MPP

[Joachim Gerhard]

This is 3 years old.

 

[Joachim Gerhard]

I build it and it worked great. Problem solved. Thread over after 3 posts.

 

[Joachim Gerhard]

Here is one channel.

 

[Joachim Gerhard]

I little bit off topic but i found this for our contributors that fly in a simulator :http://www.analog.com/static/imported-files/application_notes/AN-138.pdf

 

[as_audio]

Time to go to bed

 

[Joachim Gerhard]

What i would really like to build is the circuit you can download here. If we count a folded cascode as a one stage amplifier this can work. I have done the folded cascodes referenced to the constant current sources. That can be substituted with fixed bias.
The circuit may have some bugs but it is a starting point.

 

[Joachim Gerhard]

The values of the RIAA are only place holders. We need a simulation to find out the right values with the gain we want. I did not try the servo, it is only an idea.

 

[as_audio]

You can be sure this works fine.

The output current of the OP may not be high enough to compensate for offset
(remember Vled is a weak function of current). R15 should be zero.
Perhaps a non inverting servo is necessary here?
You may want to connect R16 to output VF3.

P3 and P4 are not required.
R4,C5 and R5 ,C* are also not required in my opinion.

 

[Joachim Gerhard]

OK, fine. When i find the time i will build it.

 

[Joachim Gerhard]

MiiB, i made a new BJT buffer, just in case we would like to try something different then the current Paradise J-Fet buffer. I call it a Szikley Diamond. Circuit comes soon.

 

[Joachim Gerhard]

Here is the buffer...

 

[MiiB]

I like the buffer...... wonder what input impedance is... could have influence on the RiAA circuit.

We can mirror in the current for the input . This way we have a good injection possibility for the servo

 

[Joachim Gerhard]

That depends on how high the idle current is in the input stage. Other then that the input BJTs are bootstrapped on CCSs so input impedance should be high.

 

[Joachim Gerhard]

Yes, of cause the CCSs on the input trannies can be a mirror.

 

[MiiB]

Ok... I'll draw something up....

 

[Joachim Gerhard]

fine

 

[FdW]

Here is the buffer...

Something like this just exercising some idea's

 

[Benedetto]

Hi Frans,
Thd looks nice !
Btw,
what are you guys trying to invent now ?

 

[Joachim Gerhard]

A one stage phono that is also a power amp.

 

[Joachim Gerhard]

For example high power output transistors could be added this way....