EL84 SE advice'n'schematics needed

[smila]

Thanks for all those hints, pushing me forward.

Alan

 

[GloBug]

The creator of this amp posted in this thread, just seemed odd nobody noticed or asked him anything. lol

 

[Radio Jules]

Hello erveryone,

First of all, I want to say that I'm new in tube amplifiers. I study electronics, but in school no one wants to explain how tubes works, or what you can do with it... So, I start on my own.

Because I had de EL84 and the ECC82 here, I build the first design given by tubemaster.
I use elco's as capacitors, probably not so good, but I had them here.
As rectifier I used the EZ80 and the DC voltage is not 350Volt as it should be, but 300Volt.

Still the amplifier sounds great! Thanks tubemaster for this design.

Now I want to know: My DC voltage is lower (300V), so I have a slightly diffrent setting on the characteristics of the tubes, right?
What components do I need to adjust to get the same (probably the best) settings as on 350Volt?

Then another question about the 50k potmeter: This is a volume control right? Ok, but shouldn't this be much more Ohms? Because I often see a very big resistance between kathode and grid, so that it is virtual grounded, and the signal gets a negative bias voltage so you are more on the lineair side of the characteristics.

With the 50k potmeter, you change your bias, so the linearity and DC setting of this amp depends on the volume setting??? Correct? Or is it nonsense?

Thank in advance,
and sorry about my bad english.

Radio Jules

 

[tommyber]

how do i get 60 mA? is it whit 3500 ohm resistor ore somthing ells ?

Hello Stuart,

operation of a KT66 in my circuit does require some design changes. The driver stage also needs a slight modification to accommodate for the larger voltage swing required. Here is a new version of the schematic:

An externally hosted image should be here but it was not working when we last tested it.

Design notes:
The KT66 is operated at 15W plate dissipation which is well below the recommended maximum of 25W. This should ensure a very long tube life.

This amplifier exhibits an extremly low distortion figure at full output due to the linearity of the KT66. At normal listening levels I would expect a distortion of less than 0.1%.

For rectification I recommend a 5R4 or GZ37. These have considerable advantages over a 5AR4/GZ34.

The heater supply should be elevated to about 50-60V as indicated in order to stay within the heater to cathode voltage rating which is 100V for both tubes. AC heating is preferable.

If you have any further questions I'd be glad to help you.

Best regards
Michael

 

[Luck5664]

I am a complete beginner so please forgive my ignorance, but how many Watts can be achieved per channel when building this amp? Secondly, which output transformer would be recommended?