This Rose RV23 preamp dates from the 90s. As standard, it already sounds good and it came to me a few years’ ago for some upgrades to the power supply, and improved coupling capacitors. With those mods it sounds really special!
This time it was in for a new volume pot, and selector switch, along with a couple of new phono sockets as the originals were very loose. A TKD pot was chosen along with a quality Elna selector switch and teflon /gold plated phono sockets. I always enjoy listening to this pre which you’d have to spend several thousand pounds to beat! No circuit digram is available and no one is even sure whether the valves should all be ECC82s or a mix of 82s and 83s…..it works with both!
It’s not every day that a pair of amps costing £23k arrive in my workshop but I have come across Shindo equipment a few times in recent years. Very iconic, high level, hand built Japanese hi fi for those with plenty of cash. These mono blocks have many things I hold dear to heart, such as parallel single ended operation and zero feedback. They are also specially voiced using some NOS valves and capacitors in key places. Nothing too seriously wrong with these boys, they are in for a check over and rebiasing.
The retro green styling I guess will please some and leave others cold. It has grown on me over the last week! And they certainly sound beautiful, being close in character to my Mastersound 845 PSE mono blocks!
As the photo below shows, build quality is exemplary.
Another really interesting amp has arrived needing a lot of tender loving care. The Radford TT100 is a hybrid solid state /valve amp. This one has been butchered over the years. While some components have been upgraded new components are held in place with Blue Tack, and others have been installed with no insulation so any movement or shock could potentially cause a major short circuit. Not the way I’d do any upgrades with 600v floating around inside! Thankfully all the transformers and chokes are in good order and having made the amplifier safe, it even made music on power up. Now for some restoration work to make this an everyday amp with decent sound quality and a lot of slam and dynamics!
Some interesting amps have come in in the last week or two! A Mastersound Dueveinte and two more Audio Innovations 500s. One of the AI500s is in for the full works and it’s always great to compare sounds before and after!
Yet another Audio Innovations amp in the workshop! This one shows the ravages of a long life but still works very well. A quick service and it will serve the owner for any a year more!
This amp is still in pristine condition despite dating from the 90s. Some new valves, a new selector switch, replacing the electrolytic capacitors and upgrading the coupling capacitors and it will be ready for another 30 years service!
These venerable mono blocks came along for some upgrades. I went down and tried and tested approach of upgrading key coupling capacitors, and making switchable feedback. These amps really come alive with these mods, providing some of the best valve sound around. With no feedback gain can become too much, so I also tried bypassing the first valve and making a few mods to the second valve stage. This worked really well but with feedback switched on, the gain was rather low at around 4v for max output. So to maintain flexibility I reduced global feedback slightly in the feedback on position to enable the amp to work with a wide range of speakers and left the feedback off option in play. With feedback off and 88db speakers the noise level is acceptable and the sound stunning. With the feedback switched on there is a small reduction in overall sound quality but the amp still sounds among the best!
As one of the 805 output valves was running slightly pink I checked the bias to find the output valves were running at 135ma dissipation, way higher than the recommended level of around 100ma. So the bias circuit was modified to bring dissipation down to 100ma. Now the amps were really singing and making a great combination along with their accompanying Ming Da MC 2A3 preamp which was also in for some upgrades.