[dta116]

As I understand it adding the crossfeed ckt. to the Meta42 requires you increase the gain by 2X.

Well a 6db loss is eqivalent to reducing the output power to 1/4th the original.

So as I calculate the new gain for my Meta42 (AD843KN), I come up with a multiloop gain of 19.9 with the inner-loop gain of 240!

Can this work with this opamp?

R3-470
R4-10k
R5-2.2k
R6-470k

This particular amp will be a new one (wall powered-will be using 24vdc)

Now what do I do with R2?

Since I am using R8 (47ohm) to match impeadence how does this figure into the equation?

Boy! I may need a little help with this one!

I am shooting for an overall gain of 12 with the crossfeed.

I will be using this with 3 phones.
Beyer 770 (250)
senn580 (300)
grato 225 (32)

 

[puppyslugg]

Your Meta will be exclusively AC powered ?

 

[dta116]

Quote:

Originally posted by puppyslugg Your Meta will be exclusively AC powered ?

Yes for sure, This will be used with my home stereo.

 

[puppyslugg]

If you have no intention of using batteries with your meta, you can eliminate vgd, buffers, etc. and it may sound better. Of course, you will need a +-psu, preferably well regulated.

 

[tangent]

Quote:

Well a 6db loss is eqivalent to reducing the output power to 1/4th the original.

No one said anything about "power" -- that implies wattage. When you talk about gain increases or decreases, you're talking about voltage, which obeys slightly different rules when you talk about decibels. A 6 dB drop in voltage means the output is 1/2 the amplitude, not 1/4.

Quote:

So as I calculate the new gain for my Meta42 (AD843KN), I come up with a multiloop gain of 19.9 with the inner-loop gain of 240!

When you increase the gain of the amp to counteract the voltage attenuation of the crossfeed circuit, you don't need to change the META42's inner loop gain. Just change R3 and R4 such that the overall gain is now 2x higher. The simplest way is to just halve the value of R3. (There are more refined ways of going about this, of course, but this suffices for common purposes.)

Keep in mind, you don't have to make the gain 2.00000 times higher -- 1.91362 times higher is close enough. (If you want to get frickin' picky, a 6 dB voltage gain isn't 2.00000x anyway...) Just find a resistor value that's close enough to half your current R3's value. Or if you want to be clever, solder a second resistor of your current R3's value on top, so that you get a parallel resistance, giving half the resistance of one resistor.

Quote:

Now what do I do with R2?

Nothing. That's irrelevant to this discussion. R2 mainly matters when talking about the pot's value. Its value also starts to matter when you're using uncommon op-amps, but nevermind that...

Quote:

Since I am using R8 (47ohm) to match impeadence how does this figure into the equation?

It's too small to matter. Yes, it's in the feedback loop, but the value is insignificant when worrying about overall gain.

 

[dta116]

Thanks for clarifiying that Tangent. I makes a lot more since now.

I think I'll build a second model w/crossfeed for wall power with the AD843's in it and swap the AD843's in my battery model for the AD8620 for portability and less current draw.

Then on to the tweaking stage, the battery model seems a little BRIGHT for me, needs more bass so the AD8620 may be a better choice.

A bigger box and more power for the wall model, and Max it out.

Thanks for your input, and setting me straight, apparantly I was confused with the multiloop thing.

I will post my findings when I get them side-by-side.