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|12th December 2007, 12:32 AM||#1|
Join Date: Jun 2002
Location: Calgary, Alberta, Canada
Magnavox/Philips CDB-692, what will it sound if I mod it?
Bought this 13 years old stuff from a goodwill shop for only CAD$9. The outlook of this machine is quite attractive. But what can I expected from it's sound?
Yes, it sound really like the music played behind a heavy curtain, dull and weak.
Opened the case, found the pcb is quite simple and neat. Not too much components, even none a transistor seen there. I wonder the design of this machine might be the desktop version of a portable CD player.
Since I don't know much about digital, so what I dare to do the mod is the op amp and power supply.
Original op amp is LM833 and I want to change it with NE5532 (bipolar) or TL072 (jfet). What will they sound like if I replace it?
Regarding the power supply, do I need to replace the transformer, it look like quite large enough to provide adequate power, isn't it?
The cap, change it with large one? But the cap is ELNA. Will it deteriorate the quality if replaced by other brand?
Hope Masters can give me some guidance to bring the brilliant to this CD player.
Thanks so much for yours help.
|12th December 2007, 05:40 AM||#3|
Join Date: Jul 2004
Location: West Australia
Well, firstly you should be looking at BURR BROWN or ANALOGUE DEVICES op. amps. Do a search on this forum for the types/numbers.
I would also replace the power transformer with a much larger TOROID type if available in the correct voltages.
The electrolytic capacitors will be bettered by ones from NATIONAL PANASONIC (FM).
Like wise the rectifier diodes should be replaced by ultra fast sost recovery types.
All this should, in theory, produce a sound that is faster, cleaner and more dynamic
|12th December 2007, 08:32 AM||#4|
Join Date: Aug 2006
...my very small contribution to encourage your search:
As a way of learning some basics without risking too much, I am in the process of trying different mods on a Philips CD471. I have two identical players, so I keep one stock, to A-B-compare the effect of each modification. Then I'll apply them in combinations, and at the end compare with higher quality players.
The advice I read here in the forums is confirmed by my small findings:
in order of "wow factor" the following gave the best results:
1. OpAmps (OPA2134 instead of LM833) = everything improved
[on another player, a Sony, I put a discrete output stage
(ultranalog bjt) and there also, the improvement is very clear
over the original 4558 opamps]
2. PSU (individual TL431 "peufeu style" to DAC supplies, with dedicated small transformer; this also keeps SAA7220 supply "away from DAC") = sound "cleaner", less "noise", more detail
3. Clock (Kwack 7) = sound cleaner, wider stereo effect, more detail
These three were immediately recognizable.
And none of them costs more than 15 Euros!
Other changes this far were to remove muting transistors and different output caps; gave improvement, but no "wow!"
I could not hear any difference by putting new elctrolytics (but no-brand), maybe masked by the other shortcomings of the cheap player...
But then all this on a TDA1541 architecture, different from yours (a "bitstream" player, right?)
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