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Old 11th February 2004, 11:19 AM   #31
AV8R is offline AV8R  United Kingdom
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Default 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.
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Old 23rd February 2004, 05:43 PM   #32
nonos is offline nonos  Hungary
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Default Ear 859 output transformer

Hi AV8R,

Thank you very much your information ! You helped a lot !

Qwad,

Did you find the article?

Nonos
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Old 23rd February 2004, 07:07 PM   #33
qwad is offline qwad  Australia
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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
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Old 5th March 2004, 08:45 PM   #34
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I have some dim recollection of TDP claiming that there was intentional mis-identification of some of the component values of this amp in the published schematic, presumably to thwart attempts to DIY this amp. Does anyone share that recollection? - Pat
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Old 5th March 2004, 11:49 PM   #35
dhaen is offline dhaen  Europe
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Default Thwartment......

Ask him!

In any case, DIY'ing a production amp is impossible without sourcing the original iron.
Different iron = different amp.
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Old 27th October 2005, 11:47 AM   #36
drobert is offline drobert  Hungary
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Hello AV8R!

Can you take any photo about this amplifier? (EAR859) I like to know what is the inside of this amplifier.

drobert
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Old 20th November 2005, 12:11 PM   #37
Fuling is offline Fuling  Sweden
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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
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Old 20th November 2005, 01:03 PM   #38
Ardee is offline Ardee  England
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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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Old 20th November 2005, 02:24 PM   #39
Fuling is offline Fuling  Sweden
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I use Hammond 1627SE (2,5K 25W) in my monoblocks.
According to Svetlanas plate curves I´d rather use 5k transformers, but 2,5k was what I had.
My prototype had OPT´s from an old Edisons 60 wired as 5,6k.
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Old 20th November 2005, 04:05 PM   #40
Ardee is offline Ardee  England
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2k5 sounds rather on the low side to me. Driving the screen gives nice triode curves but a pentode output impedance, hence the need for feedback!
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