Well, I've built at least three 303 type circuits which have successfully used 3-4MHz epi transistors, but a modern design should be using the latest 30-40MHz linear gain devices. (And these doubled the original 303 bandwidth without the "current increase" Self wrote about. Those would be harder to stabilise I suspect especially in the NPN-PNP-NPN config.
If it were stabilised it may slug the devices somewhat. A straight triple would be standard these days, which is why I wondered if the Locanthi patent had expired. Think it should have by now.
I don't think Quad had prior art. They avoided the triple of Locanthi because of the patent, not the other way round or Locanthi would not have got the patent, would he?
If it were stabilised it may slug the devices somewhat. A straight triple would be standard these days, which is why I wondered if the Locanthi patent had expired. Think it should have by now.
I don't think Quad had prior art. They avoided the triple of Locanthi because of the patent, not the other way round or Locanthi would not have got the patent, would he?
I’m not sure the dates stack up to that theory. The 303 appeared in 1967, presumably after some development work..
Well if the Quad isn’t close enough to Locanthi to be a patent infringement, how could it be sufficient to prevent the patent if it pre-existed?
From what I have read, Quad used their version because Locanthi had the patent in the works.
But I assume the patent has expired. The triple EF seems quite common now.
But I assume the patent has expired. The triple EF seems quite common now.
Quad were selling the model 50, which also used triples, in 1966. I don't think these things have nearly as much in common as you seem to be claiming. For example Locanthi's patent is explicitly about (a) emitter followers, (b) same transistor polarity throughout each side, and (c) fully complementary topology. There are many ways to arrange triples, and Quad appear to have innovated at least two of them. Douglas Self shows about six types in his Audio Amplifier book, including one which he just invented for completeness.
ejp, I don't know what point you are trying to respond to. Both the Quad 33 and Locanthi triples are/were well known. I even quoted the Locanthi patent number to you, but you outlined it as though I had not read it.
My original speculation was simply a question whether the new 303 would use the 3EF triple configuration with the new fast/linear gain transistors, and that is all. If they choose to use their old 303 configuration, which they may have, all I was wondering whether they would have to have implemented measures for stability.
As the original patent would have expired,as davidsrb says, the 3EF may be available for use.
My original speculation was simply a question whether the new 303 would use the 3EF triple configuration with the new fast/linear gain transistors, and that is all. If they choose to use their old 303 configuration, which they may have, all I was wondering whether they would have to have implemented measures for stability.
As the original patent would have expired,as davidsrb says, the 3EF may be available for use.
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John, you also posted a claim that Quad had to take steps to avoid the Locanthi patent. The evidence available to me doesn't appear to stack up. You said you read it somewhere. Where?
And what I outlined was the points of difference between the Locanthi patent and both the Quad circuits. Seems reasonable to me.
EJP
And what I outlined was the points of difference between the Locanthi patent and both the Quad circuits. Seems reasonable to me.
EJP
The nice feature of the Quad circuit, is that the output transistor temperature doesn't mess the biasing.
The Locanthi circuit has poor temperature stability
The Locanthi circuit has poor temperature stability
ejp, I may have recalled that article incorrectly. My brain cells are not as sprightly as they were and it was quite a few years ago.
It could be that Quad had their triple and were merely "aware" of the Locanthi patent (but did not see a need to change because of it).
In any case, I'll try to find the article but it will be buried deep in a pile of mags.
It was in a review of the Quad 303 development, in the 90's I think. Possibly Electronics and Wireless World, or some hifi mag.
Of the possibilities for the new Quad - they may have kept their original triplet. Many companies do not like to use other ideas. As I posted, it is possible to build a functional circuit with 4MHz type output devices, but my comment was that I suspect it would be harder to stabilise with 40MHz devices.
They could of course use a different configuration, fully complementary, using either the NPN/PNP/NPN style of the upper or the PNP/NPN/NPN of the lower, but both complementary , and as davidsrsb says, either would give a stable quiescent current. The latter option could well be easier with 40MHz devices than the former.
The straight 3EF circuit is easiest of all to use with 40MHz devices. It is worse at quiescent current stability, but with judicial temperature compensation circuitry that can be managed. (It needs to allow for the thermal resistance between the devices and heatsink and provide a degree of, in effect, overcompensation. Putting all six (or more if parallelled) devices on the one heatsink helps too. On the other hand, slight changes in current in such circuits won't affect performance significantly). Self mentioned putting the monitor device on the can - this is harder to achieve temperature monitoring with plastic devices.
It could be that Quad had their triple and were merely "aware" of the Locanthi patent (but did not see a need to change because of it).
In any case, I'll try to find the article but it will be buried deep in a pile of mags.
It was in a review of the Quad 303 development, in the 90's I think. Possibly Electronics and Wireless World, or some hifi mag.
Of the possibilities for the new Quad - they may have kept their original triplet. Many companies do not like to use other ideas. As I posted, it is possible to build a functional circuit with 4MHz type output devices, but my comment was that I suspect it would be harder to stabilise with 40MHz devices.
They could of course use a different configuration, fully complementary, using either the NPN/PNP/NPN style of the upper or the PNP/NPN/NPN of the lower, but both complementary , and as davidsrsb says, either would give a stable quiescent current. The latter option could well be easier with 40MHz devices than the former.
The straight 3EF circuit is easiest of all to use with 40MHz devices. It is worse at quiescent current stability, but with judicial temperature compensation circuitry that can be managed. (It needs to allow for the thermal resistance between the devices and heatsink and provide a degree of, in effect, overcompensation. Putting all six (or more if parallelled) devices on the one heatsink helps too. On the other hand, slight changes in current in such circuits won't affect performance significantly). Self mentioned putting the monitor device on the can - this is harder to achieve temperature monitoring with plastic devices.
It has little to do with the original 303 and 33. It is meant for old people wanting to have what they either had or could not have in their youth. Emotion, looks, memories, UK made but then in the good sense. AFAIK Quad is a chinese company for decades now.
For sure it won't last as long as the original 303, many of them are still going strong. The 303 was a landmark design in a few aspects (the 33 unfortunately was not that good). I don't know anyone that does not like the 303 at least sound wise (but rarely they still own one).
For sure it won't last as long as the original 303, many of them are still going strong. The 303 was a landmark design in a few aspects (the 33 unfortunately was not that good). I don't know anyone that does not like the 303 at least sound wise (but rarely they still own one).
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In The Closest Approach by Ken Kessler, the definitive history of Quad, Ross Walker slams the original design. He hated the "Marigold" (a make of orange coloured rubber household gloves) panel below the tone controls, and reckoned that sales would have been much higher without that. He said the original appearance design was done by his father Peter, and made it look like the earlier Quad II valved power amp and accompanying valved pre, rather than a new appearance totally.
The triples and output stage were actually originally designed by Peter Baxandall, as was the stabilized power supply. Baxandall, in an interview by Doug Self, said the stabilized supply in the 303 was because no-one knew at that time how robust the power devices were to mains power voltage variation - hence the stabilized supply.
Baxandall also wanted Quad to use a 3-transistor phono stage, with an output emitter follower driving the RIAA. PW however saved a transistor by using a two transistor phono stage.
When I was a lad, I lusted after a 33/303 so badly it almost hurt, and could never in my wildest dreams afford them back then. Now, I have a pair of originals, bought from the first owner, that drives our kitchen system. takes inputs from the wall mounted TV's optical output via a D-A, and an FM4 tuner. The 303 feeding (the horror, the horror) ceiling speakers!
I celebrate Quad's reintroductions. What is not to like? It even replicates the "Marigold" panel below the tone/balance controls!
The triples and output stage were actually originally designed by Peter Baxandall, as was the stabilized power supply. Baxandall, in an interview by Doug Self, said the stabilized supply in the 303 was because no-one knew at that time how robust the power devices were to mains power voltage variation - hence the stabilized supply.
Baxandall also wanted Quad to use a 3-transistor phono stage, with an output emitter follower driving the RIAA. PW however saved a transistor by using a two transistor phono stage.
When I was a lad, I lusted after a 33/303 so badly it almost hurt, and could never in my wildest dreams afford them back then. Now, I have a pair of originals, bought from the first owner, that drives our kitchen system. takes inputs from the wall mounted TV's optical output via a D-A, and an FM4 tuner. The 303 feeding (the horror, the horror) ceiling speakers!
I celebrate Quad's reintroductions. What is not to like? It even replicates the "Marigold" panel below the tone/balance controls!
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Because it is just looks. Like new Beetle (flop but it did have the flower vase), new Mini (a BMW with Peugeot engine) etc. Yours are the real thing and both relics, landmarks, conversation pieces and real memories and they are alive in front of you. You can touch them, smell the smell of old electronics and be glad that you managed to find a working one. Copies, reintroductions, reboots or whatever these endeavors are called are more often than not only shallow visually resembling copies and more often than not they are not up to par technically, mechanically and sound wise let alone that they are a true improvement.
It is like that photo model girl you dated with 30 years ago but after 3 marriages and 4 children she wants a relation with you today and you keep looking at that 30 year old picture she sent you yesterday.
Oh and yes, ceiling loudspeakers are horror. Real men do not install ceiling loudspeakers and definitely not connected to a 303 🙂
It is like that photo model girl you dated with 30 years ago but after 3 marriages and 4 children she wants a relation with you today and you keep looking at that 30 year old picture she sent you yesterday.
Oh and yes, ceiling loudspeakers are horror. Real men do not install ceiling loudspeakers and definitely not connected to a 303 🙂
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I love the cosmetics of the 33/303. I’ve owned a dozen or more 303s. In the end they are easily bettered.
If i had a boat load of cash i mighr pick up a pair. I don’t. Highest on my “old cosmetics stuffed with decades newer tech” stuff woukd be a NAIM NAIT 50. NAD brings us the modern 3030, and Muscical Fidelity hasjust released the A1. KLH, JBL, and Wharfedale resurrecting ancient stuff with modern bits and better engineering.
dave
If i had a boat load of cash i mighr pick up a pair. I don’t. Highest on my “old cosmetics stuffed with decades newer tech” stuff woukd be a NAIM NAIT 50. NAD brings us the modern 3030, and Muscical Fidelity hasjust released the A1. KLH, JBL, and Wharfedale resurrecting ancient stuff with modern bits and better engineering.
dave
Ha ha!
Main system are Linkwitz LX521.4 speakers, ten channels of power amp, active crossover. Inputs to the Khozmo passive pre are the Cambridge Audio streamer, and the Garrard 401/SMEIV/Zu audio DL103 cartridge via a three chassis current mode RIAA. The streamer takes inputs from my NAS drive holding all my ripped CD's, and access to Tidal. The whole analogue chain is balanced.
And two Stax electrostatic headphone rigs.
So you'll have to allow me a little latitude with the kitchen system 😎
And then sometimes, we prefer the modern version to the original version.
