Output symmetry of AU-101

[Mirilaj]

Hi folks, I've been restoring my AU-101 and when measuring the output symmetry , i discovered this:


The voltage measurements look good enough:





And here is the interesting part. After reducing the asymmetry by increasing R814, the sound changed and I am not sure if it got better. IMHO It became saturated and restricted.
As a result of the asymmetry removal, the collector current of TR802 dropped a bit and I restored it by reducing R822. Still, the sound was worse and eventually I decided to keep the factory asymmetry.
Giving that the asymmetry leads to uneven clipping, do you think Sansui would allow this for the sake of a specific sound character? Or I get a bit crazy

 

[CrSens]

If I remember correctly Au-101 is cap coupled, you can't measure offset without the load because the DMM is so sensitive it picks up minute leakage current through the capacitor. There is no offset with the speakers connected.

 

[Scott Muni]

If I remember correctly Au-101 is cap coupled, you can't measure offset without the load because the DMM is so sensitive it picks up minute leakage current through the capacitor. There is no offset with the speakers connected.

The resistance load of the speakers is enough to drop the offset to 0. All of my cap coupled amps do this.

 

[Scott Muni]

Off topic question. Have you measured the watt output of this 101?
Mine, after full resto will only output 13.2 into 8 ohm with both channels driven. A little shy of it's 15 watt rating.

 

[Mirilaj]

If I remember correctly Au-101 is cap coupled, you can't measure offset without the load because the DMM is so sensitive it picks up minute leakage current through the capacitor. There is no offset with the speakers connected.

CrSens, you are right, AU-101 is cap coupled and I meant "asymmetry" instead of "offset". I will correct the post.

 

[Mirilaj]

Off topic question. Have you measured the watt output of this 101?
Mine, after full resto will only output 13.2 into 8 ohm with both channels driven. A little shy of it's 15 watt rating.

I have not measured the power

 

[CrSens]

Hi folks, I've been restoring my AU-101 and when measuring the output symmetry , i discovered this:

View attachment 3285584
The voltage measurements look good enough:

View attachment 3285625

View attachment 3285596View attachment 3285597

And here is the interesting part. After reducing the asymmetry by increasing R814, the sound changed and I am not sure if it got better. IMHO It became saturated and restricted.
As a result of the asymmetry removal, the collector current of TR802 dropped a bit and I restored it by reducing R822. Still, the sound was worse and eventually I decided to keep the factory asymmetry.
Giving that the asymmetry leads to uneven clipping, do you think Sansui would allow this for the sake of a specific sound character? Or I get a bit crazy

If there is no provision for adjustment (trimmer) I would guess that's how they designed it.