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Old 7th November 2004, 12:16 AM   #1021
mikelm is offline mikelm  England
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Default Re: preset calculation

Quote:
Originally posted by numbernine
Mikelm: I wdispositions. Merci beaucoup.
I just discovered that constantan resistance wire sounds MUCH better than thick film resistors

28swg is about 4.2 ohms per meter

http://www.diyaudio.com/forums/showt...054#post507054

http://www.wires.co.uk/acatalog/COPPER_NICKEL.html

Mills noninductive wire wound are also good apparently but I have not heard them and they are much more expensive

mike
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Old 7th November 2004, 03:05 AM   #1022
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Quote:
Originally posted by dutch diy


Chris,

At what rail voltage and bias current were you operating?
I'm running for over a year now on 29.5V and 2.2 A on 4 mj15003's.

During testing of my first J-amp set my Shack Speaker however survived several + an - 22 V DC-offset problems, and not for milli seconds i can tell.
Hi,

For those two years they were set at 20V and 4A and the heatsinks were measured at 55 Celius with no problem. That day when it happened I was listening to them for about an hour or so and I fell to sleep. When the CD ended I woke up and change the CD then I noticed the DC Protection light came on. So I had no idea how long it had happened. I am not sure whether it would have done some sort of damage to the JX150 or not if there was no DC protection. Now I reduced the Iq setting to 20V, 3A to all four mono block JLH.

All heat sinks measured at 41Celius. As I am bi-amping I do not hear much difference whether it is set at 4A or 3A. Before bi-amping 4A sound better than 3A.

Regards,
Chris
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Old 7th November 2004, 03:02 PM   #1023
eLarson is offline eLarson  United States
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Default Re: Re: preset calculation

Quote:
Originally posted by mikelm


I just discovered that constantan resistance wire sounds MUCH better than thick film resistors

What are you using it for?

Erik
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Old 7th November 2004, 03:41 PM   #1024
mikelm is offline mikelm  England
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I just noticed that the some of the quote was missing so the post was not as clear as I intended

I am currently using constantan wire as an emitter degeneration resistor 0.1 ohms on the o/p transistor ( the bottom one ).

I was using a thick film resistor before.

The difference in quality is quite dramatic.

( The effect was similar when I swapped out a 0.5 ohm caddock in a cross-over )

mike
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Old 7th November 2004, 03:44 PM   #1025
eLarson is offline eLarson  United States
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Just a straight piece, about 2 cm or so long? Or wound 'round something? Do tell, do tell.

E.
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Old 7th November 2004, 03:58 PM   #1026
mikelm is offline mikelm  England
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The reel of wire that I have is 28 gauge and this gives about 4.2 ohms per meter

a range of gauges can be found here

http://www.wires.co.uk/acatalog/cn_wire.html

4.2 ohms per meter = 0.1 ohms per inch ( 25mm )

How you implememnt this rather depends upon you method of construction. either mount it on blank vero using posts or just put 25mm across whatever gap you have. I would not wind or coil these as this will create inductance.

If you do not already have emitter degeneration resistors you may have to re-adjust you bias current depending of the cct you are using.

I will be interested to hear what you think of this mod

mike
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Old 9th November 2004, 08:07 AM   #1027
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Default Resistance wire

Quote:
Originally posted by mikelm


I just discovered that constantan resistance wire sounds MUCH better than thick film resistors

28swg is about 4.2 ohms per meter

http://www.diyaudio.com/forums/showt...054#post507054

http://www.wires.co.uk/acatalog/COPPER_NICKEL.html

Mills noninductive wire wound are also good apparently but I have not heard them and they are much more expensive

mike
Maplin also sell it in smaller quantities (an ounce for a fiver - how many ohms per ounce, I wonder?). I'll give it a go.
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Old 9th November 2004, 09:01 AM   #1028
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I just want to make a small contribution to the use of "resistance wire". In fact it is actually possible to wind wire in a non-inductive way. This may be useful where it is not possible to find a home for the length of wire you have to use and still mange to keep it in a straight line. It saves space and is quite elegant in its use of physical principles. The only place I know that shows this technique clearly is contained in Geoff Moss's Class-A site. I guess most uses of this thread know Geoff's site. If you go there and then select "Other Class A amps" you will find the Nelson-Jones 10 Watt design. Choose the "article" (not the schematic) link and go to page 12 (of 14). There you will find a delightful diagram of a 0.56 Ohm 5% resistor wound "non-inductively".
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Old 9th November 2004, 12:38 PM   #1029
Geoff is offline Geoff  United Kingdom
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Quote:
Originally posted by Jonathan Bright
There you will find a delightful diagram of a 0.56 Ohm 5% resistor wound "non-inductively".
To save anyone interested some time, I have attached the relevant figure.
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File Type: jpg nj10wfig6.jpg (13.0 KB, 1158 views)
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Old 9th November 2004, 02:54 PM   #1030
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This type of resistors are made by industry too.
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