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Old 31st October 2004, 08:17 PM   #1
mikelm is offline mikelm  England
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Lightbulb resistance wire much better than 0.5ohm Caddocks ?

Recently I put a couple of caddock MP915 0.5 ohm resistors in my crossovers to level out the treble response a little.

Since then I have hardly listened to my system, the sound was horrible. I remember that this has been my experience in the past also when I have used similar resistors at amp outputs.

Tonight I replaced these expensive caddocks with 100mm of Constantan ( I think ) resistance wire folded twice onto a small piece of blank veroboard.

Although the wire only cost a couple of pence the sound was MUCH better than the Caddocks. I think it had some charactor but to my ears it was in a different league.

Am I using the wrong Caddocks or is this a breakthrough ?

Has anyone else tried this ?

Mike
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Old 31st October 2004, 08:56 PM   #2
markp is offline markp  United States
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Are you heatsinking the Caddocks? They are not designed for use in speaker crossovers but as emitter resistors. You might also be getting a inductive rise when using the wire wound around the vero board that rolls off the highs that you might like the sound of.
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Old 31st October 2004, 10:42 PM   #3
mikelm is offline mikelm  England
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Quote:
Originally posted by markp
Are you heatsinking the Caddocks? They are not designed for use in speaker crossovers but as emitter resistors. You might also be getting a inductive rise when using the wire wound around the vero board that rolls off the highs that you might like the sound of.
You can rest assured that there is no roll off ! The sound is clear and clean as a bell. The wire is not wound around, it is folded. Like a crushed Z so there might even be some inductive cancelling. Even if there is not -

estimate what ? about one nH / mm ? perhaps 100nH total

typical amplifier o/p choke 13uH - over 100 x more. I don't think that inductance is an issue


Heatsinks - are they necessary ?

These resistors are dealing with 3k - 20k hz - They don't get hot.

Seriouslly - unless these are duff Caddocks this is a big improvement and what's more it is about a $10 saving per pair.

If every member used this idea once that would be a $200,000 saving...
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Old 1st November 2004, 03:33 PM   #4
mgreene is offline mgreene  United States
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Default Tried the Caddocks...

...recently in my crossover and thought they sounded pretty bad too. This was direct comparison to a Mills resistor. I tried both Caddock and Vishay thick film types and got the same unexpected result both times.

Mike
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Old 1st November 2004, 04:14 PM   #5
mikelm is offline mikelm  England
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Default Re: Tried the Caddocks...

Quote:
Originally posted by mgreene
...recently in my crossover and thought they sounded pretty bad too. This was direct comparison to a Mills resistor. I tried both Caddock and Vishay thick film types and got the same unexpected result both times.

Mike
What type of resistor is the Mills ?

How much do they cost ?

Are they non inductive ?

mike
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Old 1st November 2004, 04:17 PM   #6
mgreene is offline mgreene  United States
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Default Mills

The mills is a non-inductive WW. See Michael Percy's online catalogue. Lots of values. IIRC the Mills are $4.

Mike
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Old 1st November 2004, 11:14 PM   #7
markp is offline markp  United States
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The Caddocks are rated at only 2.5watts or so free air. Peak power in a speaker crossover is many times that. Wirewound resistors can take over 10 times their rating without meltdown and as such are perfect for speakers. I use the Mills resistors too, the twelve watt type in speakers and the five watters as emitter resistors.
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Old 2nd November 2004, 07:44 AM   #8
mikelm is offline mikelm  England
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I would be amazed if this 0.5 ohm resistor in the tweeter cct was dissipating 2.5 watts - I don't listen that loud, the speakers are 90db / W / m, and there is not normally much power generated in the treble region.

but if this was the problem it would mean either a heat sink,a bigger resistor or a few resistors in paralell, all of which would cost more.

In the mean time my little piece of resistance wire which only cost a few pence is still sounding as sweet as a nut.

I think a might try a mills resistor to see if it sounds better than my piece of wire but I do not envisage buying any more of this type of thick film resistor.

mike
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Old 6th November 2004, 03:17 PM   #9
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mikelm, how did you make the electrical connection with the wire?
if I remember it right, it is quite difficult to solder resistance wire, and then the problem is that with a mechanical connection that it could cause interruptions.

/rickard
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Old 6th November 2004, 05:56 PM   #10
mikelm is offline mikelm  England
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Quote:
Originally posted by rikkitikkitavi
mikelm, how did you make the electrical connection with the wire?
if I remember it right, it is quite difficult to solder resistance wire, and then the problem is that with a mechanical connection that it could cause interruptions.

/rickard
Well, I did not know that it was difficult to solder.

I wrapped the 28swg constantan wire a few times around a PCB connector post and then soldered using a solder with some silver content. The solder seemed to flow OK.

They have been in place for 1 week now and so far the result is very satisfactory.

I am now listening to a lot of music...

mike
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