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Balance control out speakers
Balance control out speakers
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Old 3rd December 2017, 12:20 AM   #1
steven2583 is offline steven2583  United States
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Default Balance control out speakers

I have my DAC (output 75 ohms) going to my preamp Ayre K-5xeMP Input Impedance of 20kohm per channel. I have my sound processor going to my Ayre K-5xeMP. Due to the location in my room of my speakers(I'm not able to move) the balance is off in my main listening position. The sound processor adjusts the balance so I get a nice center image with movies. I would like to acquire the same thing with my DAC. The sound processor calculation says it's 1.5 dB off. I was planning on taking a pair XLS cables (to keep length the same) and cut the one where it's off and add some resistors to decrease the voltage so that the it matches. I was looking at the goldpt attenuator site and noticed that they have different ones 10K, 20K, 25K, 50K, 100K, 250K. Not sure what that means.

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R2 up to 6 DB up to -4 db. So I'm thinking I don't need to worry about that.

So my question if I just get a few resistors and make a voltage divider with R2 as 75K So what should I use for R1 values. Do I base my calculation on 20K of the pre-amp for attenuation?

Also it's balance(xls) so I need double of everything correct?
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Old 3rd December 2017, 12:43 AM   #2
rayma is offline rayma  United States
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Quote:
Originally Posted by steven2583 View Post
The sound processor calculation says it's 1.5 dB off.
You only need a series resistor before the louder preamp input. It will work against the
20k input impedance. To reduce the signal by 1.5dB, use the equation (ignoring the 75R):

-1.5 = 20 x log (20/(R+20)) so R = 3.77k, then use a standard 3.74 1% type.
For balanced system, use a resistor of half that value (1.87k) in series
with each signal polarity in the louder channel.

Last edited by rayma; 3rd December 2017 at 12:46 AM.
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Old 3rd December 2017, 01:24 AM   #3
steven2583 is offline steven2583  United States
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Dumb question but why would I split the resistor value for balanced? I would think I would want each leg of the balanced to have a 3.77K resistor?

If a use a good metal film resistor will this affect the sound quality much?
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Old 3rd December 2017, 01:27 AM   #4
steven2583 is offline steven2583  United States
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Also I'm thinking there isn't many watts so a 1/4 watt resistor should be enough?
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Old 3rd December 2017, 01:32 AM   #5
rayma is offline rayma  United States
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Quote:
Originally Posted by steven2583 View Post
why would I split the resistor value for balanced? I would think I would want each leg
of the balanced to have a 3.77K resistor? If a use a good metal film resistor will this
affect the sound quality much?
You need to use half that value for each signal polarity to get the same attenuation
as for the single ended case. A 1/4W metal film resistor is appropriate here,
and is best placed near the preamp input.
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Old 3rd December 2017, 04:23 AM   #6
PRR is offline PRR  United States
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Quote:
Originally Posted by steven2583 View Post
...why would I split the resistor value for balanced?...
Take simple case. 2:1 attenuation. 1K load.

For unbalanced, a 1K in the cable against the 1K load gives the desired 2:1 division.

For balanced, ideally you want two equal resistors, one each leg. They should still add-up to 1K, to get the desired division. So this case is two 500r resistors in the cable.
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Old 5th December 2017, 02:17 AM   #7
steven2583 is offline steven2583  United States
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Just for a bit of clarity. The resistor goes between IN and OUT and not IN and GROUND. Correct?
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Old 5th December 2017, 02:18 AM   #8
rayma is offline rayma  United States
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Quote:
Originally Posted by steven2583 View Post
Just for a bit of clarity. The resistor goes between IN and OUT and not IN and GROUND. Correct?
Yes, in series with the signal [cable center conductor], but not connected to ground.
In this illustration, Z is the added resistor, and Y is the preamp input impedance.
The bottom conductor is the audio ground.
https://upload.wikimedia.org/wikiped...ection.svg.png

Last edited by rayma; 5th December 2017 at 02:24 AM.
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Old 6th December 2017, 10:37 AM   #9
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by rayma View Post
You only need a series resistor before the louder preamp input. It will work against the
20k input impedance. To reduce the signal by 1.5dB, use the equation (ignoring the 75R):

-1.5 = 20 x log (20/(R+20)) so R = 3.77k, then use a standard 3.74 1% type.
For balanced system, use a resistor of half that value (1.87k) in series
with each signal polarity in the louder channel.
one does not need to use E92 resistors.
A 3k6 (into 20k) will give 1.44dB of attenuation compared to 3k74 giving -1.48dB
One will struggle to measure the difference of ~0.05dB
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Old 6th December 2017, 10:38 AM   #10
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by rayma View Post
You need to use half that value for each signal polarity to get the same attenuation
as for the single ended case. A 1/4W metal film resistor is appropriate here,
and is best placed near the preamp input.
inside the RCA plug at the receive end. And label the plug !
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