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There is an opened forum about this 845 with only two stages
The sound of this amplifier is fantastic, never ear before, very dry in any frequency band and without coloration.
There is a large difference if compared with the first release with LC interstage driver.
The distortion decay is perfect at 10.3Vrms on 8ohm so 13W with a power supply voltage of only 840v.
This result is similar to the first release with LC interstage driver see here.
at 50Hz the result is a little less good than the first release with LC interstage driver see here
1) 6HV5A Rk=150ohm Ck=220uF no load on sec., 845 at Ia=70mA Vp=840V (less good than the first release see here)
2) 6HV5A Rk=110ohm Ck=220uF no load on sec., 845 at Ia=70mA Vp=840V (little better of 1)
3) 6HV5A Rk=150ohm Ck=440uF no load on sec., 845 at Ia=70mA Vp=840V (bad bass freq.)
4) 6HV5A Rk=150ohm Ck=100uF no load on sec., 845 at Ia=70mA Vp=840V (bad bass freq.)
5) 6HV5A Rk=150ohm Ck=220uF no load on sec., 845 at Ia=70mA Vp=880V (same result of 1)
6) 6HV5A Rk=150ohm Ck=220uF load on interstage sec. is now 50Kohm (Caddock MK132), 845 at Ia=70mA Vp=880V (little better of 1)
7) 6HV5A Rk=150ohm Ck=220uF no load, 845 at Ia=70mA Vp=880V Cbias=4.4uF instead of only 2.2uF Wima (same result of 1)
8) 6HV5A Rk=150ohm Ck=220uF no load on sec., 845 at Ia=70mA Vp=1000V (little better of 1)
9) 6HV5A Rk=150ohm Ck=220uF Rg2=1Kohm (Caddock MP816) on Beam Plate, 845 at Ia=70mA Vp=880V (same result of 1)
10) 6HS5 Rk=150ohm Ck=220uF, 845 at Ia=70mA Vp=880V (same result of 1)
11) 6HV5A Rk=150ohm Ck=220uF load on interstage sec. is now 20Kohm (Caddock MK132), 845 at Ia=70mA Vp=880V (better of 1 but now we get a bad distortion spectrum)
The 2, 6 and 8 are a little bit better but only of 0.2db is the difference.
The best value since to be Rk=150ohm Ck=220uF on driver stage and power supply voltage near to 900-1000v
The frequency band is always about 17 - 30000 Hz at -3db so very good.
