Beginner's Gainclone, Safety and, The Power Supply Board (please contribute)

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This is for the purpose of an accessable hifi gainclone amplifier power supply board, it is in reference to http://www.diyaudio.com/forums/showthread.php?postid=1515609#post1515609, and it is by request.

After some experience with the confusion that can result from rectifiers and layout, I'm somewhat prepared to present a design that's not so confusing. And, I hope that the photographic format can overcome my lacks in writing skills.

However, I'll need some help from the guru's--especially on Earth Grounding needs for the U.K. and international requirements.

Before presenting a design, I'd like to cover safety. And, I'll need some help with that too.

Main topics for safety:
1). Wooden enclosure (safety at the workbench)
2). Safety Earth Grounding (safety during operation)
3). Drainer/bleeder resistors (safety at the workbench)
4). Light bulb operated test unit (safety for components)
5). Power LED (safety at the workbench)
 
Wooden enclosure:

Due to conflict in international safety, I can only discuss this topic in terms of using a wooden enclosure. And, personally, I'm clumsy enough that I need a wooden enclosure.

Advantages:
Low cost
Any size
Variety of appearance

One disadvantage is that a wooden enclosure doesn't shield from RF. Therefore we may want a 330 picofared capacitor from + to - of the input at the amplifier board, so that it can block the RF. That isn't vital, but can be helpful.

There's no problem in putting the entire amplifier and power supply together in the same box. An established practice is to put the transformer on the opposite side of the heatsink, so that the heatsink becomes a shield. Ground the heatsink.

Although the wooden enclosure does decrease voltage reference for fingers, etc. . ., it doesn't do a complete job.
Since audio components are all grounded together via the RCA cables, we do need safety earth grounding.
 
ibmeris said:

Thanks!!

One of the schematics shows that even if the amplifier is wooden, perhaps the interconnect cable (RCA) goes right to a metal-cased tuner. Reference Figure 1 on that link above.

For a more-complete presentation, I'd sure like a photograph of the 35A ground loop breaker. Reference Figure 3 on that link above.
 
The reason that I want a photograph is that the Faston connector of the typical 35a bridge rectifier. . . doesn't match that schematic at all.

On the Faston connector, the + is marked, leaving one to assume that the - is located in the opposite diagonal corner (farthest distance away from the +).

Therefore, the schematic doesn't show a "real" unit. We need to show the real thing.
 
Here (click photo) is an example of a heavy duty bridge rectifier.

These are super-strong and long lasting. Some are even shielded, which is a nice bonus if you enjoy listening to your radio.

We're going to use a few, so here's a photo indicating the polarity of the larger models.

Notice: The one connector at a different angle is the +
 

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disconnecting network.

connect + to -
connect ~ to ~
connect ~ to audio ground
connect + to Safety Earth

This gives a continuous 70A rating using a 35A bridge rectifier.
It survives longer (undamaged) than it takes a T8A fuse to rupture and the arc to extinguish on 240Vac mains supply.

The optional components: 10nF to 100nF cap, 2r2 to 10r power resistor and/or power thermistor, can be soldered between any pair of adjacent spades connectors. Since one has 4 spade connectors that leaves four locations for the optional components. I use the 4th location for a low inductance/low power 10r to ensure that the impedance of the network stays fairly low at all frequencies.
 
Here's the United States version for out 10 to 15 amp home circuit breakers. This can be built from parts available at Radio Shack.

Four of 6A (or better) diodes*
*Folks with fuses need the stronger UK version (above post).

A 10 ohm, 5 watt (or 10 watt) resistor

A 100nF (probably printed with "104") capacitor**
**That vendor sells the cap as 0.1uF.

And here's the photo. . .
This version is for use only if your house has 10a or 15a circuit breakers--spec for U.S. houses. Otherwise, please DO use the stronger UK model in the previous post. This weaker model was posted, because its a clear illustration.
(Click photo).
 

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Re: disconnecting network.

AndrewT said:
connect + to -
connect ~ to ~
connect ~ to audio ground
connect + to Safety Earth

This gives a continuous 70A rating using a 35A bridge rectifier.
It survives longer (undamaged) than it takes a T8A fuse to rupture and the arc to extinguish on 240Vac mains supply.

The optional components: 10nF to 100nF cap, 2r2 to 10r power resistor and/or power thermistor, can be soldered between any pair of adjacent spades connectors. Since one has 4 spade connectors that leaves four locations for the optional components. I use the 4th location for a low inductance/low power 10r to ensure that the impedance of the network stays fairly low at all frequencies.

Okay, I think I got the message on where to connect everything except. . . the amplifier side. Considering the big UK power, I came up with this:

The most likely spot to connect, seems to be the Power Star Ground / Chassis Ground, CG, because those examples are the strongest point for connection.
 
danielwritesbac said:
Here's the United States version for out 10 to 15 amp home circuit breakers. This can be built from parts available at Radio Shack.

Four of 6A (or better) diodes*
*Folks with fuses need the stronger UK version (above post).

A 10 ohm, 5 watt (or 10 watt) resistor

A 100nF (probably printed with "104") capacitor**
**That vendor sells the cap as 0.1uF.

And here's the photo. . .
This version is for use only if your house has 10a or 15a circuit breakers--spec for U.S. houses. Otherwise, please DO use the stronger UK model in the previous post. This weaker model was posted, because its a clear illustration.
(Click photo).
Have you tested your 110Vac version yet?
 
AndrewT said:
Have you tested your 110Vac version yet?

Just to be clear, its specific to 120vac with 10a or 15a home circuit breakers.

Hey, and you'll notice that I doubled the number of diodes (since our previous discussion). Yes, it tests working. In my opinion, it was important to post a photo of the small version so that everyone who looks at it can understand the "visually obvious" circuit.
I'd rather that everyone use the stronger 35A UK-rated version, so I'll show that one through the remainder of the project.

Difference between the two are:
Visual / appearance
Amperage rating
 
Right now, I'm imagining some folks laughing at this effort, because its quite unlikely for a 12ga or 14ga home wiring to fail when protected by a 10a or 15a circuit breaker. Well, stop laughing. The ground loop breaker (disconnect network) does an additional job.

Simply put, that's better bass.

Yes! Here's an example:
1). If any other electronics are running, there is return voltage on your home neutral line.
2). The power star ground is the voltage reference for your loudspeakers, specifically electronic dampening. They are reliant on the zero volt line and they deliver a (return) charge onto it.
3). The related input star ground is the voltage reference for driving your amplifier.
4). SO, you can see that "Safety Earth Grounding" can potentially help the frequency response of your audio system--when zero volts really is zero.

I hope that illustrates that there are several reasons why you should ground your amplifier. Not everyone will receive better bass; however, if you'd had a problem with "bass shy," then grounding is one of the first steps towards a solution, and its something you need to do anyway.
 
danielwritesbac said:
Right now, I'm imagining some folks laughing at this effort, because its quite unlikely for a 12ga or 14ga home wiring to fail when protected by a 10a or 15a circuit breaker. Well, stop laughing. The ground loop breaker (disconnect network) does an additional job.

Simply put, that's better bass.

Yes! Here's an example:
1). If any other electronics are running, there is return voltage on your home neutral line.
2). The power star ground is the voltage reference for your loudspeakers, specifically electronic dampening. They are reliant on the zero volt line and they deliver a (return) charge onto it.
3). The related input star ground is the voltage reference for driving your amplifier.
4). SO, you can see that "Safety Earth Grounding" can potentially help the frequency response of your audio system--when zero volts really is zero.

I hope that illustrates that there are several reasons why you should ground your amplifier. Not everyone will receive better bass; however, if you'd had a problem with "bass shy," then grounding is one of the first steps towards a solution, and its something you need to do anyway.

Daniel, please please please stop with your outrageous claims. Can't you be satisfied just sitting back and just learning a bit before trying to be some kind of neophyte guru or whatever it is you think you are (not meant in a mean spirited way)?
 
danielwritesbac said:
I'm hoping that everyone is "on the same page" with building the ground loop breaker (disconnect network)--because I'd like to move on to powering the amplifier.

You won't ever catch me putting one into one of my projects. One of the things that's glossed over on this forum is what would happen if a DIY effort was the cause of something serious, like electrocution or house fire, and someone was making a claim against their insurance, and an inspector did attribute the accident to a homebrew product with no certification sticker. It may not matter in many parts of the world, but that is a big deal in North America.
 
leadbelly said:
Daniel, please please please stop with your outrageous claims. Can't you be satisfied just sitting back and just learning a bit before trying to be some kind of neophyte guru or whatever it is you think you are (not meant in a mean spirited way)?

If your speakers don't put return voltage onto the 0v line, then I am envious of your speakers.

There are many reported cases of chipamps with lackluster results ("jukebox bass" or "excess mids") and a lesser, but certain, number of published cases where safety earth grounding was quite helpful as the repair.

Those two items are all that I have on the "side benefit" of safety earth grounding.
And, personally, that is the best I can do to accomodate your comment.

I'd like to move on to the power supply board.
But, first, some info. . .

I'm not a guru, and this thread is "by request." In fact, I didn't start this particular thread until getting some help from Mr. AndrewT, to confirm the grounding circuit. Please consider my role in this thread as like a "translator." We have Gychang's group here, all suddenly building amplifiers. ;)
Their soldering irons are hot and they're ready to go, and then. . .
Reference this Schematic:
An externally hosted image should be here but it was not working when we last tested it.

Look at the bridge rectifier.
That isn't a real rectifier, because the industry standard Faston connector isn't in that orientation. So, you can see why its beneficial to translate this into a clear photographic content, using the real-life parts.
 
leadbelly said:
You won't ever catch me putting one into one of my projects. One of the things that's glossed over on this forum is what would happen if a DIY effort was the cause of something serious, like electrocution or house fire, and someone was making a claim against their insurance, and an inspector did attribute the accident to a homebrew product with no certification sticker. It may not matter in many parts of the world, but that is a big deal in North America.

Yes, its a very big deal. In the U.K., their fuses may be stronger than their home wiring; however, in the U.S. we have laws against grounding humans in the presence of voltage. Therefore:

danielwritesbac said:
Due to conflict in international safety, I can only discuss this topic in terms of using a wooden enclosure. . .

Safety topics are about decreased risk therefore, if someone feels uncomfortable at building their own equipment--don't do it.
This document is for people who are going to build their own power supply, and thus this document represents decreased risk.

AND. . . Thanks for the reminder!! See this photo to get a close up view of this popular Carpenter's power safety device. It comes from the hardware store, and it has an inbuilt circuit breaker. (click photo)
 

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