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Which resistors have the most impact on sound on IVY?
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pinnocchio  
#1 Posted : Sunday, February 6, 2011 10:25:57 PM(UTC)
pinnocchio

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I'd like to change some resistors to try out but don't know which resistors are actually the most critical to change.

I'm using the SE output for now but will use balanced shortly.

Thanks
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pinnocchio  
#2 Posted : Friday, February 11, 2011 10:43:19 PM(UTC)
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I just want to put in some more exotic resistors to tune sound output.

Please!
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glt  
#3 Posted : Saturday, February 12, 2011 11:15:37 AM(UTC)
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I think you'd be better off matching the value of the resistors (between the + and the - leg). The common mode rejection of the balanced configuration will increase if the matching is closer...
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Brian Donegan  
#4 Posted : Saturday, February 12, 2011 11:21:38 AM(UTC)
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All the resistors in the kit (apart from the 22R output resistors) are 0.1% matched.
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pinnocchio  
#5 Posted : Sunday, February 13, 2011 1:21:05 PM(UTC)
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Okidoki!

I will stick with original design. It is quite good as it is anyway!

Thanks
Do
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glt  
#6 Posted : Sunday, February 13, 2011 10:28:49 PM(UTC)
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Brian Donegan wrote:
All the resistors in the kit (apart from the 22R output resistors) are 0.1% matched.


I was thinking matching the .1% resistors to get better than .1% matching. According to http://focus.ti.com/lit/an/sloa054d/sloa054d.pdf (p.6) you get 60 db CMRR with .1% matching. If you can match to .01% (with a good voltmeter) you can get better than 60 db...
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Russ White  
#7 Posted : Monday, February 14, 2011 4:12:03 PM(UTC)
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You actually get more than enough CMRR with .1% for this application, though to be sure the more the better. Just not likely to produce tangible results in this case.

This is actually one of those things that is very easy to simulate.
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Jon Espley  
#8 Posted : Wednesday, March 16, 2011 4:11:18 AM(UTC)
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How important is CMRR? Surely with well designed shunt regulated supplies noise is going to be well down anyway.
Some say the best resistors are non-magnetic. I'm guessing the resistors supplied probably are not.
I have used the older Holco's in my amp to good effect and they are not expensive. When Meggit Holsworthy were taken over the end caps were changed to steel which made them magnetic and sound quality suffered.
Hificollective.co.uk have a limited supply of the old Holco's and I would like to build IVY-III using these but would have to change values to the following

R1-4 1k2 1% (=750x1.6)
R5-12 560R 1% (=390Rx1.4)
R13-16 270R 1% (=180Rx1.5)
R17-24 3k3 0.25% (=2k2x1.5)
C1-4 10nf

The new values are roughly 1.5 times those specified, or do you think I would be better sticking to 0.1%
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