| perrew wrote:
|Romy,one thing that interest me is you use an active RIAA and the Allnic is passive circuit if I understood things?
Among the none-commercial, home-made correctors here is my evolution of phonostages.
1) EAR-384PT - dual mono rebuilt with Thorsten medications
2) 7788-7721 – with Thorsten-made LRC filter.
3) EAR-384PT-AIR – with air capacitors
4) 7788-7721-AIR with air capacitors and EAR-like feedback
I need to say the all 4 of them sound very nice, but the EAR-384PT-AIR, bundle with SU-2 step-up transformer made my “End of the Life Phonostage”.
I had no problem with 7788-7721, ether the LRC or with EAR-style feedback, but I feel that Expressive Technology SU-2 transformer works better with EAR input tube and sound more pliable all together.
I need to say that what Alnic at their site linked above made comparing of different RIAA methods: (from the Alnic's site)
"Active filters (Negative feedback type)
Different quantity of negative feedback applied. Deeper feedback to high frequencies and shallower to low frequencies. Improved S/N Ratio, low cost and consistent operation. Looser bass reproduction and possible a pinched and compressed high frequency playback due to excess feedback ratios.
Passive filters (CR type)
The frequencies filtered to fit that of the RIAA by varying the amount of attenuation at different frequencies through a complex resistor-capacitor network. No voltage overload, purer reproduction form no feedback, and more accurate RIAA compensation. No gain, insertion loss and impedance matching problems.
Hybrid filters (CR and Nega type)
Use of two type filters to low and high frequencies separately (Active filter to low frequencies and passive to high frequencies). The advantages and disadvantages of two types shown up at the same time.
LCR filters of H-1500 II SE
Two pieces of linear reactor (a kind of choke coil) comprises main parts, assisted by precise RC filters to lower impedances and insertion loss. In vacuum tube circuits, active and passive filters usually are operated on hundred some kilo ohms of impedance, LCR RIAA filter's impedance is 600 ohms constant! Lower the impedance, more dynamic and more detailed reproduction. Furthemore, LCR RIAA filter's series resistance, less than 13 ohms (Tango's 31 ohms) But LCR RIAA unit drawbacks are high cost, difficulty of impedance matching which has been the hindrance of commercialization of superb unit and its phono amplifiers. GIS KOREA LTD. manufactures itself the LCR RIAA Unit of high quality and develops the 600 ohms impedance matching method even without coupling transformer, Non-negative feedback circuit secures pure sound reproduction without coloration. "
The advantage of the passive LCR filtration that Alnic mention are correct it is not all that counts and there is other side of the medal. Still, I always liked the LCR phonostages and I feel that is one of the best way to go, despite that I do not use it.The Cat
"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche