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DSE amp to power amp mod.

Discussion in 'Electronics & Electrics' started by TERRA Operative, Aug 25, 2006.

  1. Corky

    Corky Member

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    sorry to bump this old thread but i don't quite understand what you mean by better polyester caps. Do you mean polyester MKT?

    I've been thinking about maybe replacing them with decent polypropylene type but unsure if it would make as much of a difference.
     
  2. OP
    OP
    TERRA Operative

    TERRA Operative Member

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    Polypropylene caps are the best to use for audio, and are recommended, if they will fit..... (see my size comparison). They are best used in the signal path in place of electrolytics as I have done. Electrolytics tend to introduce distortion, and as such are best left for low frequency (ie sub woofer) use where the electrolytics offer substantial cost and space savings.

    I can't remember if polyester caps have a rating system like ceramics (NP0 are the best for them) but I do believe the metallised MKT polyesters are better, and a suitable substitute.
     
  3. benh

    benh Member

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    Hi

    I have read the wiki about mods to the a2760 and just wanted some clarification.

    In the wiki, the steps involve removing the preamp section completely. Can I just unplug it from the fuse board and then make the changes to the plug configuration for the ins and outs?

    Thanks
    Ben
     
  4. OP
    OP
    TERRA Operative

    TERRA Operative Member

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    You can unplug the preamp, and arrange the jumper wires to bypass it no worries, but the volume control will no longer work (you will be effectively making a power amp). You will have to adjust the volume from your source unit.
     
  5. benh

    benh Member

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    Thanks, that's just what I want to do.

    Ben
     
  6. supernerd

    supernerd Member

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    Sorry to resurrect an old thread - but I'm having major trouble constructing the volume control. Now, from what I can gather from the wiki - there are 2 wires per cable - thus there are 8 cables to join onto the pot. From what I can see from the picture - you put the resistors onto the left leg, and then the red wire on the resistors. What did you do with the other wires?
     
  7. Red Spade

    Red Spade Member

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    I'm working on modding this amp as well, having picked one up second hand. I've bypassed the preamp and now want to hook up the 100k pot as a passive attenuator, but I'm unsure of the wiring. This diagram shows my understanding of how the wiring should be done:

    [​IMG]

    Can anyone confirm if I have it right, or if not, how should it be wired up?
     
  8. g4r3th_b

    g4r3th_b Member

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    I'm a total noob to this kind of thing, I've only really soldered wires together or to replace caps and the sort, so am having trouble figuring out how to make the volume control work. I've had this amp with the pre-amp bypassed for a long time, but now I'm moving this amp onto a different use and would be handy to have a volume control.

    Any help? break it down to dumb man with fat fingers who can't read circuit diagrams? (I've googled how, but nothing I've read is helping me figure out how to turn the diagram into a working something).

    I've so far got 2 resistors (twisted the ends together) soldered onto each of the left legs of the pot. Having trouble with this mainly....
    "Strip the wires a little (about 5mm max) and twist the shields together. Solder this to the middle leg on the pot closest to the shaft. Now solder the centre wires to the ends of the resistors on the corresponding 'level' of the pot. Repeat for the other wires."

    There are 2 wires per cable, a red and a black. So I solder the red wire to the middle leg on the pot, and the black wire to the resistors on the same side. Since there are 4 cables in total, I solder the black from each cable to each end of the resistors, and 2 red wires from the 2 different cables to the middle leg of the pot? So 2 red wires are soldered to each middle leg of the pot? And one black wire to each top of the resistirs? And the third leg of the pot is left without anything attached?
     
    Last edited: Feb 4, 2017
  9. azzachaz

    azzachaz Member

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    Wow. Nice thread necro.

    Its funny reading about people buying electronic components from Dick Smith.
     
  10. orbitaudio

    orbitaudio Member

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    Some good info in this thread!

    Not sure how far you got with distortion measurements - I'd be interested to see the results if you did get that far.

    At any rate, my summary from reading Audio Power Amplifer Design was to replace any Carbon Film or Carbon Composition resistors with Metal Film/Foil resistors. Specially any resistors in the feedback loop...

    From Chapter 2 - The Basics of Distortion, pg50
    Might be some thoughts for extra mods. Although hard to tell for sure, from the photos you've posted the resistors look like 1% metal film.
     
  11. Technics

    Technics Member

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    I've still got one of these amps out in the shed. in terms of distortion. The thing that stands out in the design is the negative feedback being connected from the pre-drive rather than the output. That and the VI limiter. I would think they would be targets before component swaps. I was never enamored with the sound of the thing but I think there is lots of room for improvement.
     
  12. mikeyyy

    mikeyyy Member

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    Hi I have one of these amps and was thinking about modding it for fun as a side project. My use case is that I have 3 sources (main PC, a banana Pi running shairport, and a PS3) with the amp going into my sub (and speakers from there).

    I was considering just unplugging the preamp stage first and seeing how that goes. I'd like to be able to have all my sources mixed together and going straight into the amp so I don't need to manually switch sources on the amp. I was considering buying this passive mixer https://www.amazon.com/gp/aw/d/B00102ZN40 and then using the mixer controls to control individual volumes of each source.

    Does this sound like a good idea? My main concern is after I remove the preamp stage I don't know how much power I'll be pumping to my speakers, if I plugged line-level straight in from the PC (STX essence) would I risk blowing my speakers?

    Also does the source selection knob still work after unplugging the preamp stage? If so, would it make large pops when changing source? And the passive mixer is a better idea?
     
  13. underskore

    underskore Member

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    about 2 months ago my trusty old DSE amp finally started giving me some grief... it's seen a lot of loud usage in the 10+ years that I've had it so I was a little sad when it started to let me down.

    It's symptom - a huge loss in volume/bass on one channel - there's still a bit of volume coming from a speaker when connected to that channel but only a shade of what it should be.

    I've done enough input/speaker swaps to make me think it's the power/output stage of the amp that has the problem but I've only popped the case open and had a look around so far.
    There's no components displaying obvious signs of failure. I need to find the time to have a decent poke-around with a meter :tired:

    Has anyone experienced a similar issue - have any ideas on where/what to examine first?

    as for the post above I'm surprised to see such good reviews on a passive mixer...
     
  14. g4r3th_b

    g4r3th_b Member

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    If you remove the preamp and use the line level from your pc, you would control the volume from the pc. Jut make sure the pc volume isn't up very high when you turn the amp on and you won't blow anything. The selector switch still works with the preamp removed.

    However I did end up adding the volume control back anyway. I don't get any pops changing source. I have my PC and a wireless network player/adapter plugged in and all works well.

    But before I added the volume control back, just had to make sure both sources volume was set low before turning the amp on and switching source.

     
  15. mikeyyy

    mikeyyy Member

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    Thanks for the info. :) Maybe I'll open it up mod it this weekend.

    Would adding a passive mixer affect the sound quality significantly? Perhaps I'll buy it and then compare with and without.
     
  16. driver

    driver Member

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    Still running one of these for my PC speakers - 10+ years later :D

    I picked up another DSE amp which has started doing exactly that. Turns out resistors R222 and R268 are completed toasted as per http://www.diyaudio.com/forums/solid-state/131048-dse-a2760-amplifier-aka-koda-261-a.html

    I got this unit second-hand, so I'm not sure what sort of torture it was subjected to in the past.
     
  17. underskore

    underskore Member

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    wishing I still had mine sitting in the shed to fix up after hearing that bit if info... but I've got more audio gear than I have room for so i don't feel too bad about turfing a non working unit :'(

    edit: hrmm after reading right through that maybe it wasn't really worth fixing anyway
     

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