Dimitri said than pickup can be modelled by 10-15 kohm. Now I've a question:
A MM pick up like GRADO (http://www.gradolabs.com/product_pages/cartridges.pdf)
has a resistance of 475ohm and an inductance of 45mH. That means 520 ohm @ 1kHz a lot far away from 10-15kohm od Dimitri.
What do you use to model pickup for noise and why?
Thank at all
Aiace
A MM pick up like GRADO (http://www.gradolabs.com/product_pages/cartridges.pdf)
has a resistance of 475ohm and an inductance of 45mH. That means 520 ohm @ 1kHz a lot far away from 10-15kohm od Dimitri.
What do you use to model pickup for noise and why?
Thank at all
Aiace
>but if you look at Hfe diagram you can see that gain at 100uA is half than 1mA. I think S/N at the end is almost the same.
If it's a mistake please tell me.
Yes, this is a mistake. The differential dc _voltage_ gain of the first long-tailed pair will be (R2+R3)/(2*26mV/Ie+R1). It is nothing to do with hfe - current gain.
>Dimitri said than pickup can be modelled by 10-15 kohm.
Yes, this is for typical MM pickup with a resistance of ~500ohm and an inductance of ~500mH.
I've opened the pdf of Grado, your pickup has ten times lower inductance. If it isn't a mistake I don't understand why Grado has that output
. If the inductance of your MM pickup is ~50mH, leave everything untouched. You are lucky!
If it's a mistake please tell me.
Yes, this is a mistake. The differential dc _voltage_ gain of the first long-tailed pair will be (R2+R3)/(2*26mV/Ie+R1). It is nothing to do with hfe - current gain.
>Dimitri said than pickup can be modelled by 10-15 kohm.
Yes, this is for typical MM pickup with a resistance of ~500ohm and an inductance of ~500mH.
I've opened the pdf of Grado, your pickup has ten times lower inductance. If it isn't a mistake I don't understand why Grado has that output
. If the inductance of your MM pickup is ~50mH, leave everything untouched. You are lucky!
My dear Aiace
Don’t put out your tongue at me
. Think before you type 
.
>Vu=gmd*Vd where gmd=Ie/(4*26mV)...so as high Ie as high the gain of Vd
This is not Vu-voltage, this is Iu-current! – and to remain E/2 voltage on collectors while changing Ie you should adjust R2,R3 correspondently
>I can't hear any noise from my phono
Very good
Ciao
Don’t put out your tongue at me
. Think before you type .>Vu=gmd*Vd where gmd=Ie/(4*26mV)...so as high Ie as high the gain of Vd
This is not Vu-voltage, this is Iu-current!
– and to remain E/2 voltage on collectors while changing Ie you should adjust R2,R3 correspondently>I can't hear any noise from my phono
Very good
Ciao
Ingenuously I trimmered RV1 before connecting the circuit to the pickup. After several days a suspicion is risen me.... I went to measure the outoput offset and it was 3V !!!!
So I trimmered again RV1 (with the pickup connected) and started to listen at same disks .... Fantastic !! It has been like I cleaned my glasses, or like I cleaned the kitchen windows from the vapor. Finally I obtained the transparency that I love.
Yes, my phono sounds very well, fast and deep low frequencies, very natural in human voices , extremely high dimanic sound, analytic like one x-ray, not noise at all.
I'm very happy of my work 'couse my thoeory of "virtual bilanced" was right
Thank you at all for your advices and patience
Aiace
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