Studio Reference Amplifier

[thimios]

sr200 studio refer.

Bandwidth test video.Apex sr 200 studio reference. - YouTube

 

[tinitus]

Here it is.

mine have always looked like this

ok, thanks

 

[thimios]

sr200 studio refer.

Here it is.

I can't understand nothing.
These circuits show a parallel connection of zobel and loundspeaker.
In this case this is an intuctance dummy load,not a zobel.

 

[thimios]

zobel

mine have always looked like this

ok, thanks

zobel connection.

 

[tinitus]

thats how it is, yes
I only drew how it looks on the print board

 

[AndrewT]

Dear Adrew this is shematic last modified by Apex. Red values are the modifications.
Keep in mind that original schematic is functional also with a little problem an overshot
probably.

Thank you.
just 3 changes !

The HF decoupling is not shown.
The MF decoupling is far too low in value.
The Thiele Network on the output is not shown.

 

[AndrewT]

Thi,
what are the currents through R12 & 13 and through R27 & 28?

 

[apexaudio]

Thi,
what are the currents through R12 & 13 and through R27 & 28?

900uA and 25mA per resistor with 8k2 or 500uA and 10mA with 15k value of R11.

 

[AndrewT]

Thi,
Apex gave me the theoretical currents. What are your actual currents?

 

[thimios]

sr200 studio refer.

Thank you.
just 3 changes !

The HF decoupling is not shown.
The MF decoupling is far too low in value.
The Thiele Network on the output is not shown.

I hopr this help.

 

[SERGIODS]

I hopr this help.

Hello Thimios how tall your network inductance Zovel.

 

[thimios]

Hello Thimios how tall your network inductance Zovel.

See post#1184.

 

[thimios]

sr200 studio refer.

Thi,
Apex gave me the theoretical currents. What are your actual currents?

Oh sorry .
I can measure the currents in the afternoon.
Regards.

 

[apexaudio]

Oh sorry .
I can measure the currents in the afternoon.
Regards.

Measure voltages on resistor and calculate currents (I=U/R)

 

[keantoken]

Thimios, if the resistor is soldered with its leads mostly clipped off, then it should have minimal series inductance. That is one example. With your resistor being the core material of the inductor, I don't know how this affects inductor behavior for better or worse. I wouldn't expect a film resistor to do much unless it stuck to a magnet, but I really don't know anything about magnetics.

My response was to the post I quoted, where the resistor leads were left long and soldered at the ends. This would be okay, if the connections to the L/R were right across the resistor rather then inches apart.

 

[thimios]

sr200 studio refer.

Measure voltages on resistor and calculate currents (I=U/R)

of course Sr.

 

[thimios]

sr200 studio refer.

Thi,
what are the currents through R12 & 13 and through R27 & 28?

V across R12=24mV. I=0.5mA
V across R13=54mV. I=1.14mA
V across R27=1.042V I=10.4mA
V across R28=974mv I=9.74mA

 

[AndrewT]

Thi,
you need to sort the LTP balance first.
Change the Tail current until the Vdrop on the LTP emitters is identical.

Then remeasure the R27 & 28 voltages/currents.
Also check the output offset.

 

[thimios]

Thi,
you need to sort the LTP balance first.
Change the Tail current until the Vdrop on the LTP emitters is identical.

Then remeasure the R27 & 28 voltages/currents.
Also check the output offset.

Hi Adrew
output offset is zero.(servo presence)

''Change the Tail current until the Vdrop on the LTP emitters is identical.''

probably you mean closer matched transistors.
It's in my mind to do this.
It is just a prototype for functionality check.
In any cases this is the proof that it is not enough matching hfe
Thanks for your interest
Best regards

 

[keantoken]

Thimios, it is more important to match Ic than Vbe. That is why the voltage across the LTP degeneration should be set to zero, as long as output offset remains a sane value.