Cassette headphone out shorting...

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Cassette headphone out shorting...

Post by DrummerMan » Sat Apr 11, 2020 12:34 pm

Hey All! Riddle me this if you can...

Just received a tabletop cassette player to transfer the box of cassettes I found to digital.

When I plug headphones (TRS cable) into the headphone out, sounds fine.

When I plug in a Y cable with (1) 3.5mm TRS on one end and (2) 1/4" TS on the other end, I get major grounding from my DAW/Interface inputs. Things I tried with no improvement:

- tried 2 different y cables
- tried one side at a time
- tried going directly into my headphone mixer
- tried pulling various plugs out halfway

I dont understand why the headphones are working but the same output is producing massive ground hum when I use a Y cable. I'm probably overlooking something stupid so please embarrass me with whatever you're about to tell me. Thanks!
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Re: Cassette headphone out shorting...

Post by vvv » Sat Apr 11, 2020 12:40 pm

Have you tried using the DAW/Interface inputs with something else?

Does the DAW/Interface have level adjustment? Impedance adjustment? A phase switch? A mono switch? A ground reverse or lift switch? A level switch?

My first guess would be the output of the deck is too hot; turn the output down to 0 on the headphones out of the tape deck, and if possible on the DAW/Interface, and then bring up gradually.

One other thing - try different power wall sockets, reverse the plugs if that's possible.
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Re: Cassette headphone out shorting...

Post by DrummerMan » Sat Apr 11, 2020 1:28 pm

vvv wrote:
Sat Apr 11, 2020 12:40 pm
Have you tried using the DAW/Interface inputs with something else?

Does the DAW/Interface have level adjustment? Impedance adjustment? A phase switch? A mono switch? A ground reverse or lift switch? A level switch?

My first guess would be the output of the deck is too hot; turn the output down to 0 on the headphones out of the tape deck, and if possible on the DAW/Interface, and then bring up gradually.

One other thing - try different power wall sockets, reverse the plugs if that's possible.
Yes I use the interface inputs with my mic preamps and with other things all the time. Also like I mentioned I tried going straight into my headphone mixer/amp and it was the exact same thing. So it's not the interface.

Tried different wall socket. Same thing.

Volume on the cassette deck doesnt effect anything.

I forgot to mention this but this is all happening when the tape deck is not playing. When I pull the plug from the tape machine, the grounding goes away. THOUGH, when I unplug power to the tape machine it stops as well.

This led me to try it with batteries only. This seems to work, but its only coming out of one side now.

I wonder if its miswired so one of the ends of the dc in is going to the headphone jack? I just dont understand why it would be fine with just regular headphones plugged in.
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Re: Cassette headphone out shorting...

Post by winky dinglehoffer » Sat Apr 11, 2020 1:38 pm

Odds are there's a weirdness to the way the TRS & 2 TS are wired. If you have a meter that can check continuity, figure out how everything connects to every other thing. I would definitely be suspicious of the Y connector above all else.

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Re: Cassette headphone out shorting...

Post by DrummerMan » Sat Apr 11, 2020 1:45 pm

winky dinglehoffer wrote:
Sat Apr 11, 2020 1:38 pm
Odds are there's a weirdness to the way the TRS & 2 TS are wired. If you have a meter that can check continuity, figure out how everything connects to every other thing. I would definitely be suspicious of the Y connector above all else.
It works fine with, say, my phone or ipad. Also I tried out 2 different Y cables. Don't think its that..
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Re: Cassette headphone out shorting...

Post by The Scum » Sat Apr 11, 2020 2:18 pm

So what's the exact model of tape player causing the problem? Any idea when it was manufactured?

There's a funny design shift for headphone jacks that's popped up somewhat recently...mainly driven by portable devices (MP3 players, phones, tablets, etc).

The sleeve of the headphone plug won't actually be at ground potential - it'll be sitting at 1/2 the battery voltage, and serves as a spot for current that's been run through the headphones to return to. The audio outputs are also DC-biased up by that amount, so the signal swings from 0V to the battery voltage. This circumvents the need for large AC-coupling capacitors on a device that needs to be as small as possible. For headphones, it works just fine, because they don't have an external ground reference. For most applications, the device is also battery powered, with no actual ground connection, so the 1/2 battery voltage can be tied to an external ground, and it won't really care. It's when both sides have their own ground connection that things get squirrley.

No idea if this is exactly what you're experiencing, but the symptoms seem to align. (I'd expect most wall-powered devices to be AC-coupled and properly ground referenced at their inputs and outputs, though.)

If you have a voltmeter, power up both ends of the connection, but don't connect them. Then measure voltage (DC and AC) between the sleeve connections on each end. Anything there?
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Re: Cassette headphone out shorting...

Post by DrummerMan » Sat Apr 11, 2020 2:35 pm

The Scum wrote:
Sat Apr 11, 2020 2:18 pm
So what's the exact model of tape player causing the problem? Any idea when it was manufactured?
The brand is Jensen at the model looks to be MCR-100. Its brand new so this may be the issue. It was cheap as shit so I'm guessing QC out the factory isn't the best. What you're describing sounds like the type of issue that's happening. I'll see if I can dig out a voltmeter and try it out later...
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Re: Cassette headphone out shorting...

Post by The Scum » Sat Apr 11, 2020 3:25 pm

Thanks for the model. I'd somehow pictured something more like a Marantz ENG deck.

From the Amazon feedback on that guy - check that you got the right power adapter with it.

An external power adapter like that usually isolates the device from the wall, too. So no ground reference provided, avoiding ground loops.
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Re: Cassette headphone out shorting...

Post by Snarl 12/8 » Sun Apr 12, 2020 3:44 pm

That Jensen is probably mono, y'know.
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Re: Cassette headphone out shorting...

Post by Nick Sevilla » Mon Apr 13, 2020 1:39 am

I agree with Carl.

Try to buy a cassette PLAYER. There are some out there new, and should be Stereo.

I remember recording on something similar as a kid. Whatever that one was, it was Mono. Dad, a lawyer, used it to record client testimony.

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Re: Cassette headphone out shorting...

Post by DrummerMan » Mon Apr 13, 2020 6:51 am

Snarl 12/8 wrote:
Sun Apr 12, 2020 3:44 pm
That Jensen is probably mono, y'know.
Interesting! I didnt even consider that. I found out a friend has a nice component tape deck in our lockout space that I can borrow. I think I'll just grab that and return this thing.
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Re: Cassette headphone out shorting...

Post by Snarl 12/8 » Mon Apr 13, 2020 1:42 pm

Snarl 12/8 wrote:
Sun Apr 12, 2020 3:44 pm
That Jensen is probably mono, y'know.
I call those things "1 tracks". They can be super cool and fun, but not really ever hi-fi, in my experience.
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Re: Cassette headphone out shorting...

Post by vvv » Mon Apr 13, 2020 2:45 pm

Yes, it's a bloody desktop dictaphone. :roll:
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