Components List Of 3 Valve Stereo Amplifier
Power Supply Components List
Resistors All 1or 2 Watt Cracked Carbon
R2 470K NB Do not omit this component as it insures that no dangerous charge on the electrolytic capacitors are present after the amplifier has been switched off and unplugged, Please see text for more details.
C1 C2 47uf Electrolytic 450V minimum working voltage.
Transformers And Chokes
T1 Mains Transformer
Primary 230/240V for UK AC mains.
Secondary 190V 150 ma.
The recommended transformer used in the prototype is available at the following link Amp Maker: Guitar amp kits and parts :: Power transformers :: 0-190-275V 20W power transformer and powers this amplifier very well and runs very cool. This company also has the recommended output transformers and valve holders with secure online shopping facilities.
L1 Smoothing Choke
10 H 100 ma.
The above item is available from the following link Valve Transformer Choke VT495 and the recommended output transformers are also available. I am afraid to say that this site has no instant online shopping facilities and must be ordered by post in request of an email quotation. Allow at least 2 weeks to a month for delivery.
Fuses Connectors And Other Items
FS1Mains fuse 250 ma A/S.
FS2 HT Fuse 150 ma A/S
S1A/S1B Mains Switch, Double pole 250V 10 Amp Rocker or toggle switch.
PCB mounting type for HT Fuse preferable or chassis mounting type.
Panel mounting type for mains fuse or euro plug inlet with combined fuse holder preferred. NB When using the later you will need a suitable euro mains lead and socket to suit.
KBPC104 Available from www.maplin.co.uk or 4 X 1N5408 available from the same link.
6 Amp Green/Yellow for all heater connections.
1.5 Amp Red/Black tinned copper wire for all HT interconnections.
You will need about 3 metres of 6 Amp Blue Brown and Green/Yellow mains cable for mains wiring and also cable if not using the euro inlet plug.
6 Amp 2 Way terminal block.
13 Amp mains plug fused at 3 amp minimum if not provided or not using euro inlet plug.
Rubber Grommets and mains lead cable clamp if euro plug is not used, See text.
2 X AC86 Chassis boxes NB You need 2 of these as 1 is used for the amplifier chassis as well and is available from www.maplin.co.uk code YB68Y.
You will need some sort of metal bridging straps or aluminium sheet as these are joined together to form 1 complete unit in a similar way to Maplins 4 valve 20 Watt kit amplifier project which has long since discontinued and is where I got the idea from for this project. If you wish to use alterative chassis please refer to text.
Nuts bolts and washers.
Amplifier Components List
Resistors All 1 or 2 Watt cracked carbon except where highlighted.
R1 R3 R9 4K7. R2 100R
R7 6K8 3W Wire wound.
R8 150R 3W Wire wound.
RV1 Volume Control 50K log pot if you only intend using the amplifier for CD players or other solid state equipment. NB If you intend using the amplifier with a crystal pickup or tone control circuit then a minimum of 470K to 1M Log must be used, The same also applies if you wish to use the 6 Valve VHF/FM Pulse Counting FM Tuner Using Safe 25Volt DC HT Line or the sound output will be very low.
C1 C4 100NF 600V or preferably 1000V NB These must be of high quality polypropylene type and 600V is the minimum working voltage particularly for C4.
C2 C6 47uf 25V Electrolytic.
C3 C5 10uf 450V Electrolytic.
Output Transformer NB You will need 2 of these as this is a stereo configuration
5K Primary Impedance
8R Secondary Impedance depending on the speaker impedance and must have 5 watts minimum handling power
The recommended output transformer is available from the following link Amp Maker: Guitar amp kits and parts :: Output transformers :: 5W single ended output transformer or can be ordered from the following link along with the smoothing choke from the following link Valve Transformer VT1417
You will need 3 X B9A Chassis mounting type and are also available from the following link Amp Maker: Guitar amp kits and parts :: Valves + sockets :: 9-pin valve socket
1 X ECC82 Double Triode
2 X EL84 Output Pentode
This link Watford Valves :: Watford valves is a U.K company that has become one of Europe's leading supliers of tested, graded and guaranteed valves to the professional music industry. is highly recommended for the above items, See text. Also the JJ EL84 is available from the following link Amp Maker: Guitar amp kits and parts :: Valves + sockets :: JJ EL84 power valve This brand has been used in many of my amplifier projects with very good reliability and has a very warm sound for the price.
Circuit Board For Wiring Power Supply Smoothing Circuit
Plain veroboard must be used as stripboard is prone to high voltage arcing. Also Tagboard may be used.
Speaker And Signal Input Sockets
For speaker connections you will need 2 X Twin terminal posts available from the following link Maplin Electronics and the order code is JK24B and this particular brand is well recommended as you can make solid tight screw connections.
For the signal input connections you must use this particular RCA Phono type that isolates the outer braid connection from the amplifier chassis to avoid a hum loop. The black coded socket for the left hand channel is available from the following link Maplin Electronics and the order code is JZO5F and you will need 2 of these. You also need 2 of the red sockets and the order code is JZO6G.
All links to component suppliers are correct at the time of writing but can change without notice. These are the most recommended suppliers that I have had very good service with for over the past 20 years. The following link Cricklewood Electronics has all the range of resistors and capacitors to get this amplifier project working and also sell the valves and sockets as well as other useful hardware.
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