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How can a minijack to RCA cable introduce enormous echo in a system?

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#1
So I was just asked by a colleague in the office to have a look at the system that we have in a loft that we use for business meetings and rent out via AirBnB when we don't need it. It is a full 5.1 Parasound System, I believe they spent around 20K€ or so on everything 4-5 years ago.

So, there was a huge echo in the sound which I attributed to a setting, but after hours of testing it still sounded shit. So I just went out and bought every single cable to try with new cables, and turns out it was a minijack to RCA cable. I actually went and connected the old cable to a small Yamaha system in one of the upstairs bedrooms, and yes, the same kind of hideous echo could be heard.

It's a 1.5m long cable without any external damage... I am a bit baffled, is this frequent, and what could be the actual reason causing the cable to introduce this kind of problem?
 

McFly

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#2
Test with a multimeter if any of the sheilds shorting to hot pins
Edit - or the sheild is not connected at all, causing hysteresis in the shield like an inductor
 

mansr

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#3
Maybe the "high end" cable companies are putting out cheap cables with deliberate faults through Chinese partners so as to make their branded stuff look good.
 
OP
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Thread Starter #6
Can't believe a echo. Echo means huge timedelay. Cabels usually dont do that.
Can't say I care whether you believe it or not, since I know it's true that's mostly your problem. I have the cable in my posession, actually I went back to the loft and picked it up from the garbage. It's "Syncwire" branded. Maybe I'll be bothered one day to connect it at home and record it to show what I mean.
 

solderdude

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#7
So I was just asked by a colleague in the office to have a look at the system that we have in a loft that we use for business meetings and rent out via AirBnB when we don't need it. It is a full 5.1 Parasound System, I believe they spent around 20K€ or so on everything 4-5 years ago.

So, there was a huge echo in the sound which I attributed to a setting, but after hours of testing it still sounded shit. So I just went out and bought every single cable to try with new cables, and turns out it was a minijack to RCA cable. I actually went and connected the old cable to a small Yamaha system in one of the upstairs bedrooms, and yes, the same kind of hideous echo could be heard.

It's a 1.5m long cable without any external damage... I am a bit baffled, is this frequent, and what could be the actual reason causing the cable to introduce this kind of problem?
L-R (when there is no ground) can lead to only the stereo signal to be audible in mono through both channels.
It is how the old Philips 'surround' channels worked back in the days.
You basically connected 2 speakers in series (the L and R rear) and connected that between +R and +L of the amp.
You would hear the 'echoes' and with live performances often the public cheering etc.

I expect that's what you heard... echoes, no singing (except background vocals perhaps) and weird instrument sounds, possibly distorted.
So not imagined.
Check the RCA shield of the cable whether or not it makes contact with the Sleeve of the TRS. When there is no connection you will have your answer with 100% certainty.
 
OP
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Thread Starter #8
You would hear the 'echoes' and with live performances often the public cheering etc.

I expect that's what you heard... echoes, no singing (except background vocals perhaps) and weird instrument sounds, possibly distorted.
That is EXACTLY how it sounds! I tried with Keith Don't Go and mostly I could hear the guitar, the voice was almost absent and what I could hear repeats several times, sounding like in a hollow chamber.
 

solderdude

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#9
Case solved... broken ground connection in the sleeve.

Those that want to hear what you heard should connect a speaker between L+ and R+ of their power amps.
When you put that speaker behind you it provides a poor mans surround system.
Works great with live recordings and movies.
All you need is a little extra delay and you can call it Dolby surround.
I made one using a bucket-brigade delay.. worked like a charm but was a bit noisy.
 
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xr100

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#11
[L-R signal]I expect that's what you heard... echoes, no singing (except background vocals perhaps) and weird instrument sounds, possibly distorted.
Weird instrument sounds? Hmm, like sustained chordal pads and subtle background "riffs" and so on?!

BTW, it's a good way to hear artifacts in lossy coded content.
 

solderdude

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#12
Yes, highly recording dependent. When you only listen to the L-R difference instruments can sound really weird.
It's not like you would hear sounds of weird instruments all of a sudden :D
 

xr100

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#13
Yes, highly recording dependent. When you only listen to the L-R difference instruments can sound really weird.
It's not like you would hear sounds of weird instruments all of a sudden :D

:D Yeah, it just reminded me of a time as a teenager... when I fiddled around with a minijack and found that in a certain position it would result in L-R, only I didn't know that; I thought something had failed. The background "pad" and rhythmic chordal parts were totally "weird" as far as I was concerned... "where's the song?" (Obviously the vocals were cancelled so no main melody apart from the L-R components of the reverb.)

So, the "weird instruments" thing was amusing to me as it kinda related to my own former naivety... :Do_O
 

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