Them Poundland Amps Keep Coming.
Posted: Fri Mar 11, 2022 9:16 pm
I got bored a few weeks ago so, built myself another amp with chassis made from 2 quid Poundland bamboo chopping boards. I found a pair of no name 5K, Chinese single-ended output transformers with ultralinear taps in a box of bits I’d forgotten about for 15 years, so I thought I’d put them to good use. Another old USAF potted choke and another large Hammond potting box to cover a pair of 20H Sowter chokes later and I had the basis for a decent amplifier.
Below is what I came up with: Underside: I thought I’d do something a bit different so this one breaks a few of the rules governing purist single-ended valve amplification. It is not a triode amp. It uses EL34s in single ended ultralinear configuration, to give just over 6W per channel. It also has additional feedback to the control grid of the power valve, in the form of a so called ‘E-Linear’ setup, where the high voltage supply to the driver is taken from the ultralinear tap on the output transformer, creating a loop from the anode of the output valve, back to its control grid via the driving circuit.
Rectification is solid state via a bridge of 1200V 3A SiC Schottky diodes, with an RC series Zobel network across the power transformer primary, to stomp on any remaining switching noise.
It sounds bloody fantastic. Cant fault it at all. It’ll play anything from 1920s acoustic recordings of Caruso and Louis Armstrong, all the way up to boring audiophile stuff without fuss, or favouring any music style over the other. It seems to get the best out of anything put in front of it.
Below is what I came up with: Underside: I thought I’d do something a bit different so this one breaks a few of the rules governing purist single-ended valve amplification. It is not a triode amp. It uses EL34s in single ended ultralinear configuration, to give just over 6W per channel. It also has additional feedback to the control grid of the power valve, in the form of a so called ‘E-Linear’ setup, where the high voltage supply to the driver is taken from the ultralinear tap on the output transformer, creating a loop from the anode of the output valve, back to its control grid via the driving circuit.
Rectification is solid state via a bridge of 1200V 3A SiC Schottky diodes, with an RC series Zobel network across the power transformer primary, to stomp on any remaining switching noise.
It sounds bloody fantastic. Cant fault it at all. It’ll play anything from 1920s acoustic recordings of Caruso and Louis Armstrong, all the way up to boring audiophile stuff without fuss, or favouring any music style over the other. It seems to get the best out of anything put in front of it.