SSB01 prototype build

[peranders]

The voltage across R1 is -431mV (0.4uA input offset current) and this leads to Q11 emitter sitting @~+170mV, instead of ~+600mV.

[peranders]

Please measure the used supply voltage and all voltages across resistors and all base-emitter voltages. Have you made patches on both sides? I'm interested in which currents you'll have. Short also the input so you don't include the input bias current in you measurements.

[andrewt]

Input not shorted. Output stage fitted. PSU+-15.05V
voltage across -431mV, 26.3V, 0.589V, 0.588V,  2.73mV,  2.73mV, 21.3mV, 21.3mV
.. ..  resistor  .. R1, .. .. . R4, .. . R7, .. . . R6, .. .. R9, .. . . R8 . . .  R11, . . . R12
.. current .. .. 0.43uA, . 1.2mA, 2.67mA, 2.67mA, 2.73mA, . 2.73mA, 4.3mA, . 4.3mA
output offset =-789mV


input shorted. Vr1=0.0mV output offset -6.2mV

[peranders]

Looks pretty good. If you have the opportunity I would like to hear how it works and sound in cooperation with an opamp and possibly use it as an headphone amp or preamp.

Was R5 shorted?

What about the voltages over R11 etc?

[andrewt]

r5 was shorted with solder as instructed & C1 omitted.

Attached a 100k pot to input and connected that to Rs=200r.

minimum output offset 6.7mVdc
maximum output offset 31.6mVdc
The input sees approximately 25k @ maximum (-6dB) and output sat at 0.2mVac.

previous post corrected

[peranders]

Thanks Andrew. Mission completed. Please report back if you'll ever use this buffer.