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Quad 909 upgrade/mod list

Discussion in 'classic' started by Chris88, May 7, 2017.

  1. Jim Audiomisc

    Jim Audiomisc pfm Member

    Good luck. :) You'll have to follow the advice of the "many people" who have told you what you now believe. I can't help you if you've already made up your mind about that. Personally, I tend to be cautious of "extensive research" of the *opinions* of others which you may have no way to judge the reliability of if you have no real experience of even basic electronics - let alone amplifier design.

    Your intended aim is fine. But the result may be a lot of wasted time and effort, I'm afraid. However I hope you succeed. Experiment can be a good way to learn. But it can also be costly if you may mistakes with consequences. Goes with the territory.

    Personally, if an amp works well but the results sound 'boring' I'd be more inclined to change the music, speakers, or room as experience shows those factors often make a very noticable difference. As does the simple change of adding, say, a 1 Ohm resistor in series with each speaker in many cases. :) But its your time and money. :)

    Note, though, that changes inside a loop may cause problems like instability, etc. So you risk making things worse. Indeed, if unlucky you may do damage to the amp.
  2. Chris88

    Chris88 pfm Member

    What do i base my findings on in terms of identiying sonic characteristics of different brands of capacitors? Actually countless opinions of many many DIY people from all across the internet, on sites such as this one who have years of experimenting and trying out different caps. I literally have compiled dozens and dozens of comments from peoples experiences documenting sonic characteristics of different caps.

    In terms of technical mods, tips and tweaks; Dada electronics, LesW and other people who sell their mods for cash.


    I'll work on a single amp first before i assess efficacy and safety of the mods (in other words one amp can be my guinea pig lol).

    Yes it is a risk, but nothing ventured nothing gained right? ; )

    I'm running Epos 22 speakers that are mint and hardly used, no need to change them.

    As for the room, i'm actually going to pay builders to make a purpose built audio room with it's own dedicated AC line and fusebox.

    I'm using a Ceek passive pre amp (Alps pot) which i love, very clean and clear sounding and despite what some people say, lots of bass.

    As for the amps; x3 Quad 909 amps to tri-amp my Eposs M22's : )

    So there you have it chaps!
  3. Jim Audiomisc

    Jim Audiomisc pfm Member

    How do you assess that as *evidence* if you don't understand the electronics or physics involved? There are "countless" opinions of all kinds on the internet. They aren't *all* correct. Nor is science or engineering a matter of a majority vote.

    Note also that inside a high gain feedback loop, the loop will tend to squash any such 'differences' in terms of altering the output produced by a given input. So a claimed 'difference' in one situation doesn't ensure the same happens in another.
  4. Julf

    Julf Evil brother of Mark V Shaney

    And my experience (that happens to cover not only electronics engineering at university level but also 40 years of practical electronics and audio experience) is that DIY people always hear an improvement when they make a change. :)

    Wouldn't they have a vested interest in promoting their mods?
  5. Chris88

    Chris88 pfm Member

    Would they have a vested interest? Possibly, thats why im going to try things out and listen for myself!

    I dont need a degree in electrical engineering to know what sound i like, nor do i need one to understand others peoples comments about what they like.

    If 30 people say Elna Silmic 2 is laid back and recessed in the highs, and 3 people say the opposite, what do you think would be considered consensus? Yes i would consider the comments of those 30 people as evidence.
  6. Julf

    Julf Evil brother of Mark V Shaney

    My qualifications aren't in any way extensive - just typical of what a typical electrical engineer would have.

    Happy to encourage someone in their endeavour, but electronics is the domain of engineering - a form of applied science. One of the first things an engineer learns is to have an open mind while at the same time being systematic, evidence-based and critical.

    If the 30 and 3 people are on a DIY forum, but a bunch of peer-reviewed publications say the capacitors don't make a difference in that application, guess which I would believe?
  7. linnfomaniac83

    linnfomaniac83 I bet you can’t wheelie a unicycle!

    They would but LesW is a highly credible electronic engineer. I owned one of his modded Arcam Alpha 5+ CD players along side a bone stock example. The modded one was notably better... but on that note, I'd only really be interested in mods created by an engineer who has a detailed knowledge and understanding of the design they are modifying.
  8. Tony L

    Tony L Administrator

    My attitude to this stuff tends to be to buy the amp I like the sound of in the first place rather than modify it to be something else. I very much like Walker-era Quad kit, and all of that is past the stage of needing servicing now. As such all mine (33, FM3, 34, 2 x 303, 306) has been rebuilt, though the fundamental design is unchanged. I've just had it rebuilt with good quality components that should now see me out. I have the Dada High End boards in one 303, but only because the original boards were in a poor state - they are very similar, just better quality (glass fibre and loaded with decent components). With a 909 I'd just be looking to undo any Chinese component cost-cutting and maybe remove the Quadlink circuit, the fundamental design is sound (it is really a 606 in a better finished case).
  9. linnfomaniac83

    linnfomaniac83 I bet you can’t wheelie a unicycle!

    Possibly the kind of advice you're interested in but I've done the passive bi/tri amping thing. I have heard an improvement in doing so but not nearly as big as the improvement you'll hear by spending the money you'd spend on two or three amps on one better amp. Multiple amps make much more sense in an active system but that only makes sense if the active crossovers are properly designed/tuned for the speaker. I have two active systems but they are Linn systems (surprise) where the crossovers are specifically designed for the speaker.

    If you really want to hear an improvement, sell all three 909s and spend the money on a better (or better for your taste) amp, you might not even need to spend that much. Stuff that will work nicely with your epos speakers and give more detail/excitement include Densen, Exposure, Naim, Linn and a bunch of other nice stuff. Note that this is my subjective view having listed to designs from all of these manufacturers. I tend to find Quad amps a bit mellow. Interestingly, the most exiting Quad amp I've heard is a newly restored 22 combo, it was properly good fun.
  10. JensenHealey

    JensenHealey pfm Member

    So are your speakers already tri-amped? What are you using for active crossover?
  11. linnfomaniac83

    linnfomaniac83 I bet you can’t wheelie a unicycle!

    It's possible to passively triamp ES22s and I'm guessing that's what the OP is doing hence the reason I suggested putting his efforts into one better amp.
  12. JensenHealey

    JensenHealey pfm Member

    My mistake - still using passive crossovers in the speakers.
  13. Chris88

    Chris88 pfm Member

    Can anyone advise me of the required voltage for the following resistors for the 909?

    R1; 560R 1/4W 1%
    R2; 22K 1/4W 1%
    R16 & R17; 560R 4W 5%

    The manual doesn't seem to mention the required voltage.

    Would be very grateful for any feedback.
  14. Barrymagrec

    Barrymagrec pfm Member

    Resistors are rated for power, not voltage.
  15. Chris88

    Chris88 pfm Member

    When i browse resistors on mouser/digikey ect they always list a "voltage rating" with their specs, 200V, 350V ect.

    Are you saying any voltage is ok?
  16. Barrymagrec

    Barrymagrec pfm Member

    That is what is known as the limiting element voltage.

    Obviously you should never exceed the power rating of the resistor and the voltage required for maximum power dissipation will vary according to the resistance value, in the case of a 10ohm resistor for instance 10 volts will dissipate 10 watts but for a 100 ohm resistor it would only be 1 watt.

    In the case of high value resistors it is possible that the voltage required for maximum rated dissipation is very high and this is where the limiting element voltage must not be exceeded even though the resistor is well within its power rating.

    None of this is of any worry with the relatively low values you have listed and with the voltages available in the 909.
  17. Chris88

    Chris88 pfm Member

    Thankyou Barry.

    When i'm resistor shopping on mouser, would it be fair to say i don't really need to pay attention to the Volts?

    For some of the Vishay wirewounds they don't list volts at all in the specs.
  18. Julf

    Julf Evil brother of Mark V Shaney

    Any of those voltages will do. The voltage rating is a maximum rating, and in a semiconductor amp you will never get anywhere close to the maximum voltages of typical resistors. Valve amps are a different story - they have high voltage circuits that might require paying attention to the voltage ratings of the resistors.
  19. Barrymagrec

    Barrymagrec pfm Member

    As Julf mentions, only worry if you are looking at valve amp voltages.
    Wirewound resistors will not normally be of high enough value to worry about voltage.
  20. davidsrsb

    davidsrsb pfm Member

    SMD resistors have low ratings, typically 50V for 0402 and 75V for 0603

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