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Old 26th April 2013, 02:45 AM   #11
hewo is offline hewo  United States
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Join Date: Feb 2010
Default thankyou JMFahey

1. mine is not 0.5ma consumpt, instead .08mA maybe upwards to .2mA
2. hammond sells the potted miniature tranny 107X, 300K:600 impedance without bankruptcy
3. isn't their internal supporting circuitry bjt's inside the texas instruments opamps recommended? yes they are fet input for fantastic decoupling
4. i built craig anderton's cd4049 buffers (was it six fet's inside?) but somehow the delicious wet sound signature just did not voice, i don't know why
5. my class A se tube amps have NE5532 and TL072 fet inputs because the 1st stages need to be clean as opposed to 12ax7 heater hum else dc filament support circuitry. they sound good so i put sockets to replace when their channels corrupted over time (take baseline data to show this)
6. so i must review your tl061/for any bjt's internally. they may work well in this bariuto XLR boundaries
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Old 26th April 2013, 04:59 PM   #12
00940 is offline 00940  Belgium
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Join Date: Sep 2003
Location: Paris
With the kind of thing you have built, you really cannot drive anything passive (there is simply not enough current available). So you either have to build an external active DI (something like the Bo Hansen's one with an edcor xsm 10K:600 would be pretty cheap if you can rely on phantom power) or rethink your current preamp.

Is this what you built ? I had to correct your 82K to 8.2K to get working points (output at 12VDC and current at about 60a).

Click the image to open in full size.

Using the parts you already have, it probably would work better if you used a "cathode follower" kind of preamp, even at 0.5ma.

Click the image to open in full size.

Btw, isn't the 107X 100K:1K ? Furthermore, the frequency response is pretty bad in the lower frequencies.
Attached Images
File Type: jpg jfet.JPG (25.6 KB, 21 views)
File Type: jpg jfet2.JPG (20.7 KB, 19 views)
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Old 27th April 2013, 01:42 AM   #13
hewo is offline hewo  United States
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Join Date: Feb 2010
Default thankyou belgium 00940

1. yes the 1st schem is what i built (i'll post cellphone pics, and the various modules of iterations, variant japan jfets, epoxied assemblage onto lithium dispose
2. yes i will investigate cathode derived ac output signal, floating input on dc bias, but increasing noise-prone discrete components of two (input dc blocking cap c2 and input dc bias float resistor r6
3. 0.5mA is quoted by the j201 jfet buffer literature, boasting years of battery duty. maybe i am compulsively overly energy consciencious. the energy law says you can't derive energy from nothingness, so you are correct, what we are striving for on energy conserve has a rock bottom minimum pursuant to constraints, endpoint boundaries (barium to XLR)
4. attached is the pdf of hammond's 107X and it clearly shows 100K input impedance on ONLY one half of the windings owing to CT topology meaning if the CT is unused the input impedance should be 200K
5. long back in public schooling i stumbled upon nazi germany application of magnetic transformer amplification, of course for war use. permanent magnets and transformers are PASSIVE but somehow the nazi german scientists achieved imparting energy and resultant ACTIVE amplification. so there must be something missing, such as guitar string vibration cutting fields of flux emanating out of the p90 for example, where the addition of energy clearly is the relative motion between the flux and vibrating ferrite
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File Type: pdf 107X.pdf (357.4 KB, 2 views)
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Old 27th April 2013, 04:17 AM   #14
hewo is offline hewo  United States
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Join Date: Feb 2010
Default buffer_pics

pl find attached pics
camera is not the greatest
so try zooming for values
i noticed some AAAA batteries so that's the 2sk596 operating at lowest headroom
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File Type: jpg IMG_1964.jpg (643.7 KB, 13 views)
File Type: jpg IMG_1965.jpg (675.2 KB, 5 views)
File Type: jpg IMG_1966.jpg (742.5 KB, 6 views)
File Type: jpg IMG_1967.jpg (638.1 KB, 4 views)
File Type: jpg IMG_1968.jpg (519.1 KB, 6 views)
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