#002 - my journey begins

[erwin_ve]

Also I have a ground loop with the suggested grounding scheme. Anyone else had this?

Mine is dead quiet.
A friend of mine built 2 , also dead quiet.

[Richard1001]

Thanks Erwin, yes 100k, and my mid is changed to the presence cap, and it's off

Also I have a ground loop with the suggested grounding scheme. Anyone else had this?

Hoe do you know it is a groundloop?

[Bombacaototal]

Also I have a ground loop with the suggested grounding scheme. Anyone else had this?

Mine is dead quiet.
A friend of mine built 2 , also dead quiet.

Thanks for the feedback. I would usually ground the PI supply and screens at the FX loop along with the PI ground. Having them at the power tube was a different take but this might be a cause. I will move some grounds around.

Also the input and FET I have physically at the chassis but wondering if it might be worth isolating them

[Bombacaototal]

Thanks Erwin, yes 100k, and my mid is changed to the presence cap, and it's off

Also I have a ground loop with the suggested grounding scheme. Anyone else had this?

Hoe do you know it is a groundloop?

60hz hum at the pre amp. If I turn master to zero or add a jack to the return it's dead silent. Heaters interference sounds different. Any other takes on what it may be? Based on other amps I build it sounds like a ground loop to me, but happy for suggestions

Also no issues on the reverb, if I switch off via the front switch the Hum is still there. Same if I turn the return to zero. I am also not using the headshell, therefore no interaction between PT and the reverb pan coil

Edit: here is an audio, volume and return at zero, master at max. I tried moving the screens and pi supply to FX loop but it's the same result

[erwin_ve]

Thanks Erwin, yes 100k, and my mid is changed to the presence cap, and it's off

Also I have a ground loop with the suggested grounding scheme. Anyone else had this?

Hoe do you know it is a groundloop?

60hz hum at the pre amp. If I turn master to zero or add a jack to the return it's dead silent. Heaters interference sounds different. Any other takes on what it may be? Based on other amps I build it sounds like a ground loop to me, but happy for suggestions

Also no issues on the reverb, if I switch off via the front switch the Hum is still there. Same if I turn the return to zero. I am also not using the headshell, therefore no interaction between PT and the reverb pan coil

Edit: here is an audio, volume and return at zero, master at max. I tried moving the screens and pi supply to FX loop but it's the same result

On both Reverb board and Main board there is a connection marked as "1". I remember Ryan had a slight hum problem when this(nfb wire) from "1"reverb to "1"Main was too close to certain B+ wires.
I made that wire a shielded one to have no induced hum through that wire.

[sds1]

Crude but I held spectrum analyzer up to speaker for your hum.mp3. No peaks in the mains frequency range:

[Bombacaototal]

Hoe do you know it is a groundloop?

60hz hum at the pre amp. If I turn master to zero or add a jack to the return it's dead silent. Heaters interference sounds different. Any other takes on what it may be? Based on other amps I build it sounds like a ground loop to me, but happy for suggestions

Also no issues on the reverb, if I switch off via the front switch the Hum is still there. Same if I turn the return to zero. I am also not using the headshell, therefore no interaction between PT and the reverb pan coil

Edit: here is an audio, volume and return at zero, master at max. I tried moving the screens and pi supply to FX loop but it's the same result

On both Reverb board and Main board there is a connection marked as "1". I remember Ryan had a slight hum problem when this(nfb wire) from "1"reverb to "1"Main was too close to certain B+ wires.
I made that wire a shielded one to have no induced hum through that wire.

That's a great tip Erwin. Mine is not shielded either, but I will replace it!

Thanks for the chart Sds1

Edit: so I completely floated the wire (attached) before going through replacement but no difference, maybe a tiny bit less hum, but it's still here

Edit 2: Erwin, if you turn your master to max you only have hiss and no hum at all? I am thinking that the reverb circuit is grounded at the pre amp ground, but its supply is with the PI and Screen. Probably might be one to try to separate them?

[erwin_ve]

60hz hum at the pre amp. If I turn master to zero or add a jack to the return it's dead silent. Heaters interference sounds different. Any other takes on what it may be? Based on other amps I build it sounds like a ground loop to me, but happy for suggestions

Also no issues on the reverb, if I switch off via the front switch the Hum is still there. Same if I turn the return to zero. I am also not using the headshell, therefore no interaction between PT and the reverb pan coil

Edit: here is an audio, volume and return at zero, master at max. I tried moving the screens and pi supply to FX loop but it's the same result

Edit: so I completely floated the wire (attached) before going through replacement but no difference, maybe a tiny bit less hum, but it's still here
[/quote]
And if you remove the wire of the connection "1"of the main board?

[Richard1001]

60hz hum at the pre amp. If I turn master to zero or add a jack to the return it's dead silent. Heaters interference sounds different. Any other takes on what it may be? Based on other amps I build it sounds like a ground loop to me, but happy for suggestions

Also no issues on the reverb, if I switch off via the front switch the Hum is still there. Same if I turn the return to zero. I am also not using the headshell, therefore no interaction between PT and the reverb pan coil

Edit: here is an audio, volume and return at zero, master at max. I tried moving the screens and pi supply to FX loop but it's the same result

On both Reverb board and Main board there is a connection marked as "1". I remember Ryan had a slight hum problem when this(nfb wire) from "1"reverb to "1"Main was too close to certain B+ wires.
I made that wire a shielded one to have no induced hum through that wire.

That's a great tip Erwin. Mine is not shielded either, but I will replace it!

Thanks for the chart Sds1

Edit: so I completely floated the wire (attached) before going through replacement but no difference, maybe a tiny bit less hum, but it's still here

Edit 2: Erwin, if you turn your master to max you only have hiss and no hum at all? I am thinking that the reverb circuit is grounded at the pre amp ground, but its supply is with the PI and Screen. Probably might be one to try to separate them?

I think the driver tube should be grounded at the reverb RCA plug. How did you ground the filter caps and preamp filter cap? In the pictures i see no wire connection.

This is my amp:

IMG_20210530_184700~2.jpg

[Bombacaototal]

Hi Richard, my cap can is grounded at the pre amp main ground point.

My reverb transformer is grounded at the RCA plugs but I have my RCA jacks isolated from the chassis and grounded at the pre amp ground too.

Usually I would have grounded the reverb supply at the same point, but the PCB has it joint with the PI and screens

After checking back the grounding scheme on the layout linked below, I think the input and FET are isolated on the layout, given they ground at the pre amp ground point. Mine are physically touching and grounded at the chassis. I will isolate them and see if there are any improvement. This is the only grounding difference I could see

https://github.com/colganr/steel-string ... Layout.pdf

[Bombacaototal]

Ok, so I isolated the jacks and grounded at the pre amp. I don't think much changed. New recording attached, same settings with volume and return at zero and master at max

[erwin_ve]

The can cap grounded at the preamp input?
You might have a groundloop.
The cancap has a physical connection to the chassis.
If just a bit of powdercoat is gone an the metal of the can cap touches the chassis:-->>bingo.
Just look at the layout, you can use the terminal strip of the can cap to ground . Make sure you remove the powdercoating in that spot.

[Bombacaototal]

The can cap grounded at the preamp input?
You might have a groundloop.
The cancap has a physical connection to the chassis.
If just a bit of powdercoat is gone an the metal of the can cap touches the chassis:-->>bingo.
Just look at the layout, you can use the terminal strip of the can cap to ground . Make sure you remove the powdercoating in that spot.

Thanks for the input Erwin. My other SSS amps were grounded as such without any problem. The powder coating is really thick and doesn't give much of a physical connection. But you have a fair point. I will try to remove this ground from the pre amp and move it around to see if there are improvements

[erwin_ve]

It might be a issue, I'm not sure either.
Only thing I can say:

HR3111-1032-ZINC-PL-HEX-KEP-LOCK-NUT-1_600x600@2x.jpg

When using these, the edges go right through the powdercoating.
I accidentally discovered it when checking if my tube sockets had a ground connection( for the pre amp tube cover).

[Bombacaototal]

On another note I loved having a bias pot as a permanent solution on the FET. I really recommend