pultec eq HUM *somewhere inside case*

[lassoharp]

Between moving the interstage and the output transformers i can get the hum down to -80db from -60db.

I'd consider -80db a victory.  You may not get it much better than that even with potted iron.  I built my pair of Pultecs with an external supply to avoid what you're going through now.


If you get out on a limb with the IS and OT mounting, you can try rotating the PT 90 deg.  With PT there's usually one side that radiates higher than the other and it may make it easier to find null positions for the other iron.

 

[orangechili]

Very good points!

Ok, After moving the OT far left on the case and rotating the interstage I got the 60hz hum down to -95db and the 150hz hum down to -85db. I'm not hearing low end noise anymore basically so I'm cool with that for now. Thank you guys for the help!

 

[Motorvatin]

Hey guys, whats up. I built a Pultec using the Cayocosta Layout (thank you by the way) and I love the sound; however, I'm having hum issues.

I have -65 dB of hum and its kinda noticeable when I turn the speakers up. Its volume doesn't change at all when I move the knobs (any knob) does it means that the noise comes after the amp section? perhaps its being induced into the OT?

Here you can see  how it looks in the spectrum analyzer in case its useful:

The hum is not terrible as to make the Pultec unusable, but I would like it to be lower.

In case it helps, I used a regular Primary Transformer (EI Core) and Sowter transformers everywhere else.

Thanks in advance and sorry for any typos or grammar problems.

 

[Rompstomp89]

Hey guys, whats up. I built a Pultec using the Cayocosta Layout (thank you by the way) and I love the sound; however, I'm having hum issues.

I have -65 dB of hum and its kinda noticeable when I turn the speakers up. Its volume doesn't change at all when I move the knobs (any knob) does it means that the noise comes after the amp section? perhaps its being induced into the OT?

Here you can see  how it looks in the spectrum analyzer in case its useful:

Any luck with this?

The hum is not terrible as to make the Pultec unusable, but I would like it to be lower.

In case it helps, I used a regular Primary Transformer (EI Core) and Sowter transformers everywhere else.

Thanks in advance and sorry for any typos or grammar problems.