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Old 8th August 2007, 03:16 PM   #1021
steenoe is offline steenoe  Denmark
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Quote:
Originally posted by mpmarino


Yes, very appealing! Sounds like the perfect winter setup Also, the fact that you would even mention building 12 channels of an amp tells me you truly like it beyond what you've stated. Well, since you've built everything else 'round here already your opinion carries weight


I need to settle on a low power, high resolution, very quiet, and balanced amp for the 'drek squeaks'. I'd do a 'crippled F4' but it's not balanced. Suggestions??

I think a bridged f4 can handle the woofs.

EDIT: what is a KSA? besides a Krell

Septic?
The thought has been buzzin' in my head for a few days. Nothing decided yet, though.
As for a balanced tweeter-amp, a "Mini-Babelfish" or simply a Babelfish, would be a good choice Balanced input, J-fet frontend; what is there to be wished for, other than that? For tweeters, the J-fet frontend is a real bonus.
The KSA is in fact a Krell



PS ZM, those Bylund brothers are indeed doin' great.
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Old 8th August 2007, 03:22 PM   #1022
steenoe is offline steenoe  Denmark
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Quote:
Originally posted by Russ White
BPA is always an option I think, but why not just add more output devices to scale the current?
Hi Russ. Yes, that would probably be a more sane way to do it.
Actually I was playing around with the idea of putting the F4's in a SUSY FB-loop, using your TXD's. Not sure if the TXD's can swing enough voltage, but with effective speakers it would likely be enough. Another appealing thought.



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Old 8th August 2007, 03:26 PM   #1023
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Quote:
Originally posted by steenoe

Hi Russ. Yes, that would probably be a more sane way to do it.
Actually I was playing around with the idea of putting the F4's in a SUSY FB-loop, using your TXD's. Not sure if the TXD's can swing enough voltage, but with effective speakers it would likely be enough. Another appealing thought.



Indeed... In fact i will share something here that may be even more appealing...

Cheers!
Russ
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Old 8th August 2007, 03:36 PM   #1024
steenoe is offline steenoe  Denmark
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Quote:
Originally posted by Russ White


Indeed... In fact i will share something here that may be even more appealing...

Cheers!
Russ
Now thats exciting

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Old 8th August 2007, 03:52 PM   #1025
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Quote:
Balanced input, J-fet frontend; what is there to be wished for, other than that?
D'oh! I didn't think the babelfish was balanced

Hi Russ!

I'm probably in total cranial shutdown but - what is BPA?

oops, found it. It's a chip, right? You know good and well I'm not ready for those yet . I certainly know who to call when I am though

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Old 8th August 2007, 03:52 PM   #1026
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how about something like this?

Essentially its a discrete THS41xx type opamp. I have not tested it fully yet, at least not in this configuration, but I have a similar prototype working.

I wonder what Nelson would think... It seems to be a good combination to me.

Cheers!
Russ
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Old 8th August 2007, 03:55 PM   #1027
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You could use the circuit above with the F4 in the FB loop, or out.
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Old 8th August 2007, 04:01 PM   #1028
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Forgot to mention the key point, it can swing a lot of volts.
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Old 8th August 2007, 04:12 PM   #1029
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One other note, the compensation caps (C7, C10) are only required if the F4(or some other amp) is in the FB loop. Otherwise they are omitted. The value will need to be determined to suite the power stage.
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Old 8th August 2007, 04:24 PM   #1030
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Ok another factoid.

If you have an atteuator with a sufficiently low constant(or close) output impedance, you can omit the input(gain) resistors(R17, R18) and scale the feedback resistors(R16,R18) to suit your needs.

Example for AV of 10 you could use a "Joshua Tree" attenuator which has 750R output impedance and use 7.5K resistors for FB. This works very well actually.

Cheers!
Russ
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