Altering switched attentator steps

[jahsavage]

Since the beginning of the year I've have been gradually upgrading my Almarro A318B, so far the results have been fabulous.

I've replaced all the signal capacitors with Jupters and for testing hot wired some pure silver wiring directly to the volume control.

I've also replaced the 250K volume control with a Eizz 24 step switched attenuator but I found the golden spot was between two steps. I experimented by adding a 100k series resistor to the attentuator output. This did provide many more steps but unfortunately added a buzzing/hum noise to both channels. The volume control feeds the first stage of the amplifier (6SL7), the resistors are small in size and have short leads does anyone understand why this has contributed so much noise?

Regards
jahsavage

PS

One of the pains of upgrading the Almarro's controls is that they use long shafts, short shafts are hard to extend due to wooden facade. I ended up drilling a large hole to pass the extender from the inside and gluing Eizz to the chassis. There are bolts that look like they secure the wooden bits but I was not brave enough to remove them.

[jahsavage]

I removed the 100k resistors and found the noise and benefits disappeared. I've deduced I must have altered the bias in some way, I think I need to do some additional circuit theory revision before moving on.

[Eileen Dover]

Can you gain access to the resistors inside the switch and change the ones concerned at the "golden spot" ?

[Firebottle]

If you have plenty of volume and 'spare' steps when it is too loud, try fitting the 100K or 47K in series on the input to the attenuator.