Switchable Hi-Z input impedance, how ? - Page 40 - diyAudio
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Old 29th October 2012, 01:50 PM   #391
juma is online now juma  Serbia
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Standard Q&A:
How much gain do you need ?
What's the input signal level?
What power supply you have?
What's the load ?

Source Follower can't give you voltage gain - to accomplish that the parts must be mixed together differently...
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Old 29th October 2012, 04:39 PM   #392
tinitus is offline tinitus  Europe
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ah, juma, glad you are still around

well, I thought now that Im going to use +/-12V like you suggested for the j310/CCS buffer.....
but I have regulated supply, and 2x 18Vac trafo, so it could be almost anything

not sure I have all the answers, yet
the plan was to replace the k170 in simple boz with the j310
I think you mentioned 12db
and with its lower gain I could have more gain stages, instead of buffers
and only have buffer at output

might be 3 gain stages
one at input, another at tone control, and with another one around the att before output buffer
and then the the j310/CCS buffer output

reposting old not yet revised layout, just in case
Attached Images
File Type: png bass pre layout 220 boz.png (40.6 KB, 34 views)
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Old 29th October 2012, 05:49 PM   #393
tinitus is offline tinitus  Europe
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here revised with your j310/CCS buffer
but still with jboz gain stages
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File Type: png bass pre layout 300 boz juma buff.png (40.1 KB, 33 views)
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Old 29th October 2012, 11:18 PM   #394
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btw, also thinking about putting in 'optional' 12db active low pass and high pass xo
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Old 30th October 2012, 12:05 PM   #395
juma is online now juma  Serbia
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Simple 12dB gain stage with J310 would look like this. J310 is quite different from 2sk170 so it has to be configured differently for this task (12dB gain and about 5V of clean swing). Id is low (about 1mA), Zout is high, but it works nice and buffer will be used at its output anyway...
For 9dB gain, change R2 to 3k6, it will also make the gain stage more linear.
Attached Images
File Type: gif j310-12dB.gif (3.2 KB, 29 views)

Last edited by juma; 30th October 2012 at 12:09 PM.
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Old 30th October 2012, 03:38 PM   #396
tinitus is offline tinitus  Europe
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nice, thanks

now with +30V
but I suppose thats the price to pay for good voltage sving
will see if I can find a trafo for it

would it work with 12db active xo

I have tried to mate a 12db xo with the j310/CCS buffer, but not sure it will work
apart from some tube buffered curcuits, LC audio's xo is the only discretely built xo I could find
but he connects the feedback loop to ground instead
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File Type: png bass pre 300 low high pass xo.png (26.1 KB, 28 views)
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Old 30th October 2012, 09:03 PM   #397
juma is online now juma  Serbia
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It's OK.
You don't need two resistors to ground (HP section).
Look here:
Linkwitz-Riley Electronic Crossover
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File Type: gif LR-12dB-HP.gif (14.5 KB, 23 views)
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Old 30th October 2012, 09:11 PM   #398
tinitus is offline tinitus  Europe
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ah, I see, the resistor is 80K for 200hz
great
this will be fun
better begin to order parts
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Old 31st October 2012, 08:59 AM   #399
tinitus is offline tinitus  Europe
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gosh, those J310 SMD are small...2.9 x 1.3 x 0.9mm

with SMD resitors and caps, a high or low pass wouldn't take up much space, almost like nothing
wonder if there would be a double BC547 SMD

ehh, that would be a junction type, I guess

juma, any ideas/suggestions ? or am I too crazy now ?

would that be like BC847
http://docs-europe.electrocomponents...6b80dabb08.pdf
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Old 31st October 2012, 09:21 PM   #400
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thinking about mounting buffer and active xo on small boards with a dil socket adapter
would make it easy to change xo
or if no active is wanted, just mount a buffer board without xo

Quote:
Originally Posted by tinitus View Post
now with +30V
will see if I can find a trafo for it
for the J310 gain stages
I have the 0/18Vac trafo Im using now for the simple jboz
maybe I could try with a voltage doubler
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File Type: png bass pre 300 low high pass xo.png (41.8 KB, 14 views)
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