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A tweak

A few weeks ago I made a significant tweak with the S4 DAC. And, as significant as it is, it is also very simple. Moreover, it requires no parts – it is about the removal of the parts.

And the parts that have to be removed is the pair of the capacitors located between the D/A chip and I/V stage. So, the pair of WIMA caps, marked C403/C503.

The removal brings more natural scale, dynamics, and rhythm, and transparency, and more nice things. And the difference is not about nuances.

So, what these caps are for, in the first place? They are located between the D/A chip output and I/V stage input, to keep the I/V input impedance low across the higher bandwidth, and act as a low pass (more details here), and in some cases also to stabilize the I/V stage. (Please note that you can not use the caps here with the classic opamp I/V, since in that case, it is the opamp inverting input node.) I started using the caps at this point a very long time ago, with different I/V stages, so these caps are inherited. But, once again, the devil is in details.

I checked this tweak also with the Model S Mk3. It uses the same I/V circuit, but also slightly different parts and layout - and the result was similar. I don't have any original and Mk2 Model S, and Model S USB with me, but the result will be probably the same as with Mk3.

I also tried this tweak with the AYA II / AYA 4 (here these caps are marked C405/C406). The I/V stage here is different, but the tweak was again effective. I would expect the same result with the AYA III too, since it is the same I/V as AYA II and AYA 4.

At this time I am not able to test this with The Model and D-09, again simply because I don't have any sample with me, and at this time I'm not sure if this would be a recommended tweak also for these DACs or not. Even though all my I/V stages topologies during the last 16-17 years were similar, the actual designs of these DACs I/V stages were different.

Caution: Even though it is very simple, this tweak still requires some basic electronics understanding and skills. A DIY people will normally know what to do, but if you lack the skills in this area, please refer to the qualified servicing personnel. Either way, if you have any questions, please contact me for further information, or even better, post your question here, so everyone could benefit.

Hello Pedja,

Does this tweak also apply to the Aya II DS ? Thanks!

Hello Frederick,

Yes, it applies to all AYA DACs with the OPA861 output stage.

Rgds

Thanks Pedja...

I will be sending you email soon too regarding the 100pF cap tweak to get a stable 384 kHz stream..

Best regards,

Frederick

Quote from Pedja on 08/08/2019, 18:53

...I also tried this tweak with the AYA II / AYA 4 (here these caps are marked C405/C406). The I/V stage here is different, but the tweak was again effective. I would expect the same result with the AYA III too, since it is the same I/V as AYA II and AYA 4.

Dear Pedja, to be sure.. those two red caps should be removed. Just short wires instead.. Correct?

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They only should be removed, and that's all. No wires instead, because these are the shunt caps, and wires here would short the TDA1541A outputs to the ground.

BTW, sometimes these caps can be removed even without pulling the board out of the chassis, by using small cutters or scissors, to cut the caps' leads above the board.

Regards