av arb » 2011-11-27 18:48
Thank you!
"For the 0,4 and 0,6mH coils in the T22-filters the coil resistance plus the resistor should be around 2,5ohm"
- keeping the 2R2 specified resistor then, the matching 0.4mH coil wire should be 1.0mm (DCR= 0.29ohm) and the 0.6mH coil wire 1.2mm (DCR= 0.29ohm), although 1.0mm wire would probably work as well in that case (DCR= 0.37ohm)...
- by diminishing the resistor to 1R8, a 0.7mm coil wire could be selected (DCR= 0.6-0.7ohm), reducing somewhat coil costs,
- eliminating the resistor entirely would require going down to 0.3mm wire, which, I feel, may be somewhat too extreme (with regards to current capacity).
"For the 1,8mH in OD11/OA12/OA14 the original is as you say 0,8mm resulting in about 1ohm resistance, giving an attenuation of less than 1dB at any frequency. A larger coil will reduce the attenuation at most a few tenths of a dB. That is quite insignificant, so almost anything around or more than 0,8mm goes."
- the only other valid reason to increase wire size is lowering heat dissipation somewhat, within reason though, since size (and cost) are going up almost exponentially.
- 0.8mm for all coils (the original design) looks like a very good compromise (but, that was expected...),
- 1.0mm or 1.2mm for all coils could be another one, accounting for the higher power dissipation normally requested today (the target design was for 40W back in the 1970's)...
- beyond that, money is probably better spent, on software (music) rather than hardware, at least that's how I view it...
Best regards,
ARB
