Go to your room!.... Now!!! Don't come out till christmas.

Other than that, I have no idea. I'm scared of things that can shock me. Even if its not plugged in... it'll kill me (I'm colour blind... I leave electrickety stuff to people who can see, lol)

But I'm sure alan or mike can help with alternatives.

Haha, well my intention is to help people who are wanting to start a build, and are unaware of the importantance of grounding technique.
No.1: the centre tap of the ht winding must first go to the smoothing cap negative terminal then ground.

I'm actually busy rebuilding my 5E3 (for keeps) and looking at grounding quite seriously. Knowing that you're quite the amp builder, I am quite surprised to hear you're only starting to obsess about grounding now!

Although I don't know a helluva lot about anything, as I'm fairly new to this, there's something intuitive in me that screams aversion to bus grounding and the plate grounding scheme that people sometimes use.

1st time I built the 5E3 I used a fairly controversial grounding scheme with 2 main stars and a couple of sub stars. Think this time I'm going to go with a pure-ish multi-star, with individual chassis grounds for each stage (incl surrounding circuitry like tonestacks etc). So ground for inputs + input stage + tone stacks on the input jacks, ground for 2nd pre next (but close to the input jacks), grounds for PI next and then grounds for power stage close to the OT ground.

Cap board is going outside the chassis next to PT and choke and will heed your words about the HT. Could you explain in a little more depth perhaps as to why this is a good idea?

Cheers

Was planning a bus for my next build, what's wrong with that BottledTone? I reckon one solid 5x25 copper flat like the ones you get for automation cabinets should do the trick, running along the side of the turret board. Then again, I am not too read-up about grounding :-\

In my 18 watt I have bus grounds for the preamp and power amp and a star ground point which is isolated from the chassis via a snubber network. Everything grounds via the busses to the star point or directly to the star point. The snubber keeps the potential on the star point equal to that on the chassis. Seems to work fine.

makepeace wrote: Knowing that you're quite the amp builder, I am quite surprised to hear you're only starting to obsess about grounding now!

Oh I've been obsessing for years bro, but like i said, you always come across issues that "change your mind" so to speak.
I started the thread to see if others could benefit from mistakes i've made, (or others have made) over the years. Thats all, unless no-one cares ?

Gearhead wrote: Was planning a bus for my next build, what's wrong with that BottledTone?

Nothing wrong! When the amp is done and there is no hum or hiss, it's perfect. Right?

I have just recently helped someone locally that had mad hum, and showed him some errors of his wiring, and thought a thread would help others before they build, to get it right first time.

makepeace wrote: Cap board is going outside the chassis next to PT and choke and will heed your words about the HT. Could you explain in a little more depth perhaps as to why this is a good idea?

That wire from the CT winding (or wire from the negative side of a bridge rectifier) is carrying a large current, which is why it must only go to the first smoothing cap where it will be used, then the reference ground wire to chassis(or bus). This keeps the high current out of the rest of the amp grounds. The speaker wires must also both go straight to the output jack, where the speaker will use it, and then its reference ground wire can go to the point on the chassis where the first filter (smoothing)cap has a reference. Unless the amp has a negative feedback loop, in which it can be returned to the phase inverter ground.

bottledtone wrote:

makepeace wrote: Knowing that you're quite the amp builder, I am quite surprised to hear you're only starting to obsess about grounding now!

Oh I've been obsessing for years bro, but like i said, you always come across issues that "change your mind" so to speak.
I started the thread to see if others could benefit from mistakes i've made, (or others have made) over the years. Thats all, unless no-one cares ?

Woops, seem to have misunderstood what you were saying about obsessing. :-[. I care very much!

As I said, I don't know what I'm talking about, but one day I'd love to say that I do..

Something new I learned just today from Merlin's article is that Fender have been "lying" to us with their out of chassis cap boards theory (and the "all of the power supply filters in a row" theory). Read his article about grounding in which he said that correct practice is to put your filter in amongst the circuitry its supplying.

Do you have any preferences as far as thats concerned?

That wire from the CT winding (or wire from the negative side of a bridge rectifier) is carrying a large current, which is why it must only go to the first smoothing cap where it will be used, then the reference ground wire to chassis(or bus). This keeps the high current out of the rest of the amp grounds. The speaker wires must also both go straight to the output jack, where the speaker will use it, and then its reference ground wire can go to the point on the chassis where the first filter (smoothing)cap has a reference. Unless the amp has a negative feedback loop, in which it can be returned to the phase inverter ground.

Cool get that completely. Thought there may have been more to it.

Makepeace: Yes, I do prefer that the HT filters are right amongst the stages they are supplying. The Fender cap orientation is not really the best idea, as it groups all the grounds together, allowing early current to flow into later circuitry. With new rules i am unable to show you pics of my latest build, but the filter caps are placed right at the ground nodes of a "multi-star" scheme.
There are a few things that Fender is "lying" about ?, but each to there opinion. (there is someone who always argues with me, that there is no point to valve reverb, but I am a bit of a purist and I have a very good circuit i use)

Wish I knew that before I planned my rebuild :-\. Oh well.. Guess it will win for authenticity sake, whatever that means.





I actually remember we got talking about reverb a while back. I just converted the reverb stages of an old hammond organ to a stand-alone guitar unit. 12AX7 triode into 12BH7 triodes in parallel with a choke and cap filter before the tank (2.something kohms into 1.something kohms); and then the other 12AX7 triode for recovery. It has a little too much gain when level is on full, but thats still useful for other things (like driving the preamp on my 5E3, which it manages to do).. Gave it mix, dwell and gain controls. There really isn't anything like the sound of a good tube verb. Only trouble is size and noise. I wonder if there is any viability in a miniature spring tank?



For this one, kept it in the power amp chassis for the mean time. Left the grounding the way they did it, which looks terrible on the whole, but its surprisingly quiet, more so than my amp even. Heater wiring is also a bit of a cop out.. Will have my own chassis bent up soon for a final rebuild and also throw a cab together for it.

To me the actual type of connection bus or star doesn't really matter (although using both would be pretty dandy). Using a thicker wire would be better as it has less resistance on the ground. Less resistance on ground the better.

Nicholas I believe you'll find a noticable difference between a good star grounding scheme and bus grounding.

Makepeace: A Cap driven reverb? what model reverb tank are you using?
I just like to use reverb transformers, then you could plug your reverb out into a 8 ohm speaker, and get
nice bedroom volume ?

With grounding, I draw out a schematic, and the look at separating the grounds between the coupling caps.
eg, The input ground is grouped with the valve cathode and the filter thats suppling that valve section, then there is a coupling cap from the anode of the valve, and after that a volume control, which is then grouped with the next valve cathode and filter cap etc etc. Thats the basic to start from.

All the materials that we work with have some resistance on them, so number one! always keep that first filter cap grounds from the others, or it interfence with the rest of the circuitry.

here's the schem:



not the most economic reverb, but it works nicely and as i say, parts were spare.

the tank is pretty much an accutronics 4FB1B1C.

bottledtone wrote: With grounding, I draw out a schematic, and the look at separating the grounds between the coupling caps.
eg, The input ground is grouped with the valve cathode and the filter thats suppling that valve section, then there is a coupling cap from the anode of the valve, and after that a volume control, which is then grouped with the next valve cathode and filter cap etc etc. Thats the basic to start from.

Interesting...I've been doing an amp layout for some new builds I'll be starting next year and this is exactly the grounding approach I've been looking at.....