Quad 303 / 306 / 405 / 405.2

P

Philv

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Hi

changed direction somewhat due to finances.

using kef 104/2 (very easy to drive - 4 ohms) with a quad 99 cdp2.

Im now looking at qiad amps.

I only listen at lowish volumes.

i like a warmish musical sound (like the musical fidelity A1 which sounded luvly with the kefs, but have concerns about long term reliability)

I dont need ultra dynamic or the last extraction of detail.

I would like rca inputs etc.

Does the 306 seem a good fit?

It seems quite good value?

The 303 seems more expensive that the 306? Why?

Should i use the pre in the cdp2 i have or should i go for a 33 or 44 or 36 etc?

what should i be going for?

i certainly woud like to spend less than 200.

Cheeers

 

HoopsOnToast

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If you listen at low levels, I found the Puresound A10 a most excellent match to the 104/2, only lost out a bit at higher volumes.

A little over budget as its going to be in the £200-£300 bracket but could be worth looking out for a tube amp with 4ohm output taps.

Alternatively, the Quad Elite Stereo/99 Stereo could be worth a look as well, I used one with some Magnepan MMGs and it went quite well too, sounded nicer in the top end than the Restek Challenger I moved to which ousted it in terms of bass control, depth and dynamics but had somewhat 'hard' treble.

I picked up the Elite Stereo for £250 IIRC.

The 104/2s are very efficient (92dB/2m IIRC) so as long as the amp is happy with a resistive 4ohm load, then power is not really an issue if you dont want to shake the rafters. IME.

EDIT: I realise I have suggested two amps over your budget, but that's what I have tried recently.

 
P

Philv

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Thanks for he reply.

Really trying to keep budget lower.

hence wondering if a 306 using quad cdp2 pre is good way to go. Prbably cheapest.

 

kernow

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The pre in the CDP2 I'd rather use than a separate older unit.

 

graham67

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Hi,

I never tried the 306, from all reports the circuit is very similar to the 405 just with less power and with a toridal supply instead of a big lump of transformer. If you want warm but dont need ultra dynamic or the last extraction of detail the 405-2 (and probbaly the 306) sounds ideal. you should get a good green/beige DIN version of these for well under 200 and just get someone to add the the RCA sockets in parallel, the holes are pre-drilled in the chassis already! Good Quad 405-2s swap hands on the wam for well within your budget.

If you arent fussy about comestic condition, an average condition late grey RCA equipped 405-2 can still be had for around 200. Good ones seem to be closer to 250 nowadays

And the 405 (and from all reports the 306) respond well to tweaking if more money becomes available in future.

 
P

Philv

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I presume there is no problem between the the cdp2 output at 1.5 mv and a quad 306 input at about o.4 mv?

 

SergeAuckland

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Both the 306 and 405 (and 405.2) will work well with the KEF104.2, as they present an almost purely resistive 4 ohm load. The 303 isn't such a good choice as firstly, it wasn't specified for 4 ohms, just 16 and 8, and secondly by having a series output capacitor, the bass will be down slightly and the output impedance rises. If you're intending to use a KUBE with the 104.2, then the 405 and 405.2 are better choices as the KUBE eats into amplifier headroom, not that the 306 will be lacking for quiet levels, but additional headroom is always a Good Thing.

As to sensitivity, QUAD's 0.5v sensitivity means that the volume control will be working near the bottom. A 10dB attenuator will bring the sensivity up to around 1.5v which will be a good match for the CDP2 output.

S.

 

graham67

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That is a good point about sensitivity serge. Although the 99 pre-amp output level is quite low 0.775v (so not dramatically different from the 405 or 306 at 500mV), the 99 CDP-2 output is a healthy 2.4v. So the attenuated interconnect option would be a good idea. An alterntaive is to decrease the sensitivity of the power amp input. This is done by changing a couple of resistors on the power amp. This is quite common practice, Quad even publish the requried values! It also has the benefit of increaseing the S/N ratio a little.

However I would strongly recommend the 405-2 over the 405. The early 405 (or 405-1 as it became known) struggles to generate much current into a 4 ohm load, whereas the 405-2 was redesigned to manage 4ohm loads without difficulty. Also although similar sounding, I think the 405-2 sounds better than the 405-1. I have both models and prefer the 405-2 in all cases.

And the 405-2 board design (PCB M12565 fitted from serial no 62500 onwards) is certainly better and dispenses with the separate speaker protection clamp boards which can be a pain if you want to fit better speaker terminals. The wiring used for the loom on later 405-2s is also thicker.

Happy hunting!

 

SergeAuckland

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That is a good point about sensitivity serge. Although the 99 pre-amp output level is quite low 0.775v (so not dramatically different from the 405 or 306 at 500mV), the 99 CDP-2 output is a healthy 2.4v. So the attenuated interconnect option would be a good idea. An alterntaive is to decrease the sensitivity of the power amp input. This is done by changing a couple of resistors on the power amp. This is quite common practice, Quad even publish the requried values! It also has the benefit of increaseing the S/N ratio a little.However I would strongly recommend the 405-2 over the 405. The early 405 (or 405-1 as it became known) struggles to generate much current into a 4 ohm load, whereas the 405-2 was redesigned to manage 4ohm loads without difficulty. Also although similar sounding, I think the 405-2 sounds better than the 405-1. I have both models and prefer the 405-2 in all cases.

And the 405-2 board design (PCB M12565 fitted from serial no 62500 onwards) is certainly better and dispenses with the separate speaker protection clamp boards which can be a pain if you want to fit better speaker terminals. The wiring used for the loom on later 405-2s is also thicker.

Happy hunting!
I agree that the 405.2 is a better amplifier than the original 405, especially if used with normally reactive 4 ohm loudspeakers. However, even the 405 was specified into 4 ohms, so provided the load was 4 ohms and above, then the original 405 was fine. What was a problem was that with 'normal' 4 ohm loudspeakers, the minimum impedance was well below that (even the IEC recommendation allows the impedance to drop to 3.2 ohms, and many loudspeakers go below that) such that the 405 didn't do too well under those circumstances. For the KEF104.2, the impedance doesn't drop below 4 ohms (or go above it) so a 405 can be used perfectly well.

Nevertheless, if one can get a 405.2, it's an altogether better amplifier.

By the way, one Quad recommended modification was to monoblock the two halves of a 405 in parallel (NOT bridged), which would drive down to 2 ohms. I made a few of these up for driving Mission Argonauts.

S.

 
P

Philv

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Am i missing something?

Im using a cyrus one with pre in cdo2 at the moment.

Quad 405-2 -

Sensitivity: 500mV in for 100W out (from stereophile.com

cyrus one -

Sensitivity (reference 1W output) - MM: 400uV, MC: 40uV, Line: 65mV

so doesnt this imply the quad needs about 7.5 times the input voltage to get the same output?

with the cyrus, even with the cdp2 volume turned full up, the volume control on the cyrus is fullty usable and causes no mismatch (ie not restricted to 10 degrees of rotation etc)

So, doesnt this imply no attenuation needed for the quad? And in fact id have to turn the volume dial up more etc?

quad cdp2 has max output level of 2.4v rms max

 

SergeAuckland

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Am i missing something?Im using a cyrus one with pre in cdo2 at the moment.

Quad 405-2 -

Sensitivity: 500mV in for 100W out (from stereophile.com

cyrus one -

Sensitivity (reference 1W output) - MM: 400uV, MC: 40uV, Line: 65mV

so doesnt this imply the quad needs about 7.5 times the input voltage to get the same output?

with the cyrus, even with the cdp2 volume turned full up, the volume control on the cyrus is fullty usable and causes no mismatch (ie not restricted to 10 degrees of rotation etc)

So, doesnt this imply no attenuation needed for the quad? And in fact id have to turn the volume dial up more etc?

quad cdp2 has max output level of 2.4v rms max
Yes, you've missed that the Cyrus sensitivity is quoted for 1 watt output. For the same sensitivity as the Quad (100W output) you need to add 20dB.

S.

 
P

Philv

Guest
But the ctyus is 65 mv 1 w

the wuad 500 mv 100 w

divide the 500 by 100 to get equivalent for 1 watt fpr tne quad

then have for 1 watt -

cyrus 65 mv

quad 5 mv

ah!

ok - so to produce 1w the quad needs 7.5 times less input!

so for same position on volume pot it will be 7.5 times louder?

 

SergeAuckland

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But the ctyus is 65 mv 1 wthe wuad 500 mv 100 w

divide the 500 by 100 to get equivalent for 1 watt fpr tne quad

then have for 1 watt -

cyrus 65 mv

quad 5 mv

ah!

ok - so to produce 1w the quad needs 7.5 times less input!

so for same position on volume pot it will be 7.5 times louder?
You're confusing power and voltage. Remeber Ohms law V=IR and power = VI

The Quad has sensitivity of 500mV for 100 Watts. The equivalent for the Cyrus is 650mV for 100 watts.

S.

 
P

Philv

Guest
Well - just hooked up a quad 306 with the quad 99 cdp2.

no problems with gain.

And first impressions - very pleased at low volumes (trying not to wake the girlfriend).

 

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