amp buzz no matter what i do

[richard_b939]

hey guys im the proud owner of a parts express plate amp

its the 240 watt rms @ 4 ohm model and the problem is no matter what i do i get a small hum

i did everything in the manual ...disconnected the cable tv...made sure all wiring is good.

then i phoned parts express and they said to use a 2 prong outlet rather than a grounded outlet.

Still get a small hum...doesnt get any louder with a increase in gain or changing the freq etc

however when watching films its really really annoying during a quiet or silent scene it humms and wrecks it for sure.

Changed my rca's to higher quailty also ....any other ideas?

[matg]

you are probably getting the dreaded 60 hz hum. It can come from several sources but it is basicly the electric field generated around a 120 volt power line. have you tried to move your signal wires away from all your power wires? A simple DVD player plug wire can impart the hum to a near by speaker wire or signal wire. If the plate amp is mounted in the sub box, maybe try re routing the speaker hook-up in the box to keep it clear of the amps transformer. Also, if the driver itself is near a power wire or powered unit of some kind, the driver could pick up the hum. It's like putting a 100 watt soldering gun near a speaker while trying to solder, you will get the driver to hum. Try moving all your signal wires around, as well as your power wires, signal wires and power wires, close to each other can cause a hum. hope this helps.

> hey guys im the proud owner of a parts
> express plate amp

> its the 240 watt rms @ 4 ohm model and the
> problem is no matter what i do i get a small
> hum

> i did everything in the manual
> ...disconnected the cable tv...made sure all
> wiring is good.

> then i phoned parts express and they said to
> use a 2 prong outlet rather than a grounded
> outlet.

> Still get a small hum...doesnt get any
> louder with a increase in gain or changing
> the freq etc

> however when watching films its really
> really annoying during a quiet or silent
> scene it humms and wrecks it for sure.

> Changed my rca's to higher quailty also
> ....any other ideas?

[hulan]

Provided Link: sub cable


I feel for you, man. I ask the experts here, could it be that a shielded cable might help? Or is that not the problem at all? Then again, you've already upgraded your cable. I haven't run into this problem yet, so I wish you luck.

[Æ]

Is the hum comming from/through your subwoofer, main speakers, the plate amp or where? You did not specify. Try disconnecting you signal cables and wires one at a time and see if the hum disappears. Is the hum mechanical hum from the plate amp transformer or chassis? Basically it takes time and patience to track it down. Be methodical.

> hey guys im the proud owner of a parts
> express plate amp

> its the 240 watt rms @ 4 ohm model and the
> problem is no matter what i do i get a small
> hum

> i did everything in the manual
> ...disconnected the cable tv...made sure all
> wiring is good.

> then i phoned parts express and they said to
> use a 2 prong outlet rather than a grounded
> outlet.

> Still get a small hum...doesnt get any
> louder with a increase in gain or changing
> the freq etc

> however when watching films its really
> really annoying during a quiet or silent
> scene it humms and wrecks it for sure.

> Changed my rca's to higher quailty also
> ....any other ideas?

[cptomes]

> hey guys im the proud owner of a parts
> express plate amp

> its the 240 watt rms @ 4 ohm model and the
> problem is no matter what i do i get a small
> hum

> i did everything in the manual
> ...disconnected the cable tv...made sure all
> wiring is good.

> then i phoned parts express and they said to
> use a 2 prong outlet rather than a grounded
> outlet.

> Still get a small hum...doesnt get any
> louder with a increase in gain or changing
> the freq etc

> however when watching films its really
> really annoying during a quiet or silent
> scene it humms and wrecks it for sure.

> Changed my rca's to higher quailty also
> ....any other ideas?

Does that amp have a toroid or a steel core transformer?

I have the same problem with four subs built using the -794 250W amps. All signal wires disconnected, SUB COIL WIRES DISCONNECTED, we get hum. Only possible conclusion is that the field from the transformer is exciting the vc of the sub. Ther eis hum when the power is off on the switch on the plate amp. The switch does NOT interrupt power to the xformer. Pulling power from the plate makes the hum go away.

If the 240W amp doesn't have a toroid, maybe this is it?

[baldemargarcia]

> Does that amp have a toroid or a steel core
> transformer?

> I have the same problem with four subs built
> using the -794 250W amps. All signal wires
> disconnected, SUB COIL WIRES DISCONNECTED,
> we get hum. Only possible conclusion is that
> the field from the transformer is exciting
> the vc of the sub. Ther eis hum when the
> power is off on the switch on the plate amp.
> The switch does NOT interrupt power to the
> xformer. Pulling power from the plate makes
> the hum go away.

> If the 240W amp doesn't have a toroid, maybe
> this is it?

Sounds like you guys have the problems I had. Most of my plate amps have transformer hum. This is not to be confused with 60Hz hum that is basically noise that gets to the woofer. I tried various methods of mechanically isolating the transformer from the plate amp 'chassis', but as soon as the transformer is mechanically bound to something, it starts to vibrate (hum). My solution: Get one of the BASH amps, which use a much smaller transformer, so is therefore much less likely to have this mechanical noise. I had hum even with the smaller 120W plate amp, but I have absolutely zero noise with the 300W BASH amp. I'm very bothered by this type of distracting noise, so all of my future plate amps will likely be BASH amps. Good luck, and please let us all know if you ever find a way to quiet the big transformers used in class a/b plate amps.

[daneo]

> hey guys im the proud owner of a parts
> express plate amp

> its the 240 watt rms @ 4 ohm model and the
> problem is no matter what i do i get a small
> hum

> i did everything in the manual
> ...disconnected the cable tv...made sure all
> wiring is good.

> then i phoned parts express and they said to
> use a 2 prong outlet rather than a grounded
> outlet.

> Still get a small hum...doesnt get any
> louder with a increase in gain or changing
> the freq etc

> however when watching films its really
> really annoying during a quiet or silent
> scene it humms and wrecks it for sure.

> Changed my rca's to higher quailty also
> ....any other ideas?

People may tell you this isn't a good idea and maybe its not. Try a cheater plug, no ground in the socket. I went through all of this 8 years ago with a 250 watt plate amp from Madisound. I just broke the ground pin off the plug and have never had a problem with anything since. -Dane

[envisionelec]

> Sounds like you guys have the problems I
> had. Most of my plate amps have transformer
> hum. This is not to be confused with 60Hz
> hum that is basically noise that gets to the
> woofer. I tried various methods of
> mechanically isolating the transformer from
> the plate amp 'chassis', but as soon as the
> transformer is mechanically bound to
> something, it starts to vibrate (hum). My
> solution: Get one of the BASH amps, which
> use a much smaller transformer, so is
> therefore much less likely to have this
> mechanical noise. I had hum even with the
> smaller 120W plate amp, but I have
> absolutely zero noise with the 300W BASH
> amp. I'm very bothered by this type of
> distracting noise, so all of my future plate
> amps will likely be BASH amps. Good luck,
> and please let us all know if you ever find
> a way to quiet the big transformers used in
> class a/b plate amps.

You don't have hum with the BASH because its switching frequency is upsampled to 100kHz.

It's also why the transformer is tiny.

[envisionelec]

> hey guys im the proud owner of a parts
> express plate amp

> its the 240 watt rms @ 4 ohm model and the
> problem is no matter what i do i get a small
> hum

> i did everything in the manual
> ...disconnected the cable tv...made sure all
> wiring is good.

> then i phoned parts express and they said to
> use a 2 prong outlet rather than a grounded
> outlet.

> Still get a small hum...doesnt get any
> louder with a increase in gain or changing
> the freq etc

> however when watching films its really
> really annoying during a quiet or silent
> scene it humms and wrecks it for sure.

> Changed my rca's to higher quailty also
> ....any other ideas?

Disconnect the RCA inputs?

The amp could be defective.

My 300-794 amp buzzes only during the initial surge when the dryer/refrigerator/washer turns on. The grounding in my house is miserable...

[baldemargarcia]

> You don't have hum with the BASH because its
> switching frequency is upsampled to 100kHz.

> It's also why the transformer is tiny.

But it still has to reproduce audible bass frequencies as you know. So if I had 60Hz noise getting into the audio signal, it would get to the woofer. The OP either has mechanical transformer hum, or has poor/defective power filtering in his plate amp. He's eliminated ground loop noise by trying a ground lifter, I believe. He's been given some good troubleshooting tips, let's see what he finds.

I find it interesting that the BASH amp uses a two prong power cord. This may help eliminate ground loop noise. I also find it interesting that Rythmic Audio offers a version of this popular 794 plate amp, with an improved grounding scheme which reduces 60Hz hum. Perhaps they have found that the grounding is poor in these designs. If you look into it and find the same, we'd all appreciate any tips you can give.

My 350W plate amp hummed like crazy when placed within a wooden enclosure (it's a stand alone I use to power my attic IB). When I went to figure out why, it suddenly stopped and hasn't hummed one bit again. Now it's mounted into the wall, and it's hum-free. I determined all my other plate amps with hum had noisy transformers.

[richard_b939]

> hey guys im the proud owner of a parts
> express plate amp

> its the 240 watt rms @ 4 ohm model and the
> problem is no matter what i do i get a small
> hum

> i did everything in the manual
> ...disconnected the cable tv...made sure all
> wiring is good.

> then i phoned parts express and they said to
> use a 2 prong outlet rather than a grounded
> outlet.

> Still get a small hum...doesnt get any
> louder with a increase in gain or changing
> the freq etc

> however when watching films its really
> really annoying during a quiet or silent
> scene it humms and wrecks it for sure.

> Changed my rca's to higher quailty also
> ....any other ideas?

ok to be more spefic ....here is more info you guys have been great with helping me out so fast!

The amp is model number 300-804

the subwoofer is a alpine type s [ in a 1.5 cf sealed box]

the amp is near my outlets so im hoping moving the system further away will do me good.

Would i have to move my amp and sub or just sub? since its just a small whine from far away but i do notice the closer it is to the outlet i get a increase to ear.
For example i ran it off my dvd as a source and the hummmm increased say 10 fold? the sub was at half peak excursion and freaking loud as sh#$ like i was playing a test tone.
After that i went back to the cd player as a source.

The rca's make no differnce at all...i used 5 differnt kinds of rca's from great to entry level and all made the same noise on the cd player.

to people who asked more techincal q's like about the transformer etc....please dummy it down for me i am a total newbie and dont know the terms for the life of me.

one other note is i have had it work 100% no buzz whatsoever before under the same config ....so it may be the deep freeze i got downstairs and the sh@# electrial system in my house...would that ''humm killing plug'' for outlets fix this?

[richard_b939]

could someone please say what i need to try in a certian order that makes sense like a checklist..

1.unplug wires's to see what humms....etc and so on

that way i can write it down as a list rather than looking through each post

much apperiacted guys you all rock!

[envisionelec]

> But it still has to reproduce audible bass
> frequencies as you know. So if I had 60Hz
> noise getting into the audio signal, it
> would get to the woofer. The OP either has
> mechanical transformer hum, or has
> poor/defective power filtering in his plate
> amp. He's eliminated ground loop noise by
> trying a ground lifter, I believe. He's been
> given some good troubleshooting tips, let's
> see what he finds.

> I find it interesting that the BASH amp uses
> a two prong power cord. This may help
> eliminate ground loop noise. I also find it
> interesting that Rythmic Audio offers a
> version of this popular 794 plate amp, with
> an improved grounding scheme which reduces
> 60Hz hum. Perhaps they have found that the
> grounding is poor in these designs. If you
> look into it and find the same, we'd all
> appreciate any tips you can give.

> My 350W plate amp hummed like crazy when
> placed within a wooden enclosure (it's a
> stand alone I use to power my attic IB).
> When I went to figure out why, it suddenly
> stopped and hasn't hummed one bit again. Now
> it's mounted into the wall, and it's
> hum-free. I determined all my other plate
> amps with hum had noisy transformers.

Two different things.

The power supply is a switching type. The input mains is rectified and filtered, then sent to a switching FET through the primary side of that little transformer.

The amplifier itself is not a switching design, however. Just the power supply.

Hope that helps.

[tomzarbo]

If you suspect the electrical is the problem, you could get an outlet line tester, the kind that you just plug in and the lights tell you if the outlet is wired ok or not. I know my house is wired all screwey, its 60 years old, and some of the older wiring was backwards. I had an electrician put a new panel in. I suspect you wiring might be goofed up. But I'm no expert.
Z.

[stevea]

i had to remove the green ground wire from plate on my rythmik basic 250 to get rid of hum