grounding questions

[HiGain]

Hil all,

I'm trying to sort out a reliable grounding schem for a 100 Watt amp. I've attached a pic for reference. Does this look about right to you guys?

Thanks!!!

PS, this is for a non-hrm built mainly by Bob I (who does GREAT work, BTW) with Brandon's chassis (superb quality!). It uses values mostly established by Dogears (as you might guess, it therefore sounds pretty nice!)

[mlp-mx6]

The only things I like to do differently include:

Isolate the speaker jacks and ground them to the same point as the power tube cathodes, rather than relying on the chassis/jack touchpoint.

I sometimes ground the preamp cathodes to the buss bar.

I always isolate the input jack as well and ground it separately to the same point as the buss bar - so that ground lug has 2 things on it, the input jack and the buss bar.

[Tonegeek]

Looks pretty good, although your chassis is carrying some ground return current. I have read some posts on this forum recommending against that, although i think Fender did it with no problems. You may want to read what Randall Aiken says about grounding. Also Ampgarage member DrZ400 also seems to have this thing figured out pretty well. Search this site for discussions on grounding. There is much material here that helped me immensly when I built my amp. There is more than one way to skin this cat so I am not saying your way will not work. I just prefer only one connection to the chassis near the input (not counting the ground wire from the power cable which goes to the chassis near the tranny).

[HiGain]

Thanks for the feedback, guys!

I might have to reconsider the isolated jacks.

I did check out Aiken's article on grounding (great info). So, Tonegeek, you starground EVERTHING at one point near the input?


Jake

[drz400]

Thanks for the feedback, guys!

I might have to reconsider the isolated jacks.

I did check out Aiken's article on grounding (great info). So, Tonegeek, you starground EVERTHING at one point near the input?


Jake

No ...1 star ground can get you more buzz.
Most of what I learned I took from Aiken and Kevin O'Connor really lays it out for you.
Get the O'OConnor book (london power) Ask him which volume, I forgot. you cant go wrong it absolutely works every time. throw some DC heaters on all stages except the phase and power tubes and you wont even know the amp is on. You can even get an adjustable 12VDC Switching power supply from Digikey for $25 and run your all even power tubes (in series if 50W) piece of cake, no extra trannys needed.

[Chris333]

You can even get an adjustable 12VDC Switching power supply from Digikey for $25 and run your all even power tubes (in series if 50W) piece of cake, no extra trannys needed.

Do you have a part number or brand/model number on the power supply?

[HiGain]

No ...1 star ground can get you more buzz.
Most of what I learned I took from Aiken and Kevin O'Connor really lays it out for you.
Get the O'OConnor book (london power) Ask him which volume, I forgot. you cant go wrong it absolutely works every time. throw some DC heaters on all stages except the phase and power tubes and you wont even know the amp is on. You can even get an adjustable 12VDC Switching power supply from Digikey for $25 and run your all even power tubes (in series if 50W) piece of cake, no extra trannys needed.

OK... Thanks. I have books 1 and 2, but there is not much depth on grounding.

I redrew a grounding arrangement based on comments hear and what I gleaned from TUT1 and 2.

Forgive my ignorance, but is this looking better?

[Bob-I]

OK... Thanks. I have books 1 and 2, but there is not much depth on grounding.

I redrew a grounding arrangement based on comments hear and what I gleaned from TUT1 and 2.

Forgive my ignorance, but is this looking better?

You're missing part of the ground ckt. The effects loop is grounded with a bus to the switches and speaker jacks. Also, all jacks are switchcraft metal so there's a possibility of a ground loop. As we talked on e-mail. Since the hum seems to be coming from the master volume I'd start by connecting this directly to the PI and eleminate the loop. If the hum's gone, isolate that loop from the chassis, use shielded wire on the send, or disconnect from that bus and create your own ground point.

Good Luck. If itn's not fixed in 2 weeks, I'm coming up to kill that hum once and for all!!

Again,

[drz400]

You can even get an adjustable 12VDC Switching power supply from Digikey for $25 and run your all even power tubes (in series if 50W) piece of cake, no extra trannys needed.

Do you have a part number or brand/model number on the power supply?

http://www.cui.com/pdffiles/VOF-65%20Series.pdf
You want the VOF-65-12 $26 from Digikey and you are done with all the heaters, you can also use it for 12V switching, it has a trimmer to tweak it to 12.6V

[HiGain]

You're missing part of the ground ckt. The effects loop is grounded with a bus to the switches and speaker jacks. Also, all jacks are switchcraft metal so there's a possibility of a ground loop.

I'll put that in as well. I'm researching this issue partly for my own edification.

The noise in my AC line at my place is worse than it's ever been.
The truth is, I won't know what's going on until I get a power conditioner, probably to undo the noise from all the air conditioners.

Jake

[drz400]

You're missing part of the ground ckt. The effects loop is grounded with a bus to the switches and speaker jacks. Also, all jacks are switchcraft metal so there's a possibility of a ground loop.

I'll put that in as well. I'm researching this issue partly for my own edification.

The noise in my AC line at my place is worse than it's ever been.
The truth is, I won't know what's going on until I get a power conditioner, probably to undo the noise from all the air conditioners.

Jake

That shouldnt matter if the guitar volume is off.
Personally I have never found a power conditioner to help with 60cycle.