Hi All,
I have a question for the gallery. When I first got interested in tube DIY i used to frequent the Bottlehead forum a lot. I seem to remember reading that if you connect a .1uF cap from the signal negative of a chassis mount RCA jack to the chassis as well as using a wire to establish the signal negative for it's corresponding channel that there was some benefit to be had. Is this true? Has anyone used this "trick of the trade"? Also I plan on soldering a chassis ground wire to the approximate center of my chassis and to the star ground point of my amplifier. Is the spot that I choose for the chassis ground connection crucial when using the star grounding method?
Gavin Haley
I have a question for the gallery. When I first got interested in tube DIY i used to frequent the Bottlehead forum a lot. I seem to remember reading that if you connect a .1uF cap from the signal negative of a chassis mount RCA jack to the chassis as well as using a wire to establish the signal negative for it's corresponding channel that there was some benefit to be had. Is this true? Has anyone used this "trick of the trade"? Also I plan on soldering a chassis ground wire to the approximate center of my chassis and to the star ground point of my amplifier. Is the spot that I choose for the chassis ground connection crucial when using the star grounding method?
Gavin Haley
Well, chassis ground may not be chosen as the same as small signal ground. Unless you enjoy circulating currents in the chassis.
CW says that if chassis ground differs from signal ground you ensure they are grounded in AC but you prevent DC currents from flowing. Is this a good strategy? hmmm....
I think this has been discussed before.
CW says that if chassis ground differs from signal ground you ensure they are grounded in AC but you prevent DC currents from flowing. Is this a good strategy? hmmm....
I think this has been discussed before.
Re: I SEE.
DO you have to complicate everything? Is it compulsive? I really think you need help.
The 1/2" between the jacks is IRRELEVANT. If you don't like that idea - fine! - float your jacks, and put a chassis lug inbetween them. Tie your ground bus there. Done. End of story.
fdegrove said:
DO you have to complicate everything? Is it compulsive? I really think you need help.
The 1/2" between the jacks is IRRELEVANT. If you don't like that idea - fine! - float your jacks, and put a chassis lug inbetween them. Tie your ground bus there. Done. End of story.
THE ART OF GROUNDING
Hi,
The center isn't what you need to use.although it can be a good poit to ground.
Basically you need a place where ground current activity is lowest.
Some experimenting may be called for and a scope is certainly helpful.
If you dont have one choos a place inside the chassis away from xformers and psu filtering and try it out.
Cheers,
Hi,
The center isn't what you need to use.although it can be a good poit to ground.
Basically you need a place where ground current activity is lowest.
Some experimenting may be called for and a scope is certainly helpful.
If you dont have one choos a place inside the chassis away from xformers and psu filtering and try it out.
Cheers,
IMO, using the chassis as a signal conductor is not the best.*
In a commercial design it can make the product a bit cheaper, and by experimentation, the performance can be maximized.
Much better, is to take each earth back to a (central) point in a star arrangement. Do not bunch the earth cables together, or there will be inductive coupling.
The chassis need not be directly connected to earth at all from a performance piont of view; But it is wise from a safety angle.
My preference is to connect the chassis to the mains earth, but my star earth connects to the chassis via a (big)10 ohms and 100n in parallel. This reduces circulating currents, but maintains signal potential.
RCA jacks? I don't like them Given the choice (which I have in DIY) I use XLR's, even for unbalanced interconnects.
*It may not be the case for thick copper chassis' resistivity, but atttachment of earths becomes an issue.
Frank,
I think the 100n that G was talking about will reduce buzz harmonics due to earth currents flowing. I agree that from a signal point if view, it won't have any effect below a few MHz.
In a commercial design it can make the product a bit cheaper, and by experimentation, the performance can be maximized.
Much better, is to take each earth back to a (central) point in a star arrangement. Do not bunch the earth cables together, or there will be inductive coupling.
The chassis need not be directly connected to earth at all from a performance piont of view; But it is wise from a safety angle.
My preference is to connect the chassis to the mains earth, but my star earth connects to the chassis via a (big)10 ohms and 100n in parallel. This reduces circulating currents, but maintains signal potential.
RCA jacks? I don't like them
Given the choice (which I have in DIY) I use XLR's, even for unbalanced interconnects.*It may not be the case for thick copper chassis' resistivity, but atttachment of earths becomes an issue.
Frank,
I think the 100n that G was talking about will reduce buzz harmonics due to earth currents flowing. I agree that from a signal point if view, it won't have any effect below a few MHz.
X-MASS STAR
Hello,
Overall,the best way to go IMHO.
One point I find important is to run all earthing wires as close to the bottom of the chassis as possible.
This,of course,is especially true when using hardwiring.
I agree and this is what D'haen achieves in his grounding arrangement.
Cheers,
Hello,
Overall,the best way to go IMHO.
One point I find important is to run all earthing wires as close to the bottom of the chassis as possible.
This,of course,is especially true when using hardwiring.
I agree and this is what D'haen achieves in his grounding arrangement.
Cheers,
Hold on, you two. It's a floor wax AND a dessert topping.
What you're describing is two different (but both valid) grounding schemes. In older tube amps, especially in the mono days, all grounds would run to a common bus, which would indeed be attached to the chassis at the input socket as in Joel's suggestion. As stereo emerged, so did some of the complications that Frank raised- for example, at which socket do you attach the ground bus?
I've used both schemes successfully, depending on what I'm building. For modern stereo gear with multiple inputs, it's probably best to do as Frank suggests, isolate the input sockets and return the shield to the chassis star ground point. A small cap right at the input socket shield to the chassis (0.1 uF is a bit big, I'd use an RF-quality 1 nF or so) is a great help against RFI.
For a monoblock, Joel's suggestion will work well and has the advantage of following the tradition of the great tube amps of yesteryear.
What you're describing is two different (but both valid) grounding schemes. In older tube amps, especially in the mono days, all grounds would run to a common bus, which would indeed be attached to the chassis at the input socket as in Joel's suggestion. As stereo emerged, so did some of the complications that Frank raised- for example, at which socket do you attach the ground bus?
I've used both schemes successfully, depending on what I'm building. For modern stereo gear with multiple inputs, it's probably best to do as Frank suggests, isolate the input sockets and return the shield to the chassis star ground point. A small cap right at the input socket shield to the chassis (0.1 uF is a bit big, I'd use an RF-quality 1 nF or so) is a great help against RFI.
For a monoblock, Joel's suggestion will work well and has the advantage of following the tradition of the great tube amps of yesteryear.
I agree. My preference too for a single star earth decoupled from the chassis, especially with any high gain stages in the chassis such as an RIAA stage.dhaen said:
RCA connectors? Blech! XLRs are better for line level, with Camacs even better.RCA jacks? I don't like them
In my new preamp, I'm thinking of having captive flying leads from the preamp, to match whatever is on the equiptment at the other end. I make all my own leads so it's no hardship or bother. Saves lots of connectors to get dirty, and eliminates them as an issue from the signal path.
If you don't mind something non-standard, there are lots of really high quality BNC, N etc RF connectors available for cheap compared to a Cardas RCA, which'll never be as good anyway.
Frank,fdegrove said:Hi,
Ok guys,we know that the RCA plug is a cinch.
BUT,what if you must use an RCA connector for some reason?
What would be you #1 choice?
Cardas,WBT,Eichman perhaps?Others?
BTW,Eichman is new to me,any feedback?
Thanks,
The Eichmans look good technically from what I've seen (haven't used any), but still an RCA, y'know silk purse/sows ear. Cheap plastec cased, rolled metal RCA's do quite well enough for me, with Neutriks being my second choice if I feel the need to spend money.
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