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Yamaha CX-1 Thread

Discussion in 'Yamaha' started by Bratwurst7s, Sep 30, 2017.

  1. brutal

    brutal YamaHoarder Subscriber

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  2. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    I'm not sure that the upload worked, but I tried. I probably have to many security setting active with noScript.

    Anyway, I dragged and dropped the 2x schematics, 4x layouts and 1x refurb parts list. The page seemed to react (showed a folder icon), my browser showed activity, then a window popped up telling me to sign in, then the whole page went blank and I got a "no server found" message.

    Let me know if you got them, if not I'll try again.

    Cheers,
    James
     
  3. mcgjohn

    mcgjohn Active Member

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    No problem.

    cant see it in the photo but used teflon tubing on the legs of the bridge just to insure they won't short at some point.
     
  4. Karl vd Berg

    Karl vd Berg Super Member

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    Hi there, interesting the arrangement of the bypass film caps here. Could you tell more about the values you chose (I see 5 caps in parallel for each electrolytic) and explain a bit the benefits and effects they have on the main cap they are associated?

    Thanks. :)
     
  5. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    BTW Beau Geste, a little feedback. Yesterday I made a large order from Mouser and included some of the OPA1612. LOL, they may never find their way into my pre-amp but I'll be giving them a shot in the final output position in my DCD-2700 CD player. Thanks again for the suggestion. :)

    Cheers,
    James
     
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  6. Beau Geste

    Beau Geste Rione Traiano Subscriber

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    I am convinced that you will not regret James. Now they are playing in my mono Power AmpDenon POA 6600 A. And among the many that I have tried are among the best. A little, bit of the LME 49990 is better too IMHO :)
     
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  7. brutal

    brutal YamaHoarder Subscriber

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    I think you have to have a MS Live account. Nothing there BTW.

    It's not like it's a real FTP or file sharing service, Onedrive is kinda limited but it's great for my cloud storage. For $99/year I get 5 1TB accounts and all the MS office 365 software on all my devices.

    I got tired of chasing free storage and just paid the piper.
     
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  8. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Well, I just successfully sent all 6 pages/pjg's to the AK database. At least I haven't gotten any bounce notices yet anyway. It will probably take a week or so for them to be accepted (or not). In the mean time if you want them just PM me and I can email them to you.

    When I want more storage I normally just buy another external HD. :) I really don't like the concept of remote storage on some one else's server for my data and not being a MS user or fan I don't see a MS Live account in my future. But hopefully the files will be accepted in the AK database.

    Cheers,
    James
     
  9. mcgjohn

    mcgjohn Active Member

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    Bypa
    NP.

    Bypassing filter caps is far from new in Audio Circles. Sansui added power supply bypasses with their X17 series back in the 1970s with a single large film cap, which gave many of the Sansui amps that warm sound many like. John Curl while laying out the Parasound high current designs did quite a bit of bypasses and multiple bypasses in the 1990s and 2000s with HCA series and later the Halo series..

    Each film cap value will affect certain frequencies. The CX-1 has two main filter caps in the main supply. Think I used a 0.47, 0.22, 0.047 and a 0.01uf on each of the 4700uf caps. A good starting point is a .47 or a .33 paralleled with a .01uf. From there if you want to clean up an upper midrange, you can experiment with a .047 or .022. Its also important to note the intermediate cap values will have a different effect if that .01uf is not included. Now if you go smaller than a .01uf, say a 1000pf, you will clean up super treble frequencies, but at the same time change the tonal balance of the preamp.

    But you can also over do it. As an example if a power supply has 4 caps instead of 2 (2 on each side of the center ground buss), may just want to bypass one cap on each side of the plus and minus supply. Doing all 4 may be a bit too much.

    I also added bypasses on the phono stage PS caps.

    And speaking of the phono stage, its extremely good on the CX-1. A lot of engineering efforts went into the MC and MM stages. If the listener is a phono person especially with LOMC carts, then would strongly suggest dialing the MC phono stage so its as close to ruler flat as you can get. You will be surprised at how good and organic sounding the MC carts will become. To dial in the response, you will need a NAB broadcast test disc, or similar type of LP that has the RIAA frequencies cut into it. connect a DVM up to a set of tape outputs, play each test freq. and record the AC voltage coming out of the tape loop. You can change the loading resistors to get it very flat. My favorite LOMC cart at the time was the Madrigal Carnegie One. Plugged into the MC stage on the CX-1, I was able to get the response flat within 1.5db from 30hrz to 18Khz, which is saying something. Without the dial in, most phono stages are lucky if they are flat within 5-8db, with some being a bit worse. But need to measure it before you do anything.

    If you don't want to solder resistors in each time you can temp solder in some leads to the resistor positions on the pcb, clip resistors in place measure the points calculate how much is needed, plug in the resistor value. Once you have it dialed in, then solder in the correct value.
     
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  10. 808_state

    808_state Well-Known Member

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    706
    Great info! So what do the settings for the loading switch on the back of the unit actually represent? Are they accurate or a gross approximation/attempt at loading? Do you happen to know the gain applied at the MC input?
     
  11. Karl vd Berg

    Karl vd Berg Super Member

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    mcgjohn, thank you so much for the reply!
     

     

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  12. mcgjohn

    mcgjohn Active Member

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    NP.

    No those load resistor settings on the switch are pretty accurate. If you move the switch to the 220 ohm setting you will be loading your MC cart down with 220 ohms. Same with 1K if you move the switch to the 1K setting, you will be loading your MC cart down with 1K ohms. If you have the phono switch set to MM, then the load setting switch has no effect. It is only in circuit when the MC/MM switch is engaged to the MC position.

    Each MC cart has slightly different load settings. Some guidelines are offered by the cart mfgr. But most folks set the loading by ear, which is pretty poor. Measurement is the only way to get the cart reproduction to be flat.

    but if you need a load setting of 500 ohms, no problem. All you need to do is parallel another 1K resistor between the hot lead and ground on the MC input, and electrically the cart will see 500 ohms. You can do this outside the preamp with an RCA type cheater and solder resistors to it.

    Once you have the proper value selected, can solder it in place internally.

    JOhn
     
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  13. brutal

    brutal YamaHoarder Subscriber

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    It's not about the local storage, I have plenty of that. The bulk of which is also replicated online. I too use an external drive for backup in addition to secure cloud storage, but I unplug the external drive after after each backup. With cryptolockers in the wild, one can never be too cautious.
     
  14. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Yes, good practice. My external HD's are only plugged in for the time that they are used, otherwise no connection. In the summer(+) we get a fair amount of lightning strikes around here so I tend to unplug things when they aren't in use. I have surge suppressors for everything but don't really trust them when it comes to lightning.

    Cheers,
    James
     
  15. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    So a couple of new developments.

    First, I see that the pcb layouts and schematics are now in the AK database. Many thanks to njcanuck for making the jpg's into pdf's and doing all the work to keep the database going.

    Second, I just bought another one of these pre-amps. Looks to be in very good condition and I only paid €395 for this one. It has a much higher serial nr than the 1st one so it will be interesting to see what changes might have been made in between. I'll document what I find.
    This one will be a gift for my son. It will be bundled with a pair of as-yet-unrestored Speakerlab S7WA speakers and an as-yet-undetermined power amp. He already has a resto-modded Denon DCD-2700 and my old Pioneer PL-L1000A TT that I gave him. I have about 13 months to get all of this done before his 30th birthday next year.

    Cheers,
    James
     
  16. mbz

    mbz Super Member

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    I'd like to join the chorus and thank Bratwurst7s and the others that have contributed
    to this thread. There is a whealth of information and ideas, not to mention all the
    grunt work of spreadsheet, cap sizes, discreprecies etc... Fantastic effort by all.

    I've just purchased a CX-1. It will undergo a similiar refurb to that outlined above.
    Your work will save me many hours and help me achieve a great outcome. Thanks.
     
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  17. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    You are very welcome. Being able to help another AK member and spread information is what makes all of this worthwhile. :)

    I hope that you enjoy your CX-1 as much as I'm enjoying mine. It gets used every day, fantastic piece of equipment.

    Cheers,
    James
     
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  18. mbz

    mbz Super Member

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    Appears that the CX-1 enjoyed a long production run. Yamaha added
    component numbers on both sides of the pcb including component
    symbols eg, zener, making it a easy check before removing parts.
    They also used copper screws on the back/RCA plate, the bottom and
    to secure the pcb's. Serial Number E0508850Q.

    Everything looked "new", very tempted to recap only psu, however
    image/sound stage was not great, recapped C-40 was better in this
    area, so something must be wrong... So far, all caps removed (25?)
    were with spec with exception of C539 330uf/16V, measured 260uf
    probably bad production.

    Solder joints are ok so far.
    CX1_pcb.JPG

    CX1_pcb2.JPG
     
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  19. restorer-john

    restorer-john Addicted Member

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    Use a volt meter that has a confirmed response up to 20KHz on the AC scale. Very few DMMs get much over 1KHz with any accuracy. Flukes get pretty high, but you are better off to use an oscilloscope or an analogue ACmV meter.
     
  20. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Nice to see that they eventually improved the PCBs. I enjoyed having everything so well marked when I worked on the AX-750 and it threw me when the CX-1 arrived completely unmarked.
    It would be nice to be able to decipher the S/Ns to come up with a date. What date codes do your old caps have?

    Afaik they produced this model from 1993 to ca 2000.

    While I did reflow/re-solder every single connection in the unit I don't recall seeing any connections that looked bad. But I don't think that I would want to open one of these things up and not reflow everything.
    I didn't really expect re-capping to make much of a difference and it was a pleasant surprise when the SQ had a nice improvement afterwards.

    Cheers,
    James

    edit: No, what I wrote above isn't quite true. I do recall now that a number of those heavy gold plated buss bars had connections that looked cold.
     

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