DO NOT use any test equipment to test or evaluate this amplifier, which does not have floating grounds.
If the DC voltmeter is AC powered, Float the AC ground wire.
I (sort of) understand what they mean by a "Floating Ground", but I'm not exactly sure what they mean. And, if I was to use a VTVM which is plugged into the AC line, or an Oscilloscope (also plugged into an outlet), how do I achieve a "floating ground"?
Now, lets say I use a pocket battery operated VOM. It's not plugged in, so there is no ground. Is that safe to use on this device? (Seems to me that a pocket VOM is NOT actually grounded to earth, so that WOULD be a floating ground. (I think)....
Floating ground = shared, at least in my experience.
On my early '80s GM stock stereo, there were speaker outputs for four speakers as follows:
Left-Front Positive, Left-Rear Positive, and a single Left-Minus(both left speakers Minus wires tied into that). Ditto on the Right. It was called 'floating' ground because there weren't individual negative leads for the front and rear speakers on each side.
Probably done to save space and money by using less copper.
Possibly it means that the 'ground' terminals are actually connected to the AC neutral wire (not to a third-wire ground). That connection is permitted only with limiting resistance so that shock hazard is nil, but 'test equipment' can easily see high-voltage transients.
That would make sense only if this is a two-wire AC powered gizmo. It would make MORE sense if the device were an old TV set.
I'm going to go with this as the correct answer. The audio output of a Motorola Spectra is like this, and there are warnings repeatedly through the service manual NOT to ground either side of the audio.
This has nothing to do with "hot chassis" or floating grounds.
There are 2 possibilities. The first one that comes to mind is the 'hot chassis' where one side of the AC line is connected to the chassis. Usually an isolation transformer is used, or battery powered instruments that do not have a ground or conductive case.
The other is for mainly transistor audio output amplifiers. The speaker has both leads floating above ground. If a meter is used that one side of the test leads go to the chassis and the chassis of the meter is grounded by the 3 wire AC plug, the amp will be dammaged.
The same for the battery powered meter applies. If it does not have a conductive chassis and no AC line cord then you can use it.
Another rare,but possiable case is that a 'ground loop' can be made where a lot of hum or other undesired signals can be made.
There are 2 possibilities. The first one that comes to mind is the 'hot chassis' where one side of the AC line is connected to the chassis. Usually an isolation transformer is used, or battery powered instruments that do not have a ground or conductive case.
The other is for mainly transistor audio output amplifiers. The speaker has both leads floating above ground. If a meter is used that one side of the test leads go to the chassis and the chassis of the meter is grounded by the 3 wire AC plug, the amp will be dammaged.
The same for the battery powered meter applies. If it does not have a conductive chassis and no AC line cord then you can use it.
Another rare,but possiable case is that a 'ground loop' can be made where a lot of hum or other undesired signals can be made.
There is another situation whereby some stereo power amplifiers polarity swap the inputs and outputs, so that on one channel the negative (black) speaker terminal is at ground, but the other side has the positive (red) terminal at ground, and the power amp output connected to black.
It would not be immediately obvious that one channels "black" terminal is actually the power amp output. Connecting this to ground would short the amplifier.
This is done to maximise the efficiency of the power supply common to both channels.
I just hate to agree with you, but y're right. Nobody builds AC-DC transformerless radios and audio amps these daze.
It's probably a bridge amp: That looks like this: Notice that neither speaker wire is grounded.
If you want to look at the output of a bridge amp with a scope, you need to have a scope with an A-B (that's channel A minus channel B) input. Connect one probe each from each scope channel to each speaker lead. Connect both scope ground leads to ground.
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There are 2 possibilities. The first one that comes to mind is the 'hot chassis' where one side of the AC line is connected to the chassis. Usually an isolation transformer is used, or battery powered instruments that do not have a ground or conductive case.
The other is for mainly transistor audio output amplifiers. The speaker has both leads floating above ground. If a meter is used that one side of the test leads go to the chassis and the chassis of the meter is grounded by the 3 wire AC plug, the amp will be dammaged.
The same for the battery powered meter applies. If it does not have a conductive chassis and no AC line cord then you can use it.
Another rare,but possiable case is that a 'ground loop' can be made where a lot of hum or other undesired signals can be made.
There is another situation whereby some stereo power amplifiers polarity swap the inputs and outputs, so that on one channel the negative (black) speaker terminal is at ground, but the other side has the positive (red) terminal at ground, and the power amp output connected to black.
It would not be immediately obvious that one channels "black" terminal is actually the power amp output. Connecting this to ground would short the amplifier.
This is done to maximise the efficiency of the power supply common to both channels.
To clarify, most amps using this method don't actually have red and black terminals, but use Speakon connectors, where the terminals are not visible. One Speakon is wired 1+ hot, 1- ground, the other is wired the opposite, with the signal input to the amplifier polarity reversed. The end user doesn't need to know or care this is the case when using Speakons, but a repair tech certainly does.
One notable user of this method is the Yamaha Stagepass series, which has
1/4 inch jack outputs. In this case, one side has the jack body grounded and the power amp output going to the tip, whilst the other has the tip grounded and the jack body is actually live. A terrible idea really.
You're right. First off, it has a power transformer. Secondly it is an amp made to be bridged. After reading the user manual a second time, I determined that this floating ground is only needed in Bridge mode.
I have never had an amp that was bridgable (that I know of anyhow). I dont think this is possible with the old tube amps, but I could be wrong. This amp is a solid state, with power transistors (not chips for the output). 16 power transistors to be exact.
Although I like tube amps, I could not pass this amp up for the price he wanted. It's rated at 300W per channel using 4ohm speaker load, or 200W per channel using 8 ohm speakers. Or it's brigable to be a 600W mono amp. I'm gonna have fun with this thing....
It's a Altec Lansing 9444A power amp. It appears it was made around 1988 to 1990. And Altec Lansing is top of the line equipment.
This is a commercial amp, with balanced XLR inputs, so I will have to buy or make some adaptors so I can connect 1/4" or RCA jacks to it for home use. But I know that my speakers wont handle that full power either, but I suppose I dont have to run it wide open either....
It was popular for industrial and commercial sound systems. It was a US company, and I've seen their equipment for decades. I've been out of the business for years, so I don't know if they are still around.
Some stadiums used their equipment, with thousands of watts of amplification, with each amp driving a single zone. Some had N+1 installations that would automatically switch a spare amp into service if needed.
Here is the manual, which shows how to connect an unbalanced input.
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Never piss off an Engineer!
They don't get mad.
They don't get even.
They go for over unity! ;-)
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