Technics SL-P555 (1989) first MASH ??

[Marmotus]

Hi all!,
In other thread I asked for schematics but is almost impossible to find for free info on Technics components... so, Hands On! I've sated that this CDP in stock form sounded similar to my Rotel RCD 951 as to sell it n a good trade without regrets, all in spite of good 12 years of tech advancenment... I have a good sounding TOTL SL-P999 that IS 4 linear DAC (PCM56PJ) without mods and this SL-P555 says in it's front 4 linear DAC .... BUT !! Please see the pics, is this the first MASH generation?? I used to sell Technics when First MASH 1 bit denominated models appear (SL-P370), and all of them sounded so flat, without dynamics only top models were better. Not the case of this SL-P555, good from start... well, first I swapped muting transistors and Bypassed output decoupling caps with .15 PP ... GOOD!!! Lots of definition and soundstage, better dynamics and a whole new world on highs, blame those Electrolithics caps ... all of them (these were ELNA Cerafine). After (I couldn't stop),measured offset of 2,7 and 3 mV, Caps OFF! I had to bypass some resistors to leave headphones amp operative, since signal come from "backdoor" now, Changed and beefed-up Caps of DAC ... and WOW!!!!!
Blacker than Black background, Superstage, Definition, Scary Dynamics and a Bass Foundation few times heard...
Give those old CDP's a try!!!
Cheers,
Marcelo

[Marmotus]

Here are more picsIMG_8580c.JPG

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[Marmotus]

And More

[Marmotus]

Give some listen today and compare to stock 555 (shut in, false highs and overall ringing... as added delay to explain), 999 (open and deatailed, no veil, very good) and the modded sound way past the 999 with fluid analoguish mood, and I think more res too. Every disc played souded far better than ever, not bad records worst and good ones better! I`m gonna try It in some friends super systems (just for fun) ... to name some sources like C.E.C , Lexicon, Theta, Wadia.. some news soon...

Some other pics
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[charleskcwong]

dear sir, are you able provide me a little more details how you mod your SL-P555, i have one? thank a lot

[stratus46]

Originally Posted by Marmotus

Give some listen today and compare to stock 555 (shut in, false highs and overall ringing... as added delay to explain), 999 (open and deatailed, no veil, very good) and the modded sound way past the 999 with fluid analoguish mood, and I think more res too. Every disc played souded far better than ever, not bad records worst and good ones better! I`m gonna try It in some friends super systems (just for fun) ... to name some sources like C.E.C , Lexicon, Theta, Wadia.. some news soon...

Do you have a way to create a disc with test signals on it? I'd be interested to see frequency sweeps, square wave and pulse response of the modified unit. If you don't have a scope, you could record the analog output of the CD player into the analog input of your computer and post the results.

G²

[SoNic_real_one]

I think it is a lot of whishfull thinking. The JRC 4560 OpAmp are similar with 5532, just good to be junked from that board and replaced with something more decent. They never sound good...

[stratus46]

Originally Posted by SoNic_real_one

I think it is a lot of whishfull thinking. The JRC 4560 OpAmp are similar with 5532, just good to be junked from that board and replaced with something more decent. They never sound good...

The 5532 is considerably better than the 4560. At least it isn't a 4558.

G²

[SoNic_real_one]

OK, you might be right, essentialy is that for me 4560 is good to be junked, just doesn't cut it. And if I had an 5532 in any other configuration than unity gain buffer, I would change it too.
On that board are three more OpAmps that I bet need attention - two in the I/V stage and one in the filter/differential stage.

But that's me and my ears.

[tvi]

Harmon Kardon HD-7600II had a discrete output stage for the same chip MN6471.

One channel attached for your entertainment

Rgds
James