This amp came in for repair after the client stated his girlfriend had been connecting up the speakers and had managed to short the speaker cables. There’s at least a couple of morals in that tale, the most important being ‘switch off ‘ before you connect or disconnect speakers-and inputs in fact as the resulting transient can easily damage speakers too.
Despite sophisticated protection circuitry the amplifier had blown its output transistors. Once replaced the amplifier is singing away sweetly again.
I was commissioned to build a high quality step up amplifier of moving coil cartridges and produced this little silver box. Using top quality Toshiba JFETs this step up amplifier offers silent non coloured amplification for moving coil cartridges that compares with the very expensive step up transformers. This version uses battery power (2 x 9v batteries) but it can also be supplied with a matching mains power supply.
It’s so good I now offer it as a standard product at £250 Moving Coil Step Up amplifier
This interesting amp was in the workshop for hum reduction. There is a lot of correspondence on the internet about the amp and ways to reduce hum, and in this case the hum was as much mechanical as electrical. We swapped out the input wiring for screened cable and fitted screening cans to the Edcor autoformers all with little effect on the hum levels. The next set is to try a DC blocker on the mains to see if that helps the mechanical noise from the transformer.
This preamp dates from the early 90s when it had a reputation for great sound quality. It stands the passage of time well and still sounds very decent. It had had various mods and servicing over the years, including main electrolytic capacitors, valve sockets etc.Someone had also replaced the ribbon connector with some Cat cabling.It is a hybrid valve /solid state design, with transistors used for the phono stage and valves for the line stage.
My work was to upgrade the coupling capacitors, and add a choke power supply by adding a choke and additional smoothing capacitor. Once this work was complete it transpired the original main smoothing capacitor was pretty spent, so that was replaced too.That took a while to find as it broke down after around 2 hours use, but was fine up until then.
The result was very worthwhile, performance has been lifted to a very pleasing level. The pre operates with a much quieter background, displays subtleties better and is more dynamic to boot.
This iconic little amp came in to the workshop for some TLC. Not much wrong really. A blown internal fuse but bias and every other parameter measured fine. So once checked and the fuse replaced the amp works fine and sounds good. There is a noticeable thump on switch on, which is typical for an amp of this age as capacitors and transistors age. A recap and change of transistor would cure this but for an amplifier of this age, I often simply install a slow start module as a cheaper fix for switch on thump. It really depends on how much the owner likes the amp and wants to invest in its future.
These two Canary CA303 mono blocks came in for re-biasing and an open-ended ‘could I do anything in terms of upgrades?’. Like a lot of high end American gear, the componentry is top notch, so there’s no easy wins in terms of upgrading capacitors, resistors, or rectifiers for example. But what I did do was to install a switch for the negative feedback. With feedback switched off, with my speakers, these amps really hit their stride, open up and become seriously dynamic performers.
Those with keen eyesight will notice an Audio Innovations 700, and an LFD integrated solid state amp, both of early 90s vintage I believe.
This LFD integrated amplifier came to the workshop for some TLC. This little amplifier is now 26 years old. A capacitor had spilled its guts inside, and the input selector switch and source/mute/monitor switch were very noisy. The input selector switch stopped being noisy after being stripped and cleaned, and the monitor/source/mute switch was taken out of circuit.
Following that work the amplifier is now sounding great again, and ready for a new lease of life.