Re: Ground Busses

On Mar 3, 10:19=A0am, Patrick Turner <i...@[EMAIL PROTECTED]
> wrote:
> Andre Jute wrote:
>
> =A0snip for brevity,
>
> > Most schematics don't tell you enough about earthing.
>
> This is a very true statement if ever there was one.
>
> A schematic is just how things are connected, and sure, worth a thousand
> words.
>
> But they are often utterly useless in telling folks how to layout
> the circuit and placement of parts and wiring for
> best operation, freedom from micro power supply rectifying noise
> voltages in 0V wiring,
> magnetically induced mirco voltages, and return current effects in load
> current carying wiring
> etc etc etc.
>
> A lot is left for the maker to get right.

Frankly, Patrick, my opinion after nearly twenty years in DIY tube
audio is that, were you and I to collaborate on a book on grounding,
ti would uneconomically thick, it would still be incomplete, and the
little hotheads and know-alls, as in your example below, would still
screw it up. And the self-declared "professionals" like Poopie and
Plodnick would still screech down from their ivory towers without
adding anything of any practical use to the discussion.

BTW, I use and appreciate Carda connectors. They're nice to handle and
the gold plating is done over the proper underlayers, unlike so much
American plating which is shoddy.

I have left the rest of Patrick's post because it bears on what I say,
and is funny besides.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
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containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

> Countless times diyers construct something with the exact and right
> schematic
> but are left with deafening hum and noise problems, and with
> maybe RF oscilations as well, all because of very poor understanding
> of most basic aspects of electronics. When told to spend weeks doing
> some real learning,
> they just cannot do it because they don't have a questioning mind.
>
> In a recent case a guy with an old tubes CJ preamp had me instal
> a fet cascode circuit for the MC input to suit his MC cart because the
> CJ
> had a rather poor tubed phono rendition fit only for high output MM.
> I finally got the 0V pathing adjusted after several hours to give
> negligible
> hum when the preamp gain was set to normal operation level
> with an average power amp connected with a speaker.
> He appreciated the revaltion the MC cart gave him.
> Then he wanted all the crummy old 1960s RCA sockets replaced to stop the
> intermittent noises he was getting.
>
> My time is valuable, and too valuable to do the donkey work
> of replaceing RCA sockets, so I insisted he learn to use a drill and
> make a new panel and
> pay for some Cardas sockets and do it himself.
> Of course he insisted on remaining a practical klutz, and talked his dad
> into
> doing this highly skilled but tedious task for nothing of course.
> His dad wanted to keep the exact positions of the existing RCAs the same
> so as not to
> disturb what 0V rails I had arranged initially.
> But the guy had his dad change the positions to suit two different sizes
> of new RCAs,
> so that phono input wiring was 150mm longer, and woe, he used untwisted
> 1mm thick house wire type wires.
>
> When he tried te amp, its hum was quite deafening, and ther amp
> was unusable, so he comes across town to me for a fix, cheaper than
> learning anything.
>
> I re-route the cabling internally to where it was, but get him to agree
> there was no difference
> in quality the two sizes of RCA sockets, so no need to make the
> compromise in positioning
> just because of some wacky idea about the RCA socket quality.
>
> He went away after $50 worth of work which stuffed my afternoon on a
> saturday
> but he had a Turnerized Conrad Johnson that wasn't noisy any more,
> and he had some real understanding of how bleeding im****tant
> it is to consider everything about all aspects of what you're doing
> when making any changes to circuits.
>
> Here, for
>
> > instance:
> >http://members.lycos.co.uk/fiultra/Jute-EL34-SEntry.jpg
> > I've shown the star earth being implemented but have not said anything
> > about connecting the case to earth. Mind you, on some of the Lundahl
> > Modular Series 300B schemos I showed all the 0V connections in order,
> > with a note saying "mind the order of the grounding connections", and
> > two people wrote me letters saying that DIYers are not idiots who need
> > their hands held. (I was, when I started, and I'm very grateful to
> > people who made 90 mile round trips to come check over my
> > constructions before I fired them up.)
>
> The schema above is fine, but has no chassis shown,
> so I suggest 27ohms x 5W from star 0V point to chassis point near the
> RCA inputs and well away from the PT.
>
> The mains green / yellow earth wire sould also be taken to a chassis
> point away from the
> PT, and not necessarily to where the 27ohm is anchored, to reduce
> induced chassis voltages.....
>
> I might add that 0V rails layout is even MORE critical in high powered
> SS amps...
>
> Patrick Turner.