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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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Old 3rd September 2012, 02:26 AM   #621
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Quote:
Originally Posted by RNMarsh View Post
1. If I were building in high volume, i would have the devices sorted/graded at the factory. And, with cheap labor used, the final batch can be quickly determined. This would be true with any complimentary jFET used.
Good luck, that is generally frowned upon these days and would be a huge premium. The best you get now is buy lots and maybe we'll take back the rejects. It's not like you can pair off any of them the Vp range is huge and the ones at 4-6V just are impracticle to use.

You would definately be better off buying a million pieces for 25-30K and doing it yourself and eating the rest. You could always bag them up and sell them on eBay.
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Old 3rd September 2012, 02:31 AM   #622
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-100 db of 2-3 order without negative feedback? Impossible.
There's lots of feedback there just no servo. I see the 1V @ 1kHz now, I was thinking more 20V p-p at 20kHz for -100dB at G = 26dB.
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Old 3rd September 2012, 04:12 AM   #623
RNMarsh is offline RNMarsh  United States
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Originally Posted by scott wurcer View Post
. The best you get now is buy lots and maybe we'll take back the rejects.
You would definately be better off buying a million pieces for 25-30K and doing it yourself and eating the rest. You could always bag them up and sell them on eBay.
Fine. Do that then. I did not find it a problem getting them on eBay and I didn't find it took long to match them from the 100 pc I bought. Got way more matched pair than i needed. I'd use the cheap labor available for such work. Probably do some test automation for sorting. Its all do-able.
[I get the point - but 1 million pieces is exagerated and far more than needed for the numbers talked about... that would net me 200,000 matched pair! Cost more like $2-3K worth. Again, very do-able.]

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Old 3rd September 2012, 04:15 AM   #624
RNMarsh is offline RNMarsh  United States
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Originally Posted by scott wurcer View Post
There's lots of feedback there just no servo. I see the 1V @ 1kHz now, I was thinking more 20V p-p at 20kHz for -100dB at G = 26dB.
1-2 volts rms will drive anything. What needs 20v p-p? Is that somehow a strength feature?
If using it as a line stage after a phono preamp then maybe 20+ db gain is needed. In the digital equipment (ADC/DAC/CD/DVD) and power amps used today, such gain isnt needed.
But no problem tweeking it for other outputs or gain or fb etc.

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Old 3rd September 2012, 04:17 AM   #625
RNMarsh is offline RNMarsh  United States
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Originally Posted by Wavebourn View Post
-100 db of 2-3 order without negative feedback? Impossible.
probably true.... but I never said that: w/o High gnfb and with wide open loop bw for the audiophiles was a goal.

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Old 3rd September 2012, 04:35 AM   #626
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Originally Posted by RNMarsh View Post
probably true.... but I never said that: w/o High gnfb and with wide open loop bw for the audiophiles was a goal.
Your amp actually have that High gnfb. But it is fine, since open loop bw is wide enough for high gnfb on 20 kHz; what is bad when it is low on 20 kHz, even if very high on 10-100 Hz..
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Old 3rd September 2012, 04:48 AM   #627
RNMarsh is offline RNMarsh  United States
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Originally Posted by Wavebourn View Post
Your amp actually have that High gnfb. But it is fine, since open loop bw is wide enough for high gnfb on 20 kHz; what is bad when it is low on 20 kHz, even if very high on 10-100 Hz..
Well it is relative to opamp open loop gain of 100+ db's at 10Hz.... makes my circuit look like mid-level amount. Not low nfb but not high either.

Note: It wasnt developed as an 'op-amp' competitor for this forum. It's a somewhat different animal. It was for a different project last year. I threw it up here... mostly to show the zero TC and 'audiophile' specs and features they like. Its actually over-kill for my appl but its hard to make a bad performing circuit from a good topology.

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Old 3rd September 2012, 07:05 AM   #628
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Originally Posted by fitzfish View Post
How about a simple circuit with an SE output stage...
I'm guessing that this Kaneda-inspired topology will perform/sound better with just 7 actives, although it's arguably 3-stage if you count the output CFPs as two stages. It will also work fine with a BJT LTP.
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Old 3rd September 2012, 08:53 AM   #629
zinsula is offline zinsula  Switzerland
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Originally Posted by Wavebourn View Post
-100 db of 2-3 order without negative feedback? Impossible.
Depends.

From Stereophile Measurement:
Ayre KX-R, spectrum of 1kHz sinewave, DC–10kHz, at 2V balanced into 100k ohms (linear frequency scale; left channel blue, right red).

For sure, it has no GNF.

Of couse, it will not be this performance into 30 Ohms, if you're not going to increase bias currents.
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Old 3rd September 2012, 11:59 AM   #630
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Originally Posted by Wavebourn View Post
-100 db of 2-3 order without negative feedback? Impossible.
Never say never - current-mode open-loop topologies are indeed capable of very low THD: I've built and tested a HP amplifier based on a pretty standard architecture (diamond in - transimpedance gain stage - high current diamond out) whose THD is in the -100 dB range (low order only) @ 1 kHz, 0 dBV into 30 ohm. And it sounds very good, too , but it is by far too much complex to be mentioned here (about 20 BJTs - basically a discrete CFA). You can easily convert it to closed-loop, and that's the reason why I gave a try to this architecture.

I think the Ayre KX-R is based on the same concept.

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