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

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Old 8th November 2012, 03:05 PM   #2031
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Looks good, thanks. The post notch thing is exactly one of the things I was going to try. I suspect the input null technique would also work well here. I have found the THD of the A/D and DAC's a little more than I had expected. BTW the developer got right back to me (he's actually in Romania).
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Old 9th November 2012, 12:44 AM   #2032
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No surprises on the output stage. At no load Gain = .99809, seconds -84dB, thirds -91dB. At 600 Ohm load Gain = .99098, seconds -79.4dB, thirds -80.5dB. Now to proceed to the compete amplifier. I am going to make daughter card for each variant on the input stage and compare with the output being the same.

These results are comparable to the sims, the seconds are a little bigger but that is of little consequence. 0.02% open-loop distortion is pretty good.
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Old 9th November 2012, 09:11 AM   #2033
fas42 is offline fas42  Australia
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Have had a bit of a play with Scott's output stage, trying 4 combinations of BJT models on a 600R load. Not much variation of the 3rd harmonic, about 2 1/2 db. But for the 2nd there was a variation of 10db, tending to confirm for this circuit that this is more dependent on the accuracy of the model, or characteristics of the real devices.

Frank

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Old 9th November 2012, 01:25 PM   #2034
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At 8ma of Iq, what class of operation are we in? How far can we push it into class A? Thanks, Ray
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Old 9th November 2012, 02:52 PM   #2035
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At 8ma of Iq, what class of operation are we in? How far can we push it into class A? Thanks, Ray
Well into class A at 600 Ohm load. Because the collector current of the predrivers is captured you can simply fire it up with the pot zeroed (always turns off the output) and trim measuring the total supply current until it is 8mA greater. BTW you can find the "magic" point where the thirds null, it might make an interesting experiment to adjust the 4.7 Ohm resistors so this happens at ~ 8mA. The values in the above schematic simply reflect what I had in my kit (closest 1% values). We don't stock below 10 Ohms so I simply paralleled two to make 5 Ohms.

A very esoteric point 10k source resistance actually supressed the thirds a little so there must be some vector subtraction going on at the ppm level. So one can see how counter intuitive observations can be made.
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Old 9th November 2012, 03:30 PM   #2036
KBK is offline KBK  Canada
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Looks I have a lot more to learn here than I initially thought as I only have an understanding for Scotch whiskey
Wine is a patience thing, I find.

Since I do not drink wine or alcohol in general, I'm the perfect person to buy wine and store it. Almost. (have to care enough to commit to the correct storage)

10-15 years later I can approach family or what not at a gathering and bring along "oh, just some crap I had left in the back room, for the past 12-15 years", and they tend to be quite happy with that.

(Not quite that simple, but pretty close)

But if I see a good beer in the fridge or have to pass by the +$100 bottles of hard liquor, or pass by the wine storage, I just drink water. Not even remotely tempted. I'm much happier and more clear headed with that, as experience has taught me.

Its the ~$500 an oz plant matter that keeps catching my eye.... hhhmm..uhhh... no. Must. Not.

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Old 9th November 2012, 03:35 PM   #2037
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Thumbs up Scott! Thanks! And I would like to know how to tweak the sweet spot and null the third. How warm are those 2n4401/03 getting? What voltage swing are we talking about? The JE990 used MJE171/181 to126 transistors. Are we going to have to resort to SLOW heavier output transistors for + & - 18 or 24v operation. I know there must be more modern faster transistors than MJE171/181. GREAT WORK! Ray
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Old 9th November 2012, 03:52 PM   #2038
KBK is offline KBK  Canada
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Thanks for making us all at the most just four degrees from Obama.

It's really a seemingly weird things, this.

It seems that if one stays around on the planet long enough ...and if one moves into given areas with some energetic will of some sort, one can finally (over the given time) get to the point where one can just 'pick up the phone' and make a connection (at the deepest or most rarefied levels) to just about anyone or any group.

However, one has to be careful with those connections and bridges, IMO and IME. To use them only when actually relevant and pertinent.
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Old 9th November 2012, 05:25 PM   #2039
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It's really a seemingly weird things, this.
I find the two degrees from J Edgar wierder.
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Old 9th November 2012, 05:41 PM   #2040
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I find the two degrees from J Edgar wierder.
Why? Nothing to wear?

jn
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