On Friday, 30 May 2014 22:51:13 UTC+10, Phil Allison wrote:
** Hi all tube fans,
please enjoy this U-tube made by a most famous British audio guru.
Contains all you ever wanted to know about Quad's famous tube based tuners,
pre-amps and power amps from the 1960s.
Plus a tutorial on setting up your tone arm for playing LPs.
An absolute must see !!!
https://www.youtube.com/watch?v=qxT0A-UlT20
.... Phil
I tried to watch the video where an ancient man with Yorkshire accent tried to explain about ancient Quad junk. I guess he will attract admirers, but I ain't ever gonna be one. I gave up on the man when he showed the under chassis view of a Quad-II power amp and I could see not a single original R&C part had been replaced.
Then comes his statement that the quality of the original resistors and caps were really excellent and that the resistors and caps you buy now won't even last a year.
Rather than waste any more time listening to the man, I clicked off to more urgent matters, like doing a load of washing etc. I believe there might be something he said from which someone@somewhere could benefit, but I'd much rather replace much of what Peter Walker included in his tube amps.
No doubt the man is fond of the Quad radio tuners. Just about any generic AM-FM tuner which is full of chips including a Gilbert cell based stereo decoder will give better FM than the tubed Quad.
But the AM tuner of Quad is quite good, mainly because it has ONE feature rarely ever found on any other super-het AM radios or tuners, and that is the switched tertiary winding on IFT1 which extends the 455kHz IF pass band so that you get far more HF audio content than the appalling performance of many SS tuners giving 1.5kHz or many tubed radios giving 3kHz max.
In my tubed AM radio I get 9kHz AF bandwidth by means of altering the distance between IFT coils slightly closer on their formers. This makes a normal set impossible to tune properly by ear. So I made an SS based high Q filter on a small circuit board which reacts to 455kHz, and I have an op-amp detector just for this F, and a limiter, and so when the IF = 455kHz, a meter needle swings up to a maximum, to tell you when the radio is tuned properly. This works far better than any tuning eye meter which works from the AVC voltage.
So every time I tune, I can get my radio IF to be 455khz, +/- 500Hz and the sound from local Radio National 845, or 2CY, is often better than from a good 1970s Pioneer FM tuner.
Quad could have done much more to improve AM reception, but then maybe nobody would have appreciated the efforts, let alone pay the extra for them.
Later, of course, as Poms got slightly better off after 1960s they could afford the better offerings of Quad using all SS and chips.
I can't wait to gut another pair of Quad-II amps and install a far better circuit.
Patrick Turner.