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    Building, troubleshooting and testing of these amplifiers should only be
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EAR 859 questions

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#21
😀 hi dhaen; and all interested in the ear schematics, as far as I know, some yrs ago tim de paravinci published the circuit and a description of it in the now defunct "sound practices"magazine of which I have a copy, therefore as far as the law is concerned it is public domain by the choice of the designer..... TDP! the price one pays for trying to promote ones designs so no need to over react and shake in your boots::blackcat: tim is an excentrict by choice but even he has enough common sense not to shoot himself in the foot by any legal action🙄 cheers to all my magyar countrymen TC:devilr:
 
#22
Every cloud.....

Qwad,

I hope that I have not "over reacted" as you put it.
Our aim is to keep diyAudio on the right track. Respect for Intelectual Property would seem to be an important element of this.
In fact Tim's reply was friendly, and I believe he intends to visit us.

I'm sure there are maverick fora where one may find all sorts of "iffy" material, but they will not attract the richness of membership that we enjoy 🙂
 
#31
Output impedance calculations 4.6K

How I know is by measuring actual amp of 859. To measure disconect transformer from circuit and apply a 1 KHz oscilator to primary and check at the terminal that you have 1 volt then with the same milli-voltmeter measure the 8 Ohm tap and you will see 41.7 millivolts.which is 23.98:1 squared is 575 times 8 = 4600 Ohms.
Secondly the voltage accross cathode resistor corresponds to about 80 MA.

Without measuring equipment you are guessing in the dark.
 
#33
:xeye: sorry, but I am all tied up at the moment with renovation of the kitchen/ bathrooms and painting though it is on my mind... its just a matter of finding the time to sit down and babrálni a számolo gépemmel és a skannerrel, nagyon bocsánatot kérek, de nem felejtettem el... szia tamás😉
 
#37
I´ve built a pair of monoblocks quite similar to this amp.
PC86 input stage RC-coupled to an IRF820 Mosfet driver that feeds the screen grid of the output tube.
I guess the input stage could be direct coupled to the mosfet, but I´m slightly paranoid about drifting bias and tube ageing.

In an previous version I used a 6SN7 mu-follower direct coupled to a 12B4A cathode follower, worked like a charm but it was a mess to wire up with three triode sections
 
#38
I made an EAR 859 many years ago when the design was published in Hi-Fi News and you could buy the iron from Yoshino. It was an amazing amp, and I still haven't heard an SE amp I like better. If jazz or classical is your thing, build it. Tim de Paravicini is justifiably secretive about his transformer designs, but I think the output transformers were about 6K8 impedance. They had Tim's usual complicated winding structure, so I wouldn't expect others to perform anything like so well. Note that the 47pF capacitors shown connected to the anode are probably the wrong value - try 4.7pF unless you want a very rolled off top end. If you don't use the proper tranformers, you'll have to experiment with the feedback components anyway.

I have a feeling that many people bought the ironwork for this amplifier but never got round to building it, so it might be worth trying some want ads.
 
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