Is something wrong with my ears?OR did I make a mistake in my work?

[kinsmen21]

The Six phono stage (F-1435) topology is very similar to that in the AU-9500 (F-2006A).

View attachment 1824782View attachment 1824784

Further, the F-2006 actually has an elevated bass response due to an error in the RIAA equalization (C619, C621, C623 and C625; R635 and R637); see this AK thread for further details: https://audiokarma.org/forums/index...0-phono-stage-riaa-equalization-error.716418/ Due to the similar topology, I would expect the Sansui Six to have a similar phono bass response. Since that is not your experience, I suggest that you review the installation of the new components for proper orientation or any other errors. I also suggest that the output high-pass capacitors (C615/C616) be increased to 3.3µF from 0.47uF. If you are interested, I can also suggest changes to the RIAA feedback for better adherence to the standard.

May I ask what one would expect by increasing C615/C616 to 3.3uF? I'll go in and swap mine out if it makes a noticeable difference in performance. Thanks!

 

[ConradH]

Thanks ConradH.
But i don´t know howto do ti.
Regards

Building an inverse network is easy. See http://www.hagtech.com/pdf/riaa.pdf I'd just build the first one they show. Obviously it will only be as good as the accuracy of the parts, so you need accurate capacitors.

But, to use it, you need basic test equipment. A signal generator and scope, though it can be done with a meter, so long as the meter has wide range AC response, which most DVMs don't.

Without those, all you can do is carefully check everything as has been described above, which, if you're lucky, might do the trick.

On increasing cap values, go with the recommendation of the person who did it and checked the results. I've run some Spice simulations on other circuits with the surprising result that increasing coupling or output caps didn't always change things in the direction you'd expect. No idea about this one.

 

[Leestereo]

May I ask what one would expect by increasing C615/C616 to 3.3uF? I'll go in and swap mine out if it makes a noticeable difference in performance. Thanks!

A general rule of thumb to minimize distortion within the passband of a high pass filter is to implement a cut-off frequency that is at least 2 octaves below the lowest desired frequency, i.e., in this case the F3 target is 5Hz. With the stock 0.47µF capacitor, the F3 is 17Hz, with a 3.3µF capacitor, the F3 is 2.4Hz.

 

[Leestereo]

...I've run some Spice simulations on other circuits with the surprising result that increasing coupling or output caps didn't always change things in the direction you'd expect...

Good point. A factor that may contribute to anomalous results when modifying coupling capacitor values is whether it is within the feedback loop. In this particular case, the feedback is taken before output capacitor.

 

[havols]

Thanks Moe
I will take this into account
greetings from Brazil

 

[maxhifi]

Another thing to consider, is that the AT95e is known to be a bright sounding cartridge. Perhaps you are just only now hearing it properly. Have you tried it with another phono state to confirm it is definitely the amp at fault?

 

[Quadman2]

This particular lament has come to the front before with a maj change in upgrades.

It's been pointed out that some have gotten used to the sound they had before, and the change over, albeit improved was thought to be inferior now.

Change can do strange things some times.

Q