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
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
markp said:
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...
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.
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
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
rikkitikkitavi said:
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
Well - I just replaced the 0.1 ohm thick film emitter degeneration resistors in my JLH class A type amp with 1" lenghts of the constantan wire.
seems to be the same kind of improvement - more smooth & fluid, more detail
This is worth trying.
In the UK this wire can be got from Maplin Electronics but as of yesterday they were out of stock.
It is 4.2 ohms per meter with works out about 0.1 ohms per inch
For values larger than 0.2 and less than 2.0 ohm I would suggest zig zagging it across a piece of blank vero board rather than winding which will increase inductance.
enjoy !
seems to be the same kind of improvement - more smooth & fluid, more detail
This is worth trying.
In the UK this wire can be got from Maplin Electronics but as of yesterday they were out of stock.
It is 4.2 ohms per meter with works out about 0.1 ohms per inch
For values larger than 0.2 and less than 2.0 ohm I would suggest zig zagging it across a piece of blank vero board rather than winding which will increase inductance.
enjoy !
sss said:whats a constantan wire?
Well it's a special blend of metals which I believe was developed for making one half of thermocouples
i.e. two disimilar wires ( insulated ) that when twisted together and joined at one end produce a temperature dependant voltage at the other end which can be plugged into a module that will give a calibrated reading or some other logical function
For our purposes it is wire that, at least in the UK, and hopefully elsewhere, is easlily available, that has a resistance per meter that depends on the gauge.
for more info I suggest that you google...
mike
I just found this UK website for all your wire needs ( including constantan )
http://www.wires.co.uk/
and more specifically
http://www.wires.co.uk/acatalog/COPPER_NICKEL.html
I guess there will be similar sites elsewhere.
http://www.wires.co.uk/
and more specifically
http://www.wires.co.uk/acatalog/COPPER_NICKEL.html
I guess there will be similar sites elsewhere.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.