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Pre-amp suggestions for a Quad 303 please

Discussion in 'classic' started by PWM, May 29, 2012.

  1. mr sneff

    mr sneff pfm Member

    I don't know if anyone has mentioned this, but I've heard good reports for the Tisbury passive pre http://www.ebay.co.uk/itm/Tisbury-Audio-Mini-Passive-Pre-Amp-Stepped-Attenuator-Preamplifier-/171062829201 £135 new, 30 day trial.
  2. Mignun

    Mignun pfm Member

    I have to agree with Tony here; the 303 should be treated like a low powered valve amp to give of its best. There really is something special to a good 303 - combined with a suitably updated 33 and suitable speakers it makes for a wonderfully romantic amp combo.
  3. Robert

    Robert Tapehead

    A useful tip to get better sound consistency between 8 and 4 Ohm loads on the 303 is to double the size of the output coupling caps. It won't play any louder but the 4 Ohm performance then sounds just the the 8, because the effect of the original small capacitors kick in sooner with lower impedance loads and larger values are preferable.

    4700uf does the trick though you can go higher.
    There is no downside at all. The only reason the 303 was fitted with 2000 or 2200uf caps is that back in the day these were fine for 8-16 Ohm loads common.
  4. LPSpinner

    LPSpinner pfm Member

    Hi Guys:

    As mentioned above the QUAD 303 does behave a little like a valve amp. It has a single ended input stage rather than the more modern input pair; this tends to generate a little more second harmonic distortion in much the same way as a typical tube amp would. The capacitor coupled output stage also tends to impact on bass damping and increases the output impedance particularly at low frequencies.

    Also the regulated power supply will limit the amplifiers ability to deliver large currents into low impedance loads. This mechanism coupled to the slightly higher output impedance of the capacitor coupled output stage will make the amplifier behave like a tube amp.

    I have rebuilt a couple of 303 in my time and they do sound a little warm and lush, but just a bit lush like some of the better tube amplifiers. Like Robert said, increasing the value of the output caps will also bring a few benefits in the area of bass performance. Now days with improved capacitor and electrolyte technology, I can purchase an 8000uf 80Volt capacitor that is the same physical size as the original 2000uf caps; the newer ones perform much better. Being the same physical size also means that changing over is easy and you aren’t left with any gaping holes or gaps in chassis so the job looks neat, tidy and very close to the Quad’s original appearance as well as sounding better.

    I’m of two minds about the 303, it does sounds nice and easy on the ear but I never came to terms with its limitations, I ended up preferring a 405-2 that I serviced and cleaned up. It has better current delivery and tolerates low loads much better. For the times I want to listen to a lush valve-sounding amplifier I have a couple of QUAD II’s. These can sound remarkably good when driving sympathetically matched speakers.

    Oh, and on the subject of preamps, the QUAD 34 is a really nice preamp but make sure you get it serviced and checked over. Keep in mind that the 34 is designed for 100mv DIN level inputs. Later versions had a CD input that can be internally set for 300mV and this does make the volume control a little less twitchy. I ended up padding down all the inputs on my 34 so that all inputs (except the phono input) are now set to 300 mV line level and I have developed quite a respect for little the 34 preamp.

    Another more modern alternative could be the QUAD 24 valve preamp. These use a 2111 sub-miniture tube and sound quite nice. The 24 has all the hallmarks of the older QUAD gear like a cast alloy front facia, heavy gauge steel casing with intuitive and logical control layouts. Unfortunately the QUAD 24 looses the tone controls and slope filtering which is something I kind of miss on mine and this is why I'm hanging onto my 34. I have also seen the QUAD 24 sell for quite reasonable prices on the second hand market.

  5. Robert

    Robert Tapehead

    You could pull it down a little further to 500mv using different resistor flags in the Mk2 34s. Thats quite popular with dacs and CD players. Ditto the tape input which gives at least two 'modern' inputs.
  6. Jo Sharp

    Jo Sharp Pulls on doors marked push

    In my Quad amp days, I always felt that the 33 was the limiting factor..and found that the 303 and later the 405 could show their potential with a different pre. I ended up running a Meridian 101 into the 405. But either power amp, when properly serviced, can still give excellent service if matched with suitable speakers, as others with more experience than I have already commented.
  7. nat8808

    nat8808 pfm Member

    I've an 80s (probably DIY kit) valve pre here that doesn't get on with CD or any modern source but the distortion past 3 o'clock sounds sublime...

    .... as a studio effect. A wierd richness to the top end that feels like an infinitely detailed fine smoke drifting past in sharp focus.
  8. nat8808

    nat8808 pfm Member

    Personally, I think that if you have to ask advice for a pre-amp to match your power amp perfectly then you think too much!

    There are so many beautiful pre-amps out there to try - some beautiful in design, some beautiful sonically. Some will be pretty rare.

    The chances that someone has tried anything other than the usual, run of the mill brands with a Quad 303 and will answer your thread is practically nil.

    You will miss out of a world of hi-fi discovery IMHO.

    I'm currently pairing a Toft LMPA5 with a pair of Nestorovic NA-1 valve monoblocks. I doubt very much that they have ever been paired together before in the history of the world - sound great to me.
  9. LPSpinner

    LPSpinner pfm Member

    Distortion is distortion and is usually best avoided however some people seem to perceive the distortion created by running an input level to the point of clipping as a heightened sense of urgency and tension within the music. I usually try to avoid such conditions.

    With all the line level input sensitivities now set to around 500 mV on my QUAD 34, the volume knob sits between 10 and 15 for normal listening on a scale that is graduated from 0 to 21. That’s a little less than half way to about 2/3 through the knobs range of travel. It’s a comfortable setting that gives me nice and easy control movement and good control for background “wall paper” music as well as full “serious” listening levels.

    On the other hand, on both my naim NAC72 and NAC12 everything happens within the first quarter of a turn, going from nothing to insanely loud. It’s very sensitive, very twitchy and relies heavily on the volume pots ability to track the L & R channels to within a fraction of a dB. Fortunately the Big Black Alps pot does just this otherwise the volume control would be unusable with the balance swinging wildly form left to right with just a fraction of the volume pot’s movement. I still don’t fully understand why such a high level of gain is needed even when you consider that the naim’s original sensitivity is set for DIN rather than live level.

  10. nat8808

    nat8808 pfm Member

    Is definately a good studio effect though, to add a richness to the top end to a sound.
  11. jimification

    jimification pfm Member

    TonyL, Robert, Mignun, LP Spinner: Thanks for the replies, chaps! Food for thought there. :)
  12. paskinn

    paskinn pfm Member

    I think the 'full-monty' Quad 33/FM3/303 (with wooden sleeve) should have a preservation order served on them. The audio equivalent of a listed building. Lovely beyond compare.
  13. NeilK

    NeilK pfm Member

    In appearance - yes, but lovely though it is the performance of the 33 is a little 'dated'. I would try some modifications (... sharp intake of breath). I've given quite a few a go. Firstly replacement cards, I tried some from Net Audio and another source (can't remember the name) but did not find an appreciable difference. On the other hand I have an "Avondaled" 33 and it is very good indeed. Essentially the same character and keeping the tone controls but somehow much more alive. I do a lot of listening with it.
    As with previous posters' opinions I feel the 303 is pretty good as is - but some like to replace the power board with the Net Audio replacement (very easy DIY install, solder 4 wires and do a voltage check).
  14. wibidee

    wibidee Active Member

    I'm hope it's ok to resurrect this particular thread, i haven't made any posts here for a while.
    My usual integrated amplifier is in for a service / check after c. 25 years of service (a John Shearne Phase 2 Reference), so i hunted out my 33/303 pair i had been given by a colleague years back (and had upgraded as per design). I also had a second 303 that i'd sent to Net Audio, back in 2013.
    I hadn't realised that David Pritchard had died... i needed to speak to him after i got my amplifer back from his place, as it had suffered a bent fin in transit to him to work on, and was sorry recently to learn of his passing. He did the work on my 303.

    I also bought at that time a Tisbury passive pre, which i've been using this past week with the Net Audio modded quad.

    I'm trying to like it but it just sounds too bright. I've been updating my quad knowledge on here, noting that Tony on another thread mentioning speaker phase (re Quad 303s fed from passives but that hasn't seemed to have made much difference so far.

    Sources i've been using mainly are a Marantz cd 94 , a chomecast and an old Squeezebox Touch. T

    The cd 94 in particular sounds too perky, which isn't how i remember it when used of old. It's not the gain that seems to be the issue , the stepped volume switch seems to provide reasonable steps up to 11 o'clock.

    The 303 is clearly widely regarded here , i just wonder if i'm missing something in my setup at the moment, or whether simply i'm expecting too much of it.

    I will be able to use the pre outs on the Shearne when i get it back as another test.

    The location might be an issue , as the kit is located in a converted flat roof double garage, used also to accommodate a boudoir size grand piano, although my wife played along to a Bach prelude i was playing on the quad, and the difference in tone was enormous. She pointed out that it did prove her piano was in tune though!

    My speakers are home made (not by me) , based on a pair of Seas drivers (6.5inch mid-bass and tweeter, about 88dB sensitivity, not their most costly units but second best i gather), they're pretty unforiving of poor recordings when they can end up sounding a little harsh.

    How can i get my stuff to sound like a real piano ?
  15. Tony L

    Tony L Administrator

    That is very surprising as the 303 isn’t a bright amp, it actually has a slightly falling treble. There are two big unknowns here for me: a) I have no knowledge or experience of the Net Audio mods, though would argue that if its anything more than a straight service it isn’t a Quad 303 anymore, and b) I don’t know what sort of load your speakers present. The stock 303 hates low impedances and reactive loads, only really shining into above 8 Ohm loads. By saying that it doesn’t get ‘bright’, it just loses dynamics and space and that lovely open valve-like mid and sounds sat-on and lifeless. I don’t know, as what you describe just doesn’t sound like a 303 to me.

    You imply you have two 303s (as all decent people should)? How does the other one sound?
  16. wibidee

    wibidee Active Member

    Well I've tried my other vanilla 303 and pretty similar... although comparing folk modern mixed music and a Bach cello suite both 303s sounded better. My earlier comparison to the sound of a real, relatively large piano was pretty daft too. Next up I'm going to try to use both 303s...I have a cable somewhere that splits a phono pre out into two DINs...one amp handles lower post pair on speaker, the other the upper binding posts. I can't recall technical term for this but interested in how others use two 303s at a time and how they implement this at pre stage.
  17. wibidee

    wibidee Active Member

    Speakers are 8 Ohm impeda nce i should have added...the other point i've noted is that the Net Audio 303 runs considerably warmer than the original, even at idle...I'll be able to try out our new face thermometer on it to see if i can use this to measure by how much!
    I am tempted to look out for a Glasshouse TVC meantime...or an alternative passive to my Tisbury .. to try that out too...
  18. Olsen

    Olsen pfm Member

    I would hesitate to biamp with two slightly different 303 amps unless strange load speakers
    Also require exactly same speaker wire and lenght
    I'd try going back to ordinary stereo after a short while.
  19. NeilK

    NeilK pfm Member

    I used one of Arek's Khosmo passives with a 303 - very nice indeed, bettering a Tisbury I previously used. An opinion, which does not meet with much agreement is to use a 33 - I don't think it is as bad a preamp as it is painted - particularly if it has been competently serviced - especially since you feel the 303 is a tad bright.
  20. stevec67

    stevec67 pfm Member

    I have a 303 connected to a Chinese pre costing <£50. Sounds great. Remote, 3 inputs plus 1 Bluetooth. It's a Weigang Audio ebay special. I reckon that's your "practically nil". Do I win a prize?

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