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Best resistors For I/V Conversion?
Best resistors For I/V Conversion?
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Old 10th July 2018, 12:21 PM   #61
Raj1 is offline Raj1  United Kingdom
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Quote:
Originally Posted by Zoran View Post
Hi actually not.
Bicycle has the best ratio in terms of input Jules for produced work. I think 1:7. . No engine can achieve that. For instance in agriculture, for 5 input calories in form of motor fuel, output is 1 calory. But If You are using human power and manual production that is opposite. For 1 calory input outcome is 5 cal. That is 25 times more...
So You can drive a bike with one cube of sugar energu with a distance that no engine can beat with same input energy

I doubt the Ferrari drivers care about this.
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Old 27th October 2018, 11:51 AM   #62
fralippo is offline fralippo  Italy
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Any experience with these?

GRAPHITE RESISTORS

I've been using them in loudspeakers crossovers for a while with great results! Really great.

Maybe later I will try them as I/V resistors on my PCM1704K based dac. Now there's a hand wound copper wire 1R7 resistor.
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Old 27th October 2018, 02:07 PM   #63
DF96 is offline DF96  England
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My guess would be that a significant part of the resistance of such a 'graphite' resistor is the contact between the copper and the graphite. Making good contacts is part of the secret of making a good resistor; resistor manufacturers have decades of experience in doing this reliably. Unlikely that home made resistors will be as good.

My guess would also be that 'graphite' resistors have high excess noise, like carbon comp. Possibly hgh distortion too.

Note that such a long thin resistor element would have highish inductance, the very opposite of the 'non-inductive' claim in that article. Fortunately, in most audio applications this does not matter.
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Old 27th October 2018, 02:32 PM   #64
sumotan is offline sumotan  Indonesia
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My take is there’s not best resistors, it depends in where it’s being applied to.
Graphite may work well in your speakers as there’s lots of current & voltage flowing across it but for I/V might not work too well. Example many rave about foil & rhopoint wire wounds but in my case I found the best sound using shinko. Moral of it is you got to try with many varieties to arrive at the results that your looking for Fralippo.

Cheers
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Old 27th October 2018, 03:42 PM   #65
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by fralippo View Post
Any experience with these?

GRAPHITE RESISTORS

I've been using them in loudspeakers crossovers for a while with great results! Really great.

Maybe later I will try them as I/V resistors on my PCM1704K based dac. Now there's a hand wound copper wire 1R7 resistor.
Well, the very link you posted says:
Quote:
Let me say already here: I do not find any sonic difference in performance from wire wound, graphite, MOX, Duelund and film resistors tested on my Jenzen D (diamond tweeter). The differences they may display in induction is infinitesimal and cannot count for any sonic difference. Their difference in resistance vs. temperature may vary and should be considered where high levels of current is passing. Buying seriously expensive resistors is a waste of money - to my experience. Clean woodoo. The problem here is that when we buy something expensive, it just got to be better.
What else do you need?
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Old 27th October 2018, 04:44 PM   #66
Ryelands is offline Ryelands  United Kingdom
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I've been using them in loudspeakers crossovers for a while with great results!
A while back, I fitted standard Dueland graphite resistirs to my X-overs. They made for, as you suggest, a surprising improvement. Unlike many Dueland products, they were not that expensive so it seemed a waste of time to DIY them esp as Dueland knows what it is about build-wise.

Graphite resistors are, contrary to DF96's guess, widely recognised as having a low inductance. They also have a positive temperature coefficient, making them - it is claimed - suitable for the relatively high currents encountered in passive X-Overs as they counter thermally-driven modulation in voice coil impedance. See e.g. Dueland's web site on this.

OTOH, though the claim in the Danish paper you cite that the effect is too small to matter might be correct in some cases. it is backed only by a subjective report on one - and only one - exotic and now unavailable tweeter in an unknown circuit. Your experience, like mine, is different and just as valid.

Quote:
Maybe later I will try them as I/V resistors on my PCM1704K based dac.
I'd strongly recommend against using them as I/V resistors; they are designed for and at their bext in X-Over circuits. I'd go instead for Charcroft Z-Foils, which, though not cheap, are cheaper than the Duelands, much easier to fit and electrically more suitable.

HTH

D
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Old 27th October 2018, 05:02 PM   #67
DF96 is offline DF96  England
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Something long and thin like those home-made graphite resistors cannot have a low inductance. Other graphite resistors may be different.
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Old 27th October 2018, 05:40 PM   #68
Ryelands is offline Ryelands  United Kingdom
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Quote:
Originally Posted by DF96 View Post
Something long and thin like those home-made graphite resistors cannot have a low inductance. Other graphite resistors may be different.
The Duelands are the only commercially produced pure graphite resistors I know of. They too are long and thin, very much like the home-made versions described. OTOH, they are not wound.

Measurements made by Martin Colloms and cited on Dueland's web site suggest that, while they do not have the lowest inductance of the tested range, they are still low. See:

http://duelundaudio.com/wp-content/u...tic-Hi-Res.pdf

I did not make the measurements and note that no frequencies are given. If you think Dueland/Colloms are wrong, please take it up with them.

D
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Old 27th October 2018, 11:11 PM   #69
Damon Hill is offline Damon Hill  United States
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How does one "wet" graphite to make a secure electrical connection? I think only a mechanical connection is possible, and it'll be very nonlinear with temperature and voltage.

There's graphite and then there's graphite: the soft stuff isn't mechanically formable without a binder. The graphite used in carbon composites seems like a different form that felt rough and abrasive in the few samples I've ever encountered.

Carbon has a bewildering variety of stable forms; one interesting type is vitreous or 'glassy' that may or may not be conductive. It's extremely hard and chemically stable, but I don't know if it's electrically conductive to any degree. Can it be made into films?

https://www.2spi.com/catalog/documen...arbon-Info.pdf

Graphene is very electrically conductive, but try to obtain samples suitable for actual resistors. Soft graphite >is< graphene in mass quantity, but has to be isolated to single-atom sheets to be realizable. At the moment, real graphene is extremely hard to work with, either inside or outside the laboratory.

At any rate, carbon seems intuitively a non-linear substance to produce a highly stable resistor, even though it was once the material of choice for cost-effective design as either composition or the much more stable film. While I'm very skeptical of this present conversation I'll continue to follow it just to see what we may be able to learn about this alternative.

Last edited by Damon Hill; 27th October 2018 at 11:28 PM.
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Old 28th October 2018, 12:19 PM   #70
DF96 is offline DF96  England
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It appears that 'low inductance' is being used here to mean 'not too much more inductance than a wire of similar size'. In that sense almost any non-wound resistor will be 'low inductance' so the phrase has little meaning. Fortunately, for audio it doesn't matter anyway. In reality the dominant inductance is likely to be the circuit loop in which the resistor appears.

Anyway, it seems to me that what are essentially carbon comp resistors would be a poor choice for I/V unless you want to add a little distortion and noise. CC is a poor choice for any resistor, unless you want excellent overload handling - which is why they are still made for professional use.
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