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RCruz
nhinstruments
diyAudio Member

Join Date: Sep 2006
Location: Wallis
Here it is Rev 1 with a reviewed gm factor.
Attached Files
 Simplistic calculator Rev 1.zip (83.9 KB, 51 views)
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RC

Salas
diyAudio Chief Moderator

Join Date: Oct 2002
Location: Athens-Greece
Quote:
 Originally Posted by RCruz 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.

 19th January 2013, 09:06 PM #9043 buzzforb   diyAudio Member     Join Date: Oct 2010 Location: Burlington, NC 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. __________________ ...Shape the sound , Man! Last edited by buzzforb; 19th January 2013 at 09:24 PM.
 19th January 2013, 09:24 PM #9044 Salas   diyAudio Chief Moderator     Join Date: Oct 2002 Location: Athens-Greece 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.
 19th January 2013, 09:29 PM #9045 buzzforb   diyAudio Member     Join Date: Oct 2010 Location: Burlington, NC I have 30mV across Rs, but only 5.8V at drains of jfets. Will double check orientation. __________________ ...Shape the sound , Man!
 19th January 2013, 09:44 PM #9046 buzzforb   diyAudio Member     Join Date: Oct 2010 Location: Burlington, NC Gonna replace bc560, as all else checks out. __________________ ...Shape the sound , Man!
 19th January 2013, 10:44 PM #9047 Salas   diyAudio Chief Moderator     Join Date: Oct 2002 Location: Athens-Greece Maybe you overcooked something with the iron?
 19th January 2013, 10:48 PM #9048 buzzforb   diyAudio Member     Join Date: Oct 2010 Location: Burlington, NC 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. __________________ ...Shape the sound , Man!
 19th January 2013, 10:50 PM #9049 Salas   diyAudio Chief Moderator     Join Date: Oct 2002 Location: Athens-Greece Its all over the place.
buzzforb
diyAudio Member

Join Date: Oct 2010
Location: Burlington, NC
Quote:
 Originally Posted by Salas Its all over the place.
Your saying mulitple things are wrong?
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