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Old 11th December 2012, 07:46 PM   #8061
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That is only a place holder.
Your circuit idea drawn up comes soon. It is immensely workable. Hats off.
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Old 11th December 2012, 07:47 PM   #8062
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Originally Posted by Joachim Gerhard View Post
Do you remember FSs phono i build him ? There you substituted a split supply with a single supply and it worked to my horror nevertheless.
That was the hat trick the other way around. The dove mutated into a cylinder.
This worked fine because you had a valid signal and supply ground scheme - floating
with single supply, but nevertheless at center because of equal supply currents ..

Will prepare dinner now.
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Old 11th December 2012, 07:59 PM   #8063
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I am a genius and i do not know it ! What a blessing.
Here is AS idea. It may have some small flaws but in general it should work.
Input stage could be referenced to negative supply too ?
I kept the cascoding of the J-Fets because that lowers gate current and noise. Also lowers input capacitance although with MC cartridge low impedance drive that may not be necesarry. Totally DC coupled.
Will eat some soup too and then listen to my new line stage, horror of horrors WITH CD !
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Old 11th December 2012, 08:20 PM   #8064
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And for what it is worth, this has a 'simulated' gain of just over 74dB.
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Old 11th December 2012, 08:24 PM   #8065
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Quote:
Originally Posted by Joachim Gerhard View Post
I am a genius and i do not know it ! What a blessing.
Here is AS idea. It may have some small flaws but in general it should work.
Input stage could be referenced to negative supply too ?
I kept the cascoding of the J-Fets because that lowers gate current and noise. Also lowers input capacitance although with MC cartridge low impedance drive that may not be necesarry. Totally DC coupled.
Will eat some soup too and then listen to my new line stage, horror of horrors WITH CD !
ok this is a hat off of a circuit. I really like it.
Looking at first glance it is non-inverting, has enough gain and it should be more stable offset wise than the other one and also can be completely DC coupled.
Very interesting indeed.
I will pass into simulation and try to see if capacitors from paradise (for the groupbuy we are ghaving now of the V-CAP) can be use here as well.
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Old 11th December 2012, 08:26 PM   #8066
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And for what it is worth, this has a 'simulated' gain of just over 74dB.
yeah still not enough. in practice you will have gain losses and also to get 61-62dB you will need about 80dB.
It looks like the latest approach is way better.
I have to check noise however as it might be noisier than our target!
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Old 11th December 2012, 08:35 PM   #8067
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Days of miracles and wonders....Frank Sinatra It Never Entered My Mind. - YouTube
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Old 11th December 2012, 09:07 PM   #8068
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Quote:
Originally Posted by Joachim Gerhard View Post
I am a genius and i do not know it ! What a blessing.
Here is AS idea. It may have some small flaws but in general it should work.
Input stage could be referenced to negative supply too ?
I kept the cascoding of the J-Fets because that lowers gate current and noise. Also lowers input capacitance although with MC cartridge low impedance drive that may not be necesarry. Totally DC coupled.
Will eat some soup too and then listen to my new line stage, horror of horrors WITH CD !
The npn cascode transistor is not required from an input capacitance point of view.
If you want low Vds on the Jfet it should work with the pnp alone also.

A servo will be required due to high gain and drift.

The "first" current source has to carry twice the current of the second one.
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Old 11th December 2012, 09:27 PM   #8069
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Originally Posted by as-audio View Post
The npn cascode transistor is not required from an input capacitance point of view.
If you want low Vds on the Jfet it should work with the pnp alone also.

A servo will be required due to high gain and drift.

The "first" current source has to carry twice the current of the second one.
well if you use a pair of IF3601 I bet you can get as much transconductance out of the pair with probably 10mA tot vs the 40mA of the 4 SK170!!
Can't wait for the new batch to come out....
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Old 11th December 2012, 09:28 PM   #8070
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also from a sonic standpoint strangely I always found the output stage to sound better without any cascade!!
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