AC Filtering, Grounding Boxes, Linear PSU and Balanced Power.

[sandyk]

I use 2 heavy duty mains filter in the same case . One for supplying the LED backlighted TV, and the other for my normal audio gear. They are based on a design by Silicon Chip magazine. The only mains rubbish that I get through is due to DTV reception in this low signal area with Rabbit's Ears and a low noise MHA, when the fluoro in the toilet across the hallway gets turned on.

Fortunately, 230V AC 50HZ mains supplies don't appear to normally have problems anywhere near as bad as those with 115V AC 60HZ.

[sandyk]

Yashn

Normal mains filters may not be as efficient as a specially designed heavy duty filters that also take into account SMPS rubbish coming back the other way ? SMPS gear such as DVD players etc. do have small mains filters built in, but they are only designed to comply with statutory emission requirements.

 

Alex

[sandyk]

While in fact noise and interference currents only interest is to get back to their voltage source. What is their voltage source? Why it's the Neutral of that big power company transformer down the street from your house.

 

Some of those currents also go back through mother Earth ! Chatswood Telephone Exchange in Sydney is right alongside Chatswood Railway station. Until they improved the Old Exchange earthing, occasional problems happened to trip the large 52V 2,000A Rectifiers. The same happened occasionally when Westfield shopping centre, which is 100s of metres away down the road, started up it's escalators , main lighting etc. just before opening for the day . No, the incoming A.C. voltage didn't drop much when that happened.

[sandyk]

Seldom do residential ground rods achieve less than a 25 Ohm contact resistance to Earth!

 

In Australia, Telstra required a minimum of 25 ohms for the earthing of PABXs, Payphones etc. In some areas such as French's Forest in Sydney this was often difficult to achieve. Some of the Linesmen were well known for their lunch time drinking, and it seemed funny that with one linesman in particular , that an earth that was outside of the requirements suddenly measured O.K. from the Telephone Exchange just after lunch !

[sandyk]

Why should a separate ground bypass the fuse or circuit breakers (not considering GFI)? A circuit breaker is a switch on the hot leg which switches off the hot leg when there is a over current. It does not care where to currant goes (in contrast to GFI) or is there something I have not considered?

 

Working Principle of Earth Leakage Circuit Breaker (ELCB) and Residual Current Device (RCD) | EEP

[sandyk]

Hopefully, there is no safety implications (as you would get with ground floats and cheater plugs).

 

I suspect that there may be. Where would you be for example, if the secondary of the transformer broke down to it's core ?

Perhaps a question for 1 1/2 ?

Even when I don't connect any of a circuit to mains earth, I normally mount the transformer (depending on type ) on a metal plate or a piece of copper clad PCB, where only the plate/copper side of the PCB is connected to I.E.C. mains earth.

The plate is also spaced a little above the bottom of the case to permit improved ventilation without any protruding bolt heads.

[sandyk]

Yashn

If you are able to hear differences, with and without the filter, are you able to verify that the checksums of both versions, even the upsampled versions , are still the same ? Incidentally, for a couple of years now, my rips have been done with the PC unplugged from the Broadband Modem.

 

Regards

Alex

[sandyk]

Hi John

But how many people who self installed their own Isolation Transformers would be presently using a Ground Fault Circuit Interrupter at the secondary of their isolation transformers ?

I suspect not too many.

 

Alex

[sandyk]

in many countries working direct/installing equipment with voltages 100V above requires licensing. Hobbyists are not exempt.

 

That applies to Australia, but surprisingly, not New Zealand.

240VAC is far less forgiving than the U.S. mains .

[sandyk]

actually i think 50V DC like on the phone lines hurts more than 240V AC... speaking from experience

 

Surely you jest ? I was a Principal Telecommunications Officer with Australia's Telstra, and I can assure you that being properly bitten by 240 VAC is much worse. The back EMF from a 52V DC operated relay or uniselector coil can be quite painful though, but brief, unlike 240VAC which can throw you back hard enough to knock the wind out of you, if you are able to let go ! That's why ELCBs are essential, especially in 50HZ 230VAC countries.

 

Alex

[sandyk]

Dennis Bohn has observed that placing an excessive capacitive load on the output stages of microphones and other audio equipment causes distortion of high frequency transients.]

 

That is a problem with most opamps, and the main reason for use of a low value resistor (typically 100 ohms ) in series with their output.

[sandyk]

Or do as Lukasz Fikusz used to do, and rip out complete output circuits (including their opamps and capacitors) from old CD players and replace them with a tube implementation (hence the name of Lampizator).

 

I am well aware of that, but it's simply replacing with a more euphonic form of distortion ! (smile)

Were ALL the capacitors in the signal path of his designs removed too ?

[sandyk]

not at all... im an electrician in australia and ive been booted countless times! the phone hurt me more for some reason. probably because of the DC "stickiness" compared to the pushback you get from AC

 

oh apart from one time.. i was working in a dome connecting a house and must not have been paying attention properly and i slipped and touched the metal on my screwdriver while live (domes are unprotected mains back to the main transformer supplying the area so pretty much get a boot in them and you have a good chance of kicking the bucket) but luckily my elbow was touching a temporary metal power pole we had installed so the current only went from my hand to my elbow and then down to ground.

 

That was my "i should be dead" moment.. nothing has ever hurt me so badly.

 

anyway since then you never find me working on anything live!

 

When younger, I was thrown a couple of times. The 2nd time I wasn't even able to reassure a worried child that I was O.K. for about a minute. That was from touching a 240V tag on an open frame type transformer in an amplifier while working on it. (It didn't stay exposed after that !) Impulsing relays in the old Step by Step Telephone Exchanges had a back EMF of around 800V, so that may have been what bit you ? It's what caused my hearing damage due to inadequate protection in the receivers of "Buttinskis" used for monitoring purposes at the time .

[sandyk]

But no distortion like in some SS amps

 

If you heard my SS amp, you'd love it.

 

But if you heard my Tube amp, you'd love it even more.

 

I wouldn't bet on me loving your hollow state amplifier.

Both my Preamp and 15W/Class A have THD of something like .0002% (perhaps a little lower?) due mainly to active device matching and front end balancing .

A friend nicknamed my15W Class A "The Holo Amp." ( as in Holographic )

[sandyk]

So yours would be a Holo Hollow amp?

 

No, it's fully solid state, and uses closely matched metal can dual transistors in the front end (LS313 and LS352/2N3811A)) as well as matched pairs of 30MHZ output transistors.

[sandyk]

Here is my SET Tube Amp that I made with my own hands (PCB by George @ Tubelab, KT-88 by Electro-Harmonix and other tubes from Russia, Transformers by Elcor).

 

It doesn't care about others' THD figures, just outputs fantastic sound with the fastest dynamics I have ever heard:

 

[ATTACH=CONFIG]19768[/ATTACH]

 

 

It's very heavy. I have not even yet added a choke as well as Russian Motor Start Caps.

 

Just as well we don't live in the E.U. as they are likely to ban such power thirsty relics from the middle of last century !

Even my 15W /Ch. Class A SS amplifier which consumes a little over 80W would likely be made illegal too.

[sandyk]

I was thinking about energy efficiency and EU directives. Why to deal with amps? What about the efficiency of speakers? Like putting high lumens per watt light bulbs in low efficacy lampshade which allows only a small portion of the light generated to be useable!

 

A good question for Anthony ? I bet that his speaker designs are more likely to be very low impedance, (4 ohms or less) and designed to mate with high power amplifiers.

[sandyk]

Mike

Have you actually verified by using a DMM, that the "earth" side of the RCA sockets is actually directly connected to chassis (not via a resistor)

In many modern designs they aren't.

 

Alex

 

P.S.

Using banana plugs and sockets could be another option. Make sure you scrape away any anodising or paint around the sockets though.

[sandyk]

Hi One and a half,

 

Thanks so much for your input, here. My DAC only has one pair of RCA outputs (in use), the USB input (in use), a BNC coaxial input and the optical input. The amp has an available pair of RCA inputs. I suppose I could rig up a short shield wire between the BNC connector and one of the amp's RCA connectors, as you've suggested.

 

Wanting to understand "why" - I don't understand the need to do this. In general, I can easily imagine that a short, heavy gauge connection between the two chassis would encourage ground currents to flow there rather than on the longer, narrow gauge shields of the signal interconnects, but as I described in my previous post, the RCA interconnects form a horseshoe with the DAC and amp.

 

I cannot envision any path through which a ground current could loop. That's why I think I can abandon any concern for the huge difference in supply voltage coming into the two chassis (117.5 vs. 109.9).

 

Again, with a floating-secondary isolation transformer supplying even just the DAC, a ground loop cannot form in the power lines between DAC and amp. Every other cable that's connected to the DAC and amp go to "dead end streets" (battery-operated devices that themselves share no connections - including the iPad 3 and the battery-powered USB Regen). So where's a loop going to form?

 

Are there benefits to keeping the shield voltages the same between the DAC and amp, that have nothing to do with ground loops?

 

Eager to learn - thanks for your help,

 

Mike

 

 

 

 

Thanks Alex!

 

I hadn't tried, but I just now measured 0.2 Ohm between the shields of adjacent RCA connectors on the Amp, for example. Does that mean a resistor is in use?

 

Mike

 

No, that just means they are connected together via the 0 volts (" earth") of the PSU.. You need to measure between the outer of the RCA socket and a clean metal area of the chassis with the output leads unplugged to see if the RCA sockets are isolated from the chassis or not. Typical RCA sockets are supplied these days with insulating washers.

 

e.g. 10pcs Gold Plated RCA Jack Panel Mount Chassis AV Signal Video Socket | eBay

[sandyk]

Simple Linear Power Supply build by Phil Levchenko:

 

As an aside. If you just want +5V you can use fixed resistors with a 3 to 1 ratio. e.g. 100/300,110/330,120/360 etc.

This gets you very close to +5V normally.

[sandyk]

http://www.computeraudiophile.com/f20-buy-and-sell-audio-and-computer-components-no-dealers/4-us-and-1-european-balanced-power-transformers-sale-%24450-each-shipping-and-handling-25303/

[sandyk]

It's like paralleling cables, our code mandates a minimum of 6mm (10AWG) not 2.5mm (12AWG) as practiced in the UK and not in a ring either.

 

Irrespective, the U.K, Australia, N.Z. and others with 230V 50HZ supplies don't need such thick conductors for the simple reason their single phase voltage is twice as high and current demands are typically halved.

[sandyk]

m

It's not about a components power supply, it's about a home's ring circuit.

A 30 Amp circuit (that's about 7200 Watts) needs a 6mm conductor.

 

Other than perhaps a stove or HWS, why would you need a 30A circuit ?

Is that why U.K. mains plugs have an internal fuse, whereas other countries with 230V 50HZ supplies don't ?

[sandyk]

Ben Duncan writes:

 

You can avoid this drop in voltage between your house's main intake and your studio by giving your studio's electronics its own dedicated supply (a radial or spur, rather than the usual ring circuit), and reduce voltage losses by using lower-resistance wiring than usual. If your studio is located a fair distance — say 100 feet — from the supply intake, surprisingly fat wires will be required. These will be nominally rated at unfeasible-sounding high currents (maybe over 100A), but what counts is the low total resistance. In electrician's language, very high current wiring is required to meet the part of the IEE (Institution of Electrical Engineers) regulations, which cite a maximum four-percent voltage drop between the mains intake and the furthest fixed outlet, when operated at the anticipated current. However, what electricians will find hard to understand is the high current peaks that studio gear draws

 

You Yanks and your Kilowatt domestic Power Amplifiers ! You must have very understanding wives, or a high divorce rate ?

Regularly listen for anything more than a few seconds at a time with 110 to 120dB SPLs at the listening chair and you will rapidly irreparably damage your hearing.

[sandyk]

Ben Duncan is very British!

[h=1]Identifying & Solving Mains Supply Problems In The Mains[/h] Ben Duncan

The mains (AC electrical) supply in the UK is one of the most stable, generally pure and reliable across the world. The downside of being so lucky is that unless there are blatant problems, the energy supply becomes transparent — we readily forget just how reliant we all are on its smooth continuity for musical creativity.

 

Identifying & Solving Mains Supply Problems

 

Back when Ben Duncan was in his prime, writing articles for HFNRR etc. and his Audio design books, the typical Pommy domestic amplifier was only around 30 or 40W RMS output power.

I have a copy of one of his books as well as a copy I scanned from HFNRR of his Supertuning CD series from November 1987.