Their customer base reads like a list of rock and roll royalty - and business is booming at the Doncaster factory which is the Rolls Royce of the guitar amplifier world.
Hi Watt has been turning out some of the most in-demand amplifiers in the country since the 1980s, from a small factory at the Plum Tree Farm industrial estate near Bircotes, with its users including such names as Noel Gallagher and Peter Townsend.
Jimmy Page, Dave Gilmour, the Rolling Stones and Nirvana have also used their products over the years.
Demand is high and over 100 people are on a waiting list for the top of the range equipment, with plans to take on two apprentices to learn how to built the amplifiers.
Operations manager Kee Mayer said things have got busier since the firm was taken over by Toronto based pair Darren Atkinson and Alex back two years ago.
The pair bought the firm from its previous owner, Stainforth businessman Richard Harrison, who had brought the company to Doncaster in the 1980s. It was originally based in Surbiton, in London.
Darren had previously playing in a The Who tribute band - and the band was famously linked to Hi Watt's amps.
The firm has sites all over the world. It has offices marketing the products in Australia, the US and in London. It manufactures what it describes as 'entry level and professional' amplifiers at a factory in China.
But Doncaster is home to the what is known as 'the custom shop' - the factory which makes the firm's top of the range amplifiers which are among the most sought after in the world.
They are made using similar procedures to those which were used in the 60s. They are labour intensive, but the quality is regarded as second to none.
The factory currently employs eight, but that is expected to expand soon.
Doncaster boss Mr Mayer has worked for the firm for 15 years, having moved to Doncaster from London. In a previous job, he was in the band One Minute Silence, which was signed to Virgin Records.
As a student he used to mend amplifiersfor friends. Now he is involved in making them from scratch, using techniques based on those used by the Royal Engineers in World War Two and what they call military spec wiring. The way they are wired means they are easy to service.
Most of the staff are musicians, who have a good ear for tone, so they can be certain they sound as they should. They also test them on site. With the power of the amplifiers, it means they are sometimes noisy neighbours to the other firms on the industrial estate.
The units are genuinely made in Britain, with most of the components, including their steel components, transformers, and front panels, coming from manufacturers in South Yorkshire and Derbyshire.
The woodwork is also done locally, and Mr Mayer believes one of the most important aspects of the quality of the products in the components.
The original design was from the 1960s, although there are also more modern designs which have been created by their Toronto based designer, Mike Fortin.
"The secret is great components that follow a great design by Dave Reeves in the 60s, and we adhere to old school methodologies and wiring practices," said Mr Mayer.
"We're looking at taking on two apprentices this year because sales are increasing. We make them as close as we can to how they were made in the 60s and 70s. Hi Watt have built a solid foundation over the last couple of years, with the right experts in the right places, and that is why sales are increasing.
"We have been described as the Rolls Royce of amps."
It is not all serious. In recent years they were requested to make front panel with a volume label that went up to 11 for the Girls Aloud singer Sarah Harding, following a famous joke in the afmous heavy metal spoof film This is Spinal Tap. Sarah's was used in a St Trinians film in which she appeared.
It is not just the big names which use the brand's top of the range gear, Up and coming group Circa Waves are among the latest to use them, while they will be proving amplifiers for Doncaster's own Bang Bang Romeo in their latest video, and for use when they play the Isle of Wight Festival.
"Its's great to be able to support local bands," said Mr Mayer.