Knight Audio Technologies Ltd
Deacy - Style Amplifier Kit
Build Instructions
Copyright Knight Audio Technologies Ltd 2012
Introduction
Firstly, thank you for purchasing this amplifier kit.
We have designed this amplifier based on the Mullard 1960’s schematic known to
many, but have in addition, modified the values of the components to bring that
design closer in tone and performance to the actual Deacy Amplifier.
We have also developed a pair of transformers (sold separately) that ensure this
circuit performs as closely as possible to our design. Other transformers may be
used if required.
A range of other components that complement this amplifier are also sold
separately. These include a twin cone loudspeaker, a Sapele veneered
MDF/Chipboard bookshelf speaker cabinet and a Direct Record board for Direct
connection to a mixing desk and headphone listening.
Let’s not also forget the KAT DABS (Deacy Amp Battery Simulator) unit, that will
power your Deacy-Style Amplifier Kit and save you money on pricey Batteries!
We very much hope you enjoy building this kit!
Where to start;
Start by checking off all the items in the kit by comparing it to the list
below. If you have any items missing, please contact your KAT dealer
and have your Deacy - Style Amp Kit and the missing component
details to hand.
Please do not start building the Kit until you have all
the components in place.
Copyright Knight Audio Technologies Ltd 2012
1a. Kit Check List (Amp Kit)
Amplifier Board
Resistors
47K
12K
3K9
2K2
2K2
68K
12K
330R
560R
2K2
39R
560K
4R7
120R
Capacitors
2.2uF
330uF
2.2uF
47uF
100uF
220nF
330uF
Semiconductors
AC125
AC126
AC128
AC128
Hardware
Heat-sinks
PCB
¼” Jack Socket
PP9 Battery Clip
Hook-up wire
Circuit
Ref
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
R13
R14
Circuit
Ref
C1
C2
C3
C4
C5
C6
C7
Circuit
Ref
Q1
Q2
Q3
Q4
Circuit
Ref
HSK
PCB
SKT1
LD1
Wire
Colour code/Description
Qty
Yellow/Violet/Orange/Gold
Brown/Red/Orange/Gold
Orange/White/Red/Gold
Red/Red/Red/Gold
Red/Red/Red/Gold
Blue/Grey/Orange/Gold
Brown/Red/Orange/Gold
Orange/Orange/Brown/Gold
Green/Blue/Brown/Gold
Red/Red/Red/Gold
Orange/White/Black/Gold
Green/Blue/Yellow/Gold
Yellow/Violet/Gold/Gold
Brown/Red/Brown/Gold
Colour code/Description
1
1
1
1
1
1
1
1
1
1
1
1
1
Qty
Black 2u2 63Vdc
Black 330u 25Vdc
Black 2u2 63Vdc
Black 47u 63Vdc
Black 100u 63Vdc
Yellow block cap 220n
Black 330u 25Vdc
Colour code/Description
1
1
1
1
1
1
1
Qty
Silver can transistor AC125
Silver can transistor AC126
Silver can transistor AC128
Silver can transistor AC128
Colour code/Description
1
1
1
1
Qty
Multi-Finned spring loaded Heat-sinks
Screen Printed AMP PCB
3 pole jack socket
PP9 battery clip/lead
Black/Brown/Red/Orange/Yellow/Green/Blue/Violet/Grey/White/Pink
2
1
1
1
1 ea
1b. Diagrams and Instructions
Diagrams
Instruction Booklet
Amplifier Schematic
Description
A4 Booklet
A4 Drawing
Copyright Knight Audio Technologies Ltd 2012
Qty
1
1
Building The Amplifier Assembly
2. Loading the Resistors
Firstly, sort out the resistors. Make sure you have the right values, check them
with a multi-meter if you are not totally sure of the colour codes.
The resistors need their leads dressing, so gently place a 1/8” blade screwdriver
shaft against the lead and away from the body of the resistor and wrap the lead
90 degrees around the screwdriver shaft. Do the same on the other side so that
both leads head downwards in the same direction and measure approximately
13mm between them.
Do this to all the resistors.
Next, pick up the PCB and insert the resistors into their respective locations. Try
to mount the resistors so that all the tolerance bands (gold) are either pointing
towards the top or right hand side of the board (with the Fryer Sound logo at the
top).
As you place each resistor in its respective holes, gently bend the leads apart on
the track side of the board just enough to hold their position and stop them
falling out again.
Once you have all the resistors loaded, place the board face down onto a soft
surface and carefully solder each lead in place. Do not apply too much solder.
Ensure that the finished joint has a concave web of solder surrounding the lead.
A convex web shows that you have too much solder on the joint. Once all the
leads have been soldered, they can be trimmed back to within 1mm of the joint
using a sharp pair of side cutters. Take care not to bridge adjacent tracks with
excess solder.
3. Loading the capacitors:
Most of these are polarity conscious, so care should be taken when orientating
the devices.
Start with the smallest capacitor, C6. This is the small yellow block capacitor and
it resides just above the output transformer T2. Place this in its holes and gently,
as with the resistors, bend the legs apart so as to retain the device. Solder this in
place now and trim the leads accordingly. Make sure that the capacitor is seated
squarely on the top surface of the PCB.
Copyright Knight Audio Technologies Ltd 2012
Now load the electrolytic capacitors one by one.
PLEASE NOTE THAT THESE ARE POLARISED DEVICES AND MUST BE
LOADED IN THE CORRECT ORIENTATION.
You will note that the capacitors have a silver band with minus signs running up
one side of their bodies. This is the negative leg of the capacitor meaning the
other leg is the positive. This POSITIVE leg needs to be inserted in the holes in
the PCB marked with a +.
Again, ensure each capacitor in turn is seated properly, and then solder them in
place.
BE CAREFULL WHEN SOLDERING THE 2.2UF CAPACITORS AS THE
TRACKS ARE VERY CLOSE AND CAN EASILY BE SHORTED WITH AN
OVER-LOADED SOLDER JOINT.
With the Resistors and Capacitors now loaded, it is a good time just to check
that you have all the components in the right place and in the correct
orientation. From here onwards, it will become more difficult to make changes as
the board becomes more densely populated.
4. Loading the Transformers:
It is now time to load the largest components on the board. The two
transformers (available separately) have been labelled T1 and T2 respectively.
T1 is the “driver” or “interstage” transformer, T2 is the push-pull output
transformer.
Care has to be taken to ensure both transformers are mounted in the right
positions and in the correct orientation.
Load one transformer at a time, hold it in place making sure it is seated properly
against the PCB, the solder the pins. These will not require cutting afterwards.
Do the same for the second transformer.
Copyright Knight Audio Technologies Ltd 2012
5. Loading the Semiconductors:
INITIAL NOTES AND WARNINGS:
GERMANIUM TRANSISTORS ARE EXCEPTIONALLY DELICATE DEVICES
AND CAN BE DESTROYED WITH BOTH EXCESSIVE AMOUNTS OF HEAT
OR STATIC ELECTRICITY.
Start with Q1 (AC125). Insert the transistor legs into the holes in the PCB. Note
the orientation of the device and compare it to the screen printed guide on the
PCB surface. Carefully push the device to within about 10mm of the board. In
other words, there is 10mm of lead showing between the transistor and the top
of the PCB.
Again, check the orientation of the transistor prior to the next stage.
To solder the device, choose the first lead. Wrap a rubber band around the
handles of a small pair of snipe nosed pliers and attach these to the first lead
between the board and the transistor. The rubber band will hold the pliers in
place as a heat-sink and stop the heat from the soldering iron from damaging
the device. Now solder the lead track-side.
Repeat this for the other two leads and then for the other three transistors.
6. Mounting the Heat-sinks:
Transistors Q3 and Q4 require heat-sinks to be fitted. If they are not fitted,
the transistors will over-heat during loud continuous playing and
almost certainly be damaged due to thermal runaway if the battery is
not disconnected in time.
To fit these, open them up by placing a pair of snipe nose pliers in the centre
space and gently prising them apart. Slip the heat-sinks over the body of the
transistors making sure you do not push too hard and bending the legs.
The board is now populated and ready for connections.
Copyright Knight Audio Technologies Ltd 2012
7. Installing Inter-Connecting Wires:
We would recommend the following colour codes be used for the inter-connects.
Battery
Speaker
Input Jack
(+ Red, - Black)
(+ Blue, - White)
(Signal + Yellow, Ground Green)
Strip the leads back by 6mm, twist and tin them with the soldering iron. Make
sure that any excess solder is removed otherwise the wires will not fit through
the PCB holes.
Push each wire in turn, bare end first through their respective holes from the
component side of the PCB. Carefully solder the wires track-side. Trim as per the
resistors.
ENSURE THE BATTERY + AND BATTERY – PADS ARE CONNECTED TO
THE RED AND BLACK LEADS RESPECTIVELY.
Connect the Speaker to the amp board and the jack to the input leads.
8. Congratulations, we are now ready to test!
IF YOU HAVE ONE, CONNECT A MULTIMETER AS A CURRENT
MEASURING DEVICE IN SERIES WITH THE BATTERY + LEAD (RED).
Adjust the multi-meter so that its range will read up to 1 amp DC. Connect the
battery and quickly read the meter. You should be drawing around 12 – 14mA.
If it’s significantly higher, firstly disconnect the battery quickly! Then
check that you have:
1. Installed the all transistors the right way round and in the correct
locations.
2. Installed the correct value resistors in R10 and R11 positions.
3. Installed the correct transformers in their respective locations.
4. Not got any solder bridges or splashes anywhere on the board.
Once you have found the problem, you should find the current drops to the
stated level.
Copyright Knight Audio Technologies Ltd 2012
If you do not have access to a multi-meter, turn the unit on and keep your
fingers on all the transistor cans for a minute or so. None of the transistors
should get warm whilst the amplifier is in quiescent or “Idle” mode. There should
also be a faint hiss from the speaker.
If any of the transistor cans start getting warm, disconnect the battery
quickly! Then check the items listed above.
Once you have found the problem, you should find that all transistors run cool
under “No-Signal conditions.
If you dab your finger on the yellow connection of the input jack, you should
hear a loud buzz.
The amplifier is now ready to mount in your cabinet.
9. Fault Finding:
All the components in these kits have been pre-tested by KAT Ltd.
We would advise that you build this kit as per the instructions and schematics as
any deviation from the designed circuit may result in irreparable damage to some
of the components.
If your amplifier does not work first time, it will almost definitely be caused by
one of the following:
•
•
•
•
•
•
Wrong component in a location (All components)
Wrong component orientation (capacitors/transistors)
Dry solder joint
Solder bridge (across two adjacent tracks, Check in particular, C1 and C3)
Damaged transistor due to over-heating or wrong orientation.
Polarity of battery connections
We wish you many hours of enjoyment building this kit and hope that the
resulting amplifier will add a versatile and great sounding addition to your set-up.
Cheers,
Nigel Knight
Knight Audio Technologies Ltd.
Copyright Knight Audio Technologies Ltd 2012