Makes sense, PMA. After all, it is a bipolar input. Also, your test is REASONABLE WORST CASE and this is what it takes to separate different components from each other, in many cases. Now, I am not going to scare OPPO out of using the 4562, but it is interesting what you found.
Last edited:
Actually, Ed Simon had a good trick that made a real difference- he used a small, hand-wound inductor in series with the input.
We now use it in the JC-3,(Ed's coil), but I doubt that it would make any difference in this test.
Last edited:
More results, i don't know, but it is, indeed, a good way to eliminate bad sounding devices quickly. Our ears are not the worse measuring instrument and not a hassle to plug-in.
Their is not too much to tune in an OPamp. And, once we find a good sounding device, it is always time to measure, see if everything is working as expected and ensure it fulfill our technical requirements.
jn,
May be inappropriate since I dont quite remember the post, but it sounds like just two bare drain wires wrapped around a spiral shield?
Thanks
-Antonio
It did sound kind of like that, but from Richard's post, is seemed like the designer/manu mogami came up with some design/theory whereby two wires spiralled around with a crossing angle of 90 degrees would cancel some or all of the inductance associated with the wires.
I could see trying to have the fields orthogonal such that the inductance would halve, and the 90 degree crossing angle assures orthogonality at the cross, but I'm not sure it would be so at every other point on the helix.
That's why I was asking for more detail. A web search has proven fruitless for me.
jn
That's a nice reference, well-reasoned and astute with regard to the amplifier interactions, and candid in the subjective results. And what a pleasure to see "damp" and "damping" used correctly!
Thanks John.
Several things of note:
1. Nelson also uses a zero length model, meaning that there is no accounting for the actual physical delay of a propagating signal from one end of the cable to the other.
2. He mentioned a .1 ohm non inductive resistor. I am not confident that it was non inductive. Bifilar is not, nor are the caddocks. I'll be making one soon, I have the materials at hand. Nelson, if you wish, I can send you one.
3. His high speed test setup is scary to me. I've been pondering how to get around the ground loop formed by the scope ground and the generator ground. To do it accurately, I'm going to use differential IA's at both ends.
(I suspect that I may be able to use the .1 ohm CVR at the ground of the amp to put scope ground at amp ground, then view the resultant current of the line driving an arbitrary load. The difference between the current at the amp end and the load end is only one transit time..I'm not the kinda guy to nitpick..🙄
jn
the cable length, delay properties are modeled that way - pretty universally in the literature
the lumped L,C,R are normalized per unit length - when you use the /ft values then each section models 1 ft of cable - 12 sections strung together ~= 12 ft of cable
if you want finer grained modeling of transmission line phenom then you use more, smaller lumps - the /inch values for L,C,R and 144 sections...
before going to the /inch model for speaker cable you probably should want skin/proximity effect modeling - in principle it could still be a lumped model with mutual inductances steering the current into paralleled R branches
FastHenery claims to export spice models from its sims
the lumped L,C,R are normalized per unit length - when you use the /ft values then each section models 1 ft of cable - 12 sections strung together ~= 12 ft of cable
if you want finer grained modeling of transmission line phenom then you use more, smaller lumps - the /inch values for L,C,R and 144 sections...
before going to the /inch model for speaker cable you probably should want skin/proximity effect modeling - in principle it could still be a lumped model with mutual inductances steering the current into paralleled R branches
FastHenery claims to export spice models from its sims
Last edited:
Put a scope on an isolation transformer supply. That's the only way - anytime.
You may have ONLY ONE class I instrument in one time.
You may have ONLY ONE class I instrument in one time.
Okay very different indeed. Well before my arms got all tangled just past 180 degrees, it seemed that the orthogonality held through out. But doesnt the spiral of each wire alone add to its inductance?
Thanks
-Antonio
Does the program assume a unit length, then calculates the prop delay from node to node? Do you specify unit length?
It's easy enough to make two cables of significantly different lengths but yet have the same global L and C, therefore the exact same model for the same number of lumps. I would expect two different length cables to act differently.
jn
A helical wire will have field normal to the axis as well as parallel to the axis. A return current helix of the same pitch direction would negate the axial field. From the description, the return pitch is opposite, so the axial field should increase. Hence my questions.
jn
Hear, hear. And remember, if lightening is about, you'll likely get damped.
Thanks,
Chris
- Status
- Not open for further replies.