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Tim
01-04-2011, 21:43
I have recently been looking at Quad Power Amplifiers and in particular the 909. I think I read somewhere here that somebody considered the older models to be preferable to the newer ones, can anyone enlarge on this at all?

Also, is there anyway to tell from the serial number when the product may have been manufactured or where?

Many thanks
Tim

Barry
01-04-2011, 21:56
I have recently been looking at Quad Power Amplifiers and in particular the 909. I think I read somewhere here that somebody considered the older models to be preferable to the newer ones, can anyone enlarge on this at all?

Also, is there anyway to tell from the serial number when the product may have been manufactured or where?

Many thanks
Tim

Although I have no experience of the 909, I believe it is considered to be the best development of Quad's 'current dumping' circuit.

The only advice and caution I would offer (as a loyal Quad user for the last thirty years), is to look for an early model 909 that was made in Huntingdon. Later models were made in China and used cheaper and poorer quality components.

Regards

Tim
01-04-2011, 22:03
The only advice and caution I would offer (as a loyal Quad user for the last thirty years), is to look for an early model 909 that was made in Huntingdon. Later models were made in China and used cheaper and poorer quality components.

Regards
I think that's what I remember someone saying before. It's 8 years old, so I guess that may well make it a Huntingdon model?

DSJR
01-04-2011, 22:08
I thought ALL 909's were made in China...

Seriously, the 606mk2 onwards is a great and well implemented design, but even these may need the supply caps doing by now. The later 909's apparently don't meet their spec for distortion, but replacing the supply caps and other critical ones (see the Yahoo Quad group site and the Dada Blogspot for a reference), seems to restore everything to optimum.

Of the older Quads, I reckon all of them will now need attention if they haven't been sorted in recent years. The basic designs are great IMO, but in stock production form, there is a tendency for Quad sets to sound a bit up themselves and not quite "the closest approach to the original sound" as advertised. Suitably fettled, they definitely approach this ideal IMO :)

Barry
01-04-2011, 22:10
I think that's what I remember someone saying before. It's 8 years old, so I guess that may well make it a Huntingdon model?

If it was made in Huntingdon, it will be marked as such on the rear. If it says "designed in the UK" or "made in an EU approved country", or some such description - treat with caution!

I'm sure it is possible to tell from the serial number, but I don't have that information. Quad's service department (in Huntingdon) should be able to tell you.

Regards

The Grand Wazoo
01-04-2011, 23:33
Well, I've spent many hours in the presence of a 606 & more than a few with a 909 but I reckon that Barry's latest Quad acquisition betters both of them by a healthy margin.

Tim
01-04-2011, 23:56
Well, I've spent many hours in the presence of a 606 & more than a few with a 909 but I reckon that Barry's latest Quad acquisition betters both of them by a healthy margin.
This sounds interesting?

DSJR
02-04-2011, 08:16
What and in what way? :)

jantheman
02-04-2011, 08:23
Quad's service are pretty good at answering questions. They have come back to me every time I have contacted them. Sometimes takes a couple of days but I have always got a reply.

Tim
02-04-2011, 08:27
What and in what way? :)
I guess you mean my last comment? I was referring to the bold text I had highlighted from the post made by Chris
Barry's latest Quad acquisition
I was wondering what it was exactly? I see Barry has some 405's that have been modded and I was wondering if this was what he meant? I think I should maybe ask Barry....

A 405 is also something I am interested in, as well as the 909, but I'm thinking an upgraded 405 would be a better option.

The Grand Wazoo
02-04-2011, 09:33
I recently sold a 520f power amp to Barry which I've had for a long time doing nothing. I spent a while using it before we settled on a deal, and I was surprised at just how great it sounded - better than I had remembered, especially when driven directly from my CD player. I've never done a direct comparison between it & the brick shaped amps discussed above and I've never had them in my system, but I felt I knew them well enough to tell which one I'd prefer.
Barry may have a different view.

Rare Bird
02-04-2011, 12:03
520's are current dumpers

The Vinyl Adventure
02-04-2011, 12:57
"Current dumpers"... Sounds like what rabbits do when the poo!

As you were ...

Barry
02-04-2011, 17:47
I thought ALL 909's were made in China...

I wasn't certain, so I contacted the guys on the Yahoo Quad Users site. One member has replied, stating his 909 was definitely made in Huntingdon.

There have been comments criticising the quality of capacitors used in the later, Chinese made, 909s. I am still trying to find out the serial numbers for the Huntindon built 909s. As I said, I'm sure if you were to quote a serial number to the Quad service department in Huntingdon, they would be able to tell you when and where the unit was made.

Reference has been made to the Quad 520 amp. This was a 150W/channel power amplifier designed for professional and studio use. I bought mine from Chris (TGW), as the 520f can be adapted for use with balanced line inputs (that's what the "f" stands for: floating, and hence balanced, input) and I want to eventually move to a situation where balanced line connections are used throughout my system. But I digress.

At the risk of stating the obvious: the Series 5 power amps (510, 520) come between the Series 4 (405-1 and 405-2) and the Series 6 (606). It so happens however, that the number of output 'current dumping' transistors increases: one pair was used in the 405; two pairs (in parallel) are used in the 510 and 520; and three pairs used in the 606 and later 707 and 909 models.

I have compared the circuit diagrams of both the 520 and 909 power amplifiers, and to all intents and purposes they are virtually identical in both topology and component values.

Now to the performance of the 520, especially compared to the 405-1 and 405-2 amps I have. Well, both 405s have had some work done on them: very little in the case of the 405-2; a lot more so for the 405-1. Mostly it has involved replacing certain components with ones of better quality and specification; the input ic being the most important component to upgrade.

But a comparison has been made, and to my ears the 520 is a noticable improvement. I have not compared the 520 with either a 606 or a 909. Only in comparison to the 405s would I say there is greater detail, lower noise floor and the 520 seems to have an 'authority' to the sound which is not apparent with the others. I noticed subtle detail through the 520 that I had not heard before. I will be writing up my impressions for "Strokes of Genius", but it is early days yet. I'm still assessing the amp and I don't want to come across as a 'kid with a new toy'. No doubt faults will be detected, and I'm sure compared to the super amps from the likes of darTzeel, the 520 has notable shortcomings - however fed with a Levinson preamp, the 520 could very well be my final choice of power amp: it's that good!

Regards

Tim
02-04-2011, 18:02
That's a pretty good recommendation for the 520! I was considering a 405 and getting it modded by Net Audio, but there is a very clean 909 on eBay local to me, it ends soon however, so contacting Quad re place of manufacture is not possible now.

What are your thoughts Barry on getting a 405, or should I perhaps try for a 520 like yours? I have never had a Quad amplifier, but always liked the Quad sound. I would be looking to partner it with some Harbeth speakers, probably the SHL5 eventually?

Barry
02-04-2011, 18:55
That's a pretty good recommendation for the 520! I was considering a 405 and getting it modded by Net Audio, but there is a very clean 909 on eBay local to me, it ends soon however, so contacting Quad re place of manufacture is not possible now.

What are your thoughts Barry on getting a 405, or should I perhaps try for a 520 like yours? I have never had a Quad amplifier, but always liked the Quad sound. I would be looking to partner it with some Harbeth speakers, probably the SHL5 eventually?

I would go for the 909, Tim. I have had a look at the one on eBay, ending in about a days time. It looks to be in excellent condition and bears the serial number 9090845. Ignore the '909', that's the model number, the '0845' is a low serial number suggesting it's of UK build. And, as I say, the circuit of the 909 is virtually identical to that of the 520.

520s don't come up for sale too often. They were designed for studio use and as such when they do appear, are often scruffy and well used. They are very reliable, as is required for studio items, so will be in good electrical condition. The 520 I bought from Chris, whilst not in perfect cosmetic condition was, fortunately, pretty good for an ex-studio item. The only upgrade I may do is to replace the power supply capacitors.

405s regularly come up for sale. If you are handy with a soldering iron then they can be 'fettled' to surprisingly good effect.

Regards

Rare Bird
02-04-2011, 19:02
The fisrt time i ever heard the '405' i hated it & pretty much still do, the '303' to me sounded better i still think it does.

Reid Malenfant
02-04-2011, 19:21
405s regularly come up for sale. If you are handy with a soldering iron then they can be 'fettled' to surprisingly good effect.
Unfortunately they can often have noisy transformers with buzzing windings or laminations :( The only cure is a new transformer, i had to fit a new one to a friends 405 just after he bought it.. He did get it at a very very good price though along with a matching pre & tuner, the replacement (I fitted a toroidal) still got him sorted for a superb price ;)

They are pretty bomb proof, just remember they can deliver 100W RMS into 8 ohms but suffer badly with lower impedance loads due to the crazy current limiting (unless modified) ;)

Krisbee
02-04-2011, 21:15
While it might not match the power requirements of the OP , the Quad 306 always seems to be overlooked in these type of discussions.

With a decent toroidal transformer it doesn't suffer from the problems of the 405/405-2/606 mark 1. While I agree the 606mk2/707/early 909 are worth seeking out, I reckon a Quad 306 is also worth a listen and they can be turned into monoblocks if you need the extra power. They make a nice neat combo with a Quad 34.

In Geoffery Horn's original Quad 306 review which appeared in the June 1986 edition of the "Gramaphone" magazine, he says "I personally rated the professional Quad 520 as sonically superior to even the latest version of the dear old Quad 405, and this £160 cheaper Quad 306 sounds to be its equal in every way (except, of course, power). .. " (He means, at the time, £160 cheaper than the 520 not the 405)

The quad 306 has four power caps to smooth the two split power supplies and 8 power transistors, two current dumpers and two class A power per channel. It's maximum output current is 6 amps.

The Quad 306 was £229 when it was first sold, that's about £500 in today's money. They can be had for typically around £150 now, cheaper than a bantam gold amp.

RobHolt
08-05-2011, 17:08
The 306 is a largely forgotten gem these days.
If the 50w/70w (8 & 4 Ohms respectively) rating is enough then this amplifier is technically a little better than the 405-2.
It manages to both dispense with the OP amp input stage and give near dual mono operation from a physically tiny box.

Not only are there two PSU cap banks but the toroid has dual windings and you have two rectifier bridges.

They are a bargain at today's prices and need little by way of servicing.
The PSU caps can usefully be uprated as at the time of manufacture, nothing larger in terms of capacitance rating would fit the chassis.
You can now fit 6800uf-1000uf as modern caps are physically smaller (and better).

The only snag with this amp (and also the 405) is that they don't like being driven hard for long periods. The heat sinks will quickly get very hot under such conditions and the 306 will then shut down.
Not usually a problem with music but you wouldn't chose a 306 for steady-state lab testing.

Marco
08-05-2011, 17:24
Hi Rob,

Good to see you back! You have a PM :)

Marco.

Tea24
09-05-2011, 16:50
About 18 months ago I bought a 606 Mk2 on DSJR:'s advice in this forum & I am very pleased. It seems to me to really sing ; over & above my 306 - equally a very good amp, but the 606 drives my Kef 104/2s better.

It has a very slight hum, but not enough to worry about - should I have it serviced?

I am a confirmed Quad fan also having the (underrated) 66 CD player & 66 pre-amp. Quad's service is second to none - friendly, Human & rapid. Can't ask for more.:)

RobHolt
09-05-2011, 19:46
Low level hum through the speakers can indicate drying caps on the main internal cards so might be worth a service, especially if you can't hear the problem with the 306.

The 606 and 306 use the same circuit with only two real differences.
The 606 has a larger PSU with higher voltage rails and it also uses paralleled output transistors for higher current delivery.

Tea24
10-05-2011, 07:34
No, sorry, not through the speakers at all, just at the power amp itself.

Barry
12-05-2011, 18:43
No, sorry, not through the speakers at all, just at the power amp itself.

Sounds like mechanical hum to me. The Quad 606 uses a toroidal transformer which are sensitive to DC on the mains supply. If the hum is quiet I wouldn't worry about it, especially if, as you say, it's not coming through the speakers.

Reid Malenfant
12-05-2011, 18:56
Sounds like mechanical hum to me. The Quad 606 uses a toroidal transformer which are sensitive to DC on the mains supply. If the hum is quiet I wouldn't worry about it, especially if, as you say, it's not coming through the speakers.
Of all Quad equipment i have listened to the 405 was the worst for this :rolleyes: Once the transformer had aged they often buzzed like a hornets nest that had been disturbed. A friend of mine was after some reasonable kit & i found a 405, 34 & FM3 (i think it was an FM3 :scratch:) going for £180 in a secondhand shop. We beat the guy down to £155 but discovered the buzzing power amp transformer, it's a common fault. A replacement toroidal that did the job came in at somewhere near £35, i fitted it FOC as it was for a friend.

Nice bargain system in as good as new condition, zero scratches & now fully functional & quiet :eyebrows:

spendorman
12-05-2011, 20:34
Of all Quad equipment i have listened to the 405 was the worst for this :rolleyes: Once the transformer had aged they often buzzed like a hornets nest that had been disturbed. A friend of mine was after some reasonable kit & i found a 405, 34 & FM3 (i think it was an FM3 :scratch:) going for £180 in a secondhand shop. We beat the guy down to £155 but discovered the buzzing power amp transformer, it's a common fault. A replacement toroidal that did the job came in at somewhere near £35, i fitted it FOC as it was for a friend.

Nice bargain system in as good as new condition, zero scratches & now fully functional & quiet :eyebrows:

Mechanically noisy transformer was a common fault with the early 405's. If one bought one new and it was noisy, Quad would send out a new free transformer. It was not usually the ageing of the transformer. Indeed, my 405 purchased new in 1976 was noisy.

chelsea
12-05-2011, 21:05
A friend has a pair of snell k or j i think and doesn't want to try valves.
Do you think quad would work with them?

hifi_dave
13-05-2011, 09:09
Yes of course, as will many amps.

chelsea
13-05-2011, 14:31
Sorry should have said a good match as i know valves are recommended for them and wondered if anyone had heard them paired with quad.

Barry
15-05-2011, 20:52
Of all Quad equipment i have listened to the 405 was the worst for this :rolleyes: Once the transformer had aged they often buzzed like a hornets nest that had been disturbed. A friend of mine was after some reasonable kit & i found a 405, 34 & FM3 (i think it was an FM3 :scratch:) going for £180 in a secondhand shop. We beat the guy down to £155 but discovered the buzzing power amp transformer, it's a common fault. A replacement toroidal that did the job came in at somewhere near £35, i fitted it FOC as it was for a friend.

Nice bargain system in as good as new condition, zero scratches & now fully functional & quiet :eyebrows:

Yes, I've heard that there were problems with the transformer used in the 405. I have a 405-1 bought in 1978 and a 405-2 bought a couple of years ago. Neither have any mechanical problems. I also have a 520 that uses a toroidal tansformer and that too is also silent.

I'm surprised Quad had problems with the (bi-limboid) transformers of the 405s, as they were potted in epoxy resin precisely to prevent mechanical hum due to lamination stack vibration.

Rare Bird
15-05-2011, 21:15
I used to have an huming transformer in one of mine, i changed it for a Toroidal.

Barry
15-05-2011, 22:13
I used to have an huming transformer in one of mine, I changed it for a Toroidal.

Just make sure you have no DC on the mains André. Any more than 25mV with toroids and you'll have (mechanical) hum problems.

Regards

Clive
26-03-2016, 16:54
I'm resurrecting this 5 year old thread....I'm intrigued about the Quad 306. The speakers I use are either very sensitive or at least easy to drive: 100db, 94db and 88.5db (88.5 are easy to drive with 2nd order xover). The 306 has just one pair of output devices per channel which is all my speakers should need, I tend to find that paralleled pairs don't sound as good. Certainly 50W is as much power as I need and total overkill for some of my speakers. Can someone who knows these amps characterise their sound for me?

Pieoftheday
26-03-2016, 21:08
I'm resurrecting this 5 year old thread....I'm intrigued about the Quad 306. The speakers I use are either very sensitive or at least easy to drive: 100db, 94db and 88.5db (88.5 are easy to drive with 2nd order xover). The 306 has just one pair of output devices per channel which is all my speakers should need, I tend to find that paralleled pairs don't sound as good. Certainly 50W is as much power as I need and total overkill for some of my speakers. Can someone who knows these amps characterise their sound for me?

My recent experience with a 306 has been good,used with a novafidelity x40 pre, id describe it as punchy and clean,jim

Clive
26-03-2016, 21:13
My recent experience with a 306 has been good,used with a novafidelity x40 pre, id describe it as punchy and clean,jim

Thanks Jim, that's encouraging.

Pieoftheday
26-03-2016, 21:22
I found the x40 very revealing, a little too much for me,I found myself listening to my system rather than the music,if that makes sense. Can't fault the quad though

walpurgis
26-03-2016, 21:32
My recent experience with a 306 has been good,used with a novafidelity x40 pre, id describe it as punchy and clean,jim

I'd agree. Not owned one, but heard a good few in various systems and always been impressed with the sound.