Aikido choice of valves (or tubes, if you will)

[SY]

2004: I used 287 ohms in all four cathode resistor spots.

[rjtpeters]

Originally posted by 2004ex

Helped a friend built a 6SN7/6SN7 version recently based on John's octal board. Embarassed to say that we are still struggling with hum/noise problems (I know, aikido should be good in that department and we must have been stupid and doing something wrong), but would you share what values of cathode resistors are used in your 6SN7/6SN7 built? TIA.

Dont be embarassed , i faced some hum as wel. In my case it was the floating heater supply. After grounding the heater the hum disapeared. I still have to see what the influence on sound is when i lift the heater supply to 40V above cathode.

After solving the first hum, a rattle remaind. This was because i used a smps. So then i changed the heater supply to a lineair type and now there is no back ground noise anymore.

Another problem i faced, is that the amp hums when there is no input source attached, but i guess this is because the amp is still on the bench, so there is no good reference ground.

If I can help you out on this one, let me know.

Roland

[2004ex]

Originally posted by SY
2004: I used 287 ohms in all four cathode resistor spots.

SY: Thanks. I am using 1k ohms for all four. A mistake?

Originally posted by rjtpeters



Dont be embarassed , i faced some hum as wel.
...

If I can help you out on this one, let me know.

Roland

Thanks. Embarassed because we had tried using linear dc regulated filament supply already (front left, set at +12.6V) and even using an external regulated DC HV supply (fluke 407, tried from +150V to 300V) but still could not get rid of the hum (the HV supply, front right, was disabled for debugging.)

[rjtpeters]

If I see it correct in the pic, you have tied the safety ground to the central star ground. I have read somewhere that this is terrible for hum, didnt try it myself, but this might be an issue.

[Beelzebub]

Originally posted by 2004ex


SY: Thanks. I am using 1k ohms for all four. A mistake?



Thanks. Embarassed because we had tried using linear dc regulated filament supply already (front left, set at +12.6V) and even using an external regulated DC HV supply (fluke 407, tried from +150V to 300V) but still could not get rid of the hum (the HV supply, front right, was disabled for debugging.)

Hi,
Regarding the cathode resistor values, checkout John's blog page
http://www.tubecad.com/2006/05/blog0064.htm
I'm thinking of putting sockets or tags or something on the board so I can experiment with different values without trashing it.