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Old 3rd December 2009, 06:41 PM   #21
ljfont is offline ljfont  Canada
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Nice.

Checkout
http://www.borbelyaudio.com/adobe/ae699bor.pdf

See Figure 15c and table 3. You can lower your THD even further, and reduce the DC offsets at the output.

However watch out for your XO impedances, they can introduce more THD than what you would want. Also, if you need higher XO frequencies, you may want to think about cascode to reduce input capacitance.

Leo
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Old 3rd December 2009, 09:06 PM   #22
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Also check out the Xenover Ver. 2.0 Article By Grey Rollins.

Very nice.
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Old 4th December 2009, 12:40 AM   #23
udailey is online now udailey  United States
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Default My Shot at a PCB`

Whipped this up. Was thinking of putting all resistors in a ladder formation and the 2sk170's side by side in pairs then in a ladder as well. Might try that and see how it goes but here is my first try.
This is optimized for space and for Dale 1/4W resistors or smaller. Larger resistors would work but more than 1/2W might be trouble. I imagine PRP would be fine.
This is double sided. Single sided is a pain with the power lines needing to be so close.

---What I am not sure about here is whether the caps and resistors are going to a ground or to B-...?? I see that the sign for B- on the source of the 2sK's is the same as what I have interpreted as a ground on the caps/resistors.
Uriah
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Last edited by udailey; 4th December 2009 at 12:45 AM.
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Old 4th December 2009, 02:42 AM   #24
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Quote:
Originally Posted by udailey View Post
Whipped this up. Was thinking of putting all resistors in a ladder formation and the 2sk170's side by side in pairs then in a ladder as well. Might try that and see how it goes but here is my first try.
This is optimized for space and for Dale 1/4W resistors or smaller. Larger resistors would work but more than 1/2W might be trouble. I imagine PRP would be fine.
This is double sided. Single sided is a pain with the power lines needing to be so close.

---What I am not sure about here is whether the caps and resistors are going to a ground or to B-...?? I see that the sign for B- on the source of the 2sK's is the same as what I have interpreted as a ground on the caps/resistors.
Uriah
Uriah,

My apologies for the not-so-clearly labeled schematic. This attachment should take care of that. Frankly, I didn't anticipate anyone posting a PCB layout this soon. It hasn't even been breadboarded yet

I'm having a little trouble following your board layout. I don't see the connection from the input and output buffers (Q1, Q2, Q5, Q6, Q9 and Q10) to B-. I also do not see a signal connection from the input buffer to the HP and LP sections.

Jacques
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Old 4th December 2009, 02:59 AM   #25
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And here is a frequency response plot showing the improvement in stopband attenuation of the LP section. The original is in post #4.
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Old 4th December 2009, 03:00 AM   #26
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The same plot with an expanded y range:
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File Type: gif DCB1XO-LR2-V3.2.gif (22.7 KB, 1885 views)
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Old 4th December 2009, 09:23 AM   #27
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Quote:
Originally Posted by Jacques Merde View Post
Uriah,

Frankly, I didn't anticipate anyone posting a PCB layout this soon. It hasn't even been breadboarded yet

Jacques
I think there is a lot of interest Jacques, and don't be surprised if someone else already has!! I'm certainly thinking about starting to work on a verro board layout The Spice sims look very promising, and I'm rather intrigued by your solution to the stopband response problem , though the sim certainly shows it does the Trick!

Tony.
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Old 4th December 2009, 09:38 AM   #28
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I was planning to re-do my X-over with B1 circuitry. That is the Linkwitz x-over with LR2 and dipole compensation etc.
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Old 4th December 2009, 09:41 AM   #29
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Hi all, this looks like just what I need as well. Could you post the formulae for the RC values for those of us that are challenged? Additionly I assume this is a unity gain. If so can the gain be increased.

Thanks in advance.

Terry
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Old 4th December 2009, 12:16 PM   #30
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Jacques Merde View Post
This a 2 pole (12dB/oct) LR filter at 700 Hz. It should be fairly straightforward to implement 24dB/oct.
the 2pole (-12dB/octave) has Q=0.5 to create the L-R function.
A 4pole using two cascaded sections of 2pole requires both sections with Q=sqrt(2). two cascaded Q=0.7071 gives an overall Q=0.5
This is the normal Butterworth roll off and needs the feedback components doubled up to create R & 2R in both the HP sections and C & 2C in the LP sections.
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