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Old 17th March 2012, 10:45 PM   #3661
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Quote:
Originally Posted by john curl View Post
Good approach, Wavebourn.
I would be surprised if it was not patented yet,
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Old 17th March 2012, 11:07 PM   #3662
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by dvv View Post
Which is exactly what Dan d'Agostino did and used them for, a very complex arrangment.

For audio, I usually swear by BF 720/721 - a transistor with uncommonly low distortion and actual, effective Ft. But I find that two parallelled MPSA 42/92 devices actually beat him all around, albeit by just a little. Also, their price is so ridiulously low that you can easily afford a large population from which to select them easily. In a handy, TO-92 package.
Maybe you need a good phono pre -amp ...

Mark Levinson JC2 preamp with phono (collectable) | eBay

Supposedly good .... !!!
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Old 18th March 2012, 12:35 AM   #3663
tvrgeek is offline tvrgeek  United States
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First conclusion: two 1N4148's do a far better job of being a voltage reference to the single transistor ccs than a red or green, all else the same ( emitter resistor adjusted for the same current.) What effects the high frequency response is the transistor. I wish I had models of more parts, like the 2SC1085. BC5550 does pretty well over the 2N5551. Te other curious thing is that the current with LED's does nasty glitching when the diff pair turns off.

Putting in a big cap, (220u big enough?) did not have effects in the simulator. Reality may well be a different story. I see that done on the "mx50" boards.

Now to play with zeners and maybe fancy new fast soft recovery diodes if I can find a model.
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Old 18th March 2012, 12:55 AM   #3664
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Quote:
Originally Posted by scott wurcer View Post
Wadax looks like an exercise in over-the-topness.
My sentiments too - the reviewer seemed to mention the 6.4Gbit/s bandwidth between their FPGA and the external memory somewhat in hushed tones as if spraying bits around the PCB incredibly quickly indicated superior engineering skills
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Old 18th March 2012, 01:10 AM   #3665
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Quote:
Originally Posted by tvrgeek View Post
Putting in a big cap, (220u big enough?) did not have effects in the simulator.
Of course. Dynamic resistance of the LED is 4-5 ohms... What cap you need for that?
Quote:
Originally Posted by abraxalito View Post
My sentiments too - the reviewer seemed to mention the 6.4Gbit/s bandwidth between their FPGA and the external memory somewhat in hushed tones as if spraying bits around the PCB incredibly quickly indicated superior engineering skills
You know what part of specs did make me laugh? This one:
"USB lock range(KHz): No driver is needed. 48 KHz, 16-24 bits"
Oh... really??? Awesome, only if TI would get a hold of THAT marvel...

Last edited by SoNic_real_one; 18th March 2012 at 01:22 AM.
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Old 18th March 2012, 01:55 AM   #3666
tvrgeek is offline tvrgeek  United States
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Hard to beat the original configuration. Tried cascode and feedback, tried zenier, tried cap. Small differences, give and take. Three conclusions: Pair of diodes beats an LED, transistor matters a lot more, and fancy configuration does not buy much.

I bet everyone knew that.
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Old 18th March 2012, 03:08 AM   #3667
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Quote:
Originally Posted by tvrgeek View Post
First conclusion: two 1N4148's do a far better job of being a voltage reference to the single transistor ccs than a red or green, all else the same ( emitter resistor adjusted for the same current.) What effects the high frequency response is the transistor. I wish I had models of more parts, like the 2SC1085. BC5550 does pretty well over the 2N5551. Te other curious thing is that the current with LED's does nasty glitching when the diff pair turns off.

Putting in a big cap, (220u big enough?) did not have effects in the simulator. Reality may well be a different story. I see that done on the "mx50" boards.

Now to play with zeners and maybe fancy new fast soft recovery diodes if I can find a model.
See my signature.
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Old 18th March 2012, 03:26 AM   #3668
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Quote:
Originally Posted by tvrgeek View Post
Small differences, give and take. Three conclusions: Pair of diodes beats an LED, transistor matters a lot more, and fancy configuration does not buy much.

I bet everyone knew that.
I didn't. Experimentally, a red LED gives lower impedance and noise than a pair of diodes.
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Old 18th March 2012, 04:23 AM   #3669
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Hi,

Quote:
Originally Posted by scott wurcer View Post
Lots of great work, I don't think these folks get enough credit.
Yes, cutting records (especially all manual) is a serious art and one that is dying out. I wonder how many cutting engineers are left that can simultaneously read the score, gainride (to avoid overload or automatic compressors) and control the groove spacing at the same time AND get a perfect result almost every time!

Most folks simply do not know what went into making a record, from the master tape on a Revox C37, to cutting a lacquer master, via the various stages of electroplating to punching the centre hole and eventually pressing (and how many chances to screw it up royally).

Next to that making a CD Glass Master is trivial, though most of the time the CD pressing plants get that wrong too...

Ciao T
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Old 18th March 2012, 04:28 AM   #3670
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Hi,

Quote:
Originally Posted by Wavebourn View Post
The best way is to use digital delay once, recording resulting sidechain, then apply this sidechain to direct actual recording without any delays. Just 2-step procedure: adjust well then shoot once.
Funny thing, a good cutting engineer will do just like that, listen to the tape for the whole side, take notes of the time and what stands out, maybe listen again and then just sit down, gain control in one hand, groove spacing in the other, time display, score and notes taped up somewhere and cut.

For D2D cuts replace "listen to the tape" with "attend rehearsals".

Ciao T
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