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Arcam Alpha 5 - Distorted audio output

Discussion in 'd.i.y.' started by Jim3, Jul 16, 2007.

  1. Jim3

    Jim3 Member

    Stripped the machine down this evening and inspected the suspect capacitor. There is a bit of brown gunge on the top of it that looks like its leaked out from under the film. There is also some noticeable burning on the side of it. The burning doesn't look to bad just some sooty looking stuff on the side of it. The transistor next to it, Q405 also has the same soot on it. There is a resistor near by R415, that looks like its got a fairly high power rating, so thats probably designed to run quite hot, which I reckon would account for the soot on the side of the cap and transistor.

    Jon, when you say lift on leg of the base resistor, do you mean R15 (1.3k) on the audio board on the base of transistor Q2?

    I'll try pick up a replacement cap C416 on my lunch break at work tmrw, brown gunge on the top of the existing one, probably not a good sign!

    There is a Maplin near my work, hopefully they will have one.
     
  2. JonHarrison

    JonHarrison pfm Member

    Hi,

    If you're talking about the Alpha 5 then yes R15 and R115 (on the 5+ they're 4k7).

    I'm going to replace the muting transistors with relays on mine. A better way of muting and no need to worry about any pops and clicks.

    Cheers,

    Jon
     
  3. zanash

    zanash pfm Member

    the pops and clicks are minor at best ...but the gains are considerable.

    I'd dis agree if you fit panasonic fc through the psu section and say elna stargets in the dac ...the sound is lifted consideably over the stock unit...

    best bang for buck though is to replace all the rectifier diodes with 11dq10's ...or similar the £6 spent is repaid a hundred times over with better sound [lower noise floor]
     
  4. JonHarrison

    JonHarrison pfm Member

    The pops and clicks may be minor but personally I'd rather not take the risk of damaging my speakers and use a relay to mute the output instead.

    How about Rubycon ZA/ZL for the power supply, Elna Cerafine for the analog and Oscons for the digital ?

    Has anyone tried SB1H100 diodes ? Much lower leakage than the 11DQ10s.
     
  5. RustyB

    RustyB Registered Ginga

    The clicks are so minor there's no point going to that trouble. The o/p is still capacitor coupled, so no danger.
     
  6. Jim3

    Jim3 Member

    I am now the proud owner of a fully functional Arcam Alpha 5 cd player.

    Repaired and rescued from the scrap heap for the princely sum of 39p.

    Replaced C416 with the same capacitance value but a higher voltage rating (35V). Thanks for the tip on that one Jon.

    Fantastic, I'm well chuffed.

    Currently playing my copy of Tool - Lateralus in it as a celebration.

    Sounding very nice, even with the modest equipment its playing through. (Old Kenwood KA3020 SE amp, some old Mission Book shelf speakers)

    Think the hardest part of the repair was getting the bastard front panel to go back on when I was putting all back together. Managed to break a couple of little bits of plastic off the bottom of it while wrestling with it. Nevermind hey, its back together and working now, thats all that matters.

    Thank you very very much indeed gents, I couldn't have done it without your advice.

    I wish I could buy you all a pint.

    Thanks

    Jim
     
  7. zanash

    zanash pfm Member

    well done !

    now get rid of the muting transistors ..and if your feeling adventurous remove the demhasis set too ...

    damp the case within an inch of its life ...I use bitumen roof flashing

    hold the lid by the corner and tap with a screw driver !

    now cover the lid inside with damping and repeat .....

    the same can be done with the case...

    The AA5 responds very well to a good power cable .....make using three cores of 2mm dia copper [from twin and earth ?]with a 3way braided ..fit the best iec you can get and a good plug.

    then you can play with feet ....ditch the nasty plastic feet and blu tack the unit to a tescos finest granite chopping board ....
     
  8. Jim3

    Jim3 Member

    To be honest, I'm happy with it the way it is. I'm chuffed the old dog is back in action.

    I doubt I would hear any difference modifying the case or removing parts of its circuitry. Damping the case and isolating it with a chopping board I understand help remove vibration and reduce electromagnetic interference, but you say to replace the power cable, I don't understand how this could improve the sound quality?
     
  9. ron

    ron Tweaker

    I totally missed this thread, anyway well done Jim! ;)
    That cap going leaky is quite common in the old A5, going by memory its part of the muting circuit PSU, its worth making sure the cap didn't leak onto the pcb, if so clean it off with isopropyl, if you don't that stuff tends to eat away at the copper tracks if left.
     
  10. RustyB

    RustyB Registered Ginga

    but you say to replace the power cable, I don't understand how this could improve the sound quality?[/QUOTE]

    Neither does anyone else, Jim; unfortunately however it does. :)

    The standard AA5 has excellent timing, but is seriously short on resolution.

    Doing just the easy stuff, ie opamps, o/p caps, muting, makes a big difference and will surely whet your appetite for more...
     
  11. Jim3

    Jim3 Member

    How can adding 50cm of high quality copper to the end of a mains supply which has come miles and miles from the power station to your house over the national grid, and run round bog standard 2.5mm twin and earth on your ring main be transformed by this last final bit of high quality copper?

    I just don't see it!
     
  12. London Lad

    London Lad pfm Member

    Its magic (or b*ll*cks) depending on weather or not you believe in magic :)
     
  13. dougcsv

    dougcsv Member

    Hi, New here today - found you whilst looking for a fix for my 5+ with the same symptoms - so I'm well pleased. I checked with the digital out and it is fine so it sounds identical to the others.

    I have a couple of questions though which I hope someone can clarify for me.

    I'm looking at the board now and it does look like the underside of C416 is a bit 'crusty' otherwise the whole thing looks pristine and dust/burn free. I guess I should replace C416 incase it leaks further, but if I just rmove it will that solve the prob or do I need to replace ?

    Second , If I disable the muting - can I just snip either end of R15 and R115 to get the same result and leave Q2 and Q102 in situ ?

    Many thanks,

    Doug.
     
  14. zanash

    zanash pfm Member


    Where have you been ...this argument was trotted out in the mid 80's and put to bed by a number of cable companies....

    Now if you don't believe ..thats easy take your self down to a good dealer and get a loan cable to try out. If your DIY minded and you must be to post on this section ..then build a simple one from scratch....

    get some 20 amp twin and earth strip it down ..using the three cores do a simple 3way braid ..but tightly and fit good quality plugs ...then try this against the stock issue power cable.

    don't bother replying if you can't be bothered .....remember this forum is for people that do get off there backsides.

    The AAA5 is one of those machines that seems highly sensitive to the type of mains cable used ...I've 5 different types of diy power cables and all make the cdp sound very different ....


    As to why power cables make a difference ..think of them as filter rather than a straight wire....[this is a gross generalization but will get you thinking in the right dirrection]
     
  15. lostintheozone

    lostintheozone Cabin Boy

    A touch intolerant I feel - Jim3 only joined July 20007. We all have to start somewhere and don't all come to this forum fully cognisant of what went before. I came to learn and still am.

    Guy
     
  16. RustyB

    RustyB Registered Ginga

    I feel Zanash's frustration; don't knock it till you've tried it!
     
  17. lostintheozone

    lostintheozone Cabin Boy

    That was not my point.

    I wasn't knocking it - I have no problem with a bundle of plaited wires acting as some sort of filter maybe in a +ve manner.

    Guy
     
  18. ron

    ron Tweaker

    I've had a few Arcam A5's for several years now, all of them have been modified.
    I must admit this cdp does respond well to the mains cables that’s used, I've not faffed about with silver mains cable but using a heavier gauge lead was better than that standard thin stuff normally supplied.
    These units also respond very well to good isolation feet
     
  19. dougcsv

    dougcsv Member

    Hi again, further to my earlier note - I've dismantled the chassis and it is the Cap that's gone phut. which is reassuring.

    Re: the Mods folk have been mentioning - is there a list anywhere of the parts etc. ? I'm ok at replacing bits and I can tell a Capacitor from a resistor but that's about it.

    Cheers,

    D.
     
  20. RustyB

    RustyB Registered Ginga

    I've put together a spreadsheet for the DAC board mods, I can e-mail it to you if you like.
     

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