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Old 16th October 2011, 12:42 AM   #201
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Cheers ,


I understand the matching of the caps is very important in the balanced version ....

can you explain ?

Rich
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Old 16th October 2011, 12:52 AM   #202
Arick is offline Arick  Canada
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Quote:
Originally Posted by richluvsound View Post
Cheers ,


I understand the matching of the caps is very important in the balanced version ....

can you explain ?

Rich
Which caps?
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Old 16th October 2011, 12:58 AM   #203
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I just started reading the thread you suggested - from the beginning my guess is it would be the out caps .... No ?
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Old 16th October 2011, 01:52 AM   #204
Arick is offline Arick  Canada
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Hi,
I believe you will find enough information on the previously mentioned thread. Because Mr. Pass' design is a very good one, following the recommended tolerances of the parts list will give excellent results. Personally, a friend let me use his capacitance meter (I was spoiled). I used it to try to closely match left and right side parts. However, because I did not buy an overstock there were still differences between them and honestly, I cannot hear a difference. I built 3 of them, 1 balanced and 2 unbalanced (soon to be converted to balanced).
Eric

P.S. I did not bother to match the input capacitors

Last edited by Arick; 16th October 2011 at 01:53 AM. Reason: P.S. added
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Old 16th October 2011, 09:08 AM   #205
AndrewT is offline AndrewT  Scotland
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Matching of the impedances of the balanced connection improves the Common Mode Rejection Ratio (CMRR). This is what attenuates the unwanted interference.

The closer you get the matching the better the CMRR.

Aim for <0.1% on resistor values at both send and receive ends.
Aim for <1% and preferably <0.5% on capacitor values at both the send and receive ends.

This should have no effect on the sound quality of the wanted signal. You should hear no change.
This should have an effect on the interference which will be reduced if it is present. You may not hear this improvement unless you have a system that benefits from the improved CMRR of the balanced connection.
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Old 16th October 2011, 10:05 AM   #206
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Thanks Arick & Andrew ,


I will use the Takman resistors for this and Pearl build. Iknow these are a bit flash ,but getting the Dales will cost more with all the Tory Tax . I'll measure the caps , just need a battery in my meter .

Whats the difference between Carbon and Metal film . I can get 0.125 w ,but they are carbon


Rich

Last edited by richluvsound; 16th October 2011 at 10:11 AM. Reason: .... I can't smell well !
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Old 17th October 2011, 01:16 PM   #207
shanx is offline shanx  Canada
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Quote:
Originally Posted by richluvsound View Post
Thanks Arick & Andrew ,


I will use the Takman resistors for this and Pearl build. Iknow these are a bit flash ,but getting the Dales will cost more with all the Tory Tax . I'll measure the caps , just need a battery in my meter .

Whats the difference between Carbon and Metal film . I can get 0.125 w ,but they are carbon


Rich
Hi Rich,
Especially on a preamp circuit, you will want the more stable, quieter metal film types. You can go to 1/4 W (better from a noise perspective) metal films if you can't easily source 1/8W.
FYI some info on resistor composition:
Resistor Types--Does It Matter?

Regards
Shanx
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Old 17th October 2011, 03:22 PM   #208
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Thank Shanx ,



Soniccraft have PRP Metal film in 1/8 watt ,but I have never seen them mention here before .... any opinions on them ? . They also come at 1% tolerance.


Rich
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Old 17th October 2011, 03:37 PM   #209
Atilla is offline Atilla  Norway
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PRP resistors are really nice. There was a group buy for sets fo resistors for the DC-B1 and a lot of people used them.

I haven't noticed any complaints about them and they're at a reasonable price, usually. Just go for them.

PS. Also - they're red. And round and shiny. Can't beat that
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Old 17th October 2011, 03:54 PM   #210
shanx is offline shanx  Canada
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I have not used them, so can't say either way. But stablility specs look decent, at 50 ppm /degC. One thing though is they are spec'd at 1% tolerance..so you will be doing a lot of matching by hand. As AndrewT said you should try to match to 0.1% tolerances. you should be able to get that in a precision metal film. Suggest to have a look at PTF-56 and PTF-65 series or RN55E type from same manufacture (Dale/Vishay).
Regards Shane
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