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Marantz CD42 repair and mods
Marantz CD42 repair and mods
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Old 10th March 2011, 11:31 AM   #51
lassipr is offline lassipr  Finland
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Ah, and is this true for all low ESR caps (Panasonic)?
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Old 10th March 2011, 02:21 PM   #52
poynton is offline poynton  United Kingdom
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It has to be said that there is a lot of misunderstanding about which type of cap to use and where.

For example = after regulators.
Read the specs for the 7805 type.
The cap after should not be low esr or large.
The one before can be.

In general, low esr caps can be used across devices (remote from the reg)
As for OSCONs, they are best for digital stuff.

Andy

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Old 11th March 2011, 08:16 AM   #53
Chivvyp is offline Chivvyp  United Kingdom
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Originally Posted by poynton View Post
It has to be said that there is a lot of misunderstanding about which type of cap to use and where.

For example = after regulators.
Read the specs for the 7805 type.
The cap after should not be low esr or large.
The one before can be.

In general, low esr caps can be used across devices (remote from the reg)
As for OSCONs, they are best for digital stuff.

Andy

.
Hi Andy, maybe you can clarify something that's always confused me. "After regulators" means directly after or anywhere after.
I tend to use 317 regs with tants directly on the output (as recommended) but just before the chip input I have some large, low esr caps for decoupling. Is that a problem?

Regards

Pete
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Old 11th March 2011, 11:11 AM   #54
poynton is offline poynton  United Kingdom
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As far as I read the info, that should be OK.
The low esr caps directly after the regulator causes resonant peaks in the response ( I think)
Similarly, a large cap immediately after the reg. does not allow it to "regulate".

Somewher, either on this forum or the net, there is a very good article about regulators.

Aha !!! Martin Clark Using 3-pin regulators off-piste: part 1

Andy

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Last edited by poynton; 11th March 2011 at 11:29 AM.
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Old 11th March 2011, 01:02 PM   #55
wintermute is offline wintermute  Australia
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Marantz CD42 repair and mods
Attached is a sim of two almost identical LM317 supplies. Both have low esr 100uF caps on the output. The green trace is with just the cap, the blue trace is with 0.25 ohms resistance added in series with the cap. The smaller the cap the worse the problem and the more series resistance has to be added to swamp the resonance.

The plots are showing the output impedance, mV can be read as milli ohms.

The LM317 can theoretically have large capacitance on the output, and I'm planning to try 1000uF.

Tony.
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File Type: png low_esr_effect.png (15.0 KB, 155 views)
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Old 6th October 2018, 07:33 AM   #56
andypap is offline andypap  Greece
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Originally Posted by martin clark View Post
Yes, try the oscon; 10-68uF is quite large enough - it has to charge-up through the chips internal divider, so you don't want too long a start-up time. If the 47nF thingy is SMT, leave it in place too.

This dac was used in a lot of good equipment. DPA used it in various PDM1 / Little/Bigger Bit designs. They used an active, low-noise 2.5v voltage reference with buffer to drive these pins, so if you want to really experiment...

The full Philips 'CD7' chipset is to use the SAA7350 to generate the bitsream, and the TDA1547 solely to decode it. It's a pairing capable of stunning sound.
Hi martin, it;s quite an old thread but it sounds interesting. I'm wondering what should I do to bypass the internal I/V converters og SAA7350 and get the pure curent ourput of it, to convert then into voltage by driving other external circuits. I've done it in the past on a CD-48 carrying the TDA 1549 by using external high impedance buffer IC. The diference over here is that 7350 is a balanced output switching capacitor current output, while the TDA1549 was single ended. Another difference is that TDA 1549 had indepedent supply rails feeding the internal I/V converters (where you can easily disconect from DC), whiles the 7350 is fed from the same supply which feeds the switcing capacitor stage. I'm a bit confused what should I do. I got a feeling that it can be setup.
cheers
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Old 9th October 2018, 05:48 PM   #57
martin clark is offline martin clark  Europe
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Andy

It's not something I ever tried for myself - you'd have to read the SAA7450 +TDA1547 datasheets side-by-side to work it out.

That said, a very quick look at the lattter shows there is a diagram or two - snapshot attached. Drop me an email if you can't find the datasheets and I'll send them over in reply.
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Old 9th October 2018, 07:35 PM   #58
Malefoda is offline Malefoda  France
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Also wondering what to do with a SAA7350 in a Tascam... nice infos here, still in business Martin
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Old 11th October 2018, 08:14 PM   #59
andypap is offline andypap  Greece
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Originally Posted by martin clark View Post
Andy

It's not something I ever tried for myself - you'd have to read the SAA7450 +TDA1547 datasheets side-by-side to work it out.

That said, a very quick look at the lattter shows there is a diagram or two - snapshot attached. Drop me an email if you can't find the datasheets and I'll send them over in reply.
Hi Martin , thank for your kind reply. I already have the service manual of Philips cd951, as also the deck itself. I can't swear for the magic sound of this CD player, even after very long and extended mods. Somewhere I've read that all of the missfiring comes from the chippy intergrated I/V converters in Philips DAC's. Taking the chance I initiated to deactivate TDA1549 I/V's in another CD player (Marantz CD48) and pick the current output. The outcome was really better but only after using the MUSE 8920 J-fet as external IV. Just for comparison with the modded scheme, I could never name the intergrated TDA1549 I/V's as a crap. A bit tubbie, shy and flat, but plenty of musicality and character. Just wondering how the 7350 could sing without it's own I/V's..
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Old Yesterday, 01:35 PM   #60
andypap is offline andypap  Greece
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Originally Posted by Chivvyp View Post
Hi,

As a cheaper alternative to a cheap clock.....

I've found good improvements on some players just by disconnecting the clock out feed from the chip to the std crystal and feeding a clean isolated power supply to the crystal instead. I guess by the time the standard 5v feed (or whatever is used) is routed through and out of the chip it's pretty polluted. With a cheap lm317 reg you get quite an improvement for next to nothing.

Regards

Pete
Hi Pete,
can you indicate where to to connect the external DC line to feed the crystal on the attached chematic of CD42 ? I'm a bit confused with "Xin" and "Xout" pins of the chip . Should I remove any part(resisistor) around the crystal circuit? Thanks for your advice
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