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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old Today, 06:06 AM   #11361
RNMarsh is offline RNMarsh  United States
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JC... this is all we need to know to tell if it is hiFi or not...

TestHiFi on the App Store


-RNM
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Old Today, 06:09 AM   #11362
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by jneutron View Post
I am not a member of AES. I am not opposed to a collaborative effort however.

I do not even have a stereo setup in my house, so the chances of me listening to any improvements I discuss here is probably zero.

Jn
Thats Ok. Demian and others (myself also) have the test equipment to see the reduction.

Lots of amps laying around my place. want one?


Thx-RNMarsh
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Old Today, 06:11 AM   #11363
Max Headroom is offline Max Headroom  Australia
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Originally Posted by RNMarsh View Post
I was thinking of that stick-on label attached to the back of the magnet that you mentioned ... doing some damping.
However, if it was also a metalised piece..... what affect it would have on the magnet??
I think a label does not have enough mass to do anything much, however ime an aluminised label and my 'goop' both subtly alter noise production and consequent acoustical output...Barkhausen noise I presume, maybe.


Dan.
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Old Today, 06:23 AM   #11364
Max Headroom is offline Max Headroom  Australia
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Originally Posted by nezbleu View Post
I thought you believed (without evidence) that all conductors are inherently directional. So is the idea of this project to use doubled twisted pairs in each direction, so the non-existent directionality magically cancels?
Nezbleu, I know from subjective experience that at least some cables (standard coaxial construction) and at least some wires exhibit directional properties.


Dan.
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Old Today, 06:25 AM   #11365
jneutron is offline jneutron  United States
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Quote:
Originally Posted by RNMarsh View Post
Thats Ok. Demian and others (myself also) have the test equipment to see the reduction.

Lots of amps laying around my place. want one?


Thx-RNMarsh
Thank you for the kind offer. I have no place for speakers.
I have a Bose 123 sub behind my couch, but have never gotten around to actually connecting anything. Yes I know, some here would say I am lucky..

Life has been too hectic of late to sit around and just enjoy music. A nice cognac and good company, certainly.

Jn
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Old Today, 06:31 AM   #11366
PMA is offline PMA  Europe
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Quote:
Originally Posted by jneutron View Post
The circuit I drew is a very simple gain stage. It is designed to put the correct VOLTAGE across the resistor Rs. It does that because I am feeding back the exact reading from across that resistor to the negative feedback network.

In a single coil speaker, I do not have access to the resistive part of the coil equivalent model, I can only see the sum of the two elements Ls and Rs.

Because I am using only the voltage across the Rs as feedback, I am controlling the VOLTAGE across the resistor. And, my circuit does not care what the actual resistance Rs is as I am not measuring it.
I am not contesting this, in fact we both agree on your description. The green plot below shows that voltage across the Re is kept constant.

My question is if it would be different, in distortion reduction, from current drive. It seems to me, and the simulation is saying so, that resulting driver transfer function is same as with the current drive.
Attached Images
File Type: png speaker_comp.png (31.4 KB, 12 views)

Last edited by PMA; Today at 06:34 AM.
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Old Today, 07:11 AM   #11367
KSTR is online now KSTR  Germany
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My conclusion, as of now, is quite clear: "JN-drive" implements indirect current drive, just way less feasible and most likely less effective in distortion reduction (fine-print remains to be seen). We have to mod the driver (*pita*) and the amp because we will need to install degeneration also to have some electrical damping, plus proper EQ to get a reasonable SPL curve. Wrt damping, especially those cheaply built drivers with high nonlinearity are really prone to nasty "jump resonance" chaotic phenomena with no damping even if the acoustic loading is benign.

So, why not just impress the current directly rather than trying to isolate a quasi-constant resistor and relying on V/I transfer to obtain the current by impressing a voltage, with that V/I-transfer not being perfect since the isolated transfer resistance isn't perfect (if alone from thermal drift, and I'm sure we will find residuals of other distortions as well). And then use the dual VC to best extract the velocity signal with a balanced version of the servoing Birt bridge and degenerate the current drive with this (introducing an amount of MFB), rather than using the "polluted" terminal voltage.

As I've written before, real world check by impressing a current and looking at the distortion of the "JN-Drive" voltage will most likely reveal quite a bit of distortion left, coming from the transfer impedance imperfections, matching issues etc.

While it is not completely impossible that some of this distortion might cancel with other distortions that aren't addressed by current/JN-drive like BL(x), BL(i) and reluctance force, I would think the chances are nil.

Last edited by KSTR; Today at 07:27 AM.
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