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Old 15th October 2012, 04:59 PM   #8171
Rush is offline Rush  United States
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Default DCB1 added to output

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Originally Posted by Rush View Post
I found a drawing buried in this thread that showed a B1 cap coupled out, so I modified it.
See if this would work.
Question is where to break the ground as the supply for the B1 will also be used for my crossover or it could be from my Mesmerize which ever you think best. Now that I am thinking about it the Mesmerize is closer to the phono and may provide less chance of grounding issue.

Thanks Salas, maybe others will appreciate this exercise as well.

Rush
OK, received the caps, Mundorf 0.1 uF Silver and oil.
Took out the direct coupled JFET, added a 0.1 uF cap with 1 meg to ground on the RIAA board. Then ran to an out board DCB1 sub board and pulled power and ground from the Mezmerize B1 Buffer. I am not fretting about large caps anymore and no hum issues, sounds fantastic.
This is a must do, actually the Mezmerize B1 Buffer board could have double set of DCB1s before and after the volume as I have essentially done and it wouldn't hurt. Four JFETs are a lot cheaper than high quality, large value, coupling caps.

Thank you Salas,

Wonderful stuff!

Rush
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Old 15th October 2012, 06:15 PM   #8172
Salas is offline Salas  Greece
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Cool.
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Old 15th October 2012, 06:20 PM   #8173
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Quote:
Originally Posted by RCruz View Post
After finishing the shunts I am now preparing myself to build this new toy.

For second stage cascode I have severall options:
R10 = 6200r with Vdrop=23V => Idq= 0.0037 so if Vgsq=0.141 => Rs = 38r
R10 = 6800r with Vdrop=23V => Idq= 0.0033 so Rs = 43r

Why not to use:
R10 = 5600r and Rs = 34r ?
6800 & 43 worked precisely on my breadboard. 43 gives less THD than 34 is enough reason.
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Old 15th October 2012, 06:33 PM   #8174
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Parlez vous français?
Oui... tout le monde le fait par ici
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Old 15th October 2012, 06:38 PM   #8175
RCruz is offline RCruz  Switzerland
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Quote:
Originally Posted by Salas View Post
6800 & 43 worked precisely on my breadboard. 43 gives less THD than 34 is enough reason.
Do we get more gain with 6800 ohm ?
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Old 15th October 2012, 06:39 PM   #8176
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Than 6200, 38? More or less the same.
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Old 15th October 2012, 06:49 PM   #8177
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Old 15th October 2012, 07:32 PM   #8178
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I only trying to learn in the process of building.... In the breadboard with a 8mA K170, I get only 10.7V on the BF245C Drain... is that enough ? You posted we should get 12v there.

I am using a 6800 Rd and a 43 Rs
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Old 15th October 2012, 08:05 PM   #8179
Salas is offline Salas  Greece
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Yes its enough. The most it may do is you are bit better for gain. With my parts I got 12V. Maybe your BF245C opens your K170 a bit more than mine for Vds. Or our DMMs show IDSS little different for our K170.
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Old 15th October 2012, 08:15 PM   #8180
RCruz is offline RCruz  Switzerland
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Nice.... It is a very good practice to experiment in the breadboard before actual implant

I am improving my methods with time.
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