Hi, wonder if you could help me please? I am curious- I am thinking of using my basic Sony Walkman in my car straight into line level in of my DSP, and my hifi (Denon DM41) hooked up from the headphone out jack to the line level in. A 3.5mm to 2 x RCA cable. I am nervous to do this for one reason. Back in the 1980s, I had a Realistic Karaoke Machine (Concertmate 2000) bought from Tandy here in UK (or Radio Shack in USA). The power output was poor as was the speaker, so I connected it up to my Kenwood Receiver - this again was from the headphone out to the line level in. However, it repeatedly blew internal fuses in the Karakoke machine. Sounded great, but was constantly in the repair shop. I don't understand what fuses blew, but I can remember turning it on and it just made an awful and loud humming noise through the speaker.
So - am nervous to do this again? Is it risky to connect something via headphone out vs line level out?
But more importantly - what wen't on with that machine to blow fuses? My knowledge of electronics is extremely basic - but am curious to understand what was the mismatch that went on there, as people nowadays connect their ipods, ipads, mobile phones to their hifis with the 3.5mm headphone out.
Your help would be really appreciated.
Thanks
Julian
So - am nervous to do this again? Is it risky to connect something via headphone out vs line level out?
But more importantly - what wen't on with that machine to blow fuses? My knowledge of electronics is extremely basic - but am curious to understand what was the mismatch that went on there, as people nowadays connect their ipods, ipads, mobile phones to their hifis with the 3.5mm headphone out.
Your help would be really appreciated.
Thanks
Julian
Welcome to the forum, Julian!
Technically, a pure line output will produce slightly cleaner sound output than a headphone line out.
Nowadays, however, the difference is virtually negligible. This means headphone line outs can be used to drive line-level output loads as well as headphones.
So no risk is involved and, as adason has implied, the karaoke fuse problem may forever remain a mystery!
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One thing to check is that the headphone out ground is actually ground - if not then don't connect it to anything but headphones as it probably uses a virtual ground with a DC offset driven by active circuitry (you'll see this for instance in laptops and phones to avoid needing large capacitors).
@Mark Tillotson
Thanks for bringing that up.
Would connecting a ground loop isolator between headphone out and line level in avoid the problem?
Thanks for bringing that up.
Would connecting a ground loop isolator between headphone out and line level in avoid the problem?
@julianfletcher
To be on the safe side, you could use a ground loop isolator.
I connected the Monacor one in the following link between my son's Benq computer monitor headphone out and the line in input of his Blackstar amplified speaker: https://www.amazon.co.uk/FGA-40MF-P...x=monacor+ground+loop+isolator,aps,105&sr=8-6
This device ensures galvanic isolation of the source and destination equipment by incorporating two 1:1 transformers, one for each channel. (Galvanic isolation means that no direct conduction path between source and destination is permitted while still allowing information to be exchanged.)
My addition cured a nasty interference noise without audibly affecting the signal.
To be on the safe side, you could use a ground loop isolator.
I connected the Monacor one in the following link between my son's Benq computer monitor headphone out and the line in input of his Blackstar amplified speaker: https://www.amazon.co.uk/FGA-40MF-P...x=monacor+ground+loop+isolator,aps,105&sr=8-6
This device ensures galvanic isolation of the source and destination equipment by incorporating two 1:1 transformers, one for each channel. (Galvanic isolation means that no direct conduction path between source and destination is permitted while still allowing information to be exchanged.)
My addition cured a nasty interference noise without audibly affecting the signal.
It depends.
On the Walkman, no big deal, it is designed for headphones so output level is "just that" and very close (a few hundred mV) to generic Line Out levels.
While on speaker driving power amps, that is the main output, think 15-20V RMS, and headphone out is kludged by connecting headphone jack to speaker out through a 100-200 ohm resistor.
Cheap a$$ solution.
If you connect low impedance headphones there (8 to 32 ohm) output is automatically attenuated to safe levels.
If you connect a preamp input, typically 10k or higher, there is NO attenuation, you get the FULL 15-20V RMS through, which destroy any preamp input, even a power amp one.
I bet that was your problem.
On the Walkman, no big deal, it is designed for headphones so output level is "just that" and very close (a few hundred mV) to generic Line Out levels.
While on speaker driving power amps, that is the main output, think 15-20V RMS, and headphone out is kludged by connecting headphone jack to speaker out through a 100-200 ohm resistor.
Cheap a$$ solution.
If you connect low impedance headphones there (8 to 32 ohm) output is automatically attenuated to safe levels.
If you connect a preamp input, typically 10k or higher, there is NO attenuation, you get the FULL 15-20V RMS through, which destroy any preamp input, even a power amp one.
I bet that was your problem.