ANK Mentor 2A/300B Instructions for use

Mentor SET Power Amplifier
Construction Manual
2A/300B
Version 1.00-01 (Beta), October 2019
[email protected]
1-613-822-7188

Copyright © 2019 ANK Audio Kits
www.AudioNoteKits.com
[email protected]
Page 2
Table of Contents
Section 1 —Introduction ………………………………………….……………….…………………… 6
1.1 About ANK Audio Kits ……………………………………………..………………………….…….….…….……… 7
1.2 Basic Operation of the Amplifier……………................…………………….…………………....…….……… 8
1.2.1 Overview ………………………………….……………………………………………....…….……… 8
1.2.2 Component Placement ………………………………….……..…………………………..…….……… 9
1.2.3 300B Pinout ………………………………………………………………………….……….…….……… 10
1.3 Equipment ……………………………..……………………………………………………………….…..….……… 11
1.3.1 Overview of the Kit ……………………………………………………….…………..……………… 11
1.4 Tips and Suggestions …………………………………………………….………….……………….………...…… 11
1.4.1 Soldering …………………………………………………….……….………………..….………….… 11
1.4.2 Components ……………………….…………………………….……………………………..…….….…12
1.4.3 Resistor Sizes ……………………………………………….……….………………….……….…….….…12
1.4.4 Capacitor Manufacturers and Voltage Ratings …………………………………..…….…12
1.4.5 Electrolytic Capacitors ………………………………………………………………………...………… 12
1.4.6 Diodes ………………………………………….……………………………..…………………………………… 13
1.4.7 Hardware/Mechanical …………………………………………………………………………………… 13
1.4.8 Wire Stripping and Tinning ……………………………………………………………………… 13
1.4.9 Wire Color ……………………………………………………..……………….………………………… 14
1.4.10 Optional Finishing Touches …………………………..……………….……………………….…14
1.5 Build Process …………………………………………………………………………….………………….…..………… 14
1.5.1 Some Good Rules of Thumb for Building Your Amplifier ………………………….…… 14
1.5.2 Organization of this Manual ……………………………………………………….…..…….…… 15
1.5.3 Electrical Safety Warning …………………………………….……………………...………… 17
Section 2 —Mechanical Assembly and Initial Power Supply Wiring …………….…18
2.1 Overview …………………………………………………………………………………..….………..………...…… 18
2.2 Installing the Feet ……………………………………………………………………..….………..………...…… 19
2.3 Installing the IEC Socket and Rocker Switch …………………………………….………..….….…… 21
2.4 Installing the Speaker Posts ………………………………………………………………….……..….….…… 22
2.5 Installing the RCA Jacks …………………………………………………………………….…..….….…… 23
2.6 Installing the Chassis Ground Screw …………………………………………………………...….….…… 24
2.7 Installing the Mains Transformer ……………………..………………………………………..….…… 25
2.8 Bundling the Mains Wires …………………………...................…………………………..…….…..…… 27
2.9 Preparing the Mains Ground Wire ……................................…………………….…………….…… 28
2.10 IEC PCB Wiring …………................................................................……………………………….…...…….…… 30
2.11 Connecting and Mounting the IEC Board ………….................…………………………………...…….…… 33
2.12 Installing the Choke ……………………………………………………………………………………....…….…… 35

Copyright © 2019 ANK Audio Kits
www.AudioNoteKits.com
[email protected]
Page 3
Section 3 —Power Supply Board Installation ................................................................ 37
3.1 Overview …………………………………………………………………………………..….….…..……..…….…… 37
3.2 Parts List …………………………………………………………………………………..….….………....…….…… 39
3.3 Installing the Valve Base ………………………………………………………..….………..…...…….…… 39
3.4 Installing the Resistors ……………………………………………………………………..….….………….…….…… 40
3.5 Installing the Capacitors and Diode …………………………………………..….….………….…….…… 42
Section 4 —Filament Supply Board Installation ........................................................... 44
4.1 Overview ……………………………………………………………………………….…..….………..………...…… 44
4.2 Parts List ……………………………………………………………………………….…..….…………....…….…… 46
4.3 Installing the Resistors ………………………………………………………………….…..….…………….…….…… 46
4.4 Installing the Bridge Rectifiers …………………………………………………….…..……….……....…….…… 46
4.5 Installing the Capacitors …………………………………………………….…..….………..…..…….…… 47
4.6 Installing the Regulators …………………………………………………….…..….…………….…….…… 47
Section 5 —Driver Board Installation …………….............................................................. 49
5.1 Overview ……………………………………………………………………………..………..….….……..…….…… 49
5.2 Schematic ……………………………………………………………………………..………..….….……..…….…… 51
5.3 Parts List …………………………………………………………………………………..…..….….……..…….…… 52
5.4 Installing the Valve Bases …………………………………………………………….….….……..…….…… 52
5.5 Installing the Resistors ……………………………………………………………………..………….……..…….…… 53
5.6 Installing the Capacitors ………………………………………………………..….………...…..…….…… 53
Section 6 —Output Transformers Installation ............................................................. 55
6.1 Overview …………………………………………………………………………………..….………...…….......…… 55
6.2 Installing the Output Transformers …………………………………………..….………..……..………… 56
Section 7 —Power Supply Board Interwiring ............................................................. 58
7.1 Overview ……………………………………………………………………………………..….….…….…..…...…… 58
7.2 Connecting the Choke ………………………………………………………………………………...….…...………… 60
7.3 Connecting the Mains Secondary Wires ……………………………………….…..….……………..…….…… 61
7.4 The CHS Connection …………………………………………………….……….…………………..………………… 62
7.5 The Blue/White and LED NEGATIVE Connection …………………………………….……………………… 63
7.6 The Remaining Connections ………………………………………………….……………….…….……….…… 63
7.7 Installing the Power Supply Board ……………………………………………….……………..…….…… 65

Copyright © 2019 ANK Audio Kits
www.AudioNoteKits.com
[email protected]
Page 4
Section 8 —Filament Supply Board Interwiring ................................................ 66
8.1 Overview …………………………………………………………………….………………….…..………..…….…… 66
8.2 Connecting the Mains Secondary Wires …………………………………..….……………….……..…….…… 67
8.3 Additional Connections ……………………………………………..........………………….…………..…..…….…… 68
8.4 Installing the Filament Supply Board …………………………………………....….…………....…….…… 69
Section 9 —Chassis-Mounted Output Section Installation ................................... 70
9.1 Overview …………………………………………………………………………………..………….…….…....….…70
9.2 Installing the Tag Strips………………………………………………………………………….….………..….…....…72
9.2.1 Wiring the Tag Strips …………………………………………..……...……................…..….….…… 72
9.2.2 Installing the Tag Strips ………….…………………..………..……..…….….................…76
9.3 Installing the Valve Bases ………………………………………………………..….………….....……....…77
9.3.1 Wiring the Valve Bases …………………………………………..……...................………...…….…… 77
9.3.2 Wiring the Left Valve Base ………….…………………..………..……...................…….…… 79
9.3.3 Wiring the Right Valve Base ………….…………………..………..……...................…….…… 80
9.3.4 Installing the Valve Bases ………….…………………..………..……...................…….…… 80
Section 10 —Additional Interwiring ……...................................................... 81
10.1 Connecting the RCA Jacks …………………………………………………….…..….……………..…….…… 81
10.2 Driver Board Interwiring ………………………………….……………………..…...…….………..….…… 82
10.2.1 Installing the Filament and Filament Jumper Wires ……………….........…….…… 83
10.2.2 The 6SH7 and GND Connections ……………………………………………………..……...…….…… 85
10.2.3 The O/P Connections ……………………………………………………………..….……………..…….…… 86
10.2.4 The LED POSITIVE Connection ………………….……………………………………...………...….…… 88
10.2.5 Installing the Driver Board ……………………………………………………………………..…….…… 89
10.2.6 The Signal Connections …………………………………………………………………………...…….…… 90
10.3 Connecting the Speaker Posts ……………………………..….……………………..….………..…………..…… 91
Section 11 —Testing ……………………………………………………….........................…….. 94
11.1 Overview .......................................................................................................................................... 94
11.2 Installing the Fuse .......................................................................................................................... 95
11.3 Initial Tests .......................................................................................................................................... 96
11.4 First Power-Up .......................................................................................................................................... 96
11.4.1 300 Filament Test ……………………………………………………………………………………..…….…… 97
11.5 Voltage Checks ........................................................................................................................................... 97
11.6 Sound Check .......................................................................................................................................... 102
11.7 Debugging .......................................................................................................................................... 103
11.7.1 Mains Secondary Voltages ….…………………………………………………………………..…….…… 103

Copyright © 2019 ANK Audio Kits
www.AudioNoteKits.com
[email protected]
Page 5
Section 12 —Finishing Touches ……………………..………………………………….…..………… 104
12.1 Installing the Front Faceplate ………..………………………………………..…………………………………… 104
12.2 Installing the LED ……………………..………………………………………..…………………………………… 104
12.3 Last Looks Inside ……………………..………………………………………..…………………………………… 104
12.4 Installing the Chassis Top ………..………………………………………..…………………………………… 104
Section 13 —Final Thoughts ……………………..………………………………….…...………… 105
13.1 Congratulations ……………………..………………………………………..…………………………………… 105
13.2 Cables …………………………………..………………………….……………………………………………….…...………… 105
13.3 Tube Rolling ……………………..………………………….……………………………………………….…...………… 106
13.3.1 5U4G(B) ………..…………………..……….………………………..……………………...…………… 106
13.3.2 6SH7 ……………………..…………………..……….………………………..……………………...…………… 107
13.3.3 300B and 2A3 ……………………..………………………………………………………….…….…………… 107
13.4 Thanks ……………………..…………………………………………………..……………….…………….………………….… 107
Appendix ……………………………………………..………………………………..….……….……….…… 108
Wiring for 240V ………………………………………………………………………….………….…..…….…… 109
Resistor Color Code Reference ……………………………………………………….……………….…..…….…… 112

Copyright © 2019 ANK Audio Kits
www.AudioNoteKits.com
[email protected]
Page 6
Section 1
Introduction
Thanks for purchasing the ANK Audio Kits Mentor SET Power Amplifier. Our goal is to provide you
with the highest quality kit that you will build from scratch with these instructions.
This is very high end and sophisticated piece of audio equipment that will surely become a showpiece
of your sound system. We're excited that you have chosen to join us in enjoying and appreciating
superb audio and we've created this manual to help guide you through each step of the build process
with as much detail and clarity as possible. To facilitate the process, the manual has been divided
into a number of sections, each focusing on a separate aspect of the system: follow the sections in
order and we guarantee you not only a problem-free experience, but a pleasant time as well in doing
so. If you are new to building kits —or if at any time you feel as though you need help or advice, feel
free to contact us and we will do whatever it takes to get you on the right track.

Copyright © 2019 ANK Audio Kits
www.AudioNoteKits.com
[email protected]
Page 7
1.1 About ANK Audio Kits
Audio Note (UK) started out in the early '90s developing several DIY audio kits while they were
building up their finished product business. DIY Audio has a long history and it was an opportunity
for knowledgeable customers to take advantage of world class designs and components. Audio Note
(UK) was focused on using the very finest materials and components custom-made to their
specifications, across their entire product line —from custom film and electrolytic capacitors to
tantalum resistors, transformers, binding posts, wires, etc. The Kit1 300B single-ended integrated
amplifier was born during development of the Meishu and it proved to be extremely popular
worldwide. The ANKit business was born!
As the finished product business and dealer network started to flourish, Audio Note (UK) eventually
moved the kit business off into a separate division; thus, in 2004, Audio Note Kits started up and was
supported by a website so that customers not located near Audio Note (UK) dealers could order kits
and have them shipped direct. Kit development continued in earnest during the 2000s with
development assisted by Audio Note (UK) engineering. Audio Note (UK) parts were used throughout
the kits, depending on the various levels and budgets. By 2013, ANK Audio Kits (as it came to be
called) had developed a wide product range covering all areas of two channel audio: a single-ended
300B product line, an EL34 Class AB and single-ended product line, digital to analog converters, pre-
amplifiers, phono stages, and Audio Note (UK) speaker kits. The end result today is that customers
worldwide with DIY skills can now build an entire high end audio system to their liking. With the
introduction of higher product levels in 2013 and the release of the Level 5 Mentor Pre-amplifier and
the DAC 5.1 Signature, some customers wanted these high end products assembled by a professional
builder. As a result, ANK Audio Kits began offering this service for some Level 4 and 5 products so
that a significant investment in a kit could be turned into a work of art! Since ANK Audio Kits was
born in 2004, over 2,500 kits have been shipped to customers worldwide. Clearly, there is a real
demand for high end audio kits and ANK Audio Kits has been delivering the goods now for 15 years.
We believe and hope that you will have a great experience building your kit and we look forward to
hearing from you about your experience.
Regards,
Brian Smith —Director ANK Audio Kits

Copyright © 2019 ANK Audio Kits
www.AudioNoteKits.com
[email protected]
Page 8
1.2 Basic Operation of the Amplifier
1.2.1 Overview
ANK Audio Kits is pleased to announce the new Mentor SET Power Amplifier. As anyone who has ever
heard the transcendent musicality of a single-ended amplifier will tell you, there is something very
special about the music that flows from (relatively) simple, classic Class A triode circuits. Perhaps
it's the absence of crossover distortion, perhaps it's the gorgeous midband reproduction, perhaps it's
the zero-feedback design, perhaps it's the organic (even desirable) expressiveness of the second
harmonic; more likely it's all of this and more.
ANK Audio Kits and SET amplifiers go a long way back —right to the beginning in fact, with our Kit1
300B, which has had successive and very successful anniversary editions. Our single or parallel
300B or 2A3 Legend monoblocks are much sought after and the ultimate variant, our SET 300B
Interstage C-Core monoblocks, is simply awesome!
The Mentor SET Power Amplifier's Power Supply uses the classic 5U4G(B) rectifier tube, a high
quality Mundorf capacitor to smooth the AC power, DC 300B filaments, and a substantial Choke to
supply clean, high quality DC power to the circuitry while assuring dead quiet operation. The 2 6SH7
driver tubes, selected by Andy Grove, Audio Note (UK)'s Senior Design and R&D Engineer, for reasons
related to input impedance and power amplifier sensitivity, are wired in a pentode configuration to
drive the 300B or 2A3 triodes, which in turn produce either 8.5W or 3.5W per channel respectively
driving the EI-Core or quad C-Core output transformers. In our experience, even 3.5W is usually
plenty of power for most listening, especially with higher efficiency speakers.1
1We recommend a minimum of 88db speaker sensitivity.

Copyright © 2019 ANK Audio Kits
www.AudioNoteKits.com
[email protected]
Page 9
In developing the new Mentor SET Power Amplifier we have basically built the Legend monoblock
circuit on three thick high quality printed circuit boards: a quality Power Supply board for the
rectifier, a Filament Supply board to supply the output tubes, and a Driver (6SH7) board that
includes high quality Audio Note (UK) 1W Tantalum non-magnetic resistors and four Audio Note (UK)
Copper Foil capacitors. The amplifier has an ultra sturdy 3mm aluminum chassis, powder coated
black, a new Mains transformer (T-195), a substantial Choke (CH-170), the latest Mundorf MLytic HV
4-pole capacitor technology to smooth the AC power, high quality black Teflon 4- and 8-pin valve
bases, Audio Note (UK) hardwire tag strips, and EI-Core or C-Core output transformers.
It's an ideal 300B stereo power amplifier designed to mate with the Mentor pre-amplifier. It is
modestly priced and, as such, an exceptional value.
1.2.2 Component Placement
Mentor SET Power Amplifier

Copyright © 2019 ANK Audio Kits
www.AudioNoteKits.com
[email protected]
Page 10
1.2.3 300B Pinout
The 300B tube has four pins: two filaments (one of which serves as the Cathode; we use pin 1), the
Plate/Anode, and the Grid. The two filament pins have noticeably larger diameters than the Anode
and the Grid, so it's easy to make the distinction between the pairs of pins. However, as I'm sure you
realize already, the left/right pin identification 'flips' when the valve base is viewed from the top or
bottom. Therefore, it requires that you pay special attention as to which way you're looking at
things when you wire the 300B valve bases and make the connections to the bases from other
components.
Have a look at the following diagram:
On the left is the top view of a valve base; on the right, the bottom view of a 300B tube. The wiring
graphics in the manual generally use the valve base view; in any case, you can tell which view is
being used by the different icons. Please pay special attention to this.
FYI, here's the original Western Electric pinout2:
2Rotated left 90 degrees.