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The most obvious question to our Australian designers was, had they simply bridged their existing stereo amps to arrive at monos with concomitantly doubled power ratings though compromised low-impedance stability? Or dedicated new circuits with new boards? Technical director Stuart Graeme Ralston would have those answers.
At CES 2013 marking SGR Audio's global debut and 10th year of operations
First I checked into an Oz rehab, er chat room for domestic EL30m action or not. A member with McIntosh 2301 monos driving Sonus Faber Stradivari had looked for more than incremental improvements. He'd found the Bryston 28B SST ² at best a sideways move before settling on the SGR as his new amps. I own lower-power quite simple amps: various FirstWatt, the Bakoon AMP-12R and the Crayon Audio CFA-1.2. My semi muscle amp is the compact Goldmund Job 225. The ModWright KWA-100SE and big Octave MRE-130 tube monos sold off. Job sonics fall into the same ball park as the Bakoon and Crayon against which they mostly trade ultimate refinement for more watts.
SGR at the 2013 Melbourne show
I also have a pair of AURALiC Merak monos on loan as 'poor man' Ncores, for speakers which require brute power. Not that I own any of those. I'd thus not really judge the Australians as what they are, muscle amps. I'd look at how refined they'd behave in first gear whilst delivering <10 watts. I appreciated learning how a wallet-voting buyer had gone from McIntosh to SGR via a skip over Bryston. General forum chatter on SGR amps proved virtually non-existent however. At least for its electronics and certainly this new model the brand was still a hidden player to make even more of a case for this assignment.
Stuart Ralston. "Under the hood the stereo and mono amps look almost identical. They share exactly the same PCBs but the mono amps are bridged versions of the stereo. Most bridged amplifiers use an inverting and non-inverting amplifier stage. Both halves of the EL monos are 100% identical and non-inverting. The required phase splitting to drive the bridged configuration is performed by ultra-high-performance custom made Jensen transformers to provide a perfectly balanced input whilst remaining compatible with singled-ended connections. The EL stereo amps require one Jensen transformer per channel, the mono amps two for optimal isolation and circuit symmetry.
Stuart in formal show threads
"Aside from the popular benefits of input transformers like full galvanic isolation, our ultra-quality nickel-alloy core trafos allowed us to remove all active low-level signal circuitry including associated power regulators. This reduced parts count by 15% and gained us lower noise for improved transparency. A central 40MHz microprocessor monitors the power rails, temperature sensors and signal levels for instantaneous detection of system failures or clipping. To avoid flying leads the ground-floor power supply rails connect to the upper-floor gain circuits with solid gold-plated copper buss bars."
Stuart in workplace attire with some of their active all-analog crossovers.
Power specs for the EL30m are 300 watts into 8Ω, 450 into 4Ω and 500 into 2Ω. Minimum recommended load is 4Ω. The power progression's far from doubling likely reflects the available real estate for the power supply and concomitant limits.