Valve Amplifier Study 022: Quad II Vintage British Hi-Fi Amplifier
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- Опубликовано: 27 июл 2024
- This is our proudest video to date covering the Quad II British Valve Amplifier dating from the 1950's.
We have done quite a thorough job here describing the circuit and essential work and observations to carry out before powering up after being in storage for some time.
Our next video will cover the Quad Control 22 Pre Amplifier which goes with this unit.
Further Updates: We will come back to this circuit design in the future when we cover basic theory in much greater detail and will include this in our Interactive Online Quiz. Our Studio Technician will also have a lot to say about this unit as well as the mic pre-amp stage.
Please become a member on our website www.vintageaudioworkshop.com and subscribe to our facebook page vintageaudioworkshop. You can also support us by buying us a coffee at www.buymeacoffee.com/PaulVAW
Thanks for watching. 
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I wish all videos were this comprehensive, intelligent, and well-paced.
Brilliant. I have a stock of or so Quad II's hat I am bringinge back from the grave. 10 or 15 years ago ther were the best I have ever heard. But now they need attention. These insights are pure gold!!!
Thanks for your comment. Very appreciated.
I've got four that were rescued from a demolished theatre/cinema and all appear complete. The only issue seems to be the iron chassis are bent where presumably heavy equipment came into contact with them. That metal is really tough! Thanks for this, and it will help immensely with the refurbishment project.
I have a Leak Point One Stereo valve amplifier which has been fully restored! Quad and Leak are wonderful amplifiers!
My first job after leaving tech collage was with Quad as a lab assistant under John Collinson. He would sit at his desk surrounded by a pair of Electrostatics playing Radio 3 all day!! One day after a big bust up in the office, he was gone and so was radio 3!!
The Quad 11 really was a good amplifier, well ahead of it's time, much better than the poor sounding Quad 33/303 combo. The stereo decoder bolted onto the back of the tuner, cost 16 pounds if I recall...was along time ago.
Glad to hear from you! Paul
It's OK, you can call me Paul if you like!!
This video is totally brilliant. Thank you for making it in a world of opinion.
Thanks we have a lot more to add, look out for our Quad Control 22 pre amp video soon to post. Paul
Very interesting video and information my dad had this equipment in the 60s including the decoder for stereo fm also the am tuner which if my memory serves me right was available as either medium long short and medium short short waves and dad had the latter. Quad service was brilliant back then there was a problem with one of the units out of warranty we turned up with it and the engineer said leave it with us and come back after lunch which we did and it was ready repaired and at no charge. Dad moved on to 33 303 fm2 which I still use along with my own 33 303 and 2x fm3 but wish he had also kept the valve set up too.
A thing of beauty, and a really useful video
I like the sound of KT-66
Fabulous I love quad
thank you for making such a great video
i love all your video please keep them coming
Certainly will do, thanks
i love this amp
Благодаря ви.
very good info and summary thank you
you are very welcome!
Very good video Sir.. You explained the schematic of those beautiful amplifier's as well as one can. I had never heard of the brand before (maybe they weren't exported to the U.S. in great quantities?), but they are extremely well built, the company obviously took much pride in their products.
Thanks for your comment, Quad are still going and making valve amplifiers!
Listening to quad 2 with L3/5A is best partner.
The shortcomings of the lay-out and ventilation issues add to the look and are also some of the things that make it iconic. I agree though, a remake would need more spacing and vents but the modern Quad II- Classics have the same layout albeit better ventilation.
I suppose when they were designed, the ambient temperature in British homes would've averaged 5-10C less than modern centrally heated, double glazed houses lol.
I have this set up including the AM radio - haven't switched on the radios for 20 years but I bet they still work. As I remember it the FM radio was good but suffered from signal drift as the technology to lock to a channel hadn't been developed then. I use a CD player plugged into tape input to listen to CD's. I bought a pair of Quad electrostatic speakers a couple of years ago and they sound great.
Fired up both radios this morning. They are mounted vertically under a cover with other equipment on top so we don't normally see them. I had forgotten they light up when you switch on the control unit. They needed a good clean. Got sound out of both of them even though neither has an aerial - so considered both working - I love the microscopic stereo indicator. Took a photo with my smart phone which wont be around in 60 years time. 1drv.ms/u/s!AsRQ3YcdckUvgW-XpxVbsyKg7wdF
The 'technology to lock to a channel' is called AFC for Automatic Frequency Control, and it is most certainly present in the FM tuner, along with temperature compensation. However in such a small chassis heat and heat-related oscillator drift is always going to be a problem.
EF 86 daft Mullard gimmick, 6sn7 better octal base connections and good triode input
Hi Phil,
Many thanks for the video, very interesting. I’ve got a couple to restore - and wanted to enquire further about what you would recommend. They are for me - so I’m not particularly worried about resale value - just sound quality, circuit integrity (i.e. against drift/imbalance) and safety.
1) I would assume that you approve of retrofitting a switched IEC input - any particular type, with caps/filtering or not?
2) Should I opt for 10 Ohms to chassis or a dead short?
3) Regarding C5 and R12, you mentioned that you would prefer to use two cathode resistors. Should these be 2 x 360 Ohms in series with terminal U and W - each decoupled with 12.5uF? (and C5 then shorted) - this would provide maximum balance
4) I would be concerned that the high ESR in the original C5 may have a role in stability, it provides a zero, and may have been what, 10 Ohms in the original design?
5) So, what about 20R in each cathode, un-decoupled, and R5 = 170R, 5W - this would look close to the original values including the ESR. However, not much of a help in balancing.
6) So, possibly something in-between?
Many thanks in anticipation
Bonkers
Just a thought. The sub chassis for the KT66s was resect so the KT66s would not be damaged should the amplifier be up turned.
Parece equipamiento militar de época, muy bien construido.
Agreed, absolutely
£50!!! When was that? The 1950's?
Is there a US 120V version of the quad ii or only a UK 220V?
Hi there is a USA tap on the transformer, some good info is here keith-snook.info/quad-ii-valve-power-amplifier.html
i fit a B + fuse in all the amp i fix
good point!
Just curious I have a basic hi-fi and I'm a painter, artist not an engineer at all. I see on RUclips Stereophile magazine and people like Steve Guttenberg. All great but some of the gear is thousands of pounds, even tens of thousands of pounds. Would a good vintage Quad system be as good as the latest expensive thing? Does the UK still produce hi-fi? When I was a kid in the 80's seemed pretty good: Keff, Mission and so on. Has all that gone? Hope somebody can answer my silly questions.
Not a silly question at all, I have a very good designer and builder friend (British) who makes valve amplifiers which perform outstandingly the price is around 2k you get a lifetime guarantee and they sound like £5- 10k amplifiers. The best I've heard and experienced. I have to keep his name to myself as I plan to re brand them and sell on.my website. Contact me on.my Web page for my info... Thanks
Paul
Just reading your comments about vintage gear, I think some times manufactures are trying to reinvent the wheel, they have to try and keep the cash flow coming in some how.
@@vintageaudioworkshop Hi I see on ebay Mullard valves such as ECC83 in one case it went for £100 the Chinese or Russian tubes at fraction of the price, are people thinking there is some magic in the vintage tubes that the Chinese or Russian tubes do not have ?
I have my self in the past built my own valve gear and valves dont last for ever and the cost of vintage Mullard and other vintage valves is alarming.
@@itsonlyme9938 unfortunately there is a lot of difference between them from my experience the Chinese version sounded like a cheap transistor unit when fitted to a simple record player from the early 60s the sound jumped back into life with the Mullard. Paul
Do you know the value in henry of the smooting choke L1?
Unfortunately the manual don't mention it, we will check next opportunity we get. Thanks
@@vintageaudioworkshop Thank you!
do you service Quad IIs? Can yo8u recommend someone in Europe (contiental europe or UK)
Yes I can recommend, contact is info@vintageaudioworkshop.com
Just a thought. The sub chassis for the KT66s was resect so the KT66s would not be damaged should the amplifier be up turned.