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Old 19th January 2013, 07:39 PM   #9041
RCruz is offline RCruz  Switzerland
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Here it is Rev 1 with a reviewed gm factor.
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File Type: zip Simplistic calculator Rev 1.zip (83.9 KB, 38 views)
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Old 19th January 2013, 08:47 PM   #9042
Salas is offline Salas  Greece
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Quote:
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Thank you

It was really mented as a tool for experimentation and comprehension... as is it is no substitute for a simulator and I really believe we should always breadboard before building anything.

Anyway, The scale factor of 2 in gain Equations is nominal. According to the National Semiconductor FET Handbook (1977), that factor can range from about 1.1 to 2.5 but is typically near 2, so I can easily adjust it based on your input.

Can you give me some gain figures ?
48dB build 28V output stage Rd 4k7 Vd = 11v and Rs 47r
48dB 28V input stage Rd 3k3 Vd = 14v and Rs 33r
57dB 37V output stage Rd 6k3 Vd = 10v and Rs 27r

I believe these will beenough to find a good compromise for the gain equation.
I only have the folded on breadboard right now. You should measure your builds too to see about deviations. A test record and a DMM on AC are enough. Probe the 2nd stage's input and output and you calculate gain by the out/in division.
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Old 19th January 2013, 09:06 PM   #9043
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Ok fellas, first channel fired up. Something not right. 35V rail. 8.1V at base of bc560. 5.9v at top of Jfet. 8.1through 3.9r sorce resistors of jfets. Nothing at collector of bc. I am leaning towards bad bc560.
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Old 19th January 2013, 09:24 PM   #9044
Salas is offline Salas  Greece
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Recheck the BC its a PNP and its correct orientation first. All the circuitry realization around first stage for that matter. You should get 8.1V plus Vbe on top of the input Jfet(s) and 25-30mV across each Rs.
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Old 19th January 2013, 09:29 PM   #9045
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I have 30mV across Rs, but only 5.8V at drains of jfets. Will double check orientation.
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Old 19th January 2013, 09:44 PM   #9046
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Gonna replace bc560, as all else checks out.
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Old 19th January 2013, 10:44 PM   #9047
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Maybe you overcooked something with the iron?
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Old 19th January 2013, 10:48 PM   #9048
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I am in the bermuda triangle here.

Top of BF245 12V
Base and emitter of BF245 - 8.1V
Used pot to get emitter of bc560 to 8.1V
Nothing on collector.
Jfets have 31mV acorss 3.9R source resistor.
Output gain fet has 4.7V across drain. Same thing at output, as the cap and pull down resistor are not added yet.
16V at top of the buffer.
R5/6 sitting at 6.71K
This thing should be working.

Gonna try the other channel. Just does not make sense.
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Old 19th January 2013, 10:50 PM   #9049
Salas is offline Salas  Greece
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Its all over the place.
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Old 19th January 2013, 10:52 PM   #9050
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Its all over the place.
Your saying mulitple things are wrong?
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