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The crappiness of the 3.5 mm jack and plug

post #1 of 43
12/2/09 at 6:21pm
Thread Starter 
I finally got a new soundcard so I can play with RMAA again. Some time ago I had a discussion with other members in the sound science section about the drawbacks of 3.5 mm connectors. People had a hard time believe there was a measurable difference between different sizes of connectors. I wish I knew this before I started to use 3.5 mm jacks.

The setup is (all connections are unbalanced):
1. 6.35 mm plug - 6.35 mm plug
2. 6.35 mm plug - box with 3.5 mm jacks in/out - 3.5 mm to 3.5 mm interconnect - 6.35 mm plug
3. 6.35 mm plug - same box but with phono out - 6.35 mm plug
4. 6.35 mm plug - same box with 3.5 mm out - 6.35 mm plug



I've tried different brands of 3.5 mm plugs and jacks, and the brand makes no difference, the result is the same.

I think it's quite clear what the 3.5 mm connections do to crosstalk. It seems like it only takes one 3.5 mm connection to **** it up.
LL
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post #2 of 43
12/2/09 at 6:42pm
Uhhh....ok.

Interesting results (if accurate) but if you're that concerned about sound quality you're probably already using equipment with 1/4" jacks anyways.
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post #3 of 43
12/2/09 at 6:47pm
Question - sorry you description of the test has be a little confused.

The interconnects you used where the plugs used with and without adapters? Since many even upper-end headphones have 3.5mm plug and use an adapter seems that would be an issue.
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post #4 of 43
12/2/09 at 6:50pm
you might be interested as well in how poorly even the best pot and stepped attenuator fairs at the same tests.
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post #5 of 43
12/2/09 at 6:52pm
Are you using stereo or mono jacks for the test?

The degradation in crosstalk increases with frequency, indicating that it's due to capacitive coupling.

se
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post #6 of 43
12/2/09 at 7:42pm
Thread Starter 
OK, to be clearer, the soundcard is an E-mu 1212M.

1. 6.35 mm output jack -> 6.35 mm mono plug -> ****ty cable -> 6.35 mm mono plug -> 6.35 mm input jack (left and right of course)

2. 6.35 mm output jack -> short cable with 6.35 mm mono plug -> box with 3.5 mm stereo in and out (and phono out) -> from the box's 3.5 mm stereo output jack via a short fairly high quality cable with fairly high quality 3.5 mm stereo plugs to 3.5 mm stereo input jack -> short cable with 6.35 mm mono plug -> 6.35 mm input jack

3. 6.35 mm output jack -> same box as above but this time the phono jacks were used as output -> ****ty cable -> phono to 6.35 mm adapter -> 6.35 mm mono plug -> 6.35 mm input jack

4. 6.35 mm output jack -> same box as above this time only the 3.5 mm stereo output jack was used -> ****ty cable with 3.5 mm stereo plug to 6.35 mm mono plugs -> 6.35 mm input jack

There are no capacitors, inductors or resistors on the cables or in the box, just connectors a small perfboard and wires.

You can see similar reports on the Internet. It's not just my measurements. Eg http://www.amb.org/rmaa/e-mu/compari...ck_32b_96k.htm
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post #7 of 43
12/2/09 at 7:47pm
Any way you can repeat number 1 above but using 6.35mm to 3.5mm adapters and 3.5mm mono cables?

se
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post #8 of 43
12/2/09 at 8:17pm
Thread Starter 
Quote:
Originally Posted by Koyaan I. Sqatsi View Post
Any way you can repeat number 1 above but using 6.35mm to 3.5mm adapters and 3.5mm mono cables?

se
Not at the moment. I haven't got any adapters like that, but I get your point. My first thought was that there must be cable capacitance, but no matter what cables I've used the result's the same.
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post #9 of 43
12/2/09 at 8:20pm
Quote:
Originally Posted by diditmyself View Post
Not at the moment. I haven't got any adapters like that, but I get your point. My first thought was that there must be cable capacitance, but no matter what cables I've used the result's the same.
Seems the box is the major culprit here.

se
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post #10 of 43
12/2/09 at 8:40pm
Thread Starter 
Quote:
Originally Posted by Koyaan I. Sqatsi View Post
Seems the box is the major culprit here.

se
The same box is used in examples 3 and 4, the only difference is phono jacks/plugs vs mini jacks/plugs. But yes the box degrades crosstalk, but the 3.5 mm connectors is by far worse.
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post #11 of 43
12/2/09 at 9:13pm
Quote:
Originally Posted by diditmyself View Post
The same box is used in examples 3 and 4, the only difference is phono jacks/plugs vs mini jacks/plugs. But yes the box degrades crosstalk, but the 3.5 mm connectors is by far worse.
What's the proximity of the left and right 3.5mm connectors to the left and right 6.35mm and RCA's?

se
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post #12 of 43
12/2/09 at 10:00pm
Quote:
Originally Posted by diditmyself View Post
Some time ago I had a discussion with other members in the sound science section about the drawbacks of 3.5 mm connectors.
because that test was run on different inputs(3.5 & 6.35) of a 0404USB IIRC?

I guess all that'd matter to us is :
1)6.35>6.35 cable
2)6.35>3.5 cable+6.35 adapter
don't make me butcher my 3.5 cd1k plug to fit into my new 6.35 amp
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post #13 of 43
12/3/09 at 7:05am
Thread Starter 
Quote:
Originally Posted by Koyaan I. Sqatsi View Post
What's the proximity of the left and right 3.5mm connectors to the left and right 6.35mm and RCA's?

se
About 2 cm.


leeperry, it was an E-mu 0404 pci soundcard the last time, but amb's measurements are from E-mu 0404 usb.

The question is if this crosstalk issue with 3.5 mm stereo connectors is audible. Since I do almost all my listening with a portable rig I haven't done any such listening tests. If someone has done it please report your findings.
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post #14 of 43
12/3/09 at 7:17am
I did observe that the E-MU 0404 USB 3.5mm output stereo crosstalk to rise more than the 1/4" output at high frequencies in my RMAA loopback test. However I don't think this is purely due to the connector. I don't have a schematic of the 0404 USB, nor did I open it up to inspect it, but just probing the jacks with a DMM shows that the 3.5mm jack is not simply in parallel with the 1.4" jacks. There is different circuitry in there which may account for the difference in measurements (not only is the stereo crosstalk different, but some of the other RMAA results are slightly different too).

This is of course an interesting subject, and the γ2 DAC has paralleled RCA and 3.5mm jacks at its output (which would allow a fair comparison). I will run some measurements in the next day or two and report the outcome.
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post #15 of 43
12/3/09 at 10:55am
yes, using different inputs is a deal breaker...what'd matter is a 6.35<>6.35 cable and then 6.35<>3.5+6.35 adapter, that'd be interesting if you have time
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