John Curl's Blowtorch preamplifier part II - Page 738 - diyAudio
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Old 15th December 2010, 05:42 PM   #7371
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This is our 'idealized' primitive preamp, more or less. Any questions?
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Old 15th December 2010, 05:46 PM   #7372
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Version 1.2. Resistor R3 is now 1MOhm.
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File Type: pdf Student Preamp 1.2 - TINA.pdf (47.5 KB, 99 views)
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Old 15th December 2010, 05:49 PM   #7373
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Thanks, Joachim, now what must we do to make this a practical, rather than an 'idealized' design?
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Old 15th December 2010, 05:50 PM   #7374
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Don't the 'Folk' deserve a taste of moving coil? For the price of a little K369, shunt cascode?
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Old 15th December 2010, 05:53 PM   #7375
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No, MM only.
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Old 15th December 2010, 05:55 PM   #7376
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Rod, you might as well asked if our VW should have 4 wheel drive.
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Old 15th December 2010, 06:04 PM   #7377
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I've successfully removed R3 entirely in this sort of application without a problem. However, I understand why somebody might feel the need to retain it for safety reasons. Still, Mouser has 10M non-magnetic Dale resistors in stock and PartsConnexion has 10M PRP parts, too. Not as good as the Gigohms of the opamp input, but may have to do.

Again, if you want to stick with this opamp, then higher gain is merited to keep the common mode voltage low. (For those who aren't familiar with this, look at page 9 of the data sheet.)

A single LSK389 is undoubtedly better for a line stage, but once you start down that path...
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Old 15th December 2010, 06:07 PM   #7378
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The MM stage could have too much DC offset. If we asume 1mV input offset the output could reach 500mV.
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Old 15th December 2010, 06:08 PM   #7379
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CG, please go back and look at #7253. 1 Meg is OK, 10Meg is overkill. What else is wrong with this design, as shown?
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Old 15th December 2010, 06:12 PM   #7380
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Quote:
Originally Posted by john curl View Post
Rod, you might as well asked if our VW should have 4 wheel drive.
I won't argue. I suppose we are supposed to be getting used to Austerity, in Europe. But I had imagined the DL-103 to be a kind of Voelkstonabnehmer, or pick-up.
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