ricardo wrote:Gotta admit I'm amused at these supa-dupa Phono preamps. In da old days, I spent a lot of time on discrete OPAs and also how to stick LN transistors on LM301 etc.
remember the feedforward compensation on the 301?
When NE5532/4 appeared, I swept them all into the Don't Recycle bin.
You and many others... between the 553x and 07x bifet you can cover most audio speed bases.
NE5532 has almost perfect noise & BW performance for Moving Magnet RIAA.
Perfect is noiseless with infinite gain, etc.
The Dynamic Duo (Lipshitz & Vanderkooy) have a JAES article on dreaming up accurate RIAA.
It is remarkable how much effort designers put into getting RIAA accurate to 0.1 dB and then didn't bother to dial in cartridge termination capacitance. I sold a little dip switch PCB with 4 caps that allowed you to add caps in parallel to cart termination with 25 pF resolution.
RIAA was disappointingly silent about how to handle below 20 Hz. The IEC proposed pole at 7950 uSec made a lot of sense (IMO).
All who designed their EQ to follow 75 uSec pole forever (me included) were ignoring that cutting lathes run out of boost before too long, but like the RIAA i don't care as much about response above 20 kHz as long as you don't generate spurious audible artifacts down in band so IMO real poles reject RF better.
3 important articles tell you what signals to expect. Shure show the maximum recorded velocities on real vinyl (JAES).
Yup, but RF happens so one needs to be able to roll that off harmlessly too.
Tim Holman (? the THX man) translated this to what you need in a real preamp (Audio magazine?).
Tomlinson Holman? the APT guy, etc... He did one crazy ass design where the input LTP had a JFET on one side and a bipolar transistor on the other side... Interesting concept, but i never got comfortable enough with it to consider it in anything I ever did.
The THX deal was a bit of a racket... You want your amps approved for THX theater use... you need to do it their way exactly... They don't walk on water and know more than manufacturers about how to make power amps... but they made a lot of gravy with that franchise.
One of the false prophet, Matti Otala's, students did a brilliant AES preprint in Hamburg 1981 which essentially proved that the zillion V/us slew rates he was touting as essential were NEVER encountered in real life vinyl reproduction.
The sundry new distortions imagineered by Otala was a running (slewing) joke with real designers. Unfortunately he captured the imagination of audio phools around the world, and even had some silly distortion tests find their way into real test equipment.
Wat dis mean?
Straightforward NE5532 with one of the Dynamic Duo's RIAA networks, direct coupled to cartridge, with sensible operating levels is as good as it gets for MM RIAA preamps. I defy anyone to do a better preamp for use with real life MM cartridges. You'd be hard put to measure any improvement, let alone hear any ... unless you are using a Golden Pinnae circuit with crap RIAA networks and poor overload.
For Moving Coil cartridges, I like
http://f1.grp.yahoofs.com/v1/gHldTuaW_G ... README.doc
Your link didn't open. for me.
I took the Leach circuit and by throwing out extraneous bits and changing others, transformed its performance from mediocre to the lowest noise such device in the known universe. For real life MC cartridges, this hugely complex circuit introduces negligible distortion.
I remember the oddball battery powered Leach head amp, and it was interesting but didn't float my boat as practical for anything.
I also sold a MC version of the P-10 using 2sb737s (.4 nVrt Hz) bipolar input devices and got kind words from Peter Aczel (Audio Critic magazine). But I got the sense he was looking for something more (like an advertisement) _ before saying anything good in print... He traded me a pair of loudspeakers he was pimping for one of my preamps... I knew the guy who designed the speakers too, since he consulted for Bozak (speaker design) around the same time I did some consulting (consumer delay) at Bozak too.
But I pretty much agree this P-10 is mostly over engineered, and my later P-100 was over-over-engineered.
The saddest part was the mixed good and bad reviews I got from magazines, in my judgement revealing short comings about their personal listening systems.
But that's why I ran screaming from the high end audio business, decades ago. The sound of the hardware had precious little to do with anything.
JR