Please read reviews of Spectron amplfiers.
Note also that Higher Fi lists Spectron Amplifiers with their collection of the best amplifiers in the world.
This early model has a large toroidal transformer only slightly smaller than the Musician IIIs and rated 300wpc into 8 ohms and 500wpc into 4 ohms. Since the power supply is 85% or more efficient, the original power supply is at least 2x oversized compared with standard amplifiers. This early model chassis is especially compact, with 22,000 uf power supply caps horizontally. It has the same 500khz carrier and fast feedback as the later models which allows you to hear details you were prviously unaware of - a main feature of these amplifiers. Although the original power supply was oversized, it, was been light on filtering capacitance, noise suppression RC filters and bypass capacitors due to chassis size constraints. Accordingly, as shown in the photos, separate enclosures were each filled with 24 1800uf 160 volt capacitors (Almost $5 each) and connected to the plus and minus 125 volt lines directly feeding the amplifier modules, downstream of the 10-amp fuses. This connection provides the same advantages as a typical audiophile $100 upgrade of fuses and holders, as such noise is attenuated downstream by the added 86,400 uf capacitance. The effect of paralleling many smaller capacitors lowers the ESR "equivalent series resistance" of the circuit, which is done at the factory as part of the $1595 33,000 uf upgrade to the Musician 3's. The effect was immediately audible with greatly enhanced bass definition and slam and overall smoothness. The result you hear should be no surprise since this Krell-like approach results in a total of 130,000 uf, 4x the total in new Musician 3's which have 100 x 330 = 33,000 uf total.
When I told Spectron's PHD senior engineer what I had done, he emphatically praised my solution and explained that he became associated with Spectron after the chassis designs were finalized and that he had wished for years to have larger enclosures to include more capacitance.
In other words, his own approach would have been more "Krell like" as well! It seems that John Ulrick's design was such a sonic breakthrough that elaborate power supplies were not considered.
Accordingly, Various RC networks and bypass capacitors were added to this amplifier with audible results, as they were evaluated separately. The 25-amp rectifier bridge was replaced with a 35-amp version with lower forward resisitance. Here''s a link to an article as a reference:
I have now done similar modiications to four Spectrons, all with significant improvement. The low operating temperature greatly extends component life, which, according to chemical theory, doubles with every 10 deg C or 19 deg F drop in temperature. The work was time consuming, but as a semi-retired engineer, I am considering offering to do these modifications as a sideline business. I have owned and tried many amplifiers to drive the best speakers I have ever owned, a pair of JBL M9500s of their K2 series that weigh over 300lbs each. The Spectrons are the best so far, after testing products by McIntosh, Proceed by Levinson, Krell, Crown Studio Reference 1, Classe CA2200, April Music Stella, Nakamichi PA7A mkII, PA-7, Yamaha MX1, Lexicon, Adcom5802, Emotiva XP2s and XP1 monoblocks(4 at once), Wyred4Sound, and Monster. If you are serious about audio, you owe it to yourself to check it out. I am available to answer questions at 952-944-6488.