F5 - is normal ICs twist out the Hum?

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I know much has been written about the hum, but I have done all, the last thing I did was twist the cables and ICs hum almost disappears! It remains a bit, but this is no solution.

No longer know what to do, is a small hum, touching the ear to the speaker is quite perceptible.

I made a star as the image is, the masses of the left channel and right channel bind to this connects to a central point, this point connects to the mass of the PSU.

I have the source with 8 capacitors 15,000 each, had bought a pack of 10, 2 left over, I'd better turn over these 2 who are outside? Where would be best to connect the PSU? One for each channel at the entrance of the source at 2.2 K?

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


I made a star as the image is, the masses of the left channel and right channel bind to this connects to a central point, this point connects to the mass of the PSU.

An externally hosted image should be here but it was not working when we last tested it.
 
Last edited:
Official Court Jester
Joined 2003
Paid Member
make like this , but without red bridge fat wire

if small hum residue , put red bridge fat wire directly and in shortest way , between two pcbs (grounds)
 

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I used to have hum too until I configured it like so:
No input ground from RCA's to the amp boards at all.
RCA hot to amp board, the Hot to the speaker, and the V+ and V- from the power supply. No ground at all on the amp board.
The RCA ground and speaker return I have connected to the PSU board ground then through the thermistor then chassis. AC ground is connected at the same point to the chassis as well.
 
I used to have hum too until I configured it like so:
No input ground from RCA's to the amp boards at all.
RCA hot to amp board, the Hot to the speaker, and the V+ and V- from the power supply. No ground at all on the amp board.
The RCA ground and speaker return I have connected to the PSU board ground then through the thermistor then chassis. AC ground is connected at the same point to the chassis as well.


Do not quite understand what she said!.

A scheme would be excellent. thank you
 
I've done everything, and I'm about to give up.

This hum is not a problem ground, turned off the ground while doing the experiments, the ground on or off is equal.

The problem is mass, with everything turned off and only the F5 on the speakers as makes no hum, just connect the ICs that starts right tinnitus.

I used many ICs, directional unshielded at the destination, the unshielded source, etc, etc.. and nothing, always that little hum.

I am forced to think that the problem lies in the components, or 400VA toroidal Sedlbauer of Conrad, or PCBs in the channels or the PSU pcb (Jim Audio).

The AC input wires are shielded by the toroidal.

I wonder why he only hum when I turn the ICs with the same pre Rotel off:confused::confused::confused::confused:

I have exhausted my wisdom.
 
From Blink's description it sounds like the ground loop is in the interconnects link to the amplifier/receiver.
If the Source has a common ground point for the two output phonos and the receiver also has a common link between the two input phonos, then there MUST BE a ground loop.
That loop requires that the route have a current reducing resistance inserted to minimise the voltage appearing along the interconnect return wires.
 
From Blink's description it sounds like the ground loop is in the interconnects link to the amplifier/receiver.
If the Source has a common ground point for the two output phonos and the receiver also has a common link between the two input phonos, then there MUST BE a ground loop.
That loop requires that the route have a current reducing resistance inserted to minimise the voltage appearing along the interconnect return wires.

That's exactly what happens.

With F5 only on the speakers as no hum (without interconects connected).

I have been to confirm and all the RCAs Rotel have common mass.

When I turn to only one pre interconnect (Rotel RA-1520) there is no hum, turning on the 2nd there appears hum.

If you turn off one interconnect the hum disappears. I listen to music in stereo, of course.:sax::)

I'll put the pics of the PSU.

When solving this hum, I'll open a bottle of champagne.:cheers:

Did the voltage on the output DC to AC multimeter scale and each channel has +- 0.012V, I think the PSU is okay...


An externally hosted image should be here but it was not working when we last tested it.



An externally hosted image should be here but it was not working when we last tested it.
 
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>> When I turn to only one pre interconnect (Rotel RA-1520) there is no hum, turning on the 2nd there appears hum.

At risk of stating the obvious, given the issue is with this particular preamp, why dont you just disable the input ground on one of the interconnects either in the preamp OR in the f5 amp.

Example:
left channel : Hot and Ground,
right channel: Hot only no ground.

Not ideal but if it works ....
 
Okay, I faced similar situation in another amp, not F5. It was connecting both input grounds used to start hum while disconnecting either one input ground - no hum. Yes I agree its ground loop in input return path.

The similarity here is, PS used here is too having single floating ground. Simple solution which worked for me was - separate both input RCA ground from each other and chassis. Run them to the amp PCB input ground pad. Connect PS ground separately to each amp board and speaker output. This you have done correctly. Only problem I see input ground need to run separately till amp board.

Just for curiosity , does your preamp has zero resistance between grounds of both RCA?
 
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