Audiophiles - This is what your Mega Dollar Cables Connect to inside your amps

[xrunner]

So my brother asked me to find out why his expensive Bob Carver Sunfire Woofer makes humming noise when the other equipment is turned off. To make a long story short I think it's a ground loop issue - ordered a ground loop isolator to try out.

But I thought I'd post some pics of the inside for all the audiophiles out there. You need to know what your Mega-Expensive oxygen depleted Super Duper cables are connecting to inside your amps.

Just wire. Normal everyday small basic boring plain little wires which go to plain little ordinary circuit board traces. See attached pics.

Have a nice day. 

[Zero999]

Lot's of lovely noisy carbon film resistors there to add depth and warmth to the sound stage.

[SeanB]

Turn the mains plug around in the socket and see if this helps.

[xrunner]

Lot's of lovely noisy carbon film resistors there to add depth and warmth to the sound stage.

At least the phono connector is gold plated. 

Turn the mains plug around in the socket and see if this helps.

Yea I heard that suggestion on another site. I've done some research on this woofer, and hum is a common problem. Some people claim it needs caps replaced but I tested a lot of them and couldn't find anything bad. I can't easily reverse the mains plug because it's a three prong.

Also there is no schematic available and the input from the mains / P.S. is something I've not seen before. It has two big caps and one is connected directly to neutral before the bridge rectifier. That thing has 165V on it when the amp is unplugged and it's a dangerous little beast.

Hope fully the ground loop isolated will make it better.

Edit -

[wraper]

This subwoofer seems to be a full of bullshit in its claims. 2700W RMS LOL. You cannot even draw such power from the US outlet even if considering it's amplifier is 100% efficient. And that's with 11"x11"x11" size and 43 lb weight  . My 300W speakers (seem to be more or less close to the truth, though I think it's a bit inflated) weight 48kg = 105 lb each  . And there is no amp inside too to add the weight.
Edit:
Posted this before seing second picture. 2700W hell yeah 

[Kevman]

I'm confused- that transformer only looks big enough to run the preamp/filter stages, and that bridge rectifier doesn't look connected to it... Is the main amplifier running directly off rectified mains?

[xrunner]

I'm confused- that transformer only looks big enough to run the preamp/filter stages, and that bridge rectifier doesn't look connected to it... Is the main amplifier running directly off rectified mains?

Hell if I know - I don't have the schematic but I might try to reverse engineer one. I don't know what they are doing, but I think it's part of the humming issue. Let me see if I can muster enough energy to draw part of it it. 

[wraper]

I'm confused- that transformer only looks big enough to run the preamp/filter stages, and that bridge rectifier doesn't look connected to it... Is the main amplifier running directly off rectified mains?

Yeah 1500uF 200V capacitors seem suspicious.

[Zero999]

It looks like it's a switched mode power supply. There should be a high frequency ferrite transformer but it's not visible on the photos.

The resistor, near where the yellow/white twisted pair is connected to the board, has overheated.

[wraper]

Isn't this an optocoupler? ...in the middle of preamp.

[Zero999]

Isn't this an optocoupler? ...in the middle of preamp.

Yes, it looks like an opto-coupler but you'll never know for sure without the part number.

What's on the other side of the board?

[Kjelt]

But I thought I'd post some pics of the inside for all the audiophiles out there. You need to know what your Mega-Expensive oxygen depleted Super Duper cables are connecting to inside your amps.

I don,t think audiophiles will have such subwoofers 
Try Velodyne or JBL. I have seen a lot of expensive amps but none had bare wire.
Still for the mains power cables I can only agree bigtime. But then I found out long time ago that snob audiophiles are selectively deaf.

[wraper]

Searched for the patent number. Looks like they are doing something crazy.

[Marco]

Bob Carver is probably one of the most famous anti-audiophiles.

Is that one of his subwoover drivers with a tracking switched power supply? Audiophiles only use space heaters.

[xrunner]

It looks like it's a switched mode power supply. There should be a high frequency ferrite transformer but it's not visible on the photos.

No it's not that kind of supply.

The resistor, near where the yellow/white twisted pair is connected to the board, has overheated.

No, it's fine that's just a shadow.

I'm drawing out the P.S. input and it's nothing I've ever seen. Check out the bridge - see that wire shorting across it? That's the two AC input pins they are shorting out - on purpose.  What does that give you - two sets of rectifier diodes in parallel? That's what it looks like on paper.

This thing is weird!

[PeterFW]

The first picture allready told everything you need to know without opening the speaker
Those frequency, level and phase adjustment knobs look like potentiometers.
Nothing wrong with that but the chance that the speaker is set up properly is near zero.

[calexanian]

Its a B.S. chinese plate amp. I know the guys who were making the stuff for carver. Carver went into receivership and the Chinese vendor now owns the name because they were owed the most. I actually was at a meeting with those guys a couple years ago and the new Chinese owners were here in the U.S. talking to all of the U.S. vendors for old Bob trying to figure out what to do with the dead rat of a company that had been dumped in their laps! Long and short of it now is you have Mid level AV products being sold under the Carver name. BTW if anyone wants to buy that name/company, let me know. I can broker a deal. That also goes for a number of other companies in the quickly evaporating audio market.

[macboy]

Bob Carver is probably one of the most famous anti-audiophiles.

Is that one of his subwoover drivers with a tracking switched power supply? Audiophiles only use space heaters.

Yes it is.
As for the 2700 Watt claim, well, ... it depends on how you want to look at it. The driver has a certain impedance, and the amp is capable of continuously driving a voltage into that driver that will calculate out to 2700 W if you use good old ohm's law. But it isn't that simple. His design uses a high back-EMF driver; basically the speaker in this sub acts like a motor that is not "stalled" which is in stark contrast to other speakers, which generally look like a stalled motor. This speaker produces a high back-EMF which cancels out a significant portion of the applied voltage, and therefore greatly reduces the actual power consumption and greatly improving efficiency. In other words, the "apparent power" through the speaker might be 2700W, but most of that is reactive power, not real power. The spec sheet BS numbers use the audio industries nonsensical way of calculating power (P=V²/R), but it is in line with how everyone else does it. He (Bob Carver) is very forward about the fact that the 2700 W number is both 'real' and sort of nonsense. Read the old white papers about the design of the amplifier and the driver and cabinet. This little sub went impossibly loud and low for its small 1 cu.ft. size two decades ago. This subwoofer re-defined the physics of how to produce bass by being simultaneously loud, deep, small, and efficient - a previously impossible combination. Clearly, I am impressed by the technology. I have nothing to say about how it sounds, which is a rather important trait in audio gear.

p.s. Too bad about the new ownership of the company as mentioned above.
p.p.s. This is a mkII which is very old, so clearly not made by the company's new Chinese overlords - not a "B.S. Chinese plate amp".

[SeanB]

I think that transformer is actually being used to couple the audio to the power stage, which looks like it is powered direct from rectified mains. Must be a small SMPS hidden at the back of the main board, where the bunch of caps are located.

Probably the poor earth to the front panel is the main cause of the hum, aluminium oxide, especially that which is heavily anodised, is a pretty good insulator.

[Marco]

AFAICS the Chinese owners still just sell the old designs at boutique prices.

Or maybe the dealers just paid to keep the website up to sell old stock.

[xrunner]

p.p.s. This is a mkII which is very old, so clearly not made by the company's new Chinese overlords - not a "B.S. Chinese plate amp".

Right, this was bought back in 1997 or so. Remember, it's operating as intended designed. I'm only trying to stop the hum when it's in standby (it never goes off).

So if you are interested, I drew up a schematic of the PS input, as it stands, and double checked it. This is what it shows. Anyone want to explain what's going on be my guest. CB means circuit board, I'm not going any further than that it would take way too much time.

[SeanB]

If it is wired like that then the only cure for the hum is a massive isolation transformer, so that the mains hum is not coupled through the driver circuitry.

I know Carver made some amplifiers that were seemingly designed to use the entire output of a large semiconductor fab for a week per unit, but this.........

[German_EE]

That short circuit across the input of the bridge rectifier has me puzzled. The circuit is almost like the 110V voltage doubler at the input of a PC supply, but not quite. I would be VERY reluctant to work on any part of that circuit without an isolation transformer.

[Marco]

So two half wave rectifiers going to the different capacitors to cheaply get split power from mains, what's so wrong with that?

PS. how is the isolated input amplifier coupled into the non isolated power amplifier though? I don't see a second transformer, linear optocoupler?

[Galenbo]

This subwoofer... bullshit in its claims. 2700W RMS LOL. You cannot even draw such power from the US outlet ...And that's with 11"x11"x11" size and

In thermodynamics, there is a direct relation between power, surface area and surface temperature (with some assumptions to be made)
Who is fluent in this? I would have to search for the formulas...

With that numbers, the surface temperature must be high enough to cook an egg on it.