DIY Phono Stage WIP

Discussion in 'DIY Discussion' started by BL21DE3, May 14, 2004.

  1. BL21DE3

    BL21DE3 aka 'Lucky'

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    Well after spending several weeks looking at designs and sourcing components, I've finally started the assembly process on my DIY phono stage. I've based the design around the octal variation of the Hagerman Tech 'Cornet' phono stage, my thanks to Penance for pointing me in the direction of this design. However I've gone for the complete homebrew approach of building on stripboard rather than a PCB, mostly to keep my overall costs down and for the fact that I can assemble the circuit in a smaller footprint to accomodate my case design.

    At this stage I've double checked the physical layout of all the components, drilled mounting holes for the insulated spacers and assembled the circuit for the left channel.

    [​IMG]

    To Do:

    Lots of things not least......
    Assemble the right channel.
    Assemble the circuit for the power supply.
    Tidy up soldering, trim resistor/capacitor legs and break tracks.
    Finalise and assemble case.
    Put it all together.
     
    BL21DE3, May 14, 2004
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  2. BL21DE3

    themadhippy seen it done it smokin it

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    is the cornet a valve circuit?if so what sort of voltages are going to be roaming around the strip board?
     
    themadhippy, May 14, 2004
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  3. BL21DE3

    Chea Johndle Bizarre Serpent Foomaster

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    Looks like BIG voltages to me...:D

    Regards
     
    Chea Johndle, May 15, 2004
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  4. BL21DE3

    penance Arrogant Cock

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    yep, its valve
    Around 375V on B+ supply. I think tag strip may be more suitable?
     
    penance, May 15, 2004
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  5. BL21DE3

    BL21DE3 aka 'Lucky'

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    I was under the impression that stripboard was susceptable to current rather than voltage. And as I've built the circuit to keep all the high current lines (i.e heater supply) off board I didn't see a problem with using stripboard, though I may have overlooked something as my electronics knowledge is limited. Thanks for the comments so far and I would appreciate any advice more experienced DIYer's can provide.
     
    Last edited by a moderator: May 15, 2004
    BL21DE3, May 15, 2004
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  6. BL21DE3

    themadhippy seen it done it smokin it

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    the problem with stripboard is the gap between the tracks,not the tracks themselves,if i have to use it for anything over 100v i remove the tracks either side of the power rails,as penance has mentioned tag strip is realy the thing to use.
    Anyway way one tip,dont bother with a fancy tool for breaking the tracks,a 4mm drill bit works much better.
    o and is there a circuit diagram somewere i can have a nose at;)
     
    themadhippy, May 15, 2004
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  7. BL21DE3

    BL21DE3 aka 'Lucky'

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    Well tag board seems to be as common as hens teeth so I'll look into modifying the layout to allow for removing the strips round the power rails. I assume this is just a case of scraping the copper track out to leave bare board.

    As for breaking the tracks, I've already got the 'fancy' tool courtesy of my father's tool box, but thanks for the tip.

    The circuit diagram is available here http://www.hagtech.com/pdf/cornetoctal.pdf

    Edit: Forgot to ask, on the circuit diagram I assume that the power rail is the line running from the rectifier valve through C10, R2, C4 etc.
     
    Last edited by a moderator: May 15, 2004
    BL21DE3, May 15, 2004
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  8. BL21DE3

    penance Arrogant Cock

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    tag strip is common

    FL29G - maplin 14 way single strip, they also stock double strip.
     
    penance, May 15, 2004
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  9. BL21DE3

    themadhippy seen it done it smokin it

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    cheers for the link,as for removing the copper strip,heat it up with a soldering iron and peel it of.
    see wot you meen about tagstrip,the stuff i use is discontinued by maplins (fl11m) they olny do fm34m.[​IMG]
     
    themadhippy, May 15, 2004
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  10. BL21DE3

    penance Arrogant Cock

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    yep thats the B+ supply from the 5Y tube

    World audio design stock tag strip aswell here
     
    penance, May 15, 2004
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  11. BL21DE3

    BL21DE3 aka 'Lucky'

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    Thanks for the info guys. Looking at my layout, it wouldn't be any hassle to remove the two strips around the power rails as I've not placed any components in either of these strips.
     
    BL21DE3, May 15, 2004
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  12. BL21DE3

    BL21DE3 aka 'Lucky'

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    Well I bit the bullet, ramped up the heat on the soldering iron and peeled off the tracks on either side of the power rails. Quite a neat trick and worth remembering for future builds.
    Next I'll need to put the other half of the circuit together and then it's time to finalise the design of the case, though blue LEDs are a must :D.
     
    BL21DE3, May 15, 2004
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  13. BL21DE3

    penance Arrogant Cock

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    sounding good:)
    The standard cornet responds well to tweaks, i imagine the octal wil aswell;)
     
    penance, May 16, 2004
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  14. BL21DE3

    BL21DE3 aka 'Lucky'

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    Well the other half of the circuit has been assembled along with the resistor/smoothing cap for the power rail. So now it's time to down the soldering iron and get the case building under way.

    Penance, I reckon I'll give it a bash with the stock components and then see what can be improved/tweaked. I'm looking forward to seeing how the vintage Raytheon and Sylvania valves perform.

    [​IMG]

    [​IMG]
     
    BL21DE3, May 16, 2004
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  15. BL21DE3

    BL21DE3 aka 'Lucky'

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    Well after several design revisions, the enclosures for the phono stage have finally been assembled.

    Firstly the PSU case.

    [​IMG]

    Secondly the phono stage case.

    Front
    [​IMG]

    Back
    [​IMG]

    The aluminium still needs finished and cut to accomodate the valve bases. And the boxes have to be painted, I'm thinking of a nice high-gloss black finish to match my 11L's :).
     
    BL21DE3, Jun 29, 2004
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  16. BL21DE3

    Lt Cdr Data om

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    looks fantastic, how about the top of the range hagerman?? I don't think they show the schematic with this??
     
    Lt Cdr Data, Jul 3, 2004
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  17. BL21DE3

    penance Arrogant Cock

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    no its not shown :(
     
    penance, Jul 3, 2004
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  18. BL21DE3

    BL21DE3 aka 'Lucky'

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    Thanks for the comments guys. The aluminium has been cut and finished. The cases have had their black gloss paint applied (Halford's best automotive spray paint :)). Now I've just got to wait for some less windy weather to get them outside for the final coats of clear laquer followed by some nice polish. Then it'll be time to do the final assembly of the circuit and electrics into the cases. Hopefully it'll all work.
     
    BL21DE3, Jul 7, 2004
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  19. BL21DE3

    BL21DE3 aka 'Lucky'

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    Well the stripboard layout got ditched in favour of a point-to-point layout, partly because it was proving somewhat dificult to connect the valve bases to the circuit and also because the stripboard got damaged in the process. So finally everything has been wired together in a mad three dimensional manner and stuffed into the amplifier case. Then came the fun of powering everything up. Out to the back garden with the units sat on a picnic table with a 10m extension cord and circuit breaker. Hit the power button and retreated to a safe distance. No smoke, no giant arcs of electricity and no smoke. So far so good :). Next step attached the P25 to the input sockets and the outputs to Aux 1 on the RA-02. Powered everything on carefully and chucked some vinyl on the deck. Not a peep out of the speakers, carefully brought the volume up a bit more, still nothing. So I tried swapping over some of the tubes in case they were at fault. Got nothing out apart from some microphonic noise, which at least indicated that some sort of amplification was occuring. So I've opened the amplifier section up but I can't see any immediate faults with the layout. I've also opened up and checked the PSU outputs with the only anomally being that the B+ line is at 413V DC rather than the 325V DC I expected, though checking the Hagerman Tech forum I see that this is probably due to the fact that there is no load drawing on the supply. So it looks like there's either a flaw somewhere in my circuit or all my valves are stuffed :(. Oh well back to the kitchen table to pore over the circuit and see if I can trace the fault.
     
    BL21DE3, Jul 22, 2004
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  20. BL21DE3

    themadhippy seen it done it smokin it

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    Are the valves lighting up? if not then check the heater supply
    are both channels dead? if so then its proberly something common to both sides
    have you a test amp? (a powered copmuter speaker is ideal),use it to test for signals,working backwards from the output.
     
    themadhippy, Jul 22, 2004
    #20
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