71A/45 Hashimoto H-20-7U Single Ended Amplifier DIY
Hashimoto H-20-7-U 45/71A Single Ended Amplifier his name is Fervox
this counter started on 26th May 2014
Fervox 45 and 71A Compatible Single Ended Amplifier ,only you can use 45 and 71A for JBL Horn
Just starting build up Fervox 45/71A Single Ended Amplifier,An Amplifier name is Fervox , this 45/71A(Native) and 2A3(No Native)different condition use.
customer would like to use only 45 and 45 family tubes.so I choose this high impedance audio transformer for 45 and 71A single ended.
Audio Transformer are H-20-7U semi universal audio transformer.specially for high plate load tubes.like 45 ,71A and pentodo.this time use for 45 and 71A
bias is change by 2 switch and one of switch for filament voltages. voltage regurator is using for 2.5V but 1.25V refference x N, 7A LT1083CP and 6 addtional resister with
Switch .input AC line of 6.3V and 3.8 V will be make about 5V DC and 8 V DC for regurated 2.5V DC and 5V DC.
Audio transformer are specially for 45 and 71A high impedance transformer.this one can be use for high impedance pentode valves and transmitting valves such as
VT62 and RCA 50 too.this audio transformer can be use for them.H-20-7U is model name of Hashimoto. (Department of transformer of ex Sansui CO Japan)
71A necessary 220V DC for plate ,,so using N channel MOS FET for regulator down to 220V .please see schematic diagram for detail.
This is High gain amplifier using.EF86/EF83/EF80 + E88CC + 45/71A will be make good sound.sometime need attenuator for input line.even can be use L pad.
so This Fervox SET can be use 71A , 45 and 2A3 family and 300B too . 2A3 family can be use position of 5 K ohms impedance when connected 16 ohm position with 8 ohms
speaker system.bias switch is position of 2A3 made around 818 ohms .rectifier will be use 5U4G and if use 45 with 5V4G.
7 switches are top of panel. 1)Speaker impedance selector ,2) NFB ,3) filaments voltages ,4) bias and 5) +B for 45 and 71A ,6) transformer impedance and 7) 2A3 use.
many switch to change each bias and impedance etc but you may use many valves for test.even you can use WE275A too but very expensive valve.
may be can be use 183 ,483 and WE275A too.....
183/483 also you can use position of 71A ,will be get 1.5 W rms but difficults to get one.
Filaments circuit for final power amplifier valves
Filaments circuit is show above and using LT1083CP 7A regurator(LDO) this regurator IC is just same like LM1084 National Semiconductor's.larger scale of IC show next.
2.5V for 3.8 V AC and 5V for 6.3V AC from power transformer.shottkey diode are D15XBS6
Voltage Data: 3.8 VAC => shottky diode => 5.01 V then LT1083CP 2.49 V DC for 45 and 2A3
and 6.3 VAC => shottky diode => 8.09 V then LT1083CP 5.01 V DC for 71A and 300B
change filament voltages with 2 of double throw switch.very much stable filament voltages but if 6.3 V made 2.5V 2.6A will be get high temperature of surface of heat sink.
so must be change source voltages when change voltages. (Note: 2 circuit of double throw SW can buy local shop )
this switch is very useful for DIY Amplifier ,etc and much better than digital circuit and some kind of relay.
This is Fervox 45/71A Single Ended Amplifier schematic diagram on 26th May 2014
Coupling capacitor are using Green Cacutas (Arizona Capacitor USA)
2A3 Single Ended Amplifier ,16 ohm connected 8 ohm speaker with plate imp is 5K ohm postion
45/71A Single Ended Amplifier normal conditon use
45 and 71A sound stage are good enough ,I am using 91dB/m/w low sensibility speaker, enough to use small room.hum level is less than 0.5mV
2A3 sound stage is super just like 45 sound but much power of 2A3 SET.good charactor getting from Hashimoto H20-7U high impedance transformer.
off course if do you have 843 and WE275A original can be use with this amplifier. even nothing problem with 300B .
as 2A3 single ended amplifier sound is super.....!!!!
Note: for FET regulator . please use zenner diode are 0.5W 100V + 100V + 22V in sires when connected 100K ohm .will be get source 220V +B when use
71A Single Ended Amplifier.which ever 0.5W 82V +82V + 54V are good combination too. name is RD82E E means 0.5W .and be careful to use safix is F
is 1 W so different current of Zenner current. RD82F is 1 W please calculate correct resistance value.any way use half watts zenner diode.
Stacey Kent sing 45 Single Ended Amplifier at home(using fladance mp player) 1.6W
Data: Yamaha NS300 91dB/w/m Speaker , DAC Pioneer DO6(DAT), and Yamaha old CD player.
Amplifier is H20-7U Hashimoto(Sansui) Transformer and Delco 45 + Driver E88CC JJ + EF86 EH rectifier is 5U4G RCA recorded on Sakura Chiba Japan.
Camera is small digital camera by Canon IXY. MVI change format to mp4 by Avidemux(Qt)under Linux FC18 .Disc is CANDID stacey kent the boy next door King Record 2003.
Joe MacBride plays
Diana K Sing song by Fervox Single Ended Amplifier