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Author Topic: Update on stereo to mono cable for iPod or CD source  (Read 5931 times)

George Friedman-Jimenez

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Update on stereo to mono cable for iPod or CD source
« on: February 26, 2011, 12:25:05 pm »

Following up on a thread in the old forum http://forums.prosoundweb.com/index.php/topic,287.msg2783.html#msg2783 I followed a suggestion by Brad Harris to use 1/4 watt resistors in the Rane stereo to mono circuit, and fit all 3 resistors inside a Neutrik 1/4" NP2X TS plug. I used a right angle Neutrik 1/8" NTP3RC TRS tiny plug on the other end. 1/4 watt 470 ohm resistors are more than enough to handle the low voltage output of an iPod or portable CD player, and make the soldering job much easier inside the cramped TS plug.

It works great to mix stereo from the iPod or portable CD player to mono into one channel of a tiny mixer (Soundcraft Notepad 124) that drives a single ZXA1. It sounds indistinguishable from mixing stereo to mono in the mixer, and I still have all 4 XLR mic inputs and an aux send. My concern that 470 ohms on each channel would pad the volume down too much was unfounded. I am one step closer to the ultraminiature PA I have been putting together for those small gigs when I have to carry it all on the subway or next to someone in the back seat of my car with instruments taking up the rest of the space.
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jeff grocki

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Re: Update on stereo to mono cable for iPod or CD source
« Reply #1 on: February 27, 2011, 12:55:54 pm »

Following up on a thread in the old forum http://forums.prosoundweb.com/index.php/topic,287.msg2783.html#msg2783 I followed a suggestion by Brad Harris to use 1/4 watt resistors in the Rane stereo to mono circuit, and fit all 3 resistors inside a Neutrik 1/4" NP2X TS plug. I used a right angle Neutrik 1/8" NTP3RC TRS tiny plug on the other end. 1/4 watt 470 ohm resistors are more than enough to handle the low voltage output of an iPod or portable CD player, and make the soldering job much easier inside the cramped TS plug.

It works great to mix stereo from the iPod or portable CD player to mono into one channel of a tiny mixer (Soundcraft Notepad 124) that drives a single ZXA1. It sounds indistinguishable from mixing stereo to mono in the mixer, and I still have all 4 XLR mic inputs and an aux send. My concern that 470 ohms on each channel would pad the volume down too much was unfounded. I am one step closer to the ultraminiature PA I have been putting together for those small gigs when I have to carry it all on the subway or next to someone in the back seat of my car with instruments taking up the rest of the space.

Could you put the resistors in an XLR connector on other end and still have it work?
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George Friedman-Jimenez

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Re: Update on stereo to mono cable for iPod or CD source
« Reply #2 on: February 27, 2011, 08:11:39 pm »

Physically, there is much more room inside an XLR than a 1/4" TS connector so the soldering would be easier. I haven't tried it and am not sure exactly which circuitry I would choose for the XLR connector going into abalanced XLR line level input. The Rane "Why not Wye" article only gives circuits for balanced stereo inputs to balanced mono output or unbalanced stereo to unbalanced mono, not unbalanced stereo to balanced mono output.
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David Sturzenbecher

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Re: Update on stereo to mono cable for iPod or CD source
« Reply #3 on: February 27, 2011, 10:58:24 pm »

I am pretty sure you are just making these?

http://whirlwindusa.com/catalog/black-boxes-effects-and-dis/transformers-isolation-devices/isopod

http://www.rapcohorizon.com/p-377-ltiblox.aspx

The advantage to the items in the above link is that they also have an onboard transformer for isolation.
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Brad Harris

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Re: Update on stereo to mono cable for iPod or CD source
« Reply #4 on: February 28, 2011, 12:43:08 am »

Glad its working out for you. My 'normal' way of making these specific adapters are in M-F xlr barrels.


Following up on a thread in the old forum http://forums.prosoundweb.com/index.php/topic,287.msg2783.html#msg2783 I followed a suggestion by Brad Harris to use 1/4 watt resistors in the Rane stereo to mono circuit, and fit all 3 resistors inside a Neutrik 1/4" NP2X TS plug. I used a right angle Neutrik 1/8" NTP3RC TRS tiny plug on the other end. 1/4 watt 470 ohm resistors are more than enough to handle the low voltage output of an iPod or portable CD player, and make the soldering job much easier inside the cramped TS plug.

It works great to mix stereo from the iPod or portable CD player to mono into one channel of a tiny mixer (Soundcraft Notepad 124) that drives a single ZXA1. It sounds indistinguishable from mixing stereo to mono in the mixer, and I still have all 4 XLR mic inputs and an aux send. My concern that 470 ohms on each channel would pad the volume down too much was unfounded. I am one step closer to the ultraminiature PA I have been putting together for those small gigs when I have to carry it all on the subway or next to someone in the back seat of my car with instruments taking up the rest of the space.
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Brad Harris

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Re: Update on stereo to mono cable for iPod or CD source
« Reply #5 on: February 28, 2011, 12:45:28 am »

You can. Pin 3 gets shorted to pin 1 on the unbalanced xlr end (for a unbalanced stereo to unbalanced mono adapter)

Could you put the resistors in an XLR connector on other end and still have it work?
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George Friedman-Jimenez

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Re: Update on stereo to mono cable for iPod or CD source
« Reply #6 on: February 28, 2011, 12:58:57 am »

I am pretty sure you are just making these?
http://whirlwindusa.com/catalog/black-boxes-effects-and-dis/transformers-isolation-devices/isopod
http://www.rapcohorizon.com/p-377-ltiblox.aspx
The advantage to the items in the above link is that they also have an onboard transformer for isolation.

Similar function, yes. I am using an unbalanced TS plug into a balanced/unbalanced line level inputs on my mixer, so I don't have to use up one of the XLR mic pre inputs. Cable is short, no problem with noise, no need for transformer isolation so far. The Whirlwind IsoPod device looks cool though, I guess it is so new it is not out yet, but $59 is kind of steep for what I need if a simple cable with 3 resistors will work.

Brad, using an XLRM into the mic pre, is there any danger if someone accidentally turns on the phantom power?
« Last Edit: February 28, 2011, 01:02:47 am by George Friedman-Jimenez »
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Brad Harris

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Re: Update on stereo to mono cable for iPod or CD source
« Reply #7 on: February 28, 2011, 01:13:07 am »

In short, yes. Thats where the transformer on whirlwind (and others) solutions come into play regarding phantom power. You can also go through a DI if phantom is unavaidable (ie. global phantom).

Brad, using an XLRM into the mic pre, is there any danger if someone accidentally turns on the phantom power?
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George Friedman-Jimenez

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Re: Update on stereo to mono cable for iPod or CD source
« Reply #8 on: February 28, 2011, 07:31:49 am »

Thanks. Good ideas and lots of flexibility here.
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jeff grocki

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Re: Update on stereo to mono cable for iPod or CD source
« Reply #9 on: February 28, 2011, 08:23:00 pm »

You can. Pin 3 gets shorted to pin 1 on the unbalanced xlr end (for a unbalanced stereo to unbalanced mono adapter)

Thanks Very much Brad!!
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