Op-amp sound comparisons continued: inside a player.

Hello and welcome to my new post. After the op-amp comparisons we did in a Rotel RC-970BX preamp, me and Panos were wondering if changing the op-amp would also improve the sound quality of a player. For this test we choose our victim to be the mighty Sony MDS-JB930 QS MD player, a player that as we found out is performing excellent, making CD copies that sound like the original.



The Sony MDS-JB930 QS.

In order to perform our test, Panos modified the machine by installing 8 din DIP bases; this way we can easily exchange op-amps on the fly.



An op-amp base at the analogue in part of the circuit helped us changing the op-amp on the fly.

We choose to exchange the op-amps that are in the analogue inputs of the device. We then made some analogue recordings using different op-amps and compared the tracks in order to see if we could spot any improvements in the sound quality.

This is the original op-amp that the Sony has from the factory.

As we have found out with the Rotel preamp, the Burr-Brown OPA627AP op-amp was a clear winner and that is why we focused on comparing the original op-amp that Sony came with Vs. this Burr-Brown op-amp.



The Burr-Brown OPA627AP installed inside the Sony MDS-JB930 QS.

For the listening test we used vinyl album Stan Getz / João Gilberto Featuring Antonio Carlos Jobim ‎– Getz / Gilberto (Verve Reissues / Quality Record Pressings / Analogue Productions B0015625-01). We recorded two times the same track, with everything but the op-amp being equal. The MD player was then used as a transport, digitally connected to our modified and highly revealing Parasound D/AC-1500 DAC.

As usual, the test was blind, meaning that one of us would listen and the other would change tracks, without revealing to the listening to which recording he is listening to.

To our surprise, there was no difference in the sound quality of the two recordings. The op-amp seemed that did not affect the sound quality in this experiment, unlike like it did with the Rotel preamp. We couldn't understand why and to be honest, we wondered if we are kind of stupid and deaf.

Panos even made more recordings using Dire Straight Sultans of Swing from an 180g audiophile edition vinyl album and then bringing them to my system for listening - I am a happy owner of a Sony JA20ES player. After several attempts we ended up with a slight headache, but still we called it even - the op-amp did not affect the sound!

So the lesson learned was that changing an op-amp is not a panacea of sound improvement. At the Rotel, the op-amp is sitting alone in a simple circuit and is asked to drive a power amp. At the Sony, the op-amp together with quite a few other components is asked to be part of a team and drive an ADC (Analogue to Digital Converter). I assume that the ADC is an easy load and the other components limit the role of the op-amp. But whatever the reason might be, I have to admit that in the Sony we are dealing with a well designed circuit, that is not affected by the op-amp. So Sony made a wise decision in choosing the op-amp it did.

2021 update: We made a similar test, by changing the output op-amp at a Topping D50s DAC. 

As always, happy listening!

Chris