**Insulated**Input jacks grounding question.

[Riffcaster]

Tried insulating with nylon washers and grounding the jacks,
1. Shorting jacks are each sending their grounds to the Buss (Cooper plate)
2. I also had connected a ground wire (One) of the jacks and ran it to the ground on the Amp board.

I had hoped by changing to an insulated jack configuration that I would get seemingly quite operation. However there seems to be a low hum when I’m not touching the chassis (grounding the amp through my body)

[clipless bumper]

Not sure what you are asking - you changed the Jack and now have the hum?
Is it a new build?

Maybe shielded wiring after the Jack?

[Riffcaster]

Built the amp a while ago. Played it a lot. Input jacks we’re picking up some RfI (radio static) that’s fixed now.
The buzz has gone after adding a few small (.01) caps from the sleeves to ground Buss. Not sure if I ha e done it in a way which is quite though. But the RfI signal is hardly audible or gone now.

Still puzzling?? At the moment is after adding the grounded shields on the jacks and
The amp sounds a lot cleaner now though!!!

[Riffcaster]

Have now decided to switch to a star grounding chain which is much better than a Cooper plate As a grounding point for jacks and pots.
I want to relieve the apparent low hum heard through the speakers.
I think it might be:
1.Faulty ground wiring (copper Buss not making solid contact with chassis or soldered connections are loosely contacting Cooper Buss.
2.AC current as all the grounds were to the chassis/Cooper plate.

[Riffcaster]

With the star grounding completed Im very happy with the amps noise to signal. As stated, It’s seems to be cleaner sounding with volume control on half vs. Before changing to insulated jacks and star grounding.

Is there a possibility of having better grounding that the amp has taken on a different tone as well as richer tone?

1.The shielded input wire to jacks rid the RF sounds.
2.Removing ground loops has stoped the lows hum I was getting when not grounding through earth ground. (Through my body)

B+ voltage is 390 Volts. for the 5e9-a this sounds good but very punchy almost like I should add a Zener Diode to drop B+ Voltages. Is there anything I should be careful with sowing so?

[Riffcaster]

So....amp it pretty quiet but there’s a lot of noise hummm type sound after adding the Zener. Tried without it and still same hummm. If I ground the guitar or chassis through my body it does go away And sounds fine.

[Riffcaster]

I’m Still presuming That the ( Hummm ) comes from AC current from the PT.
So if there are two star grounds, not connected together, as they are at opposite sides of the chassis.
Where can the Noisy AC current get in to the signal, or am am experiencing something else?

[ajaxlepinski]

Do you get the hum in other locations, other than your home?
Does the hum stop when you use the standby switch?
Does the hum go away when you turn down any of the knobs or, is it always there?
Could be a bad tube.

Can you post a clip of the hum?

[shep]

i feel like grounding schemes in an amp are probably one of the most sensitive and complicated parts about building an amp. there's a lot to consider.

[Riffcaster]

Thanks for trying to help with this ,Ajaxlepinski.
So far only tested it at home as I’ve got it appart and haven’t had a chance to test it anywhere.

If i power on its without any hummm until a guitar is plugged in. Which means that the jacks are correctly shorting to ground. Once plugged in still no hymn until turning up volume. Although It is not the high frequency type of 50- 60~ Hummm; which leads to making a sound clip !!!!!! I’ll post something this week.

[ajaxlepinski]

Without the guitar plugged in, volume up, no hum?

Could be that the guitar's ground wire, the connects the strings to the electronics came loose?
Do you have another guitar to try... same issue with another guitar?

If it's not the guitar, something is going on in the preamp section... that's what the volume knob, controlling the hum, would indicate.

[Riffcaster]

I had found a loose connection I believe was causing this problem. It was on the preamp section V1 tube pin 8, this seems to have (not fixed) the issue though.
I haven’t been quite able to fix issue with grounding since since adding upgrades to the originally layout 50’s tweed style ground points..??

[Riffcaster]

Here is 5E9-A schematic
Because I have added (3 position nfb loop switch)
from Aiken Amplification website on 5e3 mods-and have added it in by clipping out the bypass cap/ resistor for a nf/ bypass lift / unaltered 5E7.. there is no Tremolux tremolo position. Unless I put back the bypass cap then it adds tremolo . Would like some help. seems Im at loss on this if I add the switch??

[ajaxlepinski]

I'm a novice at all this.... what's an NFL?

[Riffcaster]

It’s a negative feedback loop.
Basic principle great result on this amp as it takes away some of the hiss from the preamp. And I have tried it reversed also, something about lifting the bypass cap/resister on pin 8 causes the tremolo to stop.

[Riffcaster]

The mark Moyer mod is a similar mod On a Vibrolux

[Riffcaster]

This is the circuit I’m trying out. Seems to clean up some for the hiss. But.... terribly noisy once I’m not touching the amplifier chassis of guitar thus grounding everything to earth or ground.

[ajaxlepinski]

Ahhh, Negative Feedback Loop.

This is a really good article: http://www.aikenamps.com/index.php/what ... e-feedback

Here's a vid that is interesting... Uncle Doug ROCKS!!!
[video]https://www.youtube.com/watch?v=H5fFb5_9xyA[/video]

[Riffcaster]

Interesting!
Have to have a look more into those controls and the variable Nfb control.

1.So far what I do know is that, the original has the Phase inverter bypass cap/resistor in the circuit to bias the power tubes for tremolo.

I have removed the bypass caps function as a variable bias on the power tubes so it isn’t making any tremolo sounds. Not sure how to work around this as my knowledge about that is minimal.

I may need a different negative voltage source and put back the bypass can for the tremolo to function.