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Model 1
Model 1
Experimenter’s SE Audio Amplifier
Experimenter’s SE Audio Amplifier
User’s Manual
User’s Manual
500-0001MR4
http://audio.engineeringvista.com Rev. 4
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Dear Customer We at ENG Vista want to take this opportunity to thank you for purchasing the Model 1 Experimenter’s SE Audio Amplifier. The people that stand behind your amplifier draw on more than a decade of professional electronics design and manufacturing experience. We are committed to providing our customers with the high quality sound at an affordable price. We have achieved this goal through modern design, quality parts, expert components sourcing and efficient manufacturing. W
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SAFETY PRECAUTIONS IMPORTANT SAFEGUARDS PLEASE READ CAREFULLY ALL THE FOLLOWING IMPORTANT SAFEGUARDS THAT ARE APPLICABLE TO YOUR EQUIPMENT SAFETY 1. Read the User’s Manual and refer to it frequently during your experimenting. 2. Retain the User’s Manual for future reference. 3. All warnings should be strictly adhered to. 4. Follow instructions to the last detail. 5. This product should be operated using only the type of power source indicated in this manual. 6. Always use an el
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17. Unplug this product from the wall outlet before making any changes. Wait until tubes have cooled down. 18. When using replacement parts, be sure to use parts with sufficient voltage and power rating and adequate current carrying capability. 19. Should it become necessary to replace your tubes, remove the AC power plug from the wall and allow thirty minutes for the high voltage capacitors to discharge. 20. If you have any questions regarding safe and reliable operation of your amplifier
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GETTING STARTED The Model 1 amplifier kit was designed to provide: 1. a universal tube amplifier suitable for everyday listening to the music from your PC or portable music source, or as a guitar amplifier easy to overdrive; 2. a headphone amplifier; 3. an amplifier for familiarizing with the sound of Single Ended (SE) configuration; 4. a platform for experimenting with different variations of an SE topology: pentode, triode or ultralinear operation, open loop or negative feedback, p
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ASSEMBLING THE KIT If you purchased an unassembled kit, you will have all the parts, including tubes and printed circuit board. Parts are in marked bags, with reference numbers and value written on a bag. Reference numbers are the ones printed on the PCB, so locating parts positions should be very easy. PCB layout printout is also part of this document and you can use it to locate parts. Output transformers are purchased separately, and not included in the kit. First step is to review
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CONNECTIONS NOTE: Before you turn the amplifier on, make sure the speaker connections are properly hooked up, or that headphone selector switch is in the headphone position. Never run the amplifier without speakers or headphones, since this may damage transformers. When turning the unit on, make sure the volume control is at its lowest setting. ELECTRICAL SCHEMATICS: The complete electrical schematics with component values is given to assist you in your experiments. Please note th
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R171 *22k/0.5W* 202-0002 All measurements at Va=250V Va J41 R161 CONN PCB 3 22k/0.5W 1 202-0002 C121 2 OPT PRIM RIGHT 1n/500V 3 100-0004 160-0003 J51 R81 R71 T CONN PCB 2 P UL T P UL C11a 220k/0.5W *220k/0.5W* 1 100n/250V 202-0001 202-0001 R231 R241 2 100-0006 OPT SEC RIGHT J131 J101 J141 1k 1k J111 200-0003 200-0003 161-0001 161-0001 161-0001 161-0001 160-0004 R11 C41 C11 J11 10u/350V V1B V3B R201 RCA-RED 100n/250V 100-0001 95-110V R131 PCL82 6 6 J61 V3A R121 *PCL82* 1k *1k* 160-0001 990-0001 R
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BOARD LAYOUT AND DIMENSIONS: The following Figure shows the component layout and dimensions of the board (in mils – 1mil=0.001inch), mounting holes and locations of tubes, potentiometers, switch and headphone connector, as well as locations of input jacks. This should help builder with designing a fitting enclosure. Please always verify dimensions by measuring the actual printed circuit board. 9
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10
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CONFIGURATION JUMPERS – MODE OF OPERATION: The Model 1 has four groups of jumpers intended for setting a mode of operation – Pentode mode (P), Ultralinear mode (UL) and Triode mode (T). Ultralinear mode can only be used with output transformer that have additional terminal for UL operation. Shorting blocks are inserted vertically so that the desired mode of operation is selected. The pair of pins on the far right side is not used. NOTE: At any time one of the P, UL or T connection
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CONFIGURATION JUMPERS – NEGATIVE FEEDBACK SELECTION: The Model 1 has optional negative feedback connection provided by jumper J161 (J162) – FBK. By moving the shorting block horizontally across the two lower pins, the negative feedback will be engaged. The upper two pins are shorting block holders when feedback is not engaged. By using negative feedback you will reduce the amplifier’s gain, increase bandwidth and reduce distortion. All the good stuff, but harmonic content will change, a
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CONNECTING POWER: As any other vacuum tube amplifier, Model 1 needs two voltages for proper operation: (1) Plate, or Anode voltage, Va and (2) Heater, or filament voltage Vf. Plate voltage should be brought to the terminal block J80 and filament voltage to J90. Picture below shows the layout detail with J80 and J90. Plate voltage (Va) should have nominal value of 250V (acceptable range is 200-270V). The power source should be able to provide 80-100mA for basic configuration and 1
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CONNECTING OUTPUT TRANSFORMERS: For basic model, the output transformers should be designed to provide 5k Ω primary resistance. For the full pack, the primary resistance should have 2.5k Ω rating. Rating of the secondary winding should correspond to the impedance of your speakers (4, 8 or 16 Ω, typically). There are many transformers in the market that have multiple taps to accommodate various combinations. Power rating should be minimum 3W for basic and 6W for full-pack configuration.
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Again, for best stereo image, they should be connected in phase. The second harmonic distortion is common with single ended amplifiers (it gives them specific, rich sound), and air transports sound with some degree of the second harmonic distortion too. It is possible to notice change in sound and reduction in distortion just by swapping plus and minus terminals, and we encourage you to experiment and find what sounds best for you. If you are swapping terminals, make sure to do it on both
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UPSIDE - DOWN ASSEMBLY The Model 1 printed circuit board (PCB) was designed with top to bottom symmetry. This symmetry enables building a tube amplifier with “tube audio look”, where tubes are mounted on top of the chassis. All parts, except tube sockets, can be mounted on the bottom of the board and soldered on the top side (top side is the one with component references in white silkscreen). That way, the PCB can be mounted close to the top of the chassis and tube sockets can be flush wi
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FINAL WORDS Once again, thank you for your purchase. We hope that the Model 1 will give you hours and hours of fun and have you experience a multitude of different qualities of the “tube sound”. Once you have exhausted all of the options, we hope that you will “retire” the amplifier from your bench into a nice chassis and have it rest on your work desk or in the bedroom accompanied by a PC or an MP3 player of some kind. Once all experiments are finished, make sure to permanently short se
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PARTS LIST Parts with asterisks in the VALUE column are used in the Full-Pack assembly. Reference Item Qty EPN Value R41, R42 1 2 N/U R11, R12, R51, R52, R121, R122, R141, R142, R181, R182, R231, R232, 2 14 R241, R242 200-0003 1k R21, R22, R61, R62, R201, R202, R391, R392 3 8 200-0003 *1k* 4 2 R71, R72 202-0001 *220k/0.5W* R81, R82 5 2 202-0001 220k/0.5W R91, R92 6 2 200-0004 *2k2* 7 2 R101, R102 200-0004 2k2 R111, R112, R131, R132 8 4 200-0005 100R 9 2 R151, R152 200-0007 470k
