Ashdown CTM-300 300 Watt Tube Bass Head User Manual
- June 12, 2024
- Ashdown
Table of Contents
ASHDOWN ENGINEERING – CTM-300
USER MANUAL
CTM-300 300 Watt Tube Bass Head
THANK YOU
Thank you for purchasing your Ashdown Engineering Amplifier and welcome to the
family! We really think you’ve made the right choice and know that this
amplifier will give you years of great tone and service. It is a machine
though and needs to be looked after, please read through this user manual
which will help you get the most out of your new Amp and keep it running as
long as some of our happiest and very famous customers.
REGISTER ONLINE
Please register this product online so we can make sure we give you years of
customer support through our friendly in-house service centre.
Here is where you need to visit to register your product:
http://www.ashdownmusic.com/pages/register-your-product
INTRODUCTION
Taking inspiration from the classic tube heads of the past, Ashdown presents the all-tube CTM-300, a 300W valve masterpiece that melds classic tones with modern features, construction and reliability.
Handbuilt in the UK Ashdown Custom Shop the CTM 300 head is housed within an 18mm Marine grade birch ply cabinet that features heavy duty flip style handles and an internal fan to keep things cool. This is an amplifier that is built to last using only the finest components to ensure years of trouble-free performance night after night.
FRONT PANEL
BACK PANEL
FACILITIES AND CONTROLS (NOTE THAT THESE VARY ACCORDING TO THE MODEL)
INPUTS
There are two instrument inputs marked LOW and HIGH. The LOW input is highly
sensitivity and also high impedance to suit the output from PASSIVE (Low
Output) basses – The HIGH input is low sensitivity and lower impedance to suit
the output from ACTIVE (High Output) basses. Plugging an active (High Output)
bass into the LOW input will overload the input, creating a fatter, warmer and
more distorted sound. Experiment by plugging your bass into either input to
achieve the desired sound. On models with a single input this will be suitable
for both Passive and Active basses.
EFFECTS SEND AND RETURN
These 1/4″ jack sockets should be used to connect to an external effects
device or pedal board. The EFFECTS SEND output should connect to the INPUT of
the effects unit, and the output of the effects unit should be connected to
the EFFECTS RETURN input Note that the signal level is at instrument level so
this loop is suitable for effects pedals.
EQ CONTROLS
Use the MIDDLE, BASS and TREBLE controls to effect the overall tone of the
sound.
MID SHIFT
Causes the MIDDLE control to operate at different points in the frequency
spectrum dependant on the button being either in or out.
BASS SHIFT
Causes the Bass control to operate at different points in the frequency
spectrum dependant on the button being either in or out.
BRIGHT
Adds an overall brightness to the sound when in the up position. (Note: The
BRIGHT switch is not effective when the GAIN control is set to full).
MELLOW
Softens the overall tone slightly
GAIN
This controls the level of the signal sent to the MASTER section. To achieve a
cleaner sound, turn the GAIN control down and the MASTER up. To achieve a
richer, more distorted sound, turn the GAIN control up and the MASTER down.
MASTER
This controls the overall output volume of the amplifier.
MUTE
In the in position, this switch mutes the out put of the amplifier (useful
for tuning, etc.).
PRE/POST
This switch determines whether the signal from the DI OUTPUT (see Rear Panel
Facilities) is taken before/PRE the EQ section (down position) or after/POST
(up position).
VU METER
The VU meter provides a visual indication of the output level of the
amplifier. It also acts as a bias meter, please see the following page for
more details.
SPECIFICATIONS:
Inputs
High Input
Low Input
Effects Return
Line Input| Impedance – 3.9M ohms
Impedance – 10k ohms
Impedance – 22k ohms
Impedance – 22k ohms| Input range 150mv to 20v p – p
Input range 300mv to 40v p – p
Input level 0dbu nominal
Input range 300mV
Outputs
Effects Send
D.I.Output
Speaker Outputs
Frequency Response| Impedance – 22k ohms
420 ohms balanced
Minimum Impedance – 2 ohms
-3db at 22hz and 25khz| Level 0dbu nominal
pre ground lift Level -20dbu nominal
Equalisation
Bass
Middle
Treble
Shape| +/- 15db @ 100hz
+/- 15db @ 660hz
+/- 15db @ 7khz shelving
+ 8db @ 50hz + 10db @ 10khz|
Signal to Noise
Distortion
Output Power| Better than 80db (E.Q. Flat)
Less than 0.5% Thd
300watts into 4 ohms|
THE VU METER
The VU meter fitted to the CTM is a dual function meter detailed as follows:
By using the push button selector switch marked “AUDIO / BIAS” the functions
are accessed in the following manner:
1/ “AUDIO” – In audio mode the meter is set to read the audio output of each
of the six power tubes and each can be measured by utilising the rotary
selector switch on the front panel. Whilst playing this is the normal mode of
operation of the meter and the reading obtained will be a direct indication of
the power being produced by each output tube, the meter is calibrated so that
when the needle reaches the start of the red section the power tube being
measured will be producing maximum clean volume.
The switch can be rotated to select any of the power tubes and its relative
output will be indicated on the meter, note that when performing this test you
will need to play at equal volume for each test.
2/ “BIAS” – In this mode the meter will glow RED. To check the bias of the output tubes proceed as follows: Run the amplifier for at least 10 mins to allow the output tubes to fully heat up with the amplifier set to mute. Standby on. Select.. Tube 1 and with an insulated jewelers screwdriver gently adjust the trimmer situated on the rear panel. The reading to aim for is the needle just at the start of the red ie 0db. Note that although each tube can be adjusted individually it is possible to get tubes that cannot be adjusted to the correct reading, these can still be used providing the reading is not in the red, a lower reading is acceptable and will note impact audibly on the power output or sound quality of the amplifier. Please also note that the trimmers are 25 turn types to make adjustment easy, This type of adjuster has no end stop so if you reach a point where the adjuster will not give any more adjustment then the output tube will have to be replaced if the reading is to high i.e. in the RED. Repeat this for each of the four output tubes in turn.
RETURN THE METER TO “audio” MODE AFTER BIASING. DO NOT RUN THE AMPLIFIER IN
BIAS MODE WHILST PLAYING.
Note there is a protection fuse fitted to each of the output tubes and if no
reading is obtained on the meter this fuse will have failed. The protection
fuses are situated next to the output they are protecting the correct rating
is 315Ma quick blow, in the event of a blown fuse they MUST be replaced with
fuses of the correct rating and type.
A continually blowing fuse would indicate either an incorrectly biased output
tube or a defective output tube.