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Old 12th February 2013, 07:59 PM   #51
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My EAR 859 is on and working as I write. Its home-built of course, working on its original valves! I used high grade caps, like paper/oil, in critical parts, and transformers from TdP. Drives PMC IB2s loud with ease...

Andrew
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Old 17th February 2013, 10:49 AM   #52
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Quote:
Originally Posted by AndrewCee View Post
My EAR 859 is on and working as I write. Its home-built of course, working on its original valves! I used high grade caps, like paper/oil, in critical parts, and transformers from TdP. Drives PMC IB2s loud with ease...

Andrew
Congratulations for your amp.
Could you share your experiences on all (intentional?) error related to schematics published by HFN? I have been aware of 2 errors so far, 47 k instaed of 4.7k and 4.7 pF instaed of 47 pF...there must be others I'm interested so much.
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Old 18th February 2013, 04:17 PM   #53
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Default Errors?

Hi, Sorry Obi, I was not aware of any errors. I built my amp to the circuit diagrams published in 1994 in HFN. On the magazine copy I have here I can see there are 2x 47pH caps in series on the anode of the PL519 (I used 40V heater valves) but otherwise I know of no errors I'm afraid. I'll be interested to know if there any mistakes in the original article???

I guess I could compare the diagram published on the web with my paper copy? Please do let me know if you find anything, I'll have a look over the web diagram in the next couple of days.

Thanks, Andrew
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Old 12th June 2016, 01:22 PM   #54
Vortex is offline Vortex  Hungary
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Hi guys, long no see .. how about this re-calculated design of the original 859 for some other tube types ? (The 2x47pF -s will be adjusted to 4.7pF)

Made by my father, we're already working on a further upgrade with XLR/balanced inputs.

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Old 12th June 2016, 04:37 PM   #55
AV8R is offline AV8R  United Kingdom
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Default EAR859,

Obi Wan, There is no error, I stated 47 pf with two in series making 23.5 pf.

Please I did this to make good stability into high capacitance loads such as QUAD ELS speakers.
I did state minus half dB at 20 KHz Of which I am sure you golden ears lot can hear perfectly every time?

Upgrade yes what does this word mean? like Balanced input by what means?

Not an upgrade in the home. KT88 can be made to work but requires way to much drive to be able to get full output. I stated 20 years ago that the EL509 or PL509/519 are ideal for this, Oh and linearity is superb thank you.

My later version with an added extra valve to make it bias accurately without selecting valves added cost to original.

It was made to an affordable price point, Hence the world wide success.

My question is "How long is a piece of string?"

Finally, trying to add motional feedback is not very clever as there is precious little spare gain. The feedback in the original is only 7 dB.
All deliberate in the original design of mine.
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Old 12th June 2016, 08:23 PM   #56
Vortex is offline Vortex  Hungary
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Well, we'll try this last design anyway and let's see how it performs.
The core principle was to play around a little bit and experiment, not to meet or match the original 859's performance - that does't matter anymore for now, at least we're not comparing our own project to that. It served as a very interesting design (and basis) for the enhanced triode mode operation, but that's all. The rest is all about having fun since we're both hobbyists.. I'll be happy if we can finish this very first amp of mine this year..

Here's the - most probably - final one, fresh as of today (we haven't read your comments yet, however, thanks for the observations).

Click the image to open in full size.

I try to translate comments into English:

1. XLR input added.

2. Grid voltage has been increased so the tube operates in a more steep and more linear section compared to our very first KT88 design.

3. Feedback has been simplified (again compared to the very first design) and will be set up based on our experiments with the final boxes.

4. If we put everything into one chassis like usual (instead of 2 monoblocks) we can use 1+1 remaining half of the 2 ECC99 tubes for something else - thinking about a separate headphone circuit now.. not sure yet.
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Old 12th June 2016, 08:29 PM   #57
Vortex is offline Vortex  Hungary
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And of course the most sick thing would be trying the same with a pair of KT150 monsters but for that I rather plan a push-pull powerhorse for the 2 fronts of my home cinema. But this is rather off-topic here (maybe the KT88 design as well)

Cheers
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