B1 builders thread

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#204
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
 
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#205
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.
 
#206
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
 
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#207
richluvsound said:
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
Click to expand...

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
 
#209
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 🙂
 
#210
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
 
#214
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#220
It worked out cheaper for me to buy PRP from the us than to order from the UK . To start with the PRP were 38 cents each and with shipping I saved 20 quid on the UK total ... this is "RIP OFF BRITAIN" after all !

If Arik is around . I had a look at the other thread . I saw a beautiful enclosure , some very clever wiring ,but no schematic !

Rich.
 
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