[quote author="SSLtech"]..not only is it genius, it sounds out of this world! :thumb:
Keith[/quote]
There sure must be a thread going on somewhere about what they did to those NE5534's, but I haven't found it yet
:wink:
OK then, there's also the iron, but that & pulling stuff into A releasing this amount of magic ? :roll:
[quote author="[url]http://www.soundonsound.com/sos/apr07/articles/rupertneveportico.htm[/url]"]The circuitry is built almost entirely using conventional-sized components, with the old familiar NE5534 op-amps doing the bulk of the work, supplemented with separate transistors in appropriate places. Rupert Neve's designs traditionally employed single-sided class-A topologies, and it is hard to square that approach with these Portico circuit boards covered in op-amps. The secret missing ingredient is that he uses a circuit technique with the 5534 op-amps which offsets the DC point of their output stages, so that for signals below about 0dBu they are effectively running in a single-sided class-A mode. This removes crossover distortion artifacts completely and is a significant contributor to the sound of this preamp.
The entire design approach is equally unorthodox. Unusually, although the input does have a transformer, this is not the first thing the mic input signal sees. Instead, after a common-mode torroid ensures that nothing above 150kHz can get into the preamp, the signal is handled by Rupert Neve's own 'transformer-like amplifier' (TLA) configuration. This is a variation on the familiar instrumentation amplifier theme, and presents the input with an unusually high input impedance — 10k(omega), in fact — which minimises the microphone loading and is claimed to improve 'transparency.'
The input transformer follows this TLA stage, and overall, the input stage can tolerate a massive +26dBu without needing a pad. Given the relatively high input impedance, the mic input is quite happy serving as a line input — provided phantom power is switched off, of course.
A second transformer has two secondaries, with one feeding the main output and the second feeding the buss output, meter, and output stage negative feedback. The main output is fully floating (ground free), to minimise the risk of ground loops and radio-frequency interference. The maximum output level is +25dBu, which is more than enough for even the hottest of A-D converters! The signal bandwidth is flat out to a -3dB point at 160kHz, and is only -0.2dB down at 10Hz. Mr Neve takes care to maintain the LF phase integrity, and he claims all his designs maintain phase below five degrees down to 10Hz. At unity gain, the unweighted noise is a very impressive -100dBu, helped, no doubt, by the fact that the mains power supply is external.[/quote]