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Old 6th September 2011, 02:09 PM   #2651
tvi is offline tvi  Australia
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Nothing like the complicated Satri circuit from japan
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Old 6th September 2011, 02:25 PM   #2652
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Biaing of Q4, Q5 can be done simpler but it is ok. The transistors cost virtually nothing.
By why do they add a criss crossed second current mirror ? To raise output impedance ?
Anyway, thanks for sending me that circuit. I have never seen a full Satri before except a rather simple Head Phone amp from Korea.

Last edited by Joachim Gerhard; 6th September 2011 at 02:38 PM.
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Old 6th September 2011, 02:31 PM   #2653
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Quote:
Originally Posted by tvi View Post
Nothing like the complicated Satri circuit from japan
I consider this a masterpiece of bull**** electronics.
Note: more similar stages can easily be added for
further complication. Would be my preferred way
if I had a semiconductor plant.

Last edited by as_audio; 6th September 2011 at 02:39 PM.
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Old 6th September 2011, 02:31 PM   #2654
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Here is what i have......
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Old 6th September 2011, 02:34 PM   #2655
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And this ....
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Old 7th September 2011, 04:17 AM   #2656
EUVL is offline EUVL  Europe
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Joachim,

Re circuit is post #2644, why not just use a 4-transistor Wilson Current Mirror ?


Patrick
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Old 8th September 2011, 03:57 PM   #2657
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The helper transistors ease matching of Hfe because they compensate the base current.
The differential feedback resistors should lower DC offset and distortion. I have not tried it in this position. See a circuit i posted on your thread where they are in the usual position.
For an I/V converter this should work well because only a rather low value resistor is needed for the desired gain at the output to ground. For an AIOG RIAA stage i need more output impedance so putting the differential feedback resistors parallel to the mirror network screws up the desired frequency curve ( RIAA ) with the high value parts i choose.. I could try a compromise. Say 100kOhm differential feedback resistors plus lower value RIAA components. The output impedance of the fed back mirror could then be assumed to be to 50kHz but maybe i am wrong here. The disadvantage of that arrangement would be that the circuit has to throw considerable current around and that lowers dynamic range i think. To put the resistors " one story up " is my attempt to end up with a use full high output impedance and still get some benefit from the feedback. There are many other mirrors possible, for example the mirror with cascode that is NOT the same as a cascode current mirror.
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Old 8th September 2011, 04:09 PM   #2658
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I designed a tone control. Basically it is a low noise version of the JLH-Baxandall with one of my buffers at the input plus a volume control ( can be left out ).
The interesting thing is that you can set it up to mimic the RIAA curve quite closely so putting the switches and potentiometers in the right position you need only a linear amplification stage with enough gain and you have an unusual phono stage. The controls can mimmic other curves too so you can make recordings that are not cut with the RIAA curve digestible. Putting a phono stage with RIAA included in front of it you can use the controls more supple for the same result. You can use it of cause in the original intent to EQ flaws in the recording, lower hiss or ruble or have some control over the speaker-room interface.
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Old 8th September 2011, 06:04 PM   #2659
MiiB is offline MiiB  Denmark
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why not 10 Kohm...and adjust the riaa accordingly...or will that reduce gain too much..??
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Old 8th September 2011, 06:29 PM   #2660
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I do not understand. The potmeters are 10kOhm.
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