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120 hz hum in catv amplifier

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WATCH RELATED VIDEO: Tracking down the source of amplifier hum.

Onkyo 605 & Orb speakers - whats settings?


David, aka Grumpy, needs our help. Great news. David is home! It was quite the ordeal to get him home and into the house, but it is done. Thank you to everyone for their support. Now a long road ahead to get him back on his feet and functioning normally. I have started a GoFundMe to help with the medical bills. Please help, if you can. Log in or Sign up. Messages: Hi all, new to the forums.

Have been reading quite a lot though. My question - in the schematics attached there is a power supply, creating DC current at a bunch of different voltages, and the power amp. Both have a number of capacitors 16 in the supply, 12 in the amp , including 2 mongo 27, uF.

Is the Hz more likely originating in the power supply, or the power amp? Is there a way to test? The 2 giant ones are actually in a reasonably accessible location. I could pop those and replace them, but if they are unlikely to be the cause, then I'm just wasting time. If they are likely to be the cause, then I can save a lot of time in a tear down to get to the others. Thanks for any advice, Jeff. JeffWired , Mar 21, The easiest way to determine if the capacitor is failing is to measure it's equivalent series resistance ESR.

Of course beside that one can easily notice if any of caps had actually have electrolyte leaked, or if it's bulging. I would first look for that obvious signs of failure. But failed capacitor don't need to have that obvious signs, that's why ESR meter is good tool. I have bought so called MK transistor tester on ebay, that is super cheap, and can measure caps, resistors, diodes etc. Few weeks ago I managed to repair my NAD , that had also buzzing noise.

It turned out to be one of the caps in preamp Messages: 1, Location: Arnhem. Does the hum occur in the sound out of the speakers, or does the amp itself hums? In the latter case, it's mechanical hum from the transformer. Oilmaster , Mar 22, Thank you for the responses, The buzz actually comes from both the speakers and the unit.

More noticeably and irritatingly from the speakers. The noise from the speakers varies as the volume is increased and decreased. It is in all speakers at roughly the same level - I have left, right, and center. Also can hear from the sub, which is connected to a line out. The buzz from the unit itself does not vary noticeably with the volume.

Only happens when applying power for the first time. Last edited: Mar 22, JeffWired , Mar 22, Looking at the circuit schematics, this unit is highly 'digital' electronics, and it's hard to say from a distance and with little further information that the hum is caused by degrading power supply capacitors. In fact, the hum can be easily picked up somewhere in the circuit and it's then becoming part of the sound signal, being amplified, etc.

Although a constant hum fixed volume hum regardless of the volume knob position would mean that it is not part of the sound signal itself.

That would direct to a sloppy power supply section. Hum can have many other reasons like external sources, injected via the mains supply, but also picked up by outgoing speaker cables and interconnects with other gear. How good or bad is the actual mains circuit feeding your system? Meaning, is there any potential hum source like a fridge, light dimmers, or electronic devices with switch mode power supplies PC, phone chargers, TVs, even DVD players connected to the same mains circuit?

How good or bad is the earthing system? The schematic shows no earth ground connection of the unit, but faulty ground loops or no filter-out path for hum may be created by interconnections with other equipment. A non-grounded PC can inject significant amounts of hum in the audio system.

You could do some simple tests like this: hook-up the unit without anything connected to it, no speaker cables, just nothing. Hopefully it has a headphone output; then connect a headphone and listen if there is hum while turning the volume knob.

Still hum? No hum? Then start connecting cable by cable and listen each time if the hum comes alive, until you hit the trouble maker. Oilmaster , Mar 25, I disconnected and moved the unit to a new circuit. In general the grounding in the house is pretty solid I know because I drove an 8 ft copper ground rod into the basement as well as the line ground. Couldn't test through the headphone jack because I don't have headphones with the larger jack size. Hooked to a different external speaker it exhibited the same buzzing that varied with volume.

Pretty sure it is Hz, I listened to a couple samples on youtube to compare to. Then it comes right back once it has internally switched source.

Must have some kind of interrupt or protection circuit in there as it switches inputs. I'll have an oscilloscope in the next couple days. Does it make sense to start at the speaker outputs and work my way back until I don't see the Hz?

Are there a couple key output points I could check on the path? JeffWired , Mar 25, Are all your peripherals plugged into the same surge protector or UPS? I've read about problems with grounding noise if even one peripheral is plugged into a different outlet. Same outlet. It is gradually worsening which also, in my mind, points to an internal problem rather than external interference. Starts looking like an internal problem, though not excluding external troublemakers yet.

Check redo all cable connectors inside this unit. If plug-in cards are used, reinsert all cards. Looking at the schematic again, in many instances the zero volt is connected to ground.

Could you perhaps open the unit and check if the zero volt is connected to the chassis or not? Refer to page 20 for the power supply section and measure if the negative pole of C16 is connected to the chassis zero resistance. Can you open the unit and tell if it is open or closed? If despite all these checks the problem remains, then a deep analysis with a scope will be required, starting at the power supply section. I wonder how this looks like in reality; any resistance build-up or misconnection in this knot is a direct cause for hum as is a failing C16 or C Oilmaster , Mar 26, Messages: 10, Location: RIP What events happened just prior to the hum showing up?

The symptoms are indicative of a ground loop. The most common point we see here at AK is from the TV cable feed from the street. The fact that it is in both channels and can be controlled by the volume indicates that there's something on one of the inputs. This isn't necessarily a problem with the ground rod you've installed, too. Start with any sort of external feed like a TV cable box. If the hum immediately appears, set it aside and move on to the other items.

Remember that if any other items are connected to the cable box, they can re-insert the ground loop when they're connected. The fact that the hum comes and goes when you switch inputs just tells me that you've got a muting circuit that's kicking in at the switchover. This may be confusing your diagnosis. Cheers, David. I have done the first advice as Oilmaster indicated and removed everything from the system.

Maybe that was not clear from my post. In a new location, removed from other electrical equipment, all inputs removed, the amp exhibits the same behavior. No inputs, one speaker connected. Buzz is same through all speaker outputs L,R,C


Why Does My Amp Buzz – How to Fix Amplifier Buzzing Noise

Log in or Sign up. Steve Hoffman Music Forums. Location: Salem, MA. My standalone phono stage, itself, seems to have grounding issues. It's not what I'm writing about, though. But a low level hum was entering my system even with my Vinyl One phono stage turned off, regardless what source I was using. Unplugging the phono stage from the power conditioner, the hum disappeared.

The CATV amplifier has wide-band and low noise and high linearity (CSO, CTB) feature over MHz; MHz and MHz. For various requirement of.

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All the input jacks were empty of Interconnect cables? Volume control set to minimum. The only interconnects connections were from the outputs of the Marantz to the Adcom power amp. Is that correct? If you have a cable TV connection to your audio system, it is probably this. I've had hum problems with my phono preamp that was corrected by re-orienting the equipment to a different location. The Marantz has double insulated AC power wiring.

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120 hz hum in catv amplifier

Effective date : Year of fee payment : 4. Year of fee payment : 8. The invention relates to a method for measuring Hum on a digital QAM carrier using a testing device for testing digital TV signals including a QAM demodulator therein, and to a testing device implementing the method.

Table Of Contents.

Hum Issues w/Turntable and/or Phono Input


Effective date : Year of fee payment : 4. The hum detection circuit detects a hum component included in an AGC signal. The time constant control circuit automatically controls the time constant of the AGC filter in accordance with the level of a detected hum component in such a manner that when the level of the hum component is large, the time constant of the AGC filter is varied to be small, while when the level of the hum component is small, the time constant of the AGC filter is varied to be large. Thus, the AGC filter outputs an AGC signal from which a noise component, particularly a hum component, is eliminated on the basis of a time constant determined by the time constant control circuit, so an AGC is carried out without the influence of the noise component included in the AGC signal.

Ground Loops - Eliminating System Hum and Buzz

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Additionally, hookups to the same amps or receivers and the same you should set your subwoofer to Hz. If you have big speakers set to the.

What causes 60hz hum?

This is going to be the best thing since sliced cake! Going to the movies is going to be old news. Instead of crisp sounds coming from every corner of the room, you hear chatter, buzz, and a gentle hum coming from the preamp. Except the sound is not gentle.

US5260792A - AGC circuit with 60 hertz hum compensation - Google Patents


Click to see full answer. Also, what causes a hum in an amplifier? An audio problem called a ground loop is a common cause of hum problems. Slight differences in the AC voltage levels between two pieces of equipment creates an audio hum. Ground loops in home stereos typically occur when turntables or other sources are plugged into different electrical outlets than the amplifier. Likewise, what is a hum eliminator?

RF amplifiers are just what you need to strengthen RF signals used in radio communication.

Noise Com Debuts Programmable Noise Generator

In electronics, noise is an unwanted disturbance in an electrical signal. In communication systems , noise is an error or undesired random disturbance of a useful information signal. The noise is a summation of unwanted or disturbing energy from natural and sometimes man-made sources. Noise is, however, typically distinguished from interference , [a] for example in the signal-to-noise ratio SNR , signal-to-interference ratio SIR and signal-to-noise plus interference ratio SNIR measures. While noise is generally unwanted, it can serve a useful purpose in some applications, such as random number generation or dither. Different types of noise are generated by different devices and different processes.

This series includes low and high impedance versions to cover a variety of application needs. The XPA is housed in a half rack width metal enclosure, conserving rack space and weighing only 2. The Extron exclusive, high efficiency design generates very little heat and allows the amplifier to be convection cooled. Before use, ensure that the device meets all regulatory requirements for your region and complies with all applicable local safety and electrical codes and standards.




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  1. Silas

    Okay, thank you very much for your help in this matter.