an ear. Sometimes, you might need to open up the top cover for an amp but for Parasound amps that has the top covers with holes, it's not necessary to open up the amp.

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    Quote Originally Posted by cfrizz View Post
    Make sure it's not coming from the speakers. Unhook them and turn the amp on. If you still get the hum it is your amp. If not, go out & get a 3 prong to 2 prong plug. Plug the amp plug into the cheater plug & plug that into the wall.

    The hum should disappear.
    Ms. Frizz,

    You will not likely to hear the transformer noise from 3-4 feet away if you disconnect the speakers from the amp. If there is an amp that you can hear mechanical noise from 3-4 ft away on it's own, immediately unplug it and take it to the repairer since it's a ticking bomb that will explode anytime now. :D
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  11. #11
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    Quote Originally Posted by cfrizz View Post
    Plug the amp plug into the cheater plug & plug that into the wall.
    While it may solve ground loop issues,removing the safety ground is IMO not a good idea.

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    Eh, maybe not but it is an effective & cheap fix.:D

    Quote Originally Posted by GV#27 View Post
    While it may solve ground loop issues,removing the safety ground is IMO not a good idea.
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    Folks, sorry I was not clear. I disconnected the amp completely. No speaker wire, no interconnects, nothing but the power cord. The hum was still there.
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    Quote Originally Posted by NewHTguy View Post
    Folks, sorry I was not clear. I disconnected the amp completely. No speaker wire, no interconnects, nothing but the power cord. The hum was still there.
    Well, it's clear enough that something inside is humming then. Parasound will take care of it for you.
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    Quote Originally Posted by NewHTguy View Post
    Folks, sorry I was not clear. I disconnected the amp completely. No speaker wire, no interconnects, nothing but the power cord. The hum was still there.
    If it's not a loose tranny, then assuming its a toroidal you may have a small DC voltage riding on the AC ,which can cause buzzing in the windings of toroids.

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    I'd still try lifting the ground with a cheater plug ala' cfrizz.

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    Spoke to a tech at Parasound. Apparently there is no spec to say whether or not the unit is defective. I'm going to see if I can get a local authorized service person to listen.
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    Quote Originally Posted by NewHTguy View Post
    Spoke to a tech at Parasound. Apparently there is no spec to say whether or not the unit is defective. I'm going to see if I can get a local authorized service person to listen.
    I would check w/ Parasound and make sure that they won't invalidate your warranty if you do that.

    You shouldn't have hum directly out of the amp of any sort. Ground loop is usually heard through the speakers. Do you have another amp that you can try in it's place?

    You may want to pick up an outlet tester. They are under $20 and will hopefully remove the outlet/s from the trouble shooting equation.

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    Quote Originally Posted by NewHTguy View Post
    Spoke to a tech at Parasound. Apparently there is no spec to say whether or not the unit is defective. I'm going to see if I can get a local authorized service person to listen.
    Won't they inspect it for you? You might need shipping it to the Parasound Authorized dealer (or repair center).
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone.

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    Jinjuku, I just want the local *authorized* Parasound dealer to hear it. I'm not going to let him open it up without getting authorization from Parasound.

    Megasat, I'm trying to avoid a $35 shipping fee (they only pay for the return) just to have them tell me the hum is normal.

    They seem to be claiming that some hum is normal, but they have no technical definition (in terms of say decibels) for what is not normal. Sounds kind of bogus to me.
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    Did OP ever get this resolved? With all the help he got he should at least come back and tell us what the final verdict was and how Parasound handled it. Also, does switching the ground lift affect the amp in any way? Does that essentially mean it's no longer grounded?

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    Sorry folks, forgot to follow up. My bad. I spoke to an authorized repair guy a few days ago. He said that a small amount of mechanical hum is not unusual. Unfortunately, he also does not have much experience repairing Parasounds (guess that is a good thing).

    The parasound tech (not to be confused with the auth repair guy mentioned above) was definitely claiming that small amount of mechanical hum is considered normal. He, however, claims that they have no technical definition of what is normal. So it is essentially subjective. If I send it to them and they say, "well you won't hear it from the listening position so there is not need to change anything out" then there is not much I can do about it.

    I searched other forums and found people inquiring about "mechanical" hums. Those people usually conclude it is not loud enough to worry about it.

    The upshot is that I have over two years of warranty period (I'm glad I bought from an authorized dealer: Audioadvisor) so I have a window of time during which I can keep an eye/ear on it. The hum is certainly minor and cannot be heard from my sofa, so letting it go for the time being is not a big deal. I was mostly concerned with prevent any damage to other components or catching a problem before it gets worse.

    If any of you believe I have received incorrect info I still would like to know. I'd like to think that Parasound is a stand-up company. But I must admit that I would have appeciated a more formal definition of how much hum is considered "normal."
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    Forgot to mention that there is nothing in the manual that addresses mechanical hum. If it is indeed normal they could at least acknowledge it.
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    The transformer hums depends very relatively to the line voltage from the wall outlet.

    Just measure the line voltage from the wall outlet with the multimeter (200V AC setting or auto setting for most meter) and let us know.

    If your line voltage is considerable less than 120V, the transformer will hum a little louder. So, the transformer noise is measured and provided by the transformer manufacturer but I don't know if parasound would care to provide that data.

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    Mega,
    Unfortunately, I don't have a meter. My experience with electricity amounts to changing light bulbs. But in another thread Rocco and Heiney have got me all psyched up about getting a power conditioner that regulates voltage (the APC H15). So if I go that route I should be able to check the quality/stability of my power.
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    NewHTguy, did you buy this as an "Open Box" item from Audio Advisor? They have a pretty decent price for them ($800) if you buy open box and I was considering getting one. But I am a bit leery of the open box stuff.

    The XPA-2 is also @ $800 which a lot of folks say is a killer amp for the price. And then there's also used amps in the 200 - 250 wpc range by Parasound, Adcom, Acurus, etc., for under $500 for sale all over online. The Rotel RB-1080 is also an amp worth considering used at close to that price point.

    I'd like to know though if this was an "Open Box" purchase or if you bought it brand new factory sealed?

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    Did you at least TRY getting a cheater plug to see if that solved your problem before you go spending a lot more money?

    Try the easy stuff first before trying to create rocket science.
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    It was an "open box" and I paid $700 plus shipping (about $35). It does have a full warranty. Just keep in mind that AA is one of the only (perhaps THE only) authorized online Parasound dealers. I say this because buying "new" from an unauthorized dealer leaves you with no warranty. Just making sure you know that.

    Personally, I don't regret my purchase because I don't believe any other amp manufacturer has a "no mechanical hum policy." Furthermore, the fact of the matter is that the hum is so low that I did not know it was there until I switched out my speakers. If I had bought used there is a chance tha I would have encountered the same problem and would have no warranty if it got worse. Given the $400 to $500 below list price that I saved, I can live with it, at least now that I know it is there. Of course, you may feel differently and there is no "right" answer to how one should spend his or her dollars. A lot of us are perfectionsists about such things and have every right to be.

    Good luck on your purchase!
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    Quote Originally Posted by cfrizz View Post
    Did you at least TRY getting a cheater plug to see if that solved your problem before you go spending a lot more money?

    Try the easy stuff first before trying to create rocket science.
    He doesn't have a ground loop issue,its mechanical hum in the transformer,removing the safety ground won't fix it.
    Last edited by GV#27; 04-28-2009 at 07:30 PM.

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    NewHTguy, I'd like to know how you like the amp sound-wise? Also, you got a very good deal, open box 2250's are now $800 on AA. My only dilemma is a Parasound 2250 or an Emotiva XPA-2. I can't find any good comparisons online. But I agree with you about buying used, its always a gamble. I always question why the person is selling when they usually describe it so wonderfully. If it's so wonderful, why get rid of it then?

    I know OP doesn't have a ground-loop issue, but can someone please tell me if switching the amp to "ground lift" on the back is the same as pluging it in with a cheater plug? i.e. is the unit no longer grounded when it's switched to ground lift?
    Last edited by Terra S; 04-28-2009 at 07:50 PM.

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