Audibility of output coils

[dimitri]

However I am now stuck with a .3 ohm resistor in each output of my power amps.

I presume, noninductive ones?

 

[john curl]

Yes, they parallel my Bybee devices.

 

[dimitri]

Yes, they parallel my Bybee devices.

where you got .6Ohm bybee? Mine are 25mOhm
or you mean .3Ohm in parallel with bybee?

 

[Hartono]

KEWL

 

[john curl]

I have OLD Bybee devices. They use .3 ohm.

 

[dimitri]

Again the same trick. You had already accumulated with Erno all valuable old Toshiba JFETs. The leftovers become 10 times more expensive than before. And now OLD bybees.

 

[Terry Demol]

.5uH only for Halcro. Why don't you folks stop talking and start calculating?

John,

Are you referring to the large coil that looks like it is made of
copper tubing and has a large brass fitting at one end?

I believe it is also to block external RF from entering the amp.

Interesting amp for sure, however it looks like the much cheaper
balanced Bruno Putzeys amp is pretty close in measured performance.

cheers

Terry

 

[john curl]

Calculate the inductance from the MEASURED 20KHz impedance as measured by 'Stereophile'. What is wrong with everybody? Are there no engineers here?

 

[andy_c]

Calculate the inductance from the MEASURED 20KHz impedance as measured by 'Stereophile'. What is wrong with everybody? Are there no engineers here?

John, I get 0.78uH. I got this from:

L = sqrt(0.14^2 - 0.1^2) / (2 * pi * 20e3)

R = 0.1 and

sqrt(R^2 + X^2) = 0.14 @ 20 kHz and

X = omega * L (neglect the parallel R)

This is for the DM88

 

[GK]

.5uH only for Halcro. Why don't you folks stop talking and start calculating?

So what John? It's still a large air wound inductor, isn't it?
You have made the claim than any output inductor compromises an amplifiers sonic ability. Are 0.5uH inductors now all of a sudden OK in your opinion?

Cheers,
Glen

 

[john curl]

0.5uH is given my qualified OK. OK? I don't NEED a coil, myself, but if you NEED one, then .5uH and 1 ohm or less in parallel is as close to OK as is practical.
It's 2-6uH that I think is too much.

 

[lumanauw]

UCD=30uH (classD). Is this bad sign?
But it is enclosed in the global feedback loop (the feedback is taken after the 30uH). Is this good sign?

 

[john curl]

This is different, because it defeats the normal operation of the output coil, which is to buffer the feedback loop from the load. Please do not confuse the situation with class D questions.

 

[lumanauw]

This is different, because it defeats the normal operation of the output coil, which is to buffer the feedback loop from the load.

There's another type of classD where the feedback is taken before the LC filter. Maybe this one operates exactly like 2uH on classAB amps?

 

[sidiy]

A different angle...

Hello all,
Very interesting thread.
I'm looking at the electro-mechanical model for a speaker and I'm inclined to believe that the output inductor may play an 'audible' role. You guys may infirm what I'm saying, as my knowledge of these matters is pretty much insignificant.

Let's take the Seas T25CF001 tweeter: this one has Re=4.8ohms; Ce=2.2F and Le=50uH. A 2uH is like 4% of Le, so...is this significant, can we just choose to neglect it...?

For sure playing with those (soooo expensive and therefore not so much playing for me actually) series capacitors in the tweeter X-over gives clearly different results. May we also blame capacitor's ESL for these more or less subtle changes, among other factors?

Sorry for derailing the thread, calling in a loudspeaker designer may bring in some ... synergy

 

[GK]

0.5uH is given my qualified OK. OK? I don't NEED a coil, myself, but if you NEED one, then .5uH and 1 ohm or less in parallel is as close to OK as is practical.
It's 2-6uH that I think is too much.

Okkaayyyy..........

After all this arguing we have now extracted from John the conviction that any inductor up to 2uH is hunky-dory. Hallelujah!

Between 2 and 6uH is cited as bad.

What about above 6uH John???


Cheers,
Glen

 

[john curl]

I said 0.5uH MIGHT be OK. Is that too hard to comprehend? 2uF and above is really a potential problem.

 

[john curl]

Remember engineers, you have to subtract the real component from the inductive component to get a better estimate.

 

[Conrad Hoffman]

I think somebody posted a free impedance converter in the Everything Else forum that's handy for this sort of thing

 

[GK]

I said 0.5uH MIGHT be OK. Is that too hard to comprehend? 2uF and above is really a potential problem.

Lighten up John. I'm just teasing.

How do you make a 2uF inductor?