Mpp

[Salas]

Originally Posted by MiiB

this is the only chritical piont as i see it....reason is that even small differences in the mirror resistors will cause the the riaa circuit offset values to slide up and down, as a product of the mirror output impedance (which is big) and of the combined DC impedance of the RIAA network and buffer impedance. even 1 ohm makes a big differnence...So this for sure needs some trimming. 10K trimmer i both positions would not be bad....
The buffer has a permanent -15 mV offset (in my simulations) which is corrected by the servo, So it could be a good idea to adjust the RIAA node to app +15 mV or simply 0 mV after the buffer

So trimmer pads can be welcome, and its value or very use of it or not can be an open option decided on initial behavior (BJTs matching level reasons in each build etc.).

[Joachim Gerhard]

I found a silicon carbide diode that is semi affordable :C4D02120A Cree, Inc. Schottky (Diodes & Rectifiers)

[MiiB]

To the best my knowledge the place to balance the circuit i by adjusting the current-mirror resistor...the servo does the same, but it dose so changing the currents through all stages, this resistor adjustment just balance's th circuit by compensating for the gain differences in NPN PNE transistors. The servo can then take care of the thermal drift.

[Bksabath]

Originally Posted by Joachim Gerhard

Bksabath, what schematic are you using ?
I miss the common mode coils.

Beter?

My PCB software has a poor library and I am using Pads
(RS has free download with much beter components library and same functionality.)
I have used 5 mm MKP outline for the 100 nF
I left the ground pads for the output capacitors out those can be aded at any time.
Probably someone will use Mundorf silver in oil there and those are preaty big.

Just noticed mistake in the Farnell book that spec coil at 100mH
On the intraweb catalog is clearly 100uM

would it be possible to arrange group buy for comon mode coils please?

I will rewiew PCB with exact size ASAP

[Joachim Gerhard]

I have published that before but i do it again :
This is the common mode choke i am using :CAF 0,6-100 - Stromkompensierte Drossel, 100mH, 20 - 30mm - Stromkompensierte Drosseln bei reichelt elektronik
We could organize a group buy.

[Bksabath]

Tanks for your patience
I will get specs for pin out and change PCB it only takes a couple of minutes

[Bksabath]

I have found Spec sheet
CA type F stand for flat encapsulated
Pin out is from dimention on botom of PDF 20 X 30
Will change that no problem

[Joachim Gerhard]

Thanks.

[Joachim Gerhard]

Hesener, C5 should be 1uF printed on the PCB and not 100nF i think, i also can not find the 1MOhm resistor from output to servo.

[Joachim Gerhard]

What is the big, single 15kOhm resistor in the middle of the PCB, left of the RIAA ?