Valve amp nostalgia
November 2005
Valves, Actuators & Pump Control
The accompanying photograph is of a recently constructed audio valve amplifier designated the 'The Mullard 5-20'. The amplifier was constructed according to the publication 'Mullard Circuits for Audio Amplifiers', published in April 1959. The original design first appeared in Wireless World - May & June 1955. For those of us who grew up in the '60s and had the privilege of listening to guitar music by the Shadows, Ventures, Beatles, etc, this type of amplifier certainly brings back memories.
The author of this press release was employed in the workshops of the SABC during the '60s and carried out maintenance work on similar amplifiers, manufactured by the 'H.J. Leak' company in England, which was the standard studio monitor amplifier for the SABC at that time.
The 'Mullard 5-20' was a very popular design during the '60s and enthusiasts believe that for some reason it is able to reproduce the music of that era more faithfully than modern solid-state amplifiers.
For those who are interested, the input stage of the circuit uses an EF86 high gain, low noise pentode. The second stage is a double triode ECC83 and fulfils the combined function of a phase splitter and driver. The output stage uses a pair of EL34 pentode output valves in a push-pull configuration with distributed (screen-grid) loading.
The amplifier operates on 465 V d.c. supply, which is provided by a full wave vacuum rectifier type GZ34. All of the valves were manufactured in the '60s by such companies as: Mullard, Philips, Telefunken, Siemens, etc. These days the valves have such names as Svetlana and Sovtek and are sourced from Russia and Eastern Europe.
In view of the success of the first amplifier built, Denver Technical Products is considering producing a small batch, if there is sufficient interest.
For more information contact Mervyn Stocks, Denver Technical Products, 011 626 2023, [email protected], www.denvertech.co.za
Further reading:
Ball valves and actuators optimise HVAC performance
Schneider Electric South Africa
Valves, Actuators & Pump Control
Schneider Electric offers the full range of innovative SpaceLogic and EasyLogic ball valves and actuators. These cutting-edge products are designed to optimise HVAC system performance, ensuring comfort and energy efficiency in commercial and residential buildings.
Read more...
Alfa Laval expands hygienic valve portfolio
Valves, Actuators & Pump Control
Alfa Laval is expanding its hygienic valve portfolio by introducing the Unique SSV pressure relief valve and the Leakage Detection butterfly valve, alongside new smaller sizes of the Unique Mixproof CIP and Unique Mixproof process valves.
Read more...
Preparing pump systems for adverse weather conditions
Valves, Actuators & Pump Control
As the severity of storms in South Africa increases, so has the rush of sediment-laden water become a major issue and a significant challenge for irrigation. When sediment levels rise to just 10 grams per litre or more, the risk of pump wear and dam silting increases dramatically.
Read more...
High-flow solenoid valve
Emerson Automation Solutions
Valves, Actuators & Pump Control
Emerson has introduced the new ASCO Series 327C solenoid valve, which features a direct-acting, high-flow design that provides superior flow-to-power ratio. It permits high flows at minimum power levels, making it ideal for use in power plants, refineries, and chemical processing facilities.
Read more...
Proportional cartridge valve series is the fastest in its class
Valves, Actuators & Pump Control
Parker Hannifin is introducing the enhanced version of the proportional cartridge throttle valve series, TFP. The new pilot valve further reduces the step response times by up to 30%, making the TFP the fastest valve in its class.
Read more...
Proportional cartridge valve series is the fastest in its class
Valves, Actuators & Pump Control
Parker Hannifin is introducing the enhanced version of the proportional cartridge throttle valve series, TFP. The new pilot valve further reduces the step response times by up to 30%, making the TFP the fastest valve in its class.
Read more...
Inspection system for leak detection in valves in hazardous areas
Extech Safety Systems
Valves, Actuators & Pump Control
Leaking valves in industrial plants not only lead to loss, safety risks and possible contamination and pollution, but also result in high economic costs. Therefore, valves in hazardous areas require regular proper inspection and preventive maintenance to ensure their functionality.
Read more...
Control head for automation of hygienic process valves
Burkert South Africa
Valves, Actuators & Pump Control
Burkert’s Type 8681 control head is optimised for decentralised automation of hygienic process valves. Thanks to its universal adapter, it can be combined with all normal commercial butterfly valves, ball valves and single- and double-seated valves.
Read more...
Hydroformed tube valve body
Burkert South Africa
Valves, Actuators & Pump Control
One of the most common necessities for manufacturing pharmaceuticals, cosmetics, food and beverages are diaphragm valves. What used to be a dull two-way race between forged and cast body variants is now being challenged by an exciting, ground-breaking technology. The hydroformed, light-weight diaphragm tube valve body will change the way you think about plant design and operation.
Read more...
Global pumping giant ready to support hydrogen economy
Valves, Actuators & Pump Control
With abundant sunshine and wind, southern Africa is perfectly positioned to become a global powerhouse in green hydrogen production. Two key projects are already in advanced stages of development in Namibia. KSB has identified the vast potential of these types of projects in southern Africa, and through its KSB Pumps and Valves subsidiaries in Namibia and South Africa is investing heavily in bringing the right skills to the region.
Read more...
printer friendly version