F5 V3.0 Help with Hum Issue

[jasonb84]

Amazing! This was a great holiday discovery. I've been using the F5 with a 97dB midrange. While I was able to get the hum down to what I considered good levels, there was still residual 120hz.

Cutting the jumpers at the bridge inputs just knocked the perceived hum down by at least 3dB or more.

 

[TheNuge]

Amazing! This was a great holiday discovery. I've been using the F5 with a 97dB midrange. While I was able to get the hum down to what I considered good levels, there was still residual 120hz.

Cutting the jumpers at the bridge inputs just knocked the perceived hum down by at least 3dB or more.

That sounds great!
Where exactly have you cut? Not sure I understand...!


Cheers


Es

 

[MEPER]

I think we should as "DIY's" be able to have hum level at least as low as expensive commercial amps…….this is the fun part of DIY to be able to that.

 

[jasonb84]

I see in the pictures of your completed amp on the power supply board you have the points labeled gnd,gnd1,gnd2,gnd3,gnd4,gnd5 jumpered together which is correct.That point should go to your amp boards as well as thru a CL60 then to the 120Volt power ground.Then on the diode bridge end of the boards you have those same points (D-1 and D+2) jumpered together again so you have created a loop,remove that jumper,you only need the gnd,gnd1 etc. point jumpered together.

I've done as described here. In your original image you have a jumper right above the board marked ST_IN2/3 on the rectifier bridge side. I did too, as do a lot of others from pictures of the power supply.

 

[TheNuge]

Hi!
I cut the "surplus" jumpers yesterday but unfortunately it didn't help....
I'll try "grounding" one RCA ground with a 10Ohm resistor as suggested next!


Cheers


Es

 

[TheNuge]

Eureka!
I think I've found the source of the problem:
My system is a 2x3 channel Sitronik DSP feeding 3 stereo amps - 2 Pass F5s and one Thel Accusound. To facilitate cable routing I've had the left Pass fire mid-range and tweeter in the left speaker and the right Pass the mid-range and tweeter in the right speaker. well, this setup appears to cause a ground loop between the DSP and Pass! I hooked up one Pass to the tweeters and one to the mid-ranges and the hum is now gone! I've ordered some longer speaker and hope the hum remains absent!


Cheers


Es

 

[jasonb84]

Glad you found your solution. How interesting too, because I'm also using twin F5s I built for my active 3 way speaker. Each F5 is in a vertical setup per channel, mid and tweeter.

I'm using a miniDSP 4x10. I wonder if how the output channels were mapped have an effect.

 

[TheNuge]

Hi!
I recabled the whole rig and the hum is gone now!


@jasonb84 if you're having hum issues with your rig, I'd definately try the "horizontal" setup with one amp for the tweeters and one for the mids! What's running your woofers?


Cheers


Es

 

[Allan]

Hi again,
I'm going to try star-grounding the amp in the following way (unless you guys tell me otherwise):
Star Ground point will be a post isolated from the housing using a CL-60 thermistor. This post attached to:
1. PSU board ground
2. F5 board grounds
3. Speaker negative posts
4. Input terminal grounds.
All using equal length wire.

The inputs signal tabs will be connected to the boards with coax wire, with the shield only attached at the board end.

Will that work in theory?

Cheers
Es

nobody did answer the above question for TheNuge, is this grounding scheme correct? I have a little hum in my F5 I'd like gone