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I've read the HRSCF article by Christopher da Costa and the threads below. And I still have a few questions. I'm trying to put this all together and would like to know if a recommended starting point is as follows:
1. Silver mica or Wima MP3X2 or MP3Y2 caps with a total of 10,000 pF (e.g. 5 x 2000pF) paralleled by 1 x 200pF and then 1 x 20pF?
2. 3 x 10 ohm PRP resistors, with each in series with the 3 caps - as shown in the da Costa article?
3. Does it matter what the voltage rating is for the caps? Can the X2 and Y2 be mixed?
4. Does it matter what the wattage is for the resistors?
5. Ideally, put the filter at both ends of each speaker cable.
6. Add TI shield to each with ground to outlet (at some point.)
Thanks a lot.
Joe
Follow Ups:
Joe,
You don't need X or Y caps for speaker cable current. In fact, these may not be the best caps for that application. As Al Sekela recommends, get the silver mica caps in the values he stated, 3 descending values by factor of 10. That's why you also don't need 10,000, 200, 20; rather 10,000, 1,000, 100 is more like it.
The resistors work in 1/2 Watt values, but you can experiment by using wirenuts to test the values at first, then do the soldered version with final values you like. 10 to 20 Ohms works for me. There is actually a formula if you know the other electrical characteristics of the cabling, which Al posted here before, but it's probably beyond you (it's certainly beyond me!) I've found 10 and 16 and 20 Ohm Rs work for me. The best sound comes from the Holco or PRP ones that Michael Percey (and others) sell, but you can use ordinary flameproof ones from your local store too.
Don't do the TI=shielding until you've settled on the rest of the formula first. Ti-Shielding isn't as straightforward as it looks. First of all, this stuff is very conductive, and too much of it is not so good sonically. Once you do the TI, then it pays to add the 12 or 10 AWG ground wire; the thickness does impact the sound here.
Here's what I'd recommend as a process, if you have some patience:
1) First make one simple R-C for each end of the speaker cable (do the simple wirenuts method for testing) with the 10,000 C. Test the different values of R till you like the sound. Then buy the better quality Rs.
2) Now make the 3 R-C parallel arrays with the descending Cs and the same value Rs you settled on above. You can solder this together at this point.
3) Then deal with the grounded Ti-Shield issue.
Do all the above at both ends of the speaker cable each time.
This is a very worthwhile project. You'll be pleased with the results.
bartc,
Does it matter how the capacitance is obtained - 1 x 10000pF vs 3 x 3333pF in parallel, etc.?
I'm assuming the voltage of the caps doesn't matter. Correct?
In the final cascading configuration, should all 3 resistors be the same value?
I originally posted this tweak with silver-mica caps based on recommendations from another inmate. I compared silver-mica with various film types and preferred the silver-mica above all but a few polystyrene. However, when I made the comparisons, I did not try metallized paper (Wima MP3) suppression caps. I still have the silver-mica caps in my system, but I've used Wima caps in AC power filters with good results. If I were to revisit this tweak, I would try Wima MP3 caps and compare them with silver-mica. A friend of mine has done this and prefers metallized paper to silver-mica.
Note: silver-mica are NOT suitable or safe for AC power filters, no matter what voltage rating!!!
The cap voltage rating should be enough to avoid breaking the caps with peaks from your power amp. A rating of 100 volts would be adequate, but don't go lower. The resistor power rating is unimportant, as the resistor only sees high frequency noise. PRP half-watt resistors are about the best for sonic reasons.
The original Walker Audio High Definition Links design is a single 0.01 microfarad capacitor (10,000 pF) in series with a single 10-ohm resistor. At the time I made my comparisons, I could get 10,000 pF silver-mica caps cheaply from a local electronics house with a surplus room, and from Hosfelt. Once I posted my results, the 10,000 pF caps from both sources quickly disappeared. I believe new ones go for more than $9 each, so putting three 3000 (or so) pF caps in parallel is a good alternative. These will have a higher self-resonance frequency, and putting them in parallel may make the resonance more complex, but the main effect will still be the same.
For the purposes of making a wider bandwidth filter, use the same resistor value in all stages. However, the smaller caps will be effective at higher frequencies, where cable resonances are more prominent. Capacitor resonances are also an issue. This means higher resistance values may work better with the smaller caps. This is something you would have to experiment with, as I've not explored this aspect with speaker cable filters.
Thanks, Al.
bartc,
Thanks so much for the straightforward step-by-step recommendation. This is exactly what I was looking for as a starting point.
That process worked for me very well. Only I did TI-shield without grounding, then with, so I had one extra step you can skip, since so many of us have found the grounding does add extra sonic value.
In fact, I even started with the R-C single on only the speaker end of the cables too. But the impact was obvious even then.
Make sure to give such things about 20 minutes warm up before you start making judgements. As I recall, there is a slight ramp up phenomenon, but I wouldn't swear to that.
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