JE EL34 Build

[Richard]

Originally Posted by colin.hepburn

Hi Richard
Yes I found it odd as I had the 470k in on the last working rebuild I did I will recheck the value and correct placement should be after the cap to ground pleas correct me if wrong
thank
Col

Hi Col, Yes that looks fine. The -3dB roll off for that RC coupling as drawn is 3.4Hz so should give you full bass.

If your resistor is 47K though the coupling will be 10x higher at 34Hz and that would give lighter bass. If it was 470R the roll off would be 3400Hz so no bass.

If the cap value is wrong it will affect things in a similar way. If the cap is really 0.01uF the coupling would be at 34Hz etc etc.

Interesting though using just one of these components without the other into the almost infinite impedance of the grid will cause almost no loss of bass even if it's a wrong value by several times.

So I'd recheck the cap and resistor values or simply swap them out for new ones close to your drawing and see if bass returns

[colin.hepburn]

Hi John /Richard
Thanks for the input
John the cap is directly connected to grid pin 1of 6Sl7 and the 470k on the leg of the cap and pin1 and to ground haven't tried removing the cap yet don't think I need too now

Richard
What I did do was clip lead a new 470k in and its working fine whether I ground it back at the input phono or any ground point on the amp really don’t know what the problem was as the old resistor tests correct value but it s working fine with the clip leads in

[Richard]

Originally Posted by colin.hepburn

Richard
What I did do was clip lead a new 470k in and its working fine whether I ground it back at the input phono or any ground point on the amp really don’t know what the problem was as the old resistor tests correct value but it s working fine with the clip leads in

Excellent

[John Caswell]

Hi Colin,
That seems to have put it to bed, so far so good. What I would also do is add a small resistor (1K-4K7) between the junction of the 0.1µF and the 470K and pin 1 of the 6SL7. Ordinary carbon types work very well here! It just helps quieten things down RF wise.

John

[colin.hepburn]

Hi John
yep all seems just fine now

I have some carbon resistors so will add them in
thanks
Colin