Valco Chicago 51 grounding
Moderators: pompeiisneaks, Colossal
Valco Chicago 51 grounding
I’m working on an old Valco and noticed an oddity with the grounding scheme. Obviously I’m not the first person in here, curious what is stock. I have worked on a fair number of old three input amps, never seen one with isolation washers on 2/3. The 6j7 gets chassis ground from the input on everything but the filter cap. That gets a chassis ground at the cap can, then the next tube socket, then everything else is grounded wherever convenient. Works fine, just seems like a strange, medium amount of care with the grounding scheme.
You do not have the required permissions to view the files attached to this post.
-
Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Valco Chicago 51 grounding
I am surprised they used kinda expensive switching jacks on such a cheap model.
On all the amps that I work on with multiple jack in parallel with no switching jacks I remove the unused ones to cut noise and install a switched jack.
I may also if the custom wants leave two jacks in and then make one a bit of a brite input, with two switched jacks.
In terms of the grounding scheme. It’s such a small chassis that I don’t think you will get if any better by messing with it.
With most of these small amps what helps the most with idle hum that I find is to move the PT to the floor of the cabinet, which is a bit of a job!
However when I have built some small amps for people that is way I do it.
On all the amps that I work on with multiple jack in parallel with no switching jacks I remove the unused ones to cut noise and install a switched jack.
I may also if the custom wants leave two jacks in and then make one a bit of a brite input, with two switched jacks.
In terms of the grounding scheme. It’s such a small chassis that I don’t think you will get if any better by messing with it.
With most of these small amps what helps the most with idle hum that I find is to move the PT to the floor of the cabinet, which is a bit of a job!
However when I have built some small amps for people that is way I do it.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Valco Chicago 51 grounding
Then where will the accordion and bass player plug in?
According to the amps owner, this was top of the line for valco at the time, hence the fancy jacks. If I change the grounding scheme at all, it will just be to make a new set of caps fit nicer than the hotglue ziptie job, not expecting improvement. Wasn't much hum to begin with. Just curious if the one grounded input jack was stock, and why? Lots of extra effort for something I doubt would make a difference. They didn't even bother to move the heater CT 1cm to the output cathode.