Martin Logan woofer amplification
I'm pretty sure the original Summits used a bi-polar amp for the woofers. I think this trickled down to the Montis and Ethos, (and of course the Summit X). The specs for the woofer amp state 200 watts at 4 ohms. I would think a class D amp would have a much higher rating, (even for just a marketing tool). |
Op amps ("operational amplifiers") are not power amplifiers, they are small signal devices used in line-level and other low power circuitry. However it is quite possible that the input circuit or other circuitry that is "ahead" of the power stage in the amplifier includes an op amp, with one of its purposes perhaps being to perform the necessary low pass filtering. Op amps tend to often be viewed negatively in high end audio, which is deserved in some cases and not deserved in others. In a bass amplifier application I would not expect the use of an op amp to necessarily mean compromised sound quality. But the dealer may not understand what an op amp is, or he may be dogmatically biased against them, or he may be anticipating that his potential customers would be dogmatically biased against them. Regards, -- Al |
I based my above assumption on this review. Here is the paragraph: "The Summit's active amplification includes toroidal power transformers, as part of a high performance bipolar amplifier that is said to offer better tracking of the input signal and reduced hysteresis. Other claimed benefits are a more open, dynamic performance than would have been expected with otherwise similar IE transformers, especially at high levels. In general terms, bass performance comes closer than previous designs to matching the speed and transparency of the electrostatic mid and treble. The hard built crossover is derived from the network used in the Statement, with air core inductors, audiophile grade polypropylene caps and point-to-point hard wiring." |
My guess is that the reviewer of the Summit was using the word "bipolar" in a very loose sense, perhaps without fully understanding what a "bipolar amplifier" is. For that matter, I don't fully understand what it is :-), and it seems like ambiguous terminology at best. I would expect that in general it would refer to an amplifier which uses bipolar (NPN or PNP) output transistors, as opposed to FETs. The ICEpower modules use some bipolar transistors, but not as the power transistors which drive their outputs. But perhaps he was using the term in reference to how the two ICEpower modules are used in conjunction with each other, perhaps in some sort of a balanced configuration. Although I'm not sure that makes sense either. Best regards, -- Al |
Martin Logan says: "MartinLogan's dedicated in-house design and engineering team created an extremely precise 24-bit Vojtko DSP engine in conjunction with a powerful 200-watt class-D amplifier to deliver a stunningly detailed low-frequency performance reaching down to 29Hz—uncommon in cabinets this compact." |
A few years back, I switched amplifiers to Bel Canto Ref1000MKII's to drive my Summits. There was an incompatibility between the amps and the crossover in the Summits that Martin Logan was aware of. I called them up and the sent me out two small replacement circuit boards. I had to disassemble the cabinets and I saw the ASC200 boards with my own eyes. |
