icon Audio LA 5TX Pure Valve Line Pre-Amplifier User Manual
- June 9, 2024
- icon Audio
Table of Contents
icon Audio LA 5TX Pure Valve Line Pre-Amplifier
IMPORTANT!
THIS MANUAL CONTAINS ESSENTIAL HEALTH & SAFETY INFORMATION FOR YOU AND YOUR
AMPLIFIER. PLEASE READ & KEEP SAFE AND REFER TO IF NECESSARY
Previous model shown with front power switch and gloss paint and upgraded CV181 (6SN7) valves
About the LA 5TX
The LA5TX is a very special pre-amplifier. Despite looking like a valve pre-
amplifier, it is in fact designed around two very high quality transformers
which have a simple low gain valve stage to act as a “buffer”.
This way the impedance of the source unit and the input of the power amplifier
are completely separated. The Transformers incorporate our uniquely wound Low
Distortion Tertiary winding, complex and time consuming to get right, but
preserving the smallest musical detail and dynamics without the problems
associated with capacitor coupling.
To get the best out of the LA5TX. Please read the enclosed notes. We have
tried to give you all the information you need. We would recommend that
everyone follows the ‘quick set up guide’. Should you be uncertain about
anything to do with your LA5TX please contact your dealer.
The LA5TX is a line amplifier designed to complement high quality valve or
transistor power amplifiers requiring an input voltage of 1volt or greater. It
will also work well with most integrated amplifiers.
Our philosophy is to use traditional valve minimalist, circuitry. The beauty
of valve amplifiers is that they are usually very simple; therefore with the
use of traditional point-to point construction, modern high performance low
tolerance components, it is possible to achieve very high sonic performance.
This simplicity enables us to avoid the use of printed circuit boards, which
are not ideal for valve amplifiers despite their common use.
Although technical performance is important, we never forget that sound
quality takes overriding priority in our design and production. The LA5TX has
a massive overload capability and even then would go into ‘soft clipping’,
which is much more benign and easier on the ear than overloaded transistors.
The simplicity of the circuit means that there are much fewer components for
the signal to pass through, fewer connections and switches, again adding to
the purity of sound. This simplicity also means that we can use higher quality
oversized components, such as 2w resistors.
The use of popular valves, which are still in production, means that obtaining
replacements is easy and inexpensive when necessary.
In the process of building the LA5TX to its high standard no corners have been
cut and we have also paid close attention to the appearance.
The remote control has its own separate power supply so the operation will not
influence sonic qualities.
The final result is an amplifier with excellent characteristics, with an
accurate yet smooth and transparent quality.
Various upgrades are available at the time of ordering or may be retro fitted.
These include “Mundorf” capacitors and various valves including “Full Music”
which will enhance the performance of the LA5TX.
inal Inspection
This amplifier has been carefully checked, tested and final adjustments made
by Icon Audio in Leicester.
It has passed our rigorous listening test and final inspection to assure you
of optimum performance and reliability.
To get the best out of your unit and to save time please read this information & keep it to hand for reference2
- Date …./…./….
- Model ……….
- Amp Serial Number ……….
- Customer ……………………………
- Check amplifier finish ……….
- Run 24 hour test ……….
- Check all inputs & tape monitor ……….
- Sound Quality ……….
- Channel Balance ……….
- Valve Microphony ……….
- Valve Seating ……….
- Hum & noise level ……….
- RF Test ……….
- Remote Control Function ……….
- Remote control in box ……….
- Serial No sticker and recorded ……….
- Mains voltage 110 / 230-240V
- IEC Mains Fuse ………A
- Sales invoice ……….
- Credit card receipt .………
- Bias meter N/A
- Transformer Protection N/A
- Upgrades:
- Input valves ……….
- Output valve ……….
- Rectifier valve ……….
- Capacitors ……….
- Interconnects ……….
- Signed off by ……………………….
Notes:
Please note we do not test the standard mains lead.
LA5TX layout
Care should be taken to site the pre-amplifier away from sources of hum e.g.
from the power transformers of other units, particularly power amplifiers.
All inputs and including the tape loop are at the same level.
Outputs 1 and 2 are at the same level.
CV181 is identical to the 6SN7
QUICK SET UP GUIDE
- Unpack unit carefully. Make sure that it is in good condition. It is important that you keep packaging for warranty/service return. Make sure the mains voltage is suitable for your area. If not contact your dealer.
- Fit the rectifier valve 274B/GZ34/5AR4. BEWARE ONLY FIT IN REAR CENTRE (see pic P1) Fit the three 6SN7/CV181, these are normally numbered so that they will be in the same position when first fitted. Otherwise they may be fitted in any order. Try not pull the 6SN7s by the glass envelope! This could cause the glass envelope to become detached from the base causing irreparable damage. Be careful to align to “spigot” or keyway of the valve with the socket before pushing in to place. Also Russian 6H8.
- Connect to source & Output units, e.g. CD, Tuner, Tape, Phono pre amp (if used) and power amp etc via appropriate phono sockets and leads. OUT 1 and OUT 2 are the same. (OUT 2 may be modified to be attenuated see below). See also Bluetooth section.
- Connect to mains supply using supplied IEC mains lead to 230/117v supply. If you need to change to a different type of mains plug, the replacement plug should be wired in the following way Brown to Live terminal, Blue to Neutral terminal and Green/Yellow to Earth terminal.
- SWITCH ON! The LED power indicator should light up and unit will take approximately 40 seconds to start working. All valves should have a visible orange glow from the cathode heaters. With the volume control set to minimum (fully anti-clockwise) there should be no sound coming from the speakers except a barely discernible gentle hum.
- Your unit should now be functioning. Select correct input and adjust volume. If not check wiring again and/Use selector/tape monitor/volume to choose source program and suitable listening volume. The best sound quality will be when the unit has warmed up for about 20 mins.
- Health and Safety. The valves when operating have high surface temperatures. Keep out of reach of children and pets. The use of the optional guard is recommend in these circumstances. Always unplug when making adjustments. Like all amplifiers there are potentially lethal high voltages inside (400v DC), which when switched off can take up to 15 mins to discharge! Do not remove bottom panel unless you are a competent engineer. There are no user serviceable parts inside. Like other household electrical appliances do not leave unattended whilst switched on.
Remote Control
When new remove the plastic tab which preserves the batteries during storage.
The 2x AAA batteries will last up to 2 years with normal use. Replace with
“Alkaline” types when the indicator LED loses brightness. The maximum range is
approximately five meters. Aim the handset directly at the LA5TX, at longer
distances multiple short clicks usually work better than long presses. After
each switch on the volume control will re-set to approximately “9 o’clock”.
Remove batteries during storage to prevent leakage damage. Spares and repairs
are available from Icon Audio (at time of writing 12/2012)
Connecting inputs & outputs
Many problems with hi fi equipment involve connecting leads which are usually
either ‘Bad, or Wrong connection’. So it’s worth making sure that you have
good connections and that your leads are the right way round.
Inputs
The amplifier will work with any standard piece of hi fi e.g. CD, Tuner, Tape
Deck, Mini Disc, TV, Video Recorder, DVD etc having an output of 200mv or
more, to get full power. The position of the volume control will vary with the
input voltage of different units, this has no effect upon performance.
If you wish to use a turntable you will need a suitable phono pre-amp. Your
dealer or Icon can assist you.
Connecting a tape deck
The LA5TX will work with any tape deck having suitable output, and it is
possible to record from any connected source using the terminals marked ‘Pre-
out’. The LA5TX has a ‘Tape Monitor’ facility, which enables you to use a
‘three head deck’ or an equalizer.
Some tape decks ‘Present a load’ to the amplifier
terminals, even when not in use, which can affect sound quality. (You can do
an audible check for this by removing the input and listening for a change in
sound quality). If so remove when not required.
General points
- Switching the pre-amp on before the power amp will reduce any “switch on thump, of the speakers” (in some cases).
- Mobile phone ‘breakthrough’ is normal, move phone away if necessary.
- A switch-off ‘click’ through the speakers is normal.
- Storage in damp conditions could damage transformers.
Connecting Leads
Use good quality screened connecting leads, which are no longer than they need
to be.
Leaving the amp switched on
Do not leave the LA4 running continuously. The warm up time of the LA4 is 5-10
minutes. Whilst the amplifier will sound at its best when it is properly
warmed up, there is no advantage leaving it switched on when it is not in use.
It is using electricity and valves have a finite life. Conversely the valves
and other components are stressed more at switch on; therefore do not switch
on and off unnecessarily. The LA4 needs about two months of regular use before
it is ‘run in’.
Cabinet Care
To remove dust from the cabinet and valves we suggest gentle brushing with a
soft paintbrush and a duster. Finger marks can usually be removed with a damp
cloth. On no account use anything wet on the amplifier, and always clean with
the power disconnected.
Trouble Shooting
Amplifier Dead
Check the mains fuse at the back of the amplifier. To gain access, remove the
mains lead. The fuse is in a small plastic drawer, which forms part of the
socket assembly. To open insert a flat bade screwdriver or similar and
priseopen. The fuse in use is the innermost the outer is a spare. Should the
replacement fuse also blow there is a fault. Replacements should be 1Amp (2Amp
USA)‘anti-surge’. If it is OK try a different IEC cable.
If that does not work refer to dealer or Icon Audio. The fuse in the UK mains
plug should be a 3 or 5 amp fuse, although unlikely, this should be checked if
the amplifier fuse is OK.
No sound
Have you selected the right input? Are the connections OK? Is everything
switched on? Are the speakers connected?
Distorted sound.
Try another source; if sound improves then it’s probably something wrong with
the first source. If no improvement try different speakers, if no improvement
could be an amplifier problem.
Hum Problems
If you experience hum, try disconnecting all inputs, if hum persists this is
probably an amplifier fault.
If not, Identify which input is causing hum. Connect one input at a time. A
common cause is a ‘hum loop’ caused by having too many earths, and may be
identified by unplugging each input source from the mains. One remedy for this
is to use an interconnect which only has the screen connected at one end.
Other causes of low-level hum can be from adjacent equipment, so experiment
with moving equipment around to see if this makes the hum better or worse.
One channel missing.
Usually ‘bad’ connection on either the input or the speakers. Try swapping the
connection over to establish if the cause is:
- Input to the amp. Sound will move to the other channel.
- Amplifier or speakers. Sound will not move.
Strange noises coming from speakers
Turn volume to minimum on unused input, if problem corrected either fault with source unit or with connection. If noise persists, problem with amplifier. A valve that is lit up is not a guarantee that it is working properly; conversely a valve that is not lit up will not be working.
Valve Replacement (see also section 2)
Valve life will depend upon such things as hours of use and number of on/off cycles. As all the valves are lightly loaded we would estimate life of approx 4 to 10 years. It is essential that only the correct valves are used as some similar looking valves have a different pin connection and insertion could result in damage to the amplifier and risk of electric shock. It is not good practice to remove the valves unnecessarily as this can strain the pins and cause tiny air leaks. Icon Audio are happy to replace valves and check to performance of your amplifier, and advise on the latest upgrades available.
Although the two original 6SN7 valves are normally identical it is important that if they are removed, that they are replaced in the same position. We normally number them.
Equivalent Valves
Designed for 274B (8 pin octal version). The GZ34, 5AR4 will also work well.
Designed for 6SN7. CV181 is identical, as is Russian or Chinese 6H8c (6N8p).
Service: Should you suspect a problem, you could return the unit to your dealer or Icon Audio for a periodic service or return the valves for testing free of charge. You should carefully remove the valves, they should be well packed in cardboard & foam or similar, and returned to Icon Audio for testing. (Valves are very rugged if packed properly).
Specification & Features
- No printed circuit board
- Japanese ALPS volume pot.
- All Triode design
- Valve rectifier, 274B/5AR4/GZ34
- High current choke regulated power supply
- 3x 6SN7 Double triode (or CV181 6H8)
- Signal to noise level -90db
- Infra red remote control, volume up/down, mute
- Freq response 10hz-30khz +0 – 0.1db
- THD 0.01%, @ 1khz, 2v rms
- Hand wired point to point components
- High quality 2w metal film resistors, for audio
- LED mains indicator
- Audio grade Polypropylene audio capacitors
- Mundorf silver/gold in oil (option)
- Wired with silver PTFE audiophile cable
- Rubicon/Nichichron power capacitors
- Inputs, CD, Tape, Tuner, Aux, Phono (line level)
- Ceramic valve holders for minimum leakage
- DC heater power supply for minimum noise.
- Gold plated Input & output terminals
- Tape monitor circuit
- Max Gain= 12db (input voltage x4)
- Output impedance 38 ohms
- Maximum output 30 volts (OUT1 & 2)
- Optional safety guard
- Transformers & choke resin sealed to minimize noise & hum.
- 230/240 Volts, 35watts 1A anti-surge fuse
- 117 Volts 35 watts 2A anti-surge fuse
- IEC mains lead, (5amp plug fuse if fitted)
- FCC, C E certified. ROHS & WEEE compliant
- 250W, 370D, 230H with 274B (or 175 with GZ34) 12kg packed. Allow for rear connections & ventilation) (Specifications subject to change, errors & omissions excepted 10/03/22)
icon Audio (UK) Ltd
351 Aylestone Road Leicester LE2 8TA UK
Email: [email protected]
www.iconaudio.com
Phone +44 (0) 116 244 0593
Mobile +44 (0) 7787 158 791