FiveFish VT-73 Assembly Manual

Hybrid-tube mic preamp kit

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FiveFish

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VT-73 Hybrid-Tube Mic Preamp Kit

Assembly Guide

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Page 2 No part of this document may be reproduced, either mechanically or electronically, posted online on the Internet, in whole or in part, without the expressed, written permission of FiveFish Audio. This document is solely provided to the kit builder of the VT-73 Hybrid-Tube Mic Preamp.
Page 3 Studios Dear Customer, Thank you for purchasing our VT-73 Hybrid Tube Mic Preamp Kit. Great care has been taken to make this assembly guide complete and as accurate as possible. Our goal is to make your assembly work easy and trouble-free, and deliver to you a working, reliable, and high-performance mic preamplifier.
Page 4: Safety Considerations
(The in-line fuses will blow if there is equipment, electronic component or personal injury. overcurrent or short-circuit condition, thus protecting the rack power supply). VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 5: General Information
The VT-73 design uses a high-performance THAT amplifier chip as the primary First Stage amplifier. This allows us to have a very quiet, balanced input front end without the need for an Input Transformer. Voltage gain for the First Stage is set using a single-turn potentiometer to allow for a wide and continuous range of dB gain.
Page 6: Tools And Equipment Required
2.5. Magnifier & Lamp - I recommend a clean and well-lighted space for your assembly area. 2.6. Other Tools (not required, but nice to have) - Component lead bender, vise, tweezers, wire stripper. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 7: Assembly Guide
Your PCB Revision may be later but assembly instructions are generally the same. There are ERRATA corrections for the Rev 1.1 PCB version. Please visit Section 4.0 for details. Photo of a finished VT-73 Mic Preamp VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 8 3.1 Solder all 1/4 watt Resistors. ERRATA: Solder a jumper wire across RTUBE resistor location. See Section 4.0 for other ERRATA corrections (R20, R21, R22) VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 9 IMPORTANT: Diodes must be installed in the correct orientation. Observe where the “white band” is located on the board silkscreen marking, and orient the Diodes to follow the same direction. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 11 TIP: One side of the IC socket will have a notch. Position this notch on the left-side, or on top for use as a guide for Pin1 location. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 12 3.5 Solder the (2) PDIP Relays. Take note of the Relay part number that came with your kit and follow the next step. IMPORTANT: Insert Relays in proper orientation. Match the “white band” on PCB silkscreen with the Relay’s line markings. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 13 If your kit came with A18W-K Relays, Do NOT install the 7812 Voltage Regulator. Instead, solder a JUMPER wire across pin 1 and pin 3 of IC4 location. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 15 ERRATA: Use 47uf/50V for C25 location. IMPORTANT: Observe the proper polarity when inserting these capacitors. Match polarity with PCB silkscreen markings. All negative (-) leads of electrolytic capacitors are orientated facing downwards. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 16 3.8 Solder Q1 Transistor. IMPORTANT: Observe proper orientation and the direction transistor is facing. Follow the PCB silkscreen markings. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 17 - for 20dB Pad, YELLOW - for polarity reverse, - for +12dB Boost IMPORTANT: LONG LEG of the LED must be oriented at the BOTTOM position as shown. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 18 3.10 Photo showing how the (4) LEDs will show through the Aluminum cut-out panel. Note: Do NOT attach the panel yet. NOTE: LEDs are mounted at the bottom of the PCB. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 19 TIP: You may use masking tape to hold the switch secure in it’s place while you solder. Solder only one of the switch terminals and review if the switch is still horizontally level. If everything looks good, solder the rest of the switch terminals. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 20 3.12 Solder all medium-sized 220uf electrolytic capacitors. IMPORTANT: Observe proper polarity and orientation of (+) and (-) leads. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 21 3.13 Solder the large C12, 3300uf capacitor. NOTE: Solder 100pf capacitor in parallel to C12, from the bottom side of PCB. Solder 100pf capacitor across C12 from behind the PCB. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 23 IMPORTANT: Use as short as possible pieces of wire to connect potentiometer to the board to minimize RFI noise pickup. Connect top and middle terminals of potentiometer together. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 24 PCB pins of the transformer. It only goes easily/correctly in one direction. If the transformer pins don’t align with the PCB holes, turn the transformer around and try again. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 25 Next, solder the Right-Angle Headers to the board as shown. Turn over the PCB, and solder the headers from the component side of the board. Take note that the shorter leg is soldered to the PCB! VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 26 C. After you’ve soldered the Vacuum Tube socket, position the Red LED into the center hole of the Tube socket. Then solder the LED leads. Figure 3.18 A Figure 3.18 B Figure 3.18 C VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 27 You may also tie and secure the tube to the PCB using a short string or cut piece of rubber band to further reduce vibrations. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 28 3.20 ERRATA: Solder a 100K resistor to bottom of PCB as shown in photo below. Make sure you also have a 100pf capacitor soldered in the location below. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 29 3.21 Install mounting spacers to PCB using the Aluminum Male-Female Hex Spacers and 4-40 nuts. Then mount PCB to aluminum sled using the provided small screws. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 30 Then install knobs by tightening the set screw on knob. NOTE: Anodized 0.125” aluminum CNC-engraved Front Panels are also available as an upgrade option. Contact FiveFish Audio for details. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 31 Polarity Reverse +12dB Boost Output Trim NOTE: VT-73 Mic Preamp Kit comes with a 3mm Transparent Gray Acrylic front panel. The lighted LEDs show through very nicely through the tinted transparent front panel. VT-73 Hybrid Tube Mic Preamp Assembly Guide...
Page 32 3.23 Insert the (3) IC chips into their sockets. There is a proper orientation for each chip. Take note of the half-circle cutout on the Chip Body, and orient the IC chip as shown in the photo below. IC1 = THAT 1510; IC2 = OPA2134; IC3 = LME49710 VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 34 4.5 Solder a 100pf capacitor in parallel to C12, from the bottom side of PCB as shown in Step 3.13 4.6 Use 100K resistor for R20 location. 4.7 Use 5R1 resistor for R21/RPOT location. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 36: Pre-Flight Check
5.6 Check if IC1, IC2, and IC3 are inserted in their correct locations and oriented correctly. 5.7 Check if 100pf capacitor is soldered, as instructed in Step 3.13 5.8 Check if 100K resistor is soldered, as instructed in Step 3.20 VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 43 PCB using a short piece of string or cut piece of rubber band. The amount of these microphonic vibrations can vary depending on the tube. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 44 In addition, here are some approximate/typical voltage readings around the Vacuum Tube section. If your voltage readings are several orders of magnitude wrong, please re-check for any missing parts or parts in the wrong location. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 45 Repeat these steps a few times. It could be the Vacuum Tube is not making a good electrical connection with the Tube Socket terminals. VT-73 Hybrid Tube Mic Preamp Assembly Guide Copyright © 2017 FiveFish Audio...
Page 46 11. RACK MOUNTING THE VT-73 MIC PREAMP MODULE You may also mount the VT-73 Mic Preamp inside a custom 1u 19” rack case. Just supply the preamp module with the necessary +/- voltages, and connect to XLR male and female jacks. Use the wiring guide below. You can use a 15-pin EDAC connector, or solder the connection wires directly to the holes provided on rear of the board.

FiveFish VT-73 Assembly Manual

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Questions and answers

Summary of Contents for FiveFish VT-73

Page 4: Safety Considerations

Page 5: General Information

Page 6: Tools And Equipment Required

Page 7: Assembly Guide

Page 36: Pre-Flight Check

Page 38: Parts List

Page 40: Schematic Diagram

FiveFish VT-73 Assembly Manual

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Need help?

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Related Manuals for FiveFish VT-73

Summary of Contents for FiveFish VT-73

Page 4: Safety Considerations

Page 5: General Information

Page 6: Tools And Equipment Required

Page 7: Assembly Guide

Page 36: Pre-Flight Check

Page 38: Parts List

Page 40: Schematic Diagram