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Old 13th August 2008, 09:29 PM   #1
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Default Mash dac rediscovered

I've read a lot of bad thing about Mash dac. I had an old Technics cdp (Slp377a: it was a degree gift) in my parents house and I wanted to give it a possibility.
I did these tweaks:

*replaced el. capacitors in power supply (x2 capacitance) and bypassed with 0.1 uf film cap.

*replaced el. capacitor at the dac pins (x2 capacitance) and bypassed with 1uf tantalum

*bypassed analogue stage connecting first opamp's outputs with new rca's via polypropylene capacitors

I've noticed a nice improvement in sound but I wasn't satisfied. That said I've found this dac not really bad: it has a warm, detailed personality. Good high and midrange (I think tantalums help) but I missed some more bass and depth. So I added a 100uf tantalum cap. between input leg and ground leg of the regulator and built a new 5v regulator feeding the dac. Wow... what a beautiful scene, very rich, wide and finally the bass I was looking for.
For me this is a little discovery: not as good as the beloved tda1541 but really worth keeping it. Next step will be to put in a new OPA2604 instead of the LM833.
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Old 15th August 2008, 03:46 PM   #2
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Default Another power supply

Another new 5v power supply feeding digital Vdd of the dac. The other one is for analogue Vdd.
The bass now is awesome, very deep and clear.
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Old 15th August 2008, 04:02 PM   #3
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Old 16th August 2008, 04:44 PM   #4
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Default Another one

Third new dedicated +5v power supply (and the last one). This feeds digital signal processor (MN6625).
The quality of sound really impress me, lot of details, clarity, the bass is very full and rich. I'm starting to adore this player
Now I'm just waiting for the OPA2604 that I've ordered. This old formerly anonymous Technics will sits as my resident cdp in the second sistem.
Please reconsider this dac
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Old 16th September 2008, 11:18 PM   #5
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I have, finally, started to mod my old Technics SL-P202A. I have ordered parts: LME49720MA to replace LM833M op. amp. and few Panasonic low ESR and Audio grade caps to replace originals (voltage regulator and analog signal path). Also, I'll bypass signal muting in output stage. I'm planning to put current filter in front of transformer and 5V PS for DAC and op. amp.
I would be interested if you could share your experience and those 5V PS schematics or even better all what you have done. Any other suggestions are welcome.

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Old 17th September 2008, 09:04 AM   #6
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This is the simple 5v regulated ps that I've used in the player: 2 for dac and 1 for digital signal processor. I've cut existing traces feeding the chips. Please place the regulators as near as possible to chip pins. Add a little heatsink to regulators.
Signal goes from opamp outputs (pin 1 and pin 7) directly to new installed rca via 5uf polypropylene capacitors.
Bypass opamp pin 4 to 8 with 0,1uF cap (very short leads). I've added also a 1uF tantalum: be careful! pin 8 is positive and pin 4 is negative.
I really love this player, it stay dangerously close to my TDA1541A based player
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