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Resistor help: IVY max gain in multichannel setup
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opnordahl  
#1 Posted : Saturday, February 2, 2013 7:51:55 PM(UTC)
opnordahl

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I am going to use 4 IVYs connected directly to poweramps (balanced input of 6 Hypex NCORE and 2 Ucd700). For 6 of the channels I plan to use 4 VRMS output. However for two of the last channels I need more gain. The IVYs are connected to one Buffalo II (2 channels) and one Buffalo III (2 + 4 channels). The I2S source is the ExaU2I.

For the IVYs connected to Buffalo III i plan the following:
2+2 channel with no channels combined:. Wanted output: 4 VRMS
Values for resistors: R1-4 = 3kOhm, R13-16 = 356ohm
Are these resistor values correct?

For the last two channels from the Buffalo III I am planning to combine two channel pairs into two channels.
However I need more gain than 4 VRMS. What is the maximum recommended gain I can get from the IVY?
If I want 8 VRMS output are the following resistor values correct to use?
R1-4 = 1.5kOhm, R13-16 = 750Ohm.

Edited by user Saturday, February 2, 2013 8:13:56 PM(UTC)  | Reason: Not specified
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Russ White  
#2 Posted : Sunday, February 3, 2013 2:38:37 AM(UTC)
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To get 4VRMs you need only double R13-R16. No other changes.

I wouldn't try to get more than maybe 6VRMs. Above that and the THD+N will really suffer.

You could try 499R at R13-R16 and see if that gets you where you want to be.
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opnordahl  
#3 Posted : Sunday, February 3, 2013 2:38:07 PM(UTC)
opnordahl

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Thank you very much Russ.

I assume you approve the values I have chosen for R1-4 in my setup.
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Russ White  
#4 Posted : Sunday, February 3, 2013 3:58:15 PM(UTC)
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No - do not increase R1-4. That stage would clip for sure. Only make R13-R16 356R and you have ~4VRMs.

Edited by user Sunday, February 3, 2013 3:59:20 PM(UTC)  | Reason: Not specified
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opnordahl  
#5 Posted : Sunday, February 3, 2013 7:14:40 PM(UTC)
opnordahl

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Maybe I have really misunderstood something but the Buffalo III Integration guide clearly states that the IVYIII value for R1-4 needs to be changed when more than 2 outputs from the Buffalo III board are used.

The calculation in the guide states: R=3000/amount of parallel output channels og Buffalo III

In my example I am planing to not combine any parallel output channels for two channel pairs (2+2)

R1-4=3000/1 = 3kOhm

For the last two channels I am planning to combine two parallel output channels into one

R1-4=3000/2 = 1.5kOhm

What am I missing?

Edited by user Sunday, February 3, 2013 7:16:14 PM(UTC)  | Reason: Not specified
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Russ White  
#6 Posted : Sunday, February 3, 2013 10:51:44 PM(UTC)
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I may have missed something not you. :)

Still I would prefer to add the gain at the second stage.
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opnordahl  
#7 Posted : Monday, February 4, 2013 10:53:15 AM(UTC)
opnordahl

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Do you have any suggestions for R values for IVYIII in both cases using the BIII then?

Case 1: Not to combine any parallel output channels from the BIII. Output = 4RMS

Case 2: Combine two parallel output channels from the BIII. Output = 4RMS or more if advisable

Edited by user Monday, February 4, 2013 5:10:01 PM(UTC)  | Reason: Not specified
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Russ White  
#8 Posted : Wednesday, February 6, 2013 1:19:44 PM(UTC)
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I have not forgotten about you.

I am doing some simulation to determine a good set of resistors for your application.
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opnordahl  
#9 Posted : Thursday, February 7, 2013 10:47:46 PM(UTC)
opnordahl

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Thank you. I am a bit at a loss here...
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opnordahl  
#10 Posted : Thursday, February 14, 2013 8:25:35 PM(UTC)
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Originally Posted by: Russ White Go to Quoted Post
I have not forgotten about you.

I am doing some simulation to determine a good set of resistors for your application.


Hi Russ,

I have done some tests with my speakers and 4vrms will do for all channels. I also have the option of increasing the gain slightly with the Hypex power amps.

According to your simulations do I already push the IVYs too much with 4vrms for case 1 and 2 mentioned above?
Which resistor combination gives the lowest SNR?
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