Blackstar Ht5 effects loop problem

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Blazes, Nov 4, 2009.

  1. Blazes

    Blazes Member

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    Blackstar Ht5 Delay Tail Boost effects loop ??
    First have a look at this vid..

    http://www.youtube.com/watch?v=bfhGaUMCGrY

    My question is should the Ht 5 act like this with a reverb or delay in the effects loop or mine have a problem?

    Wondering if some techs out there can explain to me how to fix this ...

    I e_ mailed to Blackstar . no answer ...

    I found these schematics ..
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    [​IMG]

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    [​IMG]

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  2. Blazes

    Blazes Member

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  3. oldhousescott

    oldhousescott Silver Supporting Member

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    It's the design. I'm guessing you have the dirty channel gain cranked up and the volume down compared to the clean channel volume. The dirty signal hits the reverb/delay at a high (preamp) level, the reverb/delay signal maintains that level as the channel is switched, but now is routed through the clean channel volume, which is set at a higher level so it comes out louder until the reverb/delay fades and the level from the clean channel through the reverb/delay takes over. Long sentence, but hopefully it made some sense. To prove this is the case, set the dirty and clean channel volumes the same and adjust the dirty gain so the level is about the same between the dirty and clean channels. Now try switching channels and you shouldn't notice any surge in volume in the reverb/delay tails. One way to fix it would be to relocate the loop after the mixer opamp, IC5b, but I'm sure that's not really possible with this PCB amp.
     
  4. Blazes

    Blazes Member

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    At same volume it s a little better but still has a delay tail ..

    J've noticed that the delay or reverb are much more present on the clean channel than the overdrive channel..

    Seems that the problem is limited to Time-based effects

    I thought that most effects loop are placed after the pre amp and thus not affected the playin effects volume or sound ..

    On my Traynor YCV40WR , the effects are soundin similar on both channels.
     
  5. oldhousescott

    oldhousescott Silver Supporting Member

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    Yes, that makes sense. The FX loop is after the volume controls in the Traynor, so if you've set them for a similar volume between the clean and dirty channels, there won't be much discernible difference in the reverb/delay signal.

    I can't speak for the designer of the Blackstar except to venture a guess that perhaps he was striving for the best signal-to-noise ratio by placing the FX before the volume controls. It obviously had the undesired, and I presume unintended, effect of these time-based tails jumping in volume under certain circumstances when switching channels.
     
  6. Blazes

    Blazes Member

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    Thanks for your efficient comments Oldhousescott..


    So , from what you see on the schematic, there s no way to fix it
    except perhaps by building a mod to put the effects loop after the volume control if that is possible..
     
  7. oldhousescott

    oldhousescott Silver Supporting Member

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  8. Blazes

    Blazes Member

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    Well ,my tech fix it by sending the signal post to the volume level so now the effects, mainly time-based are sounding just like they are suppose to , no more tail boost between channels..

    It seems that the amph is designed this way so before buyin a HT- 5 ,ask yourself if you want the effects loop to function this way cause you might have to modify on your own expense..

    I do not know if Blackstar has changed the design, i have never received no response or cooperation from them.
     
  9. Blazes

    Blazes Member

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    Here s a schem. of the mod. my tech made..Follow the blue line..



    [​IMG]
     
  10. MatchFive

    MatchFive Silver Supporting Member

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    Mine is doing the same thing, and I just got it for Christmas.. I was using delay and it did it to me.. Maybe it is not a buffered loop? It probably only does it on time based effects like reverb and delay.. It sounds real good even with no effects, but you expect it to work.. It is a major flaw..
     
  11. MatchFive

    MatchFive Silver Supporting Member

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    The schematic for the mod is no longer visible, does anyone have it?
     
  12. Blazes

    Blazes Member

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    It s still there 2 posts up , post # 9 ..

    Worked pretty good for me , seems simple to do ..

    Thanks to Pierre my Tech..
     
  13. MatchFive

    MatchFive Silver Supporting Member

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    Ok, I could not see it here at work.. Fileden is blocked I guess..
     
  14. radix

    radix Member

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    Hi guys, glad i found this discussion as well, have the same problem as well. kinda irritating and probably can't play live with it properly.

    Question, so after the mod, is there any downside to it? As in anything gives?

    rgds
     
  15. Blazes

    Blazes Member

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    No problemo for me ...
     
  16. epoch

    epoch Member

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    Is this a mod the average person can do?
     
  17. aurel1686

    aurel1686 Member

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    Hye Blazes
    Thanks for you post with the FX loop's mod. But do you have (or can you take) a picture of the pcb, where the mod is done ?
    Best regards
     
  18. diagrammatiks

    diagrammatiks Member

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    that's a nice looking solid state amp.
     

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