View Full Version : Any benefit to mono- blocking Quad power amps.

20-02-2011, 09:06 PM

I own a Quad 303 and 405-2 power amp. Is there any benefit sound wise in getting another one of each and mono-blocking. Thanks for any advice.

23-02-2011, 01:55 PM
I'll answer this. Actually I we covered this bi-amping concept here before. (Sorry - does anyone know where this subject is here? I should mention it in the Basic Guide section).

I used 3 x stereo 405s during the development of the M40 active, and reported at the time that the gains (loudness) of the six channels varied under static conditions by one dB or so. That's a perfectly reasonable variation for a mass-produced product but nowhere near good enough to guarantee a sonic balance across the six drive units as I intended at the design stage. I wouldn't waste your time. Drop some money in a charity collector's tin, go home and do some listening. You'll get far more listening satisfaction.

23-02-2011, 04:35 PM
Here, was it?


{Moderator's comment: on behalf of Alan - many thanks!}

23-02-2011, 11:04 PM
Hi, I may be wrong, but I think we may be talking about two different things, Bi-amping (Bi Wiring), and Mono Blocking. I am not thinking about using two sets of cable for each speaker, but rather turning each amp into a mono block and driving each speaker with an amp of its own.

24-02-2011, 11:30 AM
H...I am not thinking about using two sets of cable for each speaker, but rather turning each amp into a mono block and driving each speaker with an amp of its own.As each power amp is stereo (two channel) you have two possibilites as I see it ...

For each stereo power amp you can ...

Ignore one of the two channels, leave it unconnected and drive each entire speaker from just the one operational channel of each of the power amps or ...
Devise some circuitry to drive the inputs of the two channels in each power amplifier in push-pull and then connect each entire speaker only to the two hot (+ red) outputs of the stereo power amp in the so-called bridged mode

Is that correct?

When was your amp last serviced? I'm sure that you know that amplifier (power supply) capacitors age and degrade, and if you want the best possible original ex-factory performance from your amp the best investment is to have it serviced by the makers.

24-02-2011, 12:36 PM
Hi Alan, yes the idea would be to "connect the outputs of the quad 405 in series or parallel to produce a single channel amp capable of delivering in excess of 200watts into high (12-16ohm) or low (4ohm) impedence." Im quoting from a Quad released document. It's just about whether the overall sound quality would be improved, because lets face it, the amps are powerful enough in stereo mode. The same can be applied to the 303.

All my quads 303, 404-2 and 606 are recently serviced and i have "updated" the preamps, 33 and 44 with some "upgrade kits" , it made a huge difference to them soundwise, and made them more useable with cd players etc.

24-02-2011, 01:27 PM
I'm very curious about 'connecting the outputs in series or parallel'. This doesn't sound like a recipe for improved fidelity to me with the potential for more hiss, more non-linearities and more distortion .....

24-02-2011, 01:46 PM
I wish i could upload the Quad release sheets on this as it would give you a fuller picture, unfortunately i cannot seem to upload pictures into the thread. I am not that technically minded about the process, but Quad did sell kits to do the conversions. I have found a link to a discussion...


24-02-2011, 04:13 PM
...I am not that technically minded about the process...In my honest opinion, you should stop right now! You will need good technical skills at component level to comprehend what you are letting yourself - and your speakers - in for. The risks of damage are very great. Please don't take any risks with your precious audio equipment.

If I was attempting such a conversion I would have test equipment to hand. And at the back of my mind would be the worry about some unexpected component failure and possible destruction of the amp and/or speakers.

24-02-2011, 05:27 PM
Yes, I take your point, and think that is sound advice. It was tempting after the success I had with the preamps, but i accept my technical limits could lead me to a potential disaster. Thanks for the input.

25-02-2011, 06:12 PM
If power is not an issue with the stereo amp concerned, is there an advantage to monoblocs? (I've read about things like less crosstalk between channels but I can't say I really understand it.)

In my case I own both Quad 99 and 909 amps but slightly prefer the tonality of the 99. In the past Quad has made the 99 in monobloc form (Quad is now doing it for its new Elite series which is an update of the 99 series) so again I'm curious if it's just an issue of power.