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My audio amp is hummmmmming.

My audio amp is hummmmmming.

My audio amp is hummmmmming.

(OP)
I have a Sony STR-GX800ES I use constantly, in fact it's been on for approximately 7,380 days (175,000 hours).

This is kinda funny since I've always found Sony stuff to be short lived crap so I guess they stuck-it-in-my-eye for telling people Sony is junk.

Alas, about a month ago I started hearing a hum. I've been pretty busy and assumed it was probably coming from PC which is the only source I generally provide it with. Today while listening to a text-to-speech book (Anarchy Rising; The Survivalist Book 2){a quasi-ZA tale} while working, it really started grating on me. Doing a minute of investigation it became clear that it's the STR-GX800ES causing the hum because it never changes a bit regardless of which of the zillion sources I send to the output. It does go up and down with the volume.

It's the classic 60Hz hum. Sounds the same as standing next to any large humming transformer.

I'm guessing it's probably the main power supply and the bulk caps having probably dried out, like prunes being warmed for ++100,000 hours.

Anyone ever tracked that hum to something specific in an audio amp? Is there something else that could cause it I should focus on instead?

STR-GX800ES Schematic

Keith Cress
kcress - http://www.flaminsystems.com

RE: My audio amp is hummmmmming.

I would bet if you were powered up 24/7 for 20 years you would be humming as well ☺

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: My audio amp is hummmmmming.

Dry caps is the most likely cause, though you may want to check for a ground wire that suddenly opened at one end (or a previously open one that closed due to contamination).

Dan - Owner
http://www.Hi-TecDesigns.com

RE: My audio amp is hummmmmming.

You listen to "Anarchy Rising: The Survivalist Book 2" through a high powered stereo system in your spare time?

Do you want to be best friends?

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: My audio amp is hummmmmming.

itsmoked,

Your amp may be humming because it does not know the words!

--
JHG

RE: My audio amp is hummmmmming.

Bad ground somewhere, or bad capacitor.

20 years? That's a very good run for a domestic amplifier. smile in the early 1990's I owned a lovely Pioneer SA-9100 from the 70's but that developed a major fault and was non-repairable at the time. Wish I had kept it now that parts are so much easier to find using the 'net. Ironic that 25 years on it is now easier to get spares for a 40-odd-year-old amplifier! They are worth a small fortune now.

Does the buzz go away when you disconnect all the cables from the inputs? That would point toward a bad ground. If that doesn't clear it then start with the main reservoir caps, then move on to looking at other the other electrolytics.

The buzz is probably at 120Hz BTW - rectifier ripple frequency - and not 60Hz.

RE: My audio amp is hummmmmming.

This problem was really common back in the days of vacuum tubes. And, yes it was due to bad capacitors in the power supply.

RE: My audio amp is hummmmmming.

(OP)


Good chuckles there.

Quote:

You listen to "Anarchy Rising: The Survivalist Book 2" through a high powered stereo system in your spare time?

Do you want to be best friends?

No. :) Not spare time. I'm stuck assembling 20 double sided surface mount boards where I can solder screen one side, parts place, and reflow(solder), but the back side I have to add solder-paste by hand to 120 pads, then place the parts, then hand solder them. Listening to ZA or SciFi type books is the only way to actually retain sanity.

I'll check the ground situation today. Thanks for the suggestions.

Keith Cress
kcress - http://www.flaminsystems.com

RE: My audio amp is hummmmmming.

If it starts woofing, check the turntable for run-out. grin.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: My audio amp is hummmmmming.

All the bad jokes aside, I would say that you suffer from dried out electrolytic capacitors in the power supply, or rather your amplifier does.

RE: My audio amp is hummmmmming.

First looking for bulging cap cans.
Take you o'scope and start looking at various points in the power supply. You should find it fairly fast.
I had one of Sony's first VFET amps, it lasted 20 years, and a good part of that time it was being used as a power supply amp (fed from a HP sine wave generator) running from 50Hz to 10kHz.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: My audio amp is hummmmmming.

My friend John T. replaces all the electrolytics in his stuff with nonpolarized caps of the same value.
He says it improves the sound.

Mike Halloran
Pembroke Pines, FL, USA

RE: My audio amp is hummmmmming.

By any chance does he own one of those insanely expensive single-ended triode valve amps bought by the folks with 'golden ears' , deep pockets and zero common sense? Rhodium-plated mains power leads, hand-would paper-oil capacitors, that kind of thing? The audio subjectivists and their world of sorcery and witchcraft make me laugh, mostly.

RE: My audio amp is hummmmmming.

I doubt it.
He makes and sells high end guitar amps.

Mike Halloran
Pembroke Pines, FL, USA

RE: My audio amp is hummmmmming.

Nice. Had to be a valve amp - high voltage and relatively small capacitors. There's no sane way to replace big electrolytics with film types. smile

RE: My audio amp is hummmmmming.

Pick up some good Japanese electrolytics (Nichicon, Rubycon, Nippon Chemicon).
Match the original capacitance.
Use the same or higher voltage rating.
And replace all of them, not just a few.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: My audio amp is hummmmmming.

(OP)
Thanks Ed et. al.

Seems my amp has 88 electrolytics scattered around 9 circuit boards. I'm guessing about 10 different values. The power amp-board with the 'big six' is buried in the beast too. At the moment I don't have the time it looks like it will take to do the job, so I went to Best Buy and got their bottom-end Insignia tuner-amp for a paltry $80. It works really nicely! I'm actually kinda shocked. It even has Bluetooth so I can feed it with audio sourced from my phone.

Another repair on standby.

Keith Cress
kcress - http://www.flaminsystems.com

RE: My audio amp is hummmmmming.

Just imagine what you could get for $100.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: My audio amp is hummmmmming.

Since you seemed a bit nostalgic for that old Sony amp, perhaps something like this would fit the bill, and it's less than $100:

https://www.monoprice.com/product?p_id=16152&c...

Or if you're looking for something bit more powerful, and just a little over $100, perhaps this one:

https://www.monoprice.com/product?p_id=13194&c...

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: My audio amp is hummmmmming.

For that amount of money those can't be all bad. smile

I still occasionally repair valve guitar amps for friends, something I used to do a lot when I was younger. The last one bagged me a Marshall T-shirt as 'payment'. smile Solid state has a lot going for it but valve amps still have a lovely sound, even if it is full of even-order harmonics and far short of the distortion performance of a decent solid-state amp.

RE: My audio amp is hummmmmming.

Kieth, and that is the reason that you need an oscilloscope, 88 caps.
It is either in the power supply, or a filtering stage.
Once you narrow it down replace all of them in that (and the other channel) section.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: My audio amp is hummmmmming.

(OP)
Good point Ed. I'll do that as soon as my current maelstrom of stuff settles a bit.

Keith Cress
kcress - http://www.flaminsystems.com

RE: My audio amp is hummmmmming.

Just curious, what does ZA stand for? (I tried searching book genre "ZA", but nothing promising turned up)

RE: My audio amp is hummmmmming.

I imagine that the Z is zombie...

RE: My audio amp is hummmmmming.

As in "Zombie Apocalypse"...

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: My audio amp is hummmmmming.

Quote:

Another repair on standby.

That's given me a big smile this morning. bigsmile

Steve

RE: My audio amp is hummmmmming.

Interesting discussion over on the Audio Karma forum about caps and re-capping vintage equipment. Some of the techs there with yeeears of experience say it's a pointless exercise to recap the whole thing, you'll change the nature of the circuit and thus the sound quality, etc. Good discussion if you're into that kind of thing.

Perhaps all you did was let out the Magic Smoke?

I'd find a knowledgeable tech and send it to him. Note, not every tech out there can or will (or should!) work on vintage equipment. You need to find the right guy. Again, the Audio Karma forum is a good place to look.

RE: My audio amp is hummmmmming.

Change the sound quality tongue So if I replace this cap, that had a tolerance of +20/-80% from the start, and replace it with another of the same type/spec (or even tighter spec), somehow the "sound quality" will change. Those golden ears, they make me laugh every time...

Dan - Owner
http://www.Hi-TecDesigns.com

RE: My audio amp is hummmmmming.

I think the point is, yes, the sound quality will change with different components and it won't be what you had previously. So the distortion and harmonics you got before will be different with a different quality cap. Some folks are OK with that, and some aren't. Don't be surprised if/when it happens. Harmonics, distortion, and color (musicians call it 'timbre') set the character of the sound. This is where terms like "The JBL Sound" come from. Which I happen to like the JBL sound, myself. And I have a 1/3 octave EQ on my system. Horrors. Don't matter anyway; I now have a nasty roll-off in the left ear at about 3.5 kHz so I can't tell the difference any more! At age 56 I still turn it up to 9 and rip the knob off.

RE: My audio amp is hummmmmming.

If the sound quality of an amp changes due to a component change then it is as a result of distortion, which could be either increased or reduced. For example, distortion is the reason for 'the valve sound'. Now I quite like the sound of a valve amp, but it's not as accurate a reproduction of the input as I can get from a good solid-state amplifier. There's a world of difference between 'accuracy' and 'niceness'.

RE: My audio amp is hummmmmming.

KernOily: Magic smoke, thought that was the sole property of Lucas UK.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: My audio amp is hummmmmming.

I was told once that the reason the British drink 'warm beer' is because Lucas makes refrigerators.

Also when I was younger (in my late teens) I used to drive a motorcycle (Honda 305 Super Hawk) and some friends had British bikes. The joke was that at night you could tell it was one of them coming down the road because when they slowed down their headlights would dim and some would even start to flicker.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: My audio amp is hummmmmming.

When I was a teenager my mother had a Hillman, a small British built auto.
When I see the phrase;
"Lucas. Prince of Darkness." I can really appreciate the sentiment.
Whenever you stopped it you had to remove the paper match book from the voltage regulator.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: My audio amp is hummmmmming.

My first car was a very used Hillman.
Luckily, it had a big battery. ... or maybe that was by design.

Mike Halloran
Pembroke Pines, FL, USA

RE: My audio amp is hummmmmming.

John - They had the Lucas patented 3 position switch - Dim, Flicker and Off.

Lucas Brakes Motto: We press on where others stop.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: My audio amp is hummmmmming.

This was the most fun thread I have ever read on Eng-tips!!!!

Not to change the subject, but just get a 100mfd cap and begin sticking it across each cap on your pcb until you find the one causing the issue... then you maybe dont need to replace all those others until they start acting up.

If on the otherhand your unit was so old to have waxpaper non electrolytic caps,, then just spend $8.00 and buy all 30 of them and replace them all. (these dont usually make the hum tho).

www.KilroyWasHere<dot>com

RE: My audio amp is hummmmmming.

... or if the old electrolytics are drying out...

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

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