new 5F1 build with really loud BUZZ

[freakshow__]

Hi all!

I have recently built 2 identical 5f1 amps. The first one is great! no issues to speak of now. It works as it should and is super quiet...I just finished the 2nd one and there is a REALLY loud buzzing sound when I turn the amp on. Playing a guitar through it works...but the buzz is really quite loud to make it unusable. This is not an issue with my first build....

I have gone through and made sure everything is IDENTICAL, which it is.

My question here is: Is this possibly a bad filter cap? How would I know?

I am running a 47Uf, 16Uf, 10Uf for filter caps in this and all are F&T brand caps. FYI the amp is SS rectified as well.

Any ideas?

[Colossal]

Let's talk about your heater filaments. Is the filament string referenced to ground via 100 ohm resistors or other means?

[freakshow__]

no there is no faux center tap. There isn't on the amp that is dead quiet either.

[xtian]

no there is no faux center tap. There isn't on the amp that is dead quiet either.

You did not explicitly say, so I have to ask: Is there a true heater CT? Where is it grounded?

[freakshow__]

No there is no heater center tap on either amp. real or faux

[freakshow__]

I added the 100 ohm resistors to ground ref. and it's dead quiet now....

so my question is:

Why is one amp quiet WITHOUT the faux center tap, and one Buzzes like crazy without it? Everything is identical on these 2 amps?

[sluckey]

Are the PTs identical? If not, does the quiet one have an internally grounded filament center tap?

[freakshow__]

they are both the same PT which I got at the same time.

Hammond 270DAX model

[sluckey]

I bet your first built would benefit from an artificial CT also.