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Old 19th April 2008, 11:01 PM   #521
kevinkr is offline kevinkr  United States
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Click the image to open in full size.

Here is my listening room and lab space. (Dedicated basement room)

Click the image to open in full size.

Here is the original before the malfunction that ruined the controller board.

Click the image to open in full size.

Here is the ShigaClone "Clone" with the same mechanism as the first and a new display and controller board - all mounted on the aluminum baseplate that will be the bottom of the transport chassis when done.

This thing sounds progressively better as it warms up.

For those you who want to completely separate the power supply for the controller and the mechanism/processor board all you need to do is change the relay to a dpst, add another bridge rectifier and cap and use that to feed the LM7808 which powers the mechanism.

I have changed just a few components in the mechanism board.
I deleted the common mode choke. I also changed all of the 10uF caps on the board to stand BG, and a couple of 1000uF caps to 47uF standard black gates as well.

I bought some nice Chinese made momentary push button switches to replace the onboard push buttons and will get a momentary NC pushbotton for loading. (simulate door closed/open/closed to initiate a new toc read.)
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Old 20th April 2008, 12:14 AM   #522
johnm is offline johnm  United Kingdom
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Nice work Kevin - bet it sounds great! Mine is still running on a mouse mat!!! Bet it sounds good on that thick base with those spacers connecting the transport solidly to it.

Managed to get the sound quality back that I was missing from my upgrades. As suspected, replacing the crystal back to the original ZTT 16.93MX instantly opened out the sound, bought solidity to the bass, and that wonderful near-analogue sense of openess again, and crystal clear top end. In short - I'm VERY pleased again - I was beginning to think I'd imagined the superb sound this mechanism was/is capable of! I downloaded the datasheet for the ZTT 'ceramic resonator' and it has built-in load capacitance, which MAY be why - to me at least - it sounds better. I think perhaps my Citizen crystal needed that recommended (by Sanyo in their datasheet for the LC78601RE controller chip which is located on the JVC circuit board) pair of 8pF caps. Peter managed without, but to me the sound felt 'sat upon', lifeless and unable to blossom. I guess it will vary from transport to transport, crystal to crystal. For me the Citizen didn't work well.

So.... to sum up my experiences thus far, KEEP the 0.1uF / 50v cap (C906) and X901. Changing the PSU caps detailed by Okapi in his detailed PDF is definately an improvement however, along with the new PSU - hope this is all of help to someone!

Cheers,

- John
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Old 20th April 2008, 03:09 PM   #523
kevinkr is offline kevinkr  United States
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Hi Johnm,
Up until now I have mainly focused so far on getting the micro-controller board issues sorted out, and now that I have completed that I can proceed to the next phase and that is evaluating what if any further changes I can/should make to the mechanism and board.

So far I have changed the resonator to the Citizen Crystal Peter recommended which I thought made for a very noticeable improvement. The stock resonator made things sound a bit grainy to put it nicely.. This was done in isolation to any other changes - it was the first thing I did IIRC.

I also have removed the common mode choke and replaced a few capacitors here and there. One of these is the supply bypass for the dsp chip LC78629, and the others are used to determine various tc in the ASP (LA9241). I did notice some improvement with the replacement of these various caps. I have not replaced the tracking servo tc cap which in my unit appears to be 0.33uF - some experimentation is warranted here. I need to identify the analogs to the other caps changed in the RCEZ31, but I am probably on my own here. I do have all of the required data sheets so this should help.

Due to the fact that I am using an outboard micro-controller the PSU got rather elaborate compared to what is required for the RCEZ31 version, due to space constraints I elected to go with a single bridge (individual high speed Schottky rectifiers) and a single low ESR cap. It is possible that further improvement is possible with a separate supply for the mechanism as long as it remains under the control of the uP power control circuit. I will report that there was a pretty substantial reduction in noise and ground bounce visible on the spdif output after changing to this supply.

In terms of the sonics I can't compare to the RCEZ31 based version - not having heard that, that said I suspect they are quite similar given the similar construction and related chipset.

Cold it is not very impressive, sounds about like you would expect for about $5 worth of electronics and mechanism, and lest you think I exaggerate bear in mind what the assembled boom box costs with all profits and shipping/warehousing expense added.

As it warms up the sound seems to evolve, it always retains a certain polite understatement, but the sound blooms, by this I mean the sound stage opens up, depth and width increase greatly, you become aware of the fact that you are hearing a surprising level of background detail, highs are clean and very extended, and the music has a nice flow to it. Bass is very good even when cold. On really well recorded CDs there is an almost analog like quality to the sound.

I recently built myself a new dac, and I am sure a lot of what I hear is the dac's ability to resolve very subtle detail. It is pleasing though that this inexpensive mechanism complements it so well.

All of the above and I am having fun too. I doubt I could have bought any cd player on eBay for for what I have spent so far that would do the job as well..
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Old 20th April 2008, 04:50 PM   #524
kevinkr is offline kevinkr  United States
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I spent about an hour or so listening to it this morning, have to say that while it does a lot of things right there is a certain mechanical quality to the sound that never quite goes away.. Could be nothing more than the break in of the few BG caps I have so far installed, or it could be an indication that more work is required.

I do plan to add a considerable amount of additional mass on either side of the mechanism. This will either be aluminum or brass bar stock - basically whatever I can get my hands on.

One thing I can say is it is working quite predictably, no odd quirks at all.

Now it is just a matter of finding the level of refinement I seek.

I purchased a bunch of 75 ohm bnc from Digikey and plan to replace the current 50 ohm bnc on the clone as well as on the dac.. I will probably work on improving the supply decoupling and upgrade the remainder of decoupling caps on the mechanism board. (Yet another order to Michael Percy.. )
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Old 20th April 2008, 06:16 PM   #525
kevinkr is offline kevinkr  United States
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I think later this afternoon I will remove that ferrite on the ac power leads to the transformer. Not sure why I didn't do it before soldering the iec connector to its leads, but it was done very early in the process.

I'm debating whether or not to get another transformer as this one runs near stone cold after several hours - as does the rest of my supply in fact. This transformer is also mechanically very quiet - an important consideration in my room. Compared to the original boom box this supply is quite lightly loaded.

Can anyone say for sure that using another (larger) EI transformer makes any audible difference?

John's comments on the crystal are interesting, and like him I still have the original around.. (just seemed grainy as I commented before.) I also have a completely stock mechanism I am keeping as a spare so comparisons are possible.

I am also going to work on improving decoupling in the supply and on the mechanism board as well.

FWIW it is worth I have heard far worse from far more expensive and respected kit. My system is highly resolving and unforgiving, and yet it still manages to sound pretty good - just not quite where I want it to be yet. The fact that it works at all, and as well as it does is a small miracle given what I did to the last one..
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Old 20th April 2008, 06:52 PM   #526
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Quote:
Originally posted by kevinkr

Can anyone say for sure that using another (larger) EI transformer makes any audible difference?
I can say that I hear difference between PS configurations . I've tryed at least 5 different transformers , and the big differences are between : 4 diodes - 2 diodes . Toroidal and typical ( cant remember the name ) .

I would not go myself for more than 50VA . Also different transformer into theyr category seems to produce audible consequences .

Anyway I am indecided between a little 12 + 12 toroidal ( that runs pretty fresh ) , and a something bigger " tytpical " transformer . sorry again for the lack of the right term to use . My taste tends to the 2 diodes configuration .
I used also shottky and like them .

Not last -for me - worked greatly to disconnect all the rest of the circuitry of the boom box from the transport .
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Old 20th April 2008, 07:12 PM   #527
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I have to say I am still of the opinion that my unit sounded better when it was stock, being truthful. It's not an easy thing to admit because I've put quite a bit of work into it, and money that I don't have at present.

When stock I really hadn't heard anything quite as good as this for a LONG while.

I'm hoping it still is the infamous Black Gate burn in process. It's only really been a few days, and it can take 400+ hours I've heard (worse case) - eeeeek!

I think I should have installed the PS as Peter said, then got used to that sound, THEN have seen if the upgraded crystal and 0.1uF cap made a positive difference... perhaps the reason I didn't like the sound with the upgraded items was simply due to the Black Gates burning in. Too many variables at once

Anyway going to continue simple listening to music on it and see what happens.
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Old 20th April 2008, 07:25 PM   #528
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As a matter of fact , I am just managing with PS , didnt changed anything yet( well the inductor is not there ) , and it works very good for me . I may add , transport noise ( motors ) decreased a little with use .
And I like the output SPDIF divider with 291 and 100 ohm and 75ohm cable . It is very quiet on the background , and with good recording I can hear good placement of the instruments they seemed to me more confused either without divider than with 75 and 75 .
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Old 20th April 2008, 07:32 PM   #529
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The stock unit is quite similar PS , you can use it . You just need to turn on the 8volt regulator maually by putting a short on the board . The bridge has capacitors across each diode .
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Old 20th April 2008, 07:34 PM   #530
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I already mentioned it few times, and can't stress it enough: don't change anything on a main board exactly as I did; that it worked for me, does not neccessarily mean it will work for somebody else, in a different system and different sonic preferrences. You need to find your sound that pleases you

If I can suggest a an upgrade path, I would do it in that particular order:

1) outpboard supply: check different transformer types and power rating, diode types and bridge configurations

2) the regulator type, most likely LM7808 is a proven choice, but experiment with caps before and after regulator.

3) check the crystal, I only use that particular Citizen type, because nothing else was available form DigiKey. It also worked better than stock oscillator and one other crystal I bought locally.

4) check the first two caps on main board (470uF and 220uF). I removed the bigger one completely as it's in parallel with main cap after the regulator, 220uF was replaced by BG N 47uF only because I like "image density" of BG N caps, but your taste may be different.

Only then, change any other components on the main board, I didn't do much, only the caps that are directly on supply rails and because my main bypass is BG N, I changed other caps to BG N as well (but smaller values) and removed SMD caps. And do it one by one in steps, so you can monitor the differences each component change brings.

There is one other cap worth experimenting with (C906) but do this as the last mod.

One other thing with regards to output resistors, while I had good results with 75/75R at the output, as it increased the presence factor and improved air, especially with BG FK I was using initially and which sounded a bit mellow, after I switched to F caps (not available any longer) I have pretty good results now with resistors closer to properly calculated values (300/100R) and I'm still experimenting in that area, but as Stefano said, with calculated values it seems like imaging is more solid and less "confused".

Lastly but very important, is the mechanical construction of supporting frame. In my experience, it is probably 30% of overall sound, and it makes or brakes the sound of the unit. Some people reported good results with mechanism simply placed on some foam, but I tried and sounded rather uninteresting. A good starting point would be a wooden platform and two brass standoffs and from here you may move towards more advanced constructions.
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