2. analog
  3. 1296221300

Musical Fidelity XLP2 upgrades

Feels like this XLP2, and probably my phono interconnect, are weak links. VPI Scoutmaster, ZYX Fuji .48v, available MC loading 10R, 25R, 50R, and 100R on the LP2, interconnects are older Synergistic and not specifically designed for phono. My main question, for anyone up on the guts of a phono stage is this. I see 2 poly caps in each channel, one in signal path near input, and one in the signal path near output (105J = 1.0uF, both). Which is most important to sound quality, or both are equal? Obviously this is not a great phono preamp, but why not improve it. Also looking at replacing all the electrolitics, wiring, jacks, and load resistors. 100kohm at the MM input, by the way, not 47kohm. And it took me 2 days to figure out how the MC load resistors and switch work, with one resistor hard-wired and 3 on the switch. Confusing! ZYX recommends load to be >100. I think I'm going to put the load resistor at the jack, experiment with greater than 100, and skip the switch entirely. So any help about those poly caps, loading, and general upgrade suggestions would be appreciated. It's winter in Michigan. Even a hot soldering iron sounds good. Thanks people.
240zracer
6 responses Add your response
viridian's avatar
viridian
3,733 posts
Caps are relatively cheap, replace them all. But instead of looking at your phono preamp as an assemblege of caps, resistors and diodes, try to conceptualize it as a power supply and the regulation of that power supply, an input stage, RIAA EQ and an output stage.

I tend to attack the power supply first, as I think that this has the most positive result and it is the foundation for all other upgrades. Therefore, if you can source a higher amperage power supply, that would help. Improving the electrolytic storage caps and changing the rectifiers to soft recovery HexFet or HexFred, or at the least UF4007, will be of benefit and it will be very cheap. From there, your coupling cap upgrade will have much more value. Then again, you said "poly cap", but if you have the real estate to use paper in oil caps, they are a viable alternative with a different flavor.

While you are in there you may want to look at any ICs as well and don't forget any wiring. Good luck!
240zracer OP
121 posts
Thanks for the suggestion Veridian. This is the 3-chassis version of the Mobile Fidelity phono preamps, just to be clear. Only thing inside the power can is a fairly heavy torroidal transformer. It is not the one with the plug-in-the-wall power supply. I still need an opinion about input vs. output caps because 2 expensive caps is better than 4. Are they equal in importance, or do I put my money at the output? And then paper in oil. My analog is not lacking resolution....I think it is lacking body in the midrange and weight in the low end. Would paper in oil take me in the right direction?
viridian's avatar
viridian
3,733 posts
That's viridian with an "i". Three in fact.

Think of the circuit as a water pipe. If the water flow is restricted at the beginning of the pipe, it will be slow at the end. Likewise, if it is restricted at the end, it really doesn't matter how much water can flow into the beginning.

So yes, absolutely, change all of the caps. Oil caps will have more body, no doubt about it, but they require about 100-200 hours of break in. If you purchase the Russian K-40Y caps, they will probably only cost around $8.00 each. Pretty reasonable. You can always splash out on Jensen copper foil or AmpOhm if the budget is a bit bigger.

But again, the power supply is going to be the most important issue. Address the electrolytic power supply filter caps on the board. You may be able to replace them with film caps like Solens, but even if you have to go electrolytic, go better. Have a look into those diodes, that may be the biggest issue that you have.
240zracer OP
121 posts
One more time, Viridian. About the rectifiers. This is the layout on each of the two boards. 2 1000uF-35v caps, 2 regulators (can't read them), another 2 1000uF-35v, 2 diodes/rectifiers (looks like "symbol of some sort" and then N4000), 2 100uF-35v, 2 1N4007 diodes/rectifiers. Can I replace these rectifiers with IXYS DESI12? IE: Can I go from 1000v, 1a to 1000v, 12a? Or do you have a better suggestion altogether? Appreciate your help.
240zracer OP
121 posts
What an idiot. What I thought was a goofy symbol is the upside-down 4 in the 1N4007. Getting crosseyed.
dannylw's avatar
dannylw
169 posts
I am interested in upgrades for this unit too.

Dannylw
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