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Valve Amplification Company PA60 Monoblock Valve Amplifiers
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Truly Hi-Fi Valve monoblock amplifiers suffering from loose valves and poor quality octal valve bases. The customer insisted upon black replacement valve bases, but no suitable types were found that suited the desired connection quality. The customer came up with the idea, we used our ingenuity and came up with the implementation, and solved a difficult problem effectively and inexpensively.
Please click on the images to enlarge
- Relpaced output valve bases with better engineered types from Hifi Collective.
- The customer specified and supplied black bases for aesthetic reasons, but they would not physically fit and could not be mounted properly due to the design of the amplifier.
- The pins on the new bases were so precisely engineered, rather than send them back to the supplier, we decided to use them to make our own bases!
- We manufactured new valve bases from high quality fibreglass PCB enabling a secure fixing to the amp chassis.
- The 'old' bases were modified and used as pin separators. This also helped to keep the appearance the same, making the amp look original.
- Our bases were fitted to the extremely complex, difficult-to-access, main amplifier board.
- We re-biased the amplifier after a valve change, and it's still singing sweetly!
Description of images:
- One of the amplifier channels prior to modification sporting the old octal bases towards the rear of the top panel
- Close-up of one of the bases. The stamped two-part gold-plated copper sleeve had work-hardened apart and was no longer gripping the valve pin adequately
- The rear fixing of the valve base, showing the inaccessable fixing screws. The whole amplifier PCB had to be removed from the case to remove the screws...
- A removed valve base in isolation
- A removed amplifier board, one channel. Removal was especially difficult due to the use of hardwired internal point-to-point construction. All the connections to extra-board components were labelled and severed. This had to be done for both channels
- Valve base fixing hole through the amplifier main board
- The New black bakelite valve bases from Hifi Collective. The gold plated turned pin multi fingered construction gives far superior contact integrity to the valve pin. Note the lack of fixing flange - the base is supplied with a removable fixing bracket, but in this case there was no mating surface in the amplifiers for the base to be held aginst. They would have 'fallen' through the chassis holes
- One of our custom designed valve pin fixing plates made from high density fibreglass
- The 'new' valve bases in various stages of construction: The new black bases were disassembles and their pins were screwed onto our new fixing plates. The 'old' bases were then drilled out to accomodate the new pins, and the assembly was made
- The pins located in the new fixing plate
- The new bases installed in one amplifier channel
- Close-up of one of the new bases - note the pins are now securely fixed to our fibreglass plate preventing them from being pulled out of, or pushed into, the amplifier casing. The Hifi Collective bases as-is, with their non-clamping fixing flange, would have allowed one or the other
- Top of amplifier PCB. Note the 'old' bases separating the new pins, and providing aesthetic consistency
- The amplifier channel re-assembled in its enclosure and re-connected to the input/output sockets, output transformer and power supply connector
- One of the completed channels
- The full amplifier system with both monoblocks and central power supply after re-biasing with new valves
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