ENG Vista Model 1 User Manual

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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. We are confident that your amplifier will be a pleasure to experiment with and that
you will gain a valuable experience. When you are ready to move to the next stage in your
experimental work, the Model 1 will give you many years of listening pleasure as a part of your
audio system.

Before using this amplifier, please take the time to carefully read and understand the safety
instructions and operating procedures. Becoming familiar with all details about your amplifier will
ensure safe usage and reliable operation. Take special care when operating with high voltages
and making adjustments.

The effort you invest now will be well rewarded as the time goes by.

THANK YOU!
ENG Vista, Inc.

YOUR SAFETY IS VERY IMPORTANT TO US. PLEASE READ CAREFULLY THE
FOLLOWING NOTES AND SAFETY PRECAUTIONS. THANK YOU.

This kit is not intended for beginners. It requires familiarity with safe
procedures for tests, measurements and modifications of high voltage
equipment.

Exercise extreme caution when working with high voltages and always unplug
the power before making any changes or adjustments

NOTE: Please make sure to check our website at http://audio.engineeringvista.com for updates,

test results and latest news. On our website you can also order spare parts. Feel free to contact
us with any questions or comments. We are looking forward to hearing from you.

.

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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 electrical outlet that is grounded. If you do not know whether the outlet is
grounded, consult your electrician or local power company.

7. For continued protection against fire hazard, replace fuses with the same type and rating of
the fuses specified. When changing fuses, completely remove power from the circuit.

8. Power supply cords and all connecting cables or wires should be routed so that they are
not likely to be walked on or pinched. Pay particular attention to cords and cables at plugs,
receptacles and terminal blocks. Always use wires with adequate ratings and safety
certifications (CE, UL, etc.)

9. During operation the tubes get very hot. Do not touch the tubes since this may result in a
severe burn. Allow several minutes after removing power for tubes to cool down before
touching them.

10. Turn off the unit as soon as you stop actively using it. Unplug the power supply from the
wall during a lightning storm or when the product is to be left unattended and unused for
longer periods of time.

11. Do not use this product near water or in wet areas. Damp basements should be avoided.

12. The product should be placed away from heat sources such as radiators, heaters, stoves
or other appliances that produce heat. Also avoid putting the unit in the direct rays of the
Sun.

13. Proper ventilation is crucial for safe and reliable operation. Never place anything on top of
your amplifier that could obstruct airflow and cause the parts to overheat and damage the
amplifier. Do not place your amplifier in a rack or bookcase unless proper ventilation is
provided.

14. Care should be taken to prevent objects from falling and liquids from spilling into the unit.
Do not subject the unit to excessive smoke, dust, vibration or shock.

15. During experimenting, make sure that all jumpers are properly seated in the correct
position, that there are no foreign objects or solder bridges.

16. Always wear protective glasses and exercise caution when powering unit after any change
is made. If possible, gradually rise input voltage and look for any abnormalities – smell or
smoke, tubes overheating (excessive glow), etc.

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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, please
email us at [e-mail]

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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, parallel tubes, etc.;

5. a significant value based on a high performance to price ratio.

The Model 1 is built on a two sided printed circuit board (PCB) and uses PCL82 (16A8) tubes
which are specifically designed for audio applications. If you bought assembled kit rest assured
that all amplifiers go through rigorous testing and extended burn-in before being shipped, so you
are guaranteed to receive high quality product.

There are two versions of the Model 1 amplifier kit:

1. BASIC: this amplifier will output 2-2.5W per channel in pentode mode (depending on the
output transformer selected) and comes with single stereo input and one pair of tubes. It is
best suited as a headphone amplifier or PC amplifier. An upgrade kit is available for
conversion to the FULL-PACK version.

2. FULL PACK: this version has maximum output power of 4-5W (depending on the output
transformer), has two stereo inputs and two pairs of tubes (the two tubes per channel are
connected in parallel). It is best suited for listening in small rooms and as an instrument
amplifier.

Due to the relatively low power, the Model 1 works best with efficient speakers (SPL above
90dBm). As every other SE amplifier, the Model 1 has a low damping factor – it will perform best
with single-driver Hi-Fi speakers or, alternatively, two-way speakers with simple crossovers.

The standard unit is delivered as an unassembled kit or tested and burned-in basic assembly.
Vacuum tubes are delivered separately in original boxes, for maximum protection. The tubes need
to be inserted and firmly seated in their sockets before the power is delivered to the unit.

The optimum sound reproduction will occur after 50-100 hours of operation. In normal use, upon
power-up, the unit needs to warm up for about 30 minutes for maximum performance.

The Model 1 kit does not include output transformers or power supply, unless it is specifically
listed that it does. Output transformers and power supply are separately sold.

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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 all the materials received, compare to the part list and prepare all tools and
a well lit work area. Tools that you need are very basic – soldering iron, tweezers or flat pliers, and
cutters. You will also need solder wire and a digital multimeter. If you have an oscilloscope, that
will help in final testing and experiments, but it is not necessary.

- Start assembly with filament configuration jumpers, configuring heaters for your specific
application.

- Follow with resistors, keeping in mind that resistors should be slightly elevated off the PCB
(1/32” is sufficient). Main reason is that power resistors get warm and this will help air circulation
and prevent overheating. Also, some resistors have circuit connections underneath and there is a
possibility of malfunction if the resistor body touches exposed trace. This is not very likely, since
the PCB connections are protected by a solder mask and resistors have durable coating.
However, this could be a matter of safety and, also, troubleshooting of such problems is really
difficult, so it is better to spend some extra time up front to come up with great assembly.

- After resistors, install 2x2 headers for mode selection (Pentode, Triode, Ultralinear, FBK, etc.).

- Next step is assembly of all capacitors. Make sure to follow polarity directions for electrolytic
capacitors. All electrolytics have markings designating leads to be connected to the negative
voltage. Model 1 printed circuit board has a plus sign for the positive terminal of an electrolytic
capacitor. Positive terminal on the PCB also has a square pad around the hole, for easier
identification on the bottom of the board.

- After capacitors are installed you can proceed with connectors and, finally, with tube sockets and
volume control potentiometers.

Once everything is installed, take a short break and then come back and carefully inspect your
work. Check component locations and proper orientation of electrolytic capacitors. Inspect all
solder joints and make sure there are no solder bridges or splashes on the board. All joints should
look clean and shiny. If you are not sure that a solder joint look right, touch it with a hot soldering
iron again, until it looks right. Cold solder joints may create problems few hours (days, months)
down the road and are extremely difficult to troubleshoot.

Then, plug in the tubes, connect the output transformers and speakers (or dummy loads) and
proceed with slowly powering up the unit.

Bring the power for the filaments (Vf) first and make sure that all the tubes have about 16V on
their heater pins (depending on your supply, it may take up to a minute for this voltage to
stabilize). You should be able to see nice yellow/orange glow from the heaters.

Tubes that you received are already burned-in, so you can continue by bringing anode voltage
(Va) and measuring the most important in-circuit voltages (refer to the schematics section for test
points and voltage levels). If you followed all the instructions, everything should go smoothly and
now you can connect some music source to the inputs and start enjoying fruits of your hard work.
But, for now, keep reading the instructions…..

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