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Phono End preamplifier
This project born to be a no compromise phono preamplifier without budget limit.
These are the main characteristics:
Only 2 stages Only 2 vacuum tubes on the signal path No capacitor on the signal path (escluding RIAA network) No resistor on the signal path (escluding RIAA network) Less components of any other design Output impedance and level to drive any final amplifier without a pre-ampl. MC input option using a step-up transformer Amorphous core interstage transformers Passive power supply
this projects has been used the top of the components like only tantalum
resistors and Silver Mica Radial Capacitor in the RIAA network.
These kind of components are used by AudioNote in the top series production (price about 20000 - 30000$).
The two interstage transformers are amorphous C-core by Lundahl to get the best sonic performances.
On cathode the by-pass are good Sanyo OS-CON capacitors considered better than old ELNA Cerafine and Black Gate.
The power supply use a pair of 100H Lundahl choke and Jensen AudioGrade electrolytc capacitors.
This project can be fit in a normal chassie with height of 80mm like the GX 388 by Hi-Fi2000.
It is possible separate the power supply of each channel using one more 100H choke.
I have used a single solid copper wire for the ground from the input to the output llike Mr. Sakuma.
To calculate the RIAA network I have used the spreadsheet of Fabrizio Marignoni
The design of this phono preampl. is very simple, only 13 components per each channel.
The C3g is a very low noise pentode, made in Germary by Siemens.
This is a very long life tube, minimum of 10.000 hours.
This is a a perfect tube, if it is connected as triode (g2 -> a, g3 -> k) Ua = 200V, RK = 180 Ohm, Ia = 17 mA, S = 17mA/V, µ = 40, Ri = 2,3 KOhm.
In the measurement test I have seen 38Vrms with a distortion of only 1.5%.
I have buy the C3g from Classic Components eBay shop.
I have choiced a passive power supply
For this power supply I have used the R-CORE model R26-90 by DiyClub.Biz with primaries 2 x 115v and seconaries 0-165v(0.2A) + 2 x 0-9v (1.1A).
With an input level of 13mV rms we have about 2.1Vrms on output so the voltage gain is 161x = 44dB.
The result is incredible. I suggest this project only if you have a very good amplifier.
To use the cartridge SUMIKO BLUE POINT EVO III is not necessary the step-up LL1931 because it is a high output level MC.
LISTENING TEST by Ronan Daly
From: Ronan Daly Sent: Thursday, August 19, 2010 5:36 PMSubject: RE:
I compared it with the my Audio Innovation copy using Teflon V-caps and Vishay TX2575 resistors built using the schematic on the Audio Note website using 1 tube (two stages) per channel and no cathode follower so there was a chance to compare V cap capacitor vs transformer interstage coupling. The Audio Note was the best I ever heard up to now beating all the cathode follower units I compared it with. The phono end was however better. The units sounded similar but the phono end had slightly more definition, drums sounded more focused and cleaner sounding. Another listener in his seventies thought your unit was slightly smoother and easier to listen to.