I recently completed a mains powered Little Gate step up amplifier in black. Some folk ask what the difference is between the mains and rechargeable battery versions and the answer is very little but the mains unit pips the rechargeable version for a little bit more weight and authority. An earth lift switch provides for hum free operation in different systems.
I was commissioned bu a client to mount some Hashimoto step up transformers in a small case and this was the result. Small and neat, with the transformers top mounted to minimise real estate taken up by them. On the rear there is an earth lift switch to ensure hum free installation.
This Radford TT100 came to me in a dangerous but semi functioning state. Some folk seem to enjoy a dangerous life, otherwise how else do you explain high voltage components loosely attached to the chassis with Blue Tack? This big Radford carries 680v HT, and that’s definitely a lethal voltage. Yes, HT on spec is 600v but my mains is the highest permitted here at 253v ac, and the extra 10% is rated up by the HT supply along with tolerances. First task was to make the amp safe just to test if it worked-it did just about-and then the slow process of restoration began. The client wanted a great sounding amp for everyday use, not a restoration to exact original condition, which was a great challenge.
The full story and pictures are contained in this thread Radford Restoration 2
This was one amp I could not wait to turn on and test after completion. And it didn’t disappoint. A lazy silky smooth power with massive bass underpinning, just sounds delightful through my Tannoy Canterburys!
This 50 year old amp had been recently fitted with some NOS valves and even before any work sounded very decent. From inspection, it looked like it had had one service in all the years, at which point the main smoothing capacitor was changed. Bradford introduced the STA15 for those who didn’t want the hassle of manual bias and despite the STA15 nomenclature the amp pushes out over 20 watts.
The work agreed with the owner was to change all the electrolytic, upgrade the coupling capacitors and to use Elna Cerafine capacitors for cathode bypass duties. We also agreed to renew the input and valve socketry along with the valve riders.
The link here gives further details and the owner’s reaction to the results. Radford Restoration
It’s been a busy few weeks and the following are just some of the latest amps in for restoration, repair and upgrades. A Radford STA25 is in for repair and upgrade and is having new main electrolytic caps fitted along with upgraded cathode bypass and coupling caps and new bias pots.
I am doing a major restoration job on a Radford TT100. This is a very interesting solid state input /tube output hybrid producing 100watts a channel. A previous owner had made many mods, and left the amp in a dangerous state with 680v components held on with Blue Tack. There had a also been a major blow out on one channel which had taken out the driver transistors and bias pots on one channel. A further mod had been an attempted change to a choke input power supply but without changing the inductor. So the HT was around 100v down!
A McIntosh MA 7000 came in for new main psu caps and rebiasing.
Some Hashimoto step up transformers are in to be mounted in a decent case and wired up.
A Mastersound Dueveinte is in for the addition of a tape out socket, and a few other upgrades.
A Yaqin MC13 has been in for coupling capacitor upgrades.
And again a few Audio Innovations S500 have been in for upgrades, repair and servicing. Finally, a Copland CTA401 has arrived for repairs and servicing.
This amp had been leaking black gunge and the main power supply caps were the main suspects. A visual examination proved this to be the case, and new parts have been ordered from McIntosh to keep the original voicing.
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!