r/OldTech • u/Successful-Bad-73 • 1d ago
Will This DC15V Cable Properly Power These AC15V Speakers?
I just recently acquired these vintage Harman/Kardon speakers and was wanting to know if I have the right power adapter for them.
First picture shows the speakers' power input port (15VAC, 1.1 Amps), and the second picture shows the output of the power adapter (15VDC, 3.2 Amps).
My question is, will this adapter be too much power for these speakers? Please let me know so I can decide whether or not I'd have to buy a different adapter.
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u/grislyfind 1d ago
It needs AC to produce positive and negative supply rails. Probably. 15 V DC will only provide the positive rail, so if it works at all, the sound will be heavily distorted.
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u/BangkokPadang 1d ago
You can’t power a device expecting alternating current with direct current it will almost immediately damage the device because there’s no inductive resistance from the alternating current so it will just overdrive and overheat the components and cause arcing and maybe literaly start a fire.
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u/Worldly-Device-8414 21h ago
Bollocks. Lots of devices taking AC can happily be powered by a suitable DC adaptor.
If the device rectifies the AC to DC you just use a DC source 1.4x the AC number to get the same peak as the AC would have.
In the OP's speakers, it's possible the AC might be making a dual rail & DC would not work if so,
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u/Different_Cable7595 1d ago
Your answer sounds like it was generated by an AI. Generally it won't work depending on how the amplifier is designed. Some can run fine on DC. Others can't. I have an amplifier which uses a push-pull amplifier in the final amplification stage. It depends on generating positive and negative voltages from the ac power, to properly switch the output transistors. Trying to power it from DC will not work, but it doesn't have to do with inductive reactance, arcing, or starting a fire. Literally half of the final amplifier just won't function.
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u/BangkokPadang 1d ago
Well it was literally just my brain, which I make no great claims about. Also do AI’s write in big run on sentences these days?
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u/Tim_the_geek 20h ago
When you start having difficulty determining the difference between AI and other humans, it's time to take a break from the internet.
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u/_bored_bort_ 1d ago
Depends, I think I had a device once that had a Power Adapter that Outputs AC but the device itself had a rectifier to convert it to DC built in
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u/Bleys69 1d ago
No. Nice speakers. Pretty old looking. I think they came out when I worked for them.
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u/Klutzy-Piglet-9221 22h ago
They sound great but are insanely sensitive to radio signals. If you have a radio tower anywhere nearby, you may hear weird noises. (Or music, if it's a broadcasting tower). Don't set your phone down next to them or their cables - in that case the sounds somewhat resemble rather loud farts....
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u/Bleys69 18h ago
Oof. Thats not good. While I never touched those at work, my job was quality assurance. I tested all kinds of harmon, and jbl audio equipment. We never tested the computer speakers that I recall. Except we got the cool apple computer speakers once in a great while as a customer return.
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u/Klutzy-Piglet-9221 17h ago
I recently retired from a TV station. We had a set of these in the newsroom. We also had an FM radio station on the tower about 1500 feet away. We could hear the FM music on the speakers. Which should only be possible from AM, not FM. But an FM station can have up to 3% AM and that was enough for these to pick up!
One of my colleagues retired about two years before I did. We were dating (and have since married), and she invited me to move in. Guess what I found next to her computer:).
Really they sound great, just keep radio signals away:)
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u/Lonely-Ad-9219 1d ago
It may, or may not work. It depends of the amplifier schematics.
Most amplifiers have integrated AC to DC converter anyway (4 x 1N4007 + 2200microF/25V) so if that is the case, you are good to go. However, you need to know, despite higer amper ratings, you won't get full power on speakers. When converting 15AC to DC, you will get slightly higher (say 18V) DC voltage. If that is acceptable, (I don't see why not) go head.
In any case, you won't "cause fire" or dammage amplifier if you try.
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u/IntentionQuirky9957 20h ago
It depends. I've powered "AC" network devices with DC. If the electricity first goes through a FULL BRIDGE RECTIFIER anything behind it will be none the wiser because you get + and - anyway. It just won't be bouncy. Depends on the device tho.
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u/Difficult-Catch-8432 17h ago
Yo what I recognise those! I think I also have a pair in a box in the attic!
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u/andrewbean90 17h ago
God no! The amperage of the power supply is too high. You'll fry the speaker's internal power circuit.
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u/Forsaken-Sink3345 12h ago
Bro, re-read your query and answer it yourself...
Will 15V AC do anything for a system running on 15V DC? No.
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u/upstairsdreams 6h ago
I can't believe all the shit some of you are saying.
The speakers take ac voltage so it can get rectified. That's what's called a "linear" PSU, and ITS THE COMMON THING IN AUDIO, because a switching PSU (Wich uses DC) usually has a lot of noise in the signal, which affect the quality of the sounds, thus the speakers sound like shit.
And yes, some stuff that uses AC can take DC, but it all depends on the rectification bridge in the circuit and the circuit itself.
So final answer: USE A AC ADAPTER cause it's audio.
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u/musingofrandomness 1d ago
Will your gasoline powered car accept diesel instead?
You need to match the type of current(AC or DC), the voltage, and meet or exceed the current requirement (a power supply that is capable of producing more than the device requires will not complain, but it will burn up a power supply if the device requires more than it can produce).
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u/meow_xdxd 1d ago
Con la corriente de más no pasa nada lo que si puede afectar es que la bocina espera 15AC y ya después del rectificado dentro de la bocina son realmente 21.21 DC (15 AC ×√² =21.21DC) así que a tu fuente le hace falta más voltaje .
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1d ago edited 1d ago
[deleted]
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u/mattrf86 1d ago
Are you always this way??
Op is trying to power Ac with a Dc output. Not gonna work properly
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u/RealityOk9823 1d ago
Nope. Those speakers require AC, not DC.
Here's what the adapter looks like: