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Old 24th March 2009, 08:56 AM   #1
sajti is offline sajti  Hungary
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Default Which resistor type for emitter resistor?

I'm working on my new hybrid amplifier. It will use 0R22 ohm emitter resistors. I don't want to use cheap and bad sounding types. I checked some Welwyn, Sfernice, Beyschlag types, but I have no experience with any of them. Any advice?
Please avoid the very expensive types, because I need 32pcs. for one stereo amplifier (2x900W/2ohms)

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Old 24th March 2009, 09:28 AM   #2
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Define "bad sounding"?

One can never go wrong with Panasonic (Matsushita) resistors.

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Old 24th March 2009, 09:54 AM   #3
sajti is offline sajti  Hungary
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I can order Yageo ceramic for peanuts, but it's very hars sounding. I tried some noname types, but I get same result with them. Now I don't want to do this mistake again

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Old 24th March 2009, 10:22 AM   #4
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The cheapest solution works the best for me in this case - diy some non-inductive wirewounds using copper wire.

Just noticed your amp power and this will probably require very thick wire. May not be such a great idea.
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Old 24th March 2009, 02:06 PM   #5
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You could buy a roll of Manganin or Constantan wire and make your own. That low value would only take a short piece of the right gage wire; loop it as a hairpin and wind a short free standing coil for low inductance and solder 'em in. No commercial resistor will sound any better.
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Old 24th March 2009, 07:16 PM   #6
johnss is offline johnss  United States
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why wind your own. You can buy Nichrome resistance wire, and measure how much you'll need to obtain desired resistance, cut all pieces to that length, and solder in place. Will be much more open sounding than the ceramic power resistors that are commonly used.
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Old 25th March 2009, 02:12 PM   #7
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am not sure that Nichrome can be soldered
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Old 25th March 2009, 02:24 PM   #8
AndrewT is online now AndrewT  Scotland
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Quote:
Originally posted by Trevorferns
am not sure that Nichrome can be soldered
does baker's fluid work for soldering nichrome?
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Old 25th March 2009, 03:29 PM   #9
pjp is offline pjp  India
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Quote:
Originally posted by johnss
why wind your own.

For the same reason that nobody makes resistors out of Nichrome wire commercially.

The temperature coefficient is too high and you'll get a resistor whose resistance varies all over the place as soon as you pass current through it.
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Old 25th March 2009, 03:38 PM   #10
AndrewT is online now AndrewT  Scotland
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Quote:
Originally posted by pjp
you'll get a resistor whose resistance varies all over the place as soon as you pass current through it.
"all over the place" or follows the temp coeff?

According to this table:
TEMPERATURE COEFFICIENTS OF RESISTANCE, AT 20 DEGREES C


Material Element/Alloy "alpha" per degree Celsius
================================================== ========
Nickel -------- Element --------------- 0.005866
Iron ---------- Element --------------- 0.005671
Molybdenum ---- Element --------------- 0.004579
Tungsten ------ Element --------------- 0.004403
Aluminum ------ Element --------------- 0.004308
Copper -------- Element --------------- 0.004041
Silver -------- Element --------------- 0.003819
Platinum ------ Element --------------- 0.003729
Gold ---------- Element --------------- 0.003715
Zinc ---------- Element --------------- 0.003847
Steel* --------- Alloy ---------------- 0.003
Nichrome ------- Alloy ---------------- 0.00017
Nichrome V ----- Alloy ---------------- 0.00013
Manganin ------- Alloy ------------ +/- 0.000015
Constantan ----- Alloy --------------- -0.000074

http://www.allaboutcircuits.com/vol_1/chpt_12/6.html

Nichrome has a lot less change in resistance than copper at room temperature.

Quote:
Nickel and Chromium atoms have the same electron seating arrangement (shell structure) as Nickel and Copper - hence Nichrome also has a wide temperature range where resistance does not change.
from
http://www.seed.slb.com/v2/FAQView.cfm?ID=397
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