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The Ivy aes output measures around 2V rms at 0 dB; presumably same as the single ended output. I would like to increase this this to 4V to drive a passive attentuator.
Increasing R1 to R4 should do the trick. However this changes the filter bandwidth.
Russ, do you have tabulated values of R versus Gain versus bandwidth?
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Hi Fred, if you use the values given for the COD you well get about 4VRMs when using the Buffalo, and the filter bandwidth is noted in the manual. I don't have a table for bandwidth because there are just too many combinations possible. But I am happy to provide resistor and capacitor values for any gain and -3db point you desire.
Cheers!
Russ
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Russ White wrote:Hi Fred, if you use the values given for the COD you well get about 4VRMs when using the Buffalo, and the filter bandwidth is noted in the manual. I don't have a table for bandwidth because there are just too many combinations possible. But I am happy to provide resistor and capacitor values for any gain and -3db point you desire.
Cheers!
Russ Russ Thanks. I would like to retain Buffalo 1 values other than R1-R4 but have 4 V RMS balanced output. What R1-R4 values should I use and how does this affect Fc?. It's attractive not to change C1-C4. Fred
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Fc would be about 44khz. Should still work great.
Cheers!
Russ
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Russ, I have been able to approximate Fc using:  I was wondering what the role of the 22 ohm resistor was in the filter and also how does it affect the calculation of Fc. Thanks
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The 22 ohm resistor very slightly increases Fc and decreases the filter slope. Its primary purpose is to prevent some distortion that we measured when using the cap alone. The opamp does a better job when there is some series resistance with the cap. It measured and sounds much better this way.
Cheers!
Russ
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Russ White wrote:The 22 ohm resistor very slightly increases Fc and decreases the filter slope. Its primary purpose is to prevent some distortion that we measured when using the cap alone. The opamp does a better job when there is some series resistance with the cap. It measured and sounds much better this way.
Cheers!
Russ I am using 6800 pf C1-4 with 360R R1-4 and now get 3.6V balanced at 0dB. The Fc should be around 60 kHz. Seems to be a very good compromise at 192k playback for my system. Got rid of a little zing compared to Buffalo 1 components. The extra drive is much more suitable for balanced out. Russ, is there any need to islolate the aes output with 47R resistors to mitigate cable/input capacitance? I shall do some square wave measurements when the system is properly set up.
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I have never seen any need for this as the capacitance would have to be pretty high to cause an issue, but if you detect any ringing on the scope then you could add them.
The ESR of cable capacitance is usually fairly high, so no Rs are generally needed with a solid output stage like the one on the chip.
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Russ White wrote:The 22 ohm resistor very slightly increases Fc and decreases the filter slope. Its primary purpose is to prevent some distortion that we measured when using the cap alone. The opamp does a better job when there is some series resistance with the cap. It measured and sounds much better this way.
Cheers!
Russ Is this the same resistor as R17-R20 that is shorted with the Buffalo Slew mod? People report that with the slew mod it sounds better with the resistor shorted. Why is that?
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Yes, It was I who recommended that people jumper those spots instead of using a resistor when using the caps to GND at input. :) The reason is that the input caps give the energy fed back through filter caps the somewhere to go, that is GND. :) That is why it is extra important that those caps at input be non-inductive types. Edited by user Thursday, November 20, 2008 12:53:04 PM(UTC)
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fmak wrote:
I am using 6800 pf C1-4 with 360R R1-4 and now get 3.6V balanced at 0dB. The Fc should be around 60 kHz. Seems to be a very good compromise at 192k playback for my system. Got rid of a little zing compared to Buffalo 1 components.
The extra drive is much more suitable for balanced out.
I am also looking for the answer to the original question posted in this thread. The IVY manual specifies C1-4 and R1-4 for consumer level 2v signals. I also would like to use the balanced output at 4v professional levels. Are the component values suggested by fmak above recommended?
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Rick, The size of R1-4 is directly proportional to the output voltage. To get 2 X 2VRMS just double it. So 360-392R will do the trick. the values fmak suggested are just fine, but I would use 4.7nf for C1-4. :EDIT: if you still want 2VRMS at the SE outputs you will need to multiply the value of R9-12 by 2. Cheers! Russ Edited by user Thursday, December 18, 2008 8:32:34 AM(UTC)
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