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Type AA crossover rectangular capacitor replacement


Tizman

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3 hours ago, Curious_George said:

If for some reason, you are not skilled, there is always another hobbyist willing to help.

HA HA back to rookie school 101 for YOU Dean.

 

1 hour ago, Marvel said:

I'm sorry, but that right there is funny.

No it is hysterically funny. 

  As an aside here  I don't remember reading of so many ways to complicate an AA crossover recap job in a long time.

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25 minutes ago, captainbeefheart said:

 

First is Tiz's values

 

Second is stock values

 

Third sim

 

Changed scale up to 20kHz max

tiz.png

stock.png

schem.png

 

Okay, I saw this earlier but never commented...

 

The simulation of the autoformer isn't quite right.  There are a few good models, this is the one I came up with.  The autoformer is one big tapped inductor, not several inductors in series.  You will notice the K directive.  It tells LTspice to mutually couple all the series inductors.  The total inductance of my model is around 44mh, tap 0 to tap 5.

 

 

Screenshot (67).png

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23 minutes ago, mboxler said:

 

Okay, I saw this earlier but never commented...

 

The simulation of the autoformer isn't quite right.  There are a few good models, this is the one I came up with.  The autoformer is one big tapped inductor, not several inductors in series.  You will notice the K directive.  It tells LTspice to mutually couple all the series inductors.  The total inductance of my model is around 44mh, tap 0 to tap 5.

 

 

Screenshot (67).png

 

I have my all my directives listed away from the schematic to clean things up including the K

 

I place the DCR in the inductance model, it just isn't seen on screen

 

 

 

 

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27 minutes ago, mboxler said:

The total inductance of my model is around 44mh, tap 0 to tap 5.

 

The autoformer total inductance is 42mH

 

Each tap is reduced by -3db

 

Inductance is a squared function

 

 

Inductance going from -3db onward would roughly halve looking at it from first tap to each attenuation tap;

-3db= 21mH

-6db=10.5mH

-9db=5mH

-12db=2.5mH

 

 

But you don't write it in this way, each tap needs to be it's own inductance value, not the value from first tap to each individual tap like as i listed above.

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Sorry if I'm not following your math.  Let's say the inductance between tap 0 and tap 5 is 43mh.

 

Also, keep in mind that tap 4 on the T2A is actually -3.35db, 10 volts in = 6.8 volts out.

 

Taps       ratio of total turns    Ratio of total inductance

 

5-4         .32                             .1024 or 4.4032mh

4-3         .18                             .0324 or 1.3932mh

3-2         .144                           .020736 or 0.891648mh

2-1         .106                           .011236 or 0.483148mh

1-0         .25                             .0625 or 2.6875mh

 

Not sure if this gets us on the same page, but I tried.

 

Mike

 

 

 

 

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56 minutes ago, mboxler said:

Sorry if I'm not following your math.  Let's say the inductance between tap 0 and tap 5 is 43mh.

 

Also, keep in mind that tap 4 on the T2A is actually -3.35db, 10 volts in = 6.8 volts out.

 

Taps       ratio of total turns    Ratio of total inductance

 

5-4         .32                             .1024 or 4.4032mh

4-3         .18                             .0324 or 1.3932mh

3-2         .144                           .020736 or 0.891648mh

2-1         .106                           .011236 or 0.483148mh

1-0         .25                             .0625 or 2.6875mh

 

Not sure if this gets us on the same page, but I tried.

 

Mike

 

 

 

 

 

Let's simplify the model between inductance and turns.

 

Let's say the total inductance of the entire winding is 44mH to make math easy

 

If you place a center tap it would be half the turns ratio, but each side of the center tap is not 22mH like you would think, they would be 11mH because of the squared function.

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editing- I am trying to do other work while I think of this and I am old!!! 👴

 

Once I finish up I will help dissect and explain the exact individual inductances and not the total inductance between each tap(1-5) to tap 0.

 

With 10vac at input, across pins 0 and 5, you will get 10vac or 0db attenuation if you take the output from pin 5. Each tap down 4,3,2,1 are increments of -3db. We want to put into the simulator each of those individual inductance values.

 

 

 

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1 hour ago, captainbeefheart said:

 

Let's simplify the model between inductance and turns.

 

Let's say the total inductance of the entire winding is 44mH to make math easy

 

If you place a center tap it would be half the turns ratio, but each side of the center tap is not 22mH like you would think, they would be 11mH because of the squared function.

 

Agree!  Taps 0 - 3 equals one half, or 5/10 of the total turns.

 

So...(5*5)/(10*10) = 25/100 = .25

 

44mh * .25 = 11mh.

 

I can do the same everywhere.

 

Taps 5 - 4 equal 3.2/10 of the total turns.

 

(3.2*3.2)/(10*10) = 10.24/100 = .1024

 

44mh * .1024 equals 4.5056mh

 

Taps 4 - 0 equal 6.8/10 of the total turns.

 

(6.8*6.8)/(10*10) = 46.24/100 = .4624

 

44mh * .4624 equals 20.3456mh

 

If you really want easy -3db, use 2.93/10 for taps 5 - 4 and 7.07/10 for 4 - 0.

 

We're probably stating the same thing in different ways (Isn't math great)!

 

Mike

 

 

 

 

 

 

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2 hours ago, mboxler said:

 

Agree!  Taps 0 - 3 equals one half, or 5/10 of the total turns.

 

So...(5*5)/(10*10) = 25/100 = .25

 

44mh * .25 = 11mh.

 

I can do the same everywhere.

 

Taps 5 - 4 equal 3.2/10 of the total turns.

 

(3.2*3.2)/(10*10) = 10.24/100 = .1024

 

44mh * .1024 equals 4.5056mh

 

Taps 4 - 0 equal 6.8/10 of the total turns.

 

(6.8*6.8)/(10*10) = 46.24/100 = .4624

 

44mh * .4624 equals 20.3456mh

 

If you really want easy -3db, use 2.93/10 for taps 5 - 4 and 7.07/10 for 4 - 0.

 

We're probably stating the same thing in different ways (Isn't math great)!

 

Mike

 

 

 

 

 

 

 

Yes same thing different math to show it.

 

BUT, we need the individual values of each "inductor"

 

So the halfway tap (0-3) we have each side totaling 11mH giving a total winding inductance of 42mH.

 

11/4=2.75mH

 

^^^This would be cutting the halfway points in half again down to a value of 2.75mH each "inductor", I just used 2.8mH instead of 2.75mH because that is what the actual autoformer measures because the total winding inductance is closer to 43mH-44mH.

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20 minutes ago, Deang said:

The autoformer isn’t even part of the tweeter circuit. Why do we care about this?

 

The discussion about the different tweeter network values led to a simulation of the entire network which led to a question about the simulation. A little sidetracked but in my opinion a good sidetracked, some folks want a better understanding of the entire filter network and the autoformer is often misunderstood.

 

We can steer this train back to the tweeter you watch 😜

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29 minutes ago, Deang said:

The autoformer isn’t even part of the tweeter circuit. Why do we care about this?

My fault.

 

I noticed differences in the plots and was curious why.  Although the major difference had to do with the load resistor (I use 8 ohm), I couldn't help but notice the autoformer model difference as well.

 

Apologies to the OP.

 

Mike 

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22 minutes ago, mboxler said:

My fault.

 

I noticed differences in the plots and was curious why.  Although the major difference had to do with the load resistor (I use 8 ohm), I couldn't help but notice the autoformer model difference as well.

 

Apologies to the OP.

 

Mike 


it was a sincere question. 

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9 hours ago, mboxler said:

 

 

We're probably stating the same thing in different ways (Isn't math great)!

 

Mike

 

Reminds me of the great mathematician chess player Emanuel Lasker who said there is always another mathematician that claims to have a better solution to a mathematical equation but in chess I just checkmate them. 

 

For chess lovers the Chess championship is happening right now in Dubai and is available on youtube. Carson vs Nepomniachtchi. All ties so far. 

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