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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old 21st August 2019, 01:25 PM   #27951
Bonsai is offline Bonsai  Europe
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I don’t think you can ‘unstore’ magnetic energy stored in the cross over magnetic s or returned to the system via that in the speaker suspension in the manner you describe. Any stored energy will share between Joe’s damping network and the rest absorbed by the amplifier. On a big amp you will need a huge amount of energy to cause the OPS to lose control and for example to swing the output to either of the rails against its will (I am deliberately talking anthropomorphic terms here and not electrical engineering terminology).
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Old 21st August 2019, 01:27 PM   #27952
vacuphile is offline vacuphile  Netherlands
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Originally Posted by mountainman bob View Post
So if itís old hat, has anyone implemented it commercially before? Examples?
Not that I am aware of because it just doesn't make much sense.
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Old 21st August 2019, 01:31 PM   #27953
DPH is online now DPH  United States
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Originally Posted by mountainman bob View Post
If itís just impedance matching or amp loading than itís a lot of hoopla over nothing but it sure seems to me like heís impressing more than that?
The hoopla theory is what seems closest to observation.

The problem is a lot of folks have their pet theories which don't have either any data to back them up, or worse, are in contradiction to the known world. Then there's the backfire effect when said theory gets nuked by people who know better and the emotional agenda takes foot. It doesn't take long to see the results of that especially in this thread, doubly so because Joe, not alone but more than anyone else, is dying to be taken seriously with methods that are in direct opposition to his aim.
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Old 21st August 2019, 01:35 PM   #27954
TNT is offline TNT  Sweden
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Originally Posted by KSTR View Post
I understand his language and he understands mine, I'm quite sure.
He used a text description of what actually happens "inside" of the formula I posted, e(t) = k*v(t) + (Ze+Zout)*i(t):

I see no point of disagreement anywhere between him and especially his explicit notion of the feedback mechanism is worthwhile because it is a key point in the amp<-->loudspeaker interface.
If otherwise, he should join the discussion personally.
So it is most probable that Joe don't understand his own EE fellows - either.

//
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Old 21st August 2019, 01:36 PM   #27955
PMA is offline PMA  Europe
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Originally Posted by DF96 View Post
As Ohm's law is not a law but merely a summary of common behaviour you cannot violate it. You can either follow it (e.g. most metals) or ignore it (e.g. semiconductors).

No. Ohm's law says that for a given substance/item the current and voltage are proportional i.e. the ratio between current and voltage is a constant.
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Originally Posted by DF96 View Post
Then I was surprised at people like PMA (who is usually correct on technical matters).

R=V/I is not Ohm's law. You need to add 'R is constant' to make it Ohm's law. An extension of Ohm's law is R=dV/dI, which is slope resistance (sometimes called AC resistance).
During my university years, which is really long ago (I graduated 40 years ago), we learned much wider form of the Ohm's law, than you are suggesting. To prevent incorrectness, please find it attached as a snapshot.
Attached Images
File Type: jpg Ohm.JPG (92.3 KB, 207 views)
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Last edited by PMA; 21st August 2019 at 01:40 PM.
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Old 21st August 2019, 01:46 PM   #27956
Max Headroom is offline Max Headroom  Australia
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Quote:
Originally Posted by Bonsai View Post
I don’t think you can ‘unstore’ magnetic energy stored in the cross over magnetics or returned to the system via that in the speaker suspension in the manner you describe. Any stored energy will share between Joe’s damping network and the rest absorbed by the amplifier. On a big amp you will need a huge amount of energy to cause the OPS to lose control and for example to swing the output to either of the rails against its will (I am deliberately talking anthropomorphic terms here and not electrical engineering terminology).
The amplifier output/nfb senses and tracks back EMF but there is no return energy because of R's in the RC networks, ie loudspeaker is overall resistive load characteristic. This is not different to an office floor full of ballast type flouro lights....compensation caps are required inside each lamp fixture to ensure overall non-reactive load characteristic for the reasons any electrician/technician/EE should know.

Last edited by Max Headroom; 21st August 2019 at 01:54 PM.
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Old 21st August 2019, 01:50 PM   #27957
DPH is online now DPH  United States
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That doesn't and cannot make sense, Dan
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Old 21st August 2019, 02:02 PM   #27958
nezbleu is offline nezbleu  Canada
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John Curl's Blowtorch preamplifier part III
Quote:
Originally Posted by mountainman bob View Post
I’m under the impression that what he’s trying to get across, it seems as though he’s saying the impedance is no longer frequency dependent?

And that the byproduct is leveled phase and a ‘locked crossover’ ?
Nice try, you can't make me re-read 5 of JR's posts that easily!

I don't know what "locked crossover" means. Nothing stuck in front of the driver changes the fact that the voice coil is a big fat inductor in a strong magnetic field. The magnitude of that impedance is strongly frequency dependent.
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Old 21st August 2019, 02:03 PM   #27959
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by DF96 View Post
R=V/I is not Ohm's law. You need to add 'R is constant' to make it Ohm's law.
It would be easier to say that "R" needs to be expanded into a full description taking into account all functional dependencies (including time dependent ones).

For many problems this has been done, IIRC Tom Lee has a wonderful paper on noise in diode ring mixers where noise (4KTR) depends on the instantaneous diode resistance.

Best to end now, but in my observation this is always brought up in a negative spirit, i.e. the audience here are simpleton's that think a carbon comp resistor has no distortion mechanisms even at 1/2 rated power.
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Old 21st August 2019, 02:06 PM   #27960
Max Headroom is offline Max Headroom  Australia
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Originally Posted by mountainman bob View Post
So if it’s old hat, has anyone implemented it commercially before? Examples?
There are cables with RC networks to compensate loudspeaker rising impedance characteristic. Joe hinted of speakers implementing this input side impedance EQ but the manufacturers keeping quiet about it. You can try terminating your fig8 type speaker cables (100R or so) and IME this makes nice improvement in Mids/HF clarity. Joe's networks will further improve clarity and stability in the sound.

Dan.
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