Luxman Integrated phono stage improvements

[Kei]

Got some of the components through over the last few days. Sorted out a majority of the signal path resistors, the riaa op-amp, a few of the remaining electrolytic caps and some of the new film caps. The difference in sound already is actually quite surprising. The low-end has really picked up a lot. The mids and highs don't sound particularly different perhaps "slightly" more detailed but not a big difference like the LF. The change in the riaa was huge (probably down to the op-amp) the brightness and sibilance is gone and it sounds almost perfect already. (even without the rest of the new film caps which I'm waiting for.) I found some mistakes in the service manual as well. C202a/b are 4.7uF not 47uF.


Some pictures for those interested.


New vs old PSU filter caps


New vs old rectifying diodes


Main filter cap decoupling (EPCOS 305Vac 100nF were supposed to be those wima FKP 100v 1nF caps but they were way too small)


Transformer decoupling, left out the series resistors for now (can't think of a way to fit them neatly)


RIAA, BurrBrown OPA2134 fitted via a nice socket. 3.3uF electrolytic caps replaced with panasonic ecwf polypropylene. (rather large)


Amp, New Wima FKP caps in place, the silver mica in place of the old ceramic and some of the metal film resistors. Not sure if i'm going to go the whole lot on the resistors. Another pair of panasonics in place of the original electrolytic caps too.


Switches, All metal film resistors done and vishay MKP1837 in place. (not the neatest here due to their size)


Function switch, all electrolytic caps replaced with PP film.


Tone control, two of the film caps done (smaller for a change) and all of the resistors done.

[Mooly]

Thanks for the update (and piccys).
I thought the opamp would make a big difference and with a socket you can always evaluate others too. Always best to listen for quite a few days I find if you try anything like that as your expectations often get in the way.

[Kei]

I've being testing it every couple of changes to make sure I haven't done anything wrong. (or a new component not working properly so it can be found easily) The biggest differences have been the opamp and the large filter caps. Those film caps i did today made next to no difference. (that i can hear at least)

[Kei]

The polystyrene capacitors finally turned up today (been waiting since mid january), so i got straight to fitting them. They are slightly big but fit OK in most of the locations. Upon listening, i believe that there is a slight audible difference. There is one substantial difference i have noticed and that is the crosstalk between inputs has disappeared completely. The phono stage is sounding very nice now which i am extremely pleased about.





One problem i have created is the treble tone control no longer works properly, it causes the left channel volume to increase/decrease when the tone control is enabled (rather than defeated) The bass control works as it should and the right channel is unaffected. What have i done?

[Mooly]

Check for any components shorting or touching something. In that last pic a cap looks to be forced into contact with the chassis.

[Kei]

Was wondering whether that might potentially be the cause. I know that the problem lies with an A channel cap. (which that one is) I'll swap the muse cap out for a smaller rubycon which will give me some more space to work with.

[Kei]

Done and fixed, must have been that axial cap touching the chassis. I'll look into replacing the old rubycons with something smaller than the nichicon KZ. (only needed 16v caps and they were 50v)

[Mooly]

That's good... all working