Aleph 2 Power resistors = V2/R
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 26th March 2002, 11:36 AM #1 macka diyAudio Member     Join Date: Dec 2001 Location: Australia Aleph 2 Power resistors = V2/R Has anyone tried or using 2 watt metal film power resistors in their Aleph 2 project? I am thinking about this and tossing up whether to use plain 5 watt ceramic wire wound or go for 2 watt power film resistors. My sums suggest the power disipation will be 0.50 watts per resistor where V 2sq / R where V=voltage = 0.50 volts R = 1.00 ohm (A=0.50 amps) ie 6 x 0.50 amps = 3 amps bias current. Alternatively if more power is needed 2.2 ohm and 1.8 ohm (0.99 ohms) could be placed in parrellel for 4 watts due to temperature drift. Please forgive me if my sums are wrong. If this correct then I could use obtainable Philips metal film resistors in 2 watt ratings from Farnel! This assumes of course metal film resistors be preferable over standard ceramic cased wire wound versions? All comments and opinions are most welcome. regards macka
 26th March 2002, 02:58 PM #2 UrSv   diyAudio Member     Join Date: Jan 2002 Location: Sweden As far as I can tell calculation would be that you have 1*0.5*0.5 W (R*I*I) per resistor which is 0.25 W which then gives some room for using 2 W metal oxide at 1R and not think more about it. I would go for it. If you do not feel comfortable with that 2 0R47 in series works as well giving 4 W maximum pwer handling for the resistors. /UrSv
 1st April 2002, 02:19 AM #3 Jmertz diyAudio Member   Join Date: Jan 2002 Location: Philadelphia I have also looked into this issue and in my opinion 2W will be just fine. If it helps any, I emailed NP to ask the same question and he agrees that 2W is plenty. Jake __________________ audio4life
 1st April 2002, 02:20 AM #4 Jmertz diyAudio Member   Join Date: Jan 2002 Location: Philadelphia Also, I am using 3W metal films for my Aleph2 __________________ audio4life
 7th April 2002, 09:33 AM #5 promitheus   diyAudio Member     Join Date: Jan 2001 Location: Germany for 0,5 A bias for each fet 2-3 watts resistors are ok. I will use 3 watt ones.
 9th April 2002, 01:29 PM #6 Jakeh diyAudio Member   Join Date: Feb 2001 Location: London UK Anyone who needs power resistors, I have spare Caddock MP816 1R resistors - from memory they're about 2 or 3W without a heatsink, and 15W with. £1.25 each. Cheers Jake
 9th April 2002, 02:36 PM #7 Salmacis diyAudio Member   Join Date: Feb 2002 Location: Norway Opinions on Vishay RS5 / RS2B / Mills MRB I guess a lot of people use Caddock power resistors for the 0.47 and 1.0 ohm resistors, but has anyone tried either Vishay RS5, RS2B or Mills ‘MRB’ Series? The Mills MRB series are non inductive, but does it matter? How much do the power resistors actually influence sound quality? Thx and regards Axel
 9th April 2002, 06:08 PM #8 BrianGT   diyAudio Moderator Emeritus     Join Date: Jan 2002 Location: near Atlanta, GA If you look at the Aleph 2 in the PassDIY gallery by Wayne Sankey. instead of using 6 - .47 ohm resistors, he used 7 .5 ohm RS2B Vishay resistors. He seems to have no problems, and I have planned to go the same route. The RS2B resistors are 3W and work fine for the .47. He used the RS5 for the 1 ohm resistors, also with no problems. If you wanted, you could use 2 RS2B 2 ohm resistors in place of the 1 ohm resistors, as suggested by some people in earlier discussions. -- Brian gte619j@prism.gatech.edu
 10th April 2002, 12:45 AM #9 Peter Daniel   diyAudio Member     Join Date: Jul 2002 Location: Toronto, Canada Another good choice for .47ohm resistors would be one Caddock MP-930 .10ohm 30W resistor.
 10th April 2002, 01:16 AM #10 HarryHaller   Banned   Join Date: Feb 2002 Location: Dallas,Texas Power resistors Yes the 0.47 power resistors are in the signal path and act as degeneration for the output fets and have an influence on the open loop linearity on the amp. Using a good resistor here will have sonic benefits. The Mills MRA-5 non inductive wire wounds have an excellent reputation for this type application and would be on my short list. I use two Dale 1 ohm 1 watt wire wounds SMTs in parallel in my modified Aleph 3 and they sound great. Surplus shoppers look for 1% wire wounds. CaddockMP-820s would also be excellent. There are some real sonic differences in small value wire wounds. H.H.

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