LTspice: P3A bias

[jacques antoine]

I am learning LTspice using the excellent tutorial provided by Mooly (many thanks!). I can now calculate THD and op values on Rod Elliott's P3A.
However, when I simulate the recommended P3A bias setting, it does not seem to work properly: I cannot get it low enough. I must be missing something. Could someone help? Thanks.

Files are attached

Jacques

 

[djoffe]

Your BD-139 and BD-140 spice models are not good. I see they are the standard models from Onsemi, but they aren't correct.

If you check the fairchild data sheet, (google BD139.pdf) you'll see that the Vbe(on) with 10 mA of collector current is about 0.65 volts.

If you look at the sim, it says something like 327 mV under similar conditions.

Use Bob Cordell's models:

* BD139C - created April 13, 2011 copyright Cordell Audio
.MODEL BD139C npn
+IS=150e-15 BF=260 VAF=99
+IKF=1.2 ISE=70e-15 NE=1.2 NF=1.0
+RB=5 RC=0.01 RE=0.08
+CJE=293e-12 MJE=0.33 VJE=0.67
+CJC=49e-12 MJC=0.39 VJC=0.52 FC=0.5
+TF=585e-12 XTF=10000 VTF=35 ITF=20
+TR=10e-9 BR=78 IKR=0.14
+EG=1.21 XTB=1.14 XTI=3 NC=1.45
+ISC=19e-12 NR=1.0 VAR=7.5 IRB=0.03
+RBM=0.001 XCJC=0.53 mfg=CA041311
*
*
* BD140C - created April 13, 2011 copyright Cordell Audio
.MODEL BD140C pnp
+IS=120e-15 BF=113 VAF=140
+IKF=1.5 ISE=1000e-15 NE=1.5 NF=1
+RB=5 RC=0.01 RE=0.1
+CJE=220e-12 MJE=0.35 VJE=0.7
+CJC=68e-12 MJC=0.35 VJC=0.6 XCJC=0.5 FC=0.5
+TF=320e-12 XTF=10000 VTF=35 ITF=20
+TR=100e-9 BR=25 IKR=0.1
+EG=1.2 XTB=1.5 XTI=3 NC=1.4
+ISC=7e-12 NR=1.0 VAR=8 IRB=0.01 RBM=0.01 mfg=CA041311
*

They give me good results, though to get 65 mA of bias current you need to make wiper=0.6.

If you're stuck, I can send you updated files.


Update My Dynaco

Akitika GT-101 Audio Power Amplifier Kit

 

[jacques antoine]

Your BD-139 and BD-140 spice models are not good. I see they are the standard models from Onsemi, but they aren't correct.

Thanks Djoffe, it now works like a charm.
Not only there's fake transistors around but also fake models !
Cheers,

Jacques