With lock-down in place a good thing to kill time is to open every piece of gear around and play with their guts as many of you might know.
It is time to mess with an MM & MC phono preamp, a Music Hall PA1.2. Lets see what we can do to improve the SQ shall we.
Unfortunately I don´t have the schematic that would make things easier.
Possibilities:
- Replace the pair of NE5532 with a pair of LM4562NA (I have a pair handy). Worth it? Drop in replacement?
-Add film caps to each IC at the positive & negative supply Vcc (one cap from Vcc+ to ground and another cap to Vcc- to ground)
-Replace the Nichicon 4u7 50v Fine Gold caps with Solen 5uF 250v Film caps that I have left from a Xover project. I assume these caps are in the output.
All recommendations and comments welcomed!
Saludos,
Rob.
It is time to mess with an MM & MC phono preamp, a Music Hall PA1.2. Lets see what we can do to improve the SQ shall we.
Unfortunately I don´t have the schematic that would make things easier.
Possibilities:
- Replace the pair of NE5532 with a pair of LM4562NA (I have a pair handy). Worth it? Drop in replacement?
-Add film caps to each IC at the positive & negative supply Vcc (one cap from Vcc+ to ground and another cap to Vcc- to ground)
-Replace the Nichicon 4u7 50v Fine Gold caps with Solen 5uF 250v Film caps that I have left from a Xover project. I assume these caps are in the output.
All recommendations and comments welcomed!
Saludos,
Rob.
Attachments
no one!?
None of all this is likely to appreciably improve performance. I am not a fan of using huge crossover caps where they don't belong either.
That's a bit of a weird board layout.
Looks like a 3-stage job, which may imply that they are using just the 5532 in MM and adding the 5534 in MC, but then again there's a film capacitor which seems to be associated with the 5534 and is likely to be determining one of the RIAA time constants. 😕 So I'm afraid you will have to do some reverse-engineering to find out what's actually going on, including what the MM/MC switch does apart from switching input impedance. Taking photos of both sides of the board straight on, coloring and overlaying them may help.
What I will say is that having a 5534 up front would be great for MM, as the part is hard to beat noise-wise in this application. I don't see anything that would bring voltage noise down to the levels required for good MC performance, however. A look at the schematic would have to show whether it is possible to hack in a super low noise part, otherwise in external MC prepre may be the better idea.
That's a bit of a weird board layout.
Looks like a 3-stage job, which may imply that they are using just the 5532 in MM and adding the 5534 in MC, but then again there's a film capacitor which seems to be associated with the 5534 and is likely to be determining one of the RIAA time constants. 😕 So I'm afraid you will have to do some reverse-engineering to find out what's actually going on, including what the MM/MC switch does apart from switching input impedance. Taking photos of both sides of the board straight on, coloring and overlaying them may help.
What I will say is that having a 5534 up front would be great for MM, as the part is hard to beat noise-wise in this application. I don't see anything that would bring voltage noise down to the levels required for good MC performance, however. A look at the schematic would have to show whether it is possible to hack in a super low noise part, otherwise in external MC prepre may be the better idea.