1979 Amplifier kit

Hi Folks, Wondered if any of you have either built this kit, or heard the complete unit in action?

Practical Wireless Winton 50w/ch mosfet amplifier April 1979.

I bought this a few years ago and had forgotten all about it, I rediscovered while looking for something else, haven't decided whether to build or sell it, comments or advice welcome.
 

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Mooly

Administrator
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2007-09-15 8:14 am
A pal of my mine at college (we were on the same electronics course) built this... and I built the PW Purbeck 'scope.

I seem to remember it was pretty decent (was it based on the Hitachi lateral FET application notes ?) but its all a long time ago...

If you have the complete kit and case etc then I'd say its well worth a go :)
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
If I were you I would definitely build it. Power it up with a bulb tester initially to help "reform" the PSU caps (and I'm sure they will still be fine). Any small cheapo electrolytics could usefully be replaced by modern but that's about it.

I think you'll be surprised how good it is.
 
Reforming is nice for electrolytic caps. I start with the ohmmeter, up to 2 vdc for the oxide dielectric. Then I look at discharge of volts over time and throw some away right there. Any electrolytic cap more than a year from the distributor. There is a shockingly short shelf life on the cap spec sheets, even big distributors have sales to get rid of electrolytics that need reforming. Reforming doesn't do **** for the cap rubber seal. I put a new CDE can cap in my ST70 in 1982, ran it a couple of hours, measured the watts and put it away since I couldn't buy non-Soviet output tubes. In 2011 I bought some Euro Union made tubes (JJ), checked the caps with the DVM, warmed up with a 70 VAC transformer (stuck variac), played it 3 hours on main power. Very nice, adequate power on 8 ohm resistors. The next day it blew the fuse. Slime had leaked everywhere out of the 5 hour running +29 years idle cap. Oxygen never sleeps, running or not. Tubes, disc caps, high quality (mallory, sprague, ) film caps don't deteriorate over storage time. Carbon comp resistors can, depends on the quality of the paint to seal out moisture. *****y resistors can look just like AB or Sprague ones. Measure them. Semiconductors, sometimes the leads rust off, depends how close you are to the sea. People that own Farfisas say on those the transistor metal cans rust off.
 
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Hi Folks, Wondered if any of you have either built this kit, or heard the complete unit in action?

Practical Wireless Winton 50w/ch mosfet amplifier April 1979.

I bought this a few years ago and had forgotten all about it, I rediscovered while looking for something else, haven't decided whether to build or sell it, comments or advice welcome.

I have the original article somewhere, but gee, what a find :cool:
 
I built it. A long time ago. The power amplifier part was very good (Or it was for those times). The pre-amplifier and tone controls were bad. Maybe they could improve if you replace the original TL082 and TL072 ICs with something better.

Hi Dankop,

Could you describe in what way was the pre-amp disappointing?
Could you suggest which op amps might improve the pre-amp section?

Regards,
Mike
 
I do not have schematic diagram any more, and I am sorry that I can not help you very much. What I do remember is that I added the switch that was completely bypassing preamplifier section and tone controls and that I was amazed with the sound improvement (I also replaced phono section with the new one). Winton amplifier was one of my first (fully successful) DIY audio projects. My friends and me were organizing listening sessions where we were comparing this amplifiers with some Rotels, NADs and other “beasts” that in that time and place we had access to, and Winton (with the bypass on) was always the winner. Without the bypass, the sound was flat and lifeless.
Anyhow, nobody is using TL072 and TL082 for audio any more. Whichever of operational amplifiers recommended on this forum you try, you will for sure get better results. Starting with NE5532. In my modest experience, LME49720 sounds very ice.
Anyhow, you can start by soldering IC sockets on the board and switch between ICs and compare them.
I do not know what is the level of your experience, and maybe you already know this:
If I do remember well, one of used IC's was dual version and one was not. Also, one was unity gain stable and the other was not. You have to pay attention to those things when replacing ICs.

For a long time I read this forum, and I think that I never before posted here a single comment. But mentioning of this amplifier brings me some very fond memories (other century, other country, other weight, …). I would be very grateful if you post here your impression after finishing your project.

By the way, if the original electrolytic capacitors from the kit are 20 years old as I think they are, do not use them. Replace them with the new ones.

Good luck