Saturday, 16 December 2017

100V line: Using a normal hifi amp and an 8 ohm speaker


My project for today involved making my standard hifi amplifier that is designed to drive an 8 ohm load be capable of driving a 100V speaker line. To do this, it is actually really simple and easy.
100V lines are a lot like how the National Grid works. Electricity is distributed by stepping the voltage up, and then down again, with power transformers to avoid power loss.
This is the same idea in 100V line. A 100V line amplifier is just a normal 8 ohm low impedance amplifier at it's heart, it just has a step up transformer built inside it, whereas a normal hifi amplifier doesn't. You can make a standard hifi amplifier run a 100V speaker line by simply using a 100V line speaker transformer in reverse. You connect where the speaker would normally go to the amplifier outputs, and then you connect the ground of the 100V line input to your speaker line and then the highest tap as the positive of your speaker line. This is basically allowing the transformer to work in reverse.
Each speaker then must have a step down transformer built in. In the picture above, I show a Wharfedale Programme 30D.6 speaker with no transformer built in. In order to use that, you must use an external step down transformer. I did this with a transformer pulled from a speaker that I scrapped recently, and it does work perfectly fine. There is no loss in volume at all.

Wednesday, 6 December 2017

Background music system upgrade - (Part 2): More speaker installations

I found cheap on eBay some Wharfedale Programme 30 speakers. These are used in pubs throughout the UK, including pretty much all of my local pubs that are still open.
My local pubs have changed hands from private landlords, to pub chains, and have been remodelled multiple times. But, the Wharfedales have always remained after being installed in the late 90s! This emphasises the fact how awesome these speakers are, they are an installation classic. They weren't just installed in pubs in my home town of Yorkshire, this was a nation wide thing back in the 90s.
They really do offer a nice warm sound, like JBL, they have a certain sound signature which just simply cannot compete with the cheaper install speaker brands such as Adastra. I bought a pair of these. One will find itself in the kitchen, whereas the other will find itself as a spare for future installation in the system somewhere.
Either way, these speakers are an installation classic, used throughout many pubs. The fact they remain after so many changes of ownership and other renovations, truly represents how awesome they are. The signal sources and the amplification I have noticed has changed over the years, but these always remain.
Note the model Programme 30 in your head, and if you see any (they are rather cheap as they are almost always pulled from pub installs before a pub is knocked down...), get them, they are incredible value for money, and who doesn't want a speaker that was used back when the pub trade was booming in the 90s and early 2000s when things were more exciting than 2017.

Wharfedale Diamond 6R Upgrade Project

These Wharfedale Diamond 6R speakers were manufactured in 1995. These at the time were a budget speaker for around the £200/pair price ran...