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Post subject: Buzzing amp
Posted: Sun Dec 05, 2010 9:07 pm
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Amp buzzing when powered by a generator. How can I fix this ?


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Post subject: Amp buzzing
Posted: Sun Dec 05, 2010 9:41 pm
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Hi HG4700,

You probably need a power conditioner between the amp and generator, that should do it. If you could sufficiently ground the generator, it might help with the noise also. I can't recommend any particular model for a power conditioner, but I know that others here use them, hopefully they will chime in. :idea:

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Posted: Sun Dec 05, 2010 9:54 pm
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A power conditioner *may* help but the problem is actually inherent to any generator and its proximity to the devices it is powering. The continuous movement between rotor and stator in any generator creates an electro-magnetic field that translates into a low-frequency RF energy field. And as we're all aware, the preamp stages of many amps can emulate an RF detector (with the instrument acting for all the world like an antenna). Shielding can help up to a point, as can lengthening the distance between the generator and the amp. But the longer the power cable, the less current it is able to safely carry.

Not much of a usable solution I'm afraid but I HTH nonetheless.

Arjay

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Posted: Mon Dec 06, 2010 2:52 pm
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+ 1 on "But the longer the power cable, the less current it is able to safely carry.
8) or increase cable section 8)
:cry: heavy,costy :cry:

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Posted: Mon Dec 06, 2010 7:04 pm
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I used to use an isolation transformer between generator and amp for those outdoor gigs. Worked well for me. But I never really researched the science involved. Art

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Post subject:
Posted: Mon Dec 06, 2010 7:45 pm
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That is interesting aclempoppi. I think that it may be a combination of two factors involved. Common no longer being the grounded conductor, and the "choke" effect of the transformer on the generator noise, at least on the higher frequencies. I think that it may, in part, be similar to some microphone setups that use transformers, and they offer isolation as compared to direct inputs, which helps eliminate or reduce noise. My Navy buddies all say that systems that have the ungrounded neutral (which would no longer be neutral), like on the ships, is better and safer than with a grounded neutral. I don't know if they ever mentioned anything about noise reduction though. :idea:

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Posted: Mon Dec 06, 2010 10:33 pm
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Shipboard systems generally run on 3-phase, 1000 Hz, 208 VAC -- the ripple factor is substantially reduced with this type of input voltage.

Arjay

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Post subject:
Posted: Mon Dec 06, 2010 10:59 pm
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Thanks Lou, I really didn't know what the heck, but seemed like a good idea back then. Arjay, that's why I put in my app with the "Love Boat". I'm still waiting for their reply. Art

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Post subject:
Posted: Mon Dec 06, 2010 11:04 pm
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I'm sure that HR mailed you a "welcome aboard" package with your acceptance letter......back in 1977.

You know how the post office is.

:mrgreen:

Arjay

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Posted: Mon Dec 06, 2010 11:14 pm
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Wow, 1K Hz, I didn't know that they used that high a frequency. You can use some really small transformers at that frequency. I have worked on generators for commercial aircraft, they used 400 hz, mainly for the space/weight savings over a 60 Hz system. :idea:

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Post subject:
Posted: Mon Dec 06, 2010 11:25 pm
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shimmilou wrote:
Wow, 1K Hz, I didn't know that they used that high a frequency. You can use some really small transformers at that frequency. I have worked on generators for commercial aircraft, they used 400 hz, mainly for the space/weight savings over a 60 Hz system. :idea:


Indeed.

Most Army and Air Force systems are powered by 400 Hz AC (or 24 VDC) which is industry-standard in commercial aviation as well. I'm not sure how the Navy arrived at the conclusion that 1000 Hz was necessary.

Arjay

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Post subject:
Posted: Tue Dec 07, 2010 8:54 am
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Retroverbial wrote:
shimmilou wrote:
Wow, 1K Hz, I didn't know that they used that high a frequency. You can use some really small transformers at that frequency. I have worked on generators for commercial aircraft, they used 400 hz, mainly for the space/weight savings over a 60 Hz system. :idea:


Indeed.

Most Army and Air Force systems are powered by 400 Hz AC (or 24 VDC) which is industry-standard in commercial aviation as well. I'm not sure how the Navy arrived at the conclusion that 1000 Hz was necessary.

Arjay


In a previous life, I spent a lot of time around equipment designed to operate on various classified aircraft. You haven't lived until you have experienced the thrill of a bank of equipment cooled by 400 Hz fans! :shock: :lol:

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Posted: Tue Dec 07, 2010 8:56 am
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bluesky636 wrote:
You haven't lived until you have experienced the thrill of a bank of equipment cooled by 400 Hz fans!


I've "lived", Bill.

:mrgreen:

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject:
Posted: Tue Dec 07, 2010 9:10 am
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Retroverbial wrote:
bluesky636 wrote:
You haven't lived until you have experienced the thrill of a bank of equipment cooled by 400 Hz fans!


I've "lived", Bill.

:mrgreen:

Arjay


:lol: :lol: :lol:

Then you know exacly what I am talking about.

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Post subject:
Posted: Tue Dec 07, 2010 9:25 am
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Indeed!

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This is the type of radar set I worked on for about twelve years, the Westinghouse AN/TPS-43. Everything in it was convection-cooled via over 100 boxer fans except for the transmitter which was cryogenically cooled. As irritating as the headsets were to wear, they did provide some relief from all the fan noise. The heat exchanger outside was even worse!

Arjay

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