Pass F5 - Duder made me do it!

[The Dude]

All is working properly, sounds great except for a low level hum that only occurs with my preamps connected - some sort of ground loop I suspect.

Alright, this hum has been bothering me, so I decided to tackle it today. The power supply board was the culprit.

It was fairly simple, I just had to re-locate the grounds in a Star grounding configuration, no more noise.

From what I can tell is you disconnected the ground from the power supply on the left side. Then connected that and the ground coming from the right side output board, to a ground lug that everything connects to right.

I am still trying to make sure I have the right idea for a star ground.

[Guest David H]

From what I can tell is you disconnected the ground from the power supply on the left side. Then connected that and the ground coming from the right side output board, to a ground lug that everything connects to right.

Exactly. After I figured it out I ran across DIY Audio page #1191 where someone came up with a similar but not exact solution.

This is a popular amp, to say the least.

http://www.diyaudio.com/forums/pass-labs/121228-f5-power-amplifier-1191.html

This amp is unbelievably quiet. I connected a K-77 directly to the output,- Not even a hiss.

Dave

[Johnny's Jill]

Dave brought this amp over for a demo. I am here to tell ya it's sweet Carolina.

No noise, bass was spot on as a leopard. Top end smooth and detailed.

Demo done on my Ambiance Reference speakers.

Its all I ever needed.

Craig.

[Tillerman]

GotHover,

Do you have a fuse in this build? I couldn't tell from the photo.

[Guest David H]

GotHover,

Do you have a fuse in this build? I couldn't tell from the photo.

You don't like to live dangerously?

The fuse is part of the IEC connector.

Dave

[mike stehr]

GotHover,

Do you have a fuse in this build? I couldn't tell from the photo.

You don't like to live dangerously?

The fuse is part of the IEC connector.

Dave

Reminds of when I used to visit my retired EE friend. We were looking over a amplifier on his bench. Something needed to be swapped out and soldered. "You can see better than I, and seem to solder pretty good, go ahead and swap that out." So I grabbed the iron and a pair of pliers and started in..."Oh, lemme turn off the variac first."

"Yeah, that would be nice." "What? Are you chicken?"

Edited April 20, 2014 by mike stehr

[The Dude]

GotHover,

Do you have a fuse in this build? I couldn't tell from the photo.

You don't like to live dangerously?

The fuse is part of the IEC connector.

Dave

FAB, Fearless amp builders, bias that puppy up as high as can, just keep fire extinguisher handy.

[Tillerman]

GotHover,

Do you have a fuse in this build? I couldn't tell from the photo.

You don't like to live dangerously?

The fuse is part of the IEC connector.

Dave

Thanks - Another new thing I learned today. Out of curiosity, how many amp fuse do you need for the F5?

[Guest David H]

2.5A slow

[John Chi-town]

All joking aside, Nelson Pass could make a toaster sound incredible. Known as Pappa in the DIY community, he is one of the few people that assist DIYers as well as his Pass LAB's amps and preamps business.

Best regards,

John

[Guest David H]

All joking aside, Nelson Pass could make a toaster sound incredible. Known as Pappa in the DIY community, he is one of the few people that assist DIYers as well as his Pass LAB's amps and preamps business.

Best regards,

John

True, Nelson is very talented.

Dave