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Old 31st January 2006, 03:18 PM   #471
SimontY is offline SimontY  United Kingdom
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Quote:
Originally posted by poynton
hi.

Bigger VA, Lower Off-load voltage =
Better Regulation = Better PSU

If a bigger VA toroid is available for a few cents more and it will fit, then this is the better option.

It does not matter whether discrete or 7805-type regulators are used, the whole idea of a psu is to provide a stable output voltage, regardless of the load conditions. The psu will not perform to its best if an inadequate Tx is used ( like the oem!!!)

The idea or replacing the Tx must be considered to be part of the rebuilding of the PSU section along with diodes, caps, pre-regulator if required etc.

For those worried about the offload voltage, you can always use an (extra) preregulator - it will NOT degrade performance.

Andy


PS Lower noise is a beneficial by-product of PSU regulation!
Yeh, oversize it!
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Old 31st January 2006, 03:54 PM   #472
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Hi all,

I'll get a quote for the 50VA toroid
- but I need new VA ratings for the secondaries then...
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Old 31st January 2006, 04:40 PM   #473
6h5c is offline 6h5c  Netherlands
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Ehm,

Guys...are you sure? The tranny is already oversized. A bigger tranny will have better regulation, but that's the off-load voltage compared to the FULL LOAD, which we won't be using. The difference in regulation between a 30VA and a 50VA is not that big. You must realize that if you make the windings even higher current, with the small load we draw from it, it will make the voltages even higher and more unpredictable. We really should stick with the configuration we have.

Regards,

Ray.
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Old 31st January 2006, 04:44 PM   #474
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Quote:
Originally posted by 6h5c
Ehm,

Guys...are you sure?
Hi, no, I'm not sure, just sounds cool to have overspecced parts. I always thought with a TX the bigger it is the better it is, all else being equal.
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Old 31st January 2006, 04:55 PM   #475
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Simon . In Amps where there is a big current demand you are more right but the cdp only demand mA and therefore needs very little headroom.

The KI TX appears to have it about right interms of headroom.
Making a custom version of this seems to be the way to go, with extra windings for 5v circuits etc
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Old 31st January 2006, 06:27 PM   #476
6h5c is offline 6h5c  Netherlands
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I agree Brent. The KI tranny is something like 13W max. and probably has some headroom already. Since most of the power demand is constant, not dynamic, the 50VA would just sit there and do nothing.
If space and cost would be a problem you could even do it with a 15VA.

Regards,

Ray.
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Old 1st February 2006, 09:37 PM   #477
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Hi all,

Sorry for posting so late in this thread, only recently registered.

I've been modding my cd63 for a little over a year now, thanks to all on the forum for the help.

Basically the work consisted of:
Kwak clock
BB2107 opamps
silver mica caps and 0.1% resistances around output stage
upgrading of reservoir caps generally around the CDP
removed muting
removed output caps
deadsheeting and caulking of main board (I did this on a friends cd63, will do on mine soon)
etc, etc

I have had the chance to compare the cdp to a micromega stage 2, and was pleased to find them comparable, despite the micromega having a slight edge in the instrument seperation stakes.
Since then, and from this thread, I have bypassed the HDAM (though haven't completely disabled it yet, hope that will help too!) and added a regulator per power line on the DAC. I'm amazed by these two mods alone and can't wait for a rematch

I haven't done anything deliberate with the servo driver circuitry or around the decoder. Has anybody made any great improvements in this field?

Also, I haven't tried browndogs yet (the 2107 on paper is cracking, but perhaps not quite a 627), Is cost the main reason, or maybe lower bandwidth of the lesser opamp (can't remember what was recommended, was it the 2134?), the reason to use only one 627 per adaptor?

Anyway, thanks to you all for your help. Very much appreciated!

Cheers,
Phil
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Old 2nd February 2006, 08:55 AM   #478
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Hi philpoole

I have also seperated the rails to the decoder, it as 2 digital 5v rails and one analogue rail.
There is an error you have to rectify on the 5v rail to the decoder as it is wired the wrong side of the 4.7 ohm resistor but the diagram shows otherwise. The track need cutting and wiring to correct place.

Use the output of the correct regs you already have powering the DAC and drop in some nice caps (I used 16V 470uf Black Gates).

You need to fully remove the HDAM from the signal and supply line, not sure what effect it will have but it certainly wont benefit you!!


Also with the muting and HDAM removed the only thing using the +/- 12V rails are the op amps. What I did was remove the 12v regs from their location and fit some Audiocom regs right next to the opamps. Doing this removes any noise being picked up on the rail from it winding across the pcb (IMHO).

You can see here Marantz CD63 & CD67 mods list

I have also fitted bigger caps around servo etc, I did this so there is always enough juice if needed.

The next mod for me is to upgrade the components in the HF amp stage to the decoder.

I have browndog pcbs with OPA132 and OPA627 and previously had OPA2134 fitted. The 2134 was brilliant especially for the cost but the new browndog combo is utterly amazing.Save up and go for this combo much more air and openness.

Also before I stop ranting on..... change the diodes in the unit to HexFRED's or schottky


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Old 2nd February 2006, 10:08 AM   #479
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Quote:
Originally posted by rowemeister
Hi philpoole

I have also...
Great post Brent.

Will just add that the reason to not use two OPA627s is that a combo of OPA627 and OPA132 could be even better.

I have not [yet] tried this and absolutely love my OPA627s. Worlds ahead of JRC2114, OPA2604, OPA2132 (my previous trys).
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Old 2nd February 2006, 10:17 AM   #480
6h5c is offline 6h5c  Netherlands
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Or.....try a tubestage!

Whooohoooo!!!!!

SOUNDSTAGE!

DYNAMICS!

EMOTION!

....MUSIC!

No opamp can compete with this. I even dare to say that it sounds more....ANALOG .

This is the first attempt to get Thorstens Delta-Sigma circuit working and see what it does. So I mostly built it out of components I had laying around (especially notice the ugly blue ceramic suppression caps, since I didn't have 100n film caps...).

Ray.
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