Alto MINITUBE User Manual [ru]

User's Manual

MINI-TUBE

MONO TUBE PREAMP

LTO

www.altoproaudio.com

Version 1.0 August 2004

English

R

SAFETY RELATED SYMBOLS

CAUTION

RISK OFELECTRIC SHOCK

DO NOTOPEN

This symbol, wherever used, alerts
you to the presence of un-insulated
and dangerous voltages within the
product enclosure. These are voltages
that may be sufficient to constitute the
risk of electric shock or death.

This symbol, wherever used, alerts
you to important operating and ma­intenance instructions. Please read.
Protective Ground Terminal
AC mains (Alternating Current)
Hazardous Live Terminal

ON:

Denotes the product is turned on.

OFF:

Denotes the product is turned off.

WARNING

Describes precautions that should be
observed to prevent the possibility of
death or injury to the user.

CAUTION

Describes precautions that should be
observed to prevent damage to the
product.

WARNING

Power Supply

Ensure that the mains source voltage (AC
outlet) matches the voltage rating of the
product. Failure to do so could result in
damage to the product and possibly the user.
Unplug the product before electrical storms
occur and when unused for long periods of
time to reduce the risk of electric shock or
fire.

External Connection

Always use proper ready-made insulated
mains cabling (power cord). Failure to do
so could result in shock/death or fire. If
in doubt, seek advice, from a registered
electrician.

Do not Remove any Covers

Within the product are areas where high
voltages may present. To reduce the risk
of electric shock do not remove any
covers unless the AC mains power cord
is removed.

Covers should be removed by qualified
service personnel only.

No user serviceable parts inside.

Fuse

To prevent fire and damage to the
product, use only the recommended
fuse type as indicated in this manual.
Do not short-circuit the fuse holder.
Before replacing the fuse, make sure
that the product is OFF and disconnected
from the AC outlet.

Protective Ground

Before turning the product ON, make sure
that it is connected to Ground. This is to
prevent the risk of electric shock.
Never cut internal or external Ground wires.
Likewise, never remove Ground wiring
from the Protective Ground Terminal.

Operating Conditions

Always install in accordance with the
manufacturer's instructions.
To avoid the risk of electric shock and
damage, do not subject this product to
any liquid/rain or moisture. Do not use this
product when in close proximity to water.

1

Do not install this product near any direct
heat source.
Do not block areas of ventilation. Failure
to do so could result in fire.
Keep product away from naked flames.

IMPORTANT SAFETY INSTRUCTIONS

Read these instructions
Follow all instructions
Keep these instructions. Do not discard.
Heed all warnings.
Only use attachments/accessories
specified by the manufacturer.

Power Cord and Plug

Do not tamper with the power cord or plug.
These are designed for your safety.
Do not remove Ground connections!
If the plug does not fit your AC outlet seek
advice from a qualified electrician.
Protect the power cord and plug from any
physical stress to avoid risk of electric shock.
Do not place heavy objects on the power
cord. This could cause electric shock or fire.

Cleaning

When required, either blow off dust from
the product or use a dry cloth.
Do not use any solvents such as Benzol
or Alcohol.
For safety, keep product clean and free
from dust.

Servicing

Refer all servicing to qualified service
personnel only.
Do not perform any servicing other than
those instructions contained within the
User's Manual.

2

Preface

Dear Customer,

Thanks for choosing LTO Mini-Tube Mono Preamplifier and thanks for choosing one
of the results of LTO AUDIO TEAM job and researches.

For our LTO AUDIO TEAM, music and sound are more than a job...are first of all
passion and let us say...our obsession!

We have been designing professional audio products for a number of years in cooperation
with many of the world's major brands in audio field.
The LTO line presents unparalleled analogue and digital products made by Musicians
for Musicians in our R&D centers in Italy, Netherlands, United Kingdom and Taiwan.
We provide you with world -class designs, while our software development teams continue

.
to develop and impressive range of audio specific algorithms.

Because we are convinced you are the most important member of LTO AUDIO TEAM
and the one confirming the quality of our job, we would like to share with you our work
and our dreams, pay attention to your suggestions and your comments. Following this
idea we create our products and we will create the new ones! From our side, we guar­antee you and we will supply you also in future the best quality, and the best fruits of
our continuous researches and the best prices.

Our Mini-Tube Mono Preamplifier is the result of many hours of listening and tests
involving common people, area experts, musicians and technicians. The result of this
effort is a half rack space unit, the heart of which is an extremely low-noise microphone
pre-amp circuit that uses discrete components to produce a highly transparent sound.

Nothing else to add, but that we would like to thank all the people that made the LTO
Mini-Tube Preamplifier a reality available to our customers, thank our designers and
all the LTO staff, there to make possible the realization of products containing our
idea of music and sound and there to support you, our customers, in the best way, con­scious that you are our best richness.

Thank you very much.

LTO AUDIO TEAM

3

TABLE OF CONTENT

1. INTRODUCTION ............................................................................................5

2. FEATURE LIST ..............................................................................................5

3. CONTROL ELEMENTS .................................................................................5

3.1 The Front Panel

a. Guidepost of The Front Panel

b. Supplementary Descriptions

3.2 The Rear Panel

a. Power Supply Connection
b. Analogue Inputs/Outputs

4. INSTALLATION & CONNECTION..................................................................8

4.1 Mains Connection

4.2 Audio Connection

a. Wiring Configuration
b. In Line Connection

4.3 Rack Mounting

5. APPLICATIONS..............................................................................................9

5.1 The Mini-Tube as icrophone reamplifierAM P

5.2 The Mini-Tube as Direct-Injection ox (DI Box)AB

5.3 The as evel ranslatorAL TMini-Tube

6. TECHNICAL SPECIFICATIONS .................................................................11

6.1 Block Diagram

6.2 Specifications

7. WARRANTY .................................................................................................13

4

1. INTRODUCTION

Thank you very much for expressing your confidence in LTO products by purchasing
our Mini-Tube Mono Preamplifier. With the Mini-Tube you have acquired an extremely
musical and flexible Mono Microphone Preamplifier which is based on many years of
experience and findings in amplifier technology and is used through the world in renowned
studios, sound reinforcement systems as well as in broadcast and television studios.
The LTO Mini-Tube meets highest and no-compromise requirements in terms of operation,
sound, specifications and workmanship.

The LTO Mini-Tube is a half rack space unit, the heart of the MINI-TUBE is an extremely
low-noise microphone pre-amp circuit that uses discrete components such as 12AX7WA
Tube and NJM4580 Quad Operational Amplifier IC to produce a highly transparent sound!
The switchable +48V Phantom Power supply allows you to operate your condenser micro­phone more conveniently.

2. FEATURE LIST

Half rack space

Robust and compact design

Servo microphone preamplifier

20dB pad

+48V phantom power

Phase reverse

VU meter

Clip LED

12AX7WA low-noise tube

XLR and 1/4" connectors for both input and output

High quality and fidelity components

SMD technology for top performance

Manufactured under QS9000, VDA6.1 certified management system

3. CONTROL ELEMENTS

3.1 The Front Panel:

LTO

3

6

0

10

3

20

POWER OUTPUT

50 10050 100

VU

LTO

5

(1) (3) (5) (7) (8)

(2)

PAD

PHASE

(4)

(6)

T

M

MONO TUBE PREAMP

MINI-TUBE

+48V

40 20

00

GAIN

80HZ

LOW CUT

DRIVE

CLIP

5

a. Guidepost of the front panel

(1) VU Meter (volume indicator for output signal)
(2) 20dB PAD
(3) Phase Reverse Switch
(4) +48V Phantom Power Switch
(5) 80Hz Low Cut Switch (filter low frequencies below 80Hz)
(6) Gain Control (0 to +40 dB)
(7) Drive Control (0 to +20 dB)
(8) CLIP Indicator (indicating for clipped signal over +20dBu)

b. Supplementary Descriptions

-

Phantom Power Switch (4):

This switch activates the +48 volts phantom power to supply condenser mics and
any other devices requiring continuous power by means of the XLR cable. The +48V
is applied both to the positive (pin2) and negative inputs (pin3) of the XLR connector:

XLR Connector

PIN1 ( Ground ) GND
PIN2 ( Positive ) +48V
PIN3 ( Negative ) +48V

Caution: Please make sure that you are using an appropriate microphone before
you activate this switch to supply the +48V phantom power. Read the operating
instructions accompanying the microphone. Some condenser mics might need
another type of power supply, old dynamic microphones could be damaged by
the +48V voltage, and unbalanced microphones should never be operated in
combination with a +48V power supply.

-

Phase Reverse Switch (3):

This Phase Reverse Switch reverses the audio signal's phase by 180 , Normally,
you won't need this switch, however, in some cases, it might be necessary, for
example: the inversion of the pins of the XLR connector may be necessary to
alter the audio phase of linked microphone to compensate for phase cancellation.
It may be required that the wiring of a cable's XLR connector be switched to success­fully utilize Phantom power.

-

20dB Pad (2):

A 20dB Pad is designed to attenuate the incoming signal level to provide increased
"headroom" for the operator.

-

Gain Control (6):

This control sets the amount of boost to the signal being processed by this pre­amplifier. Use this control to adapt the Mini-Tube to either home recording level

6

Phantom

Power Supply

-10dBV ) or professional level (+4dbu). When the gain is too low, the tube effect
becomes less audible and the S/N (Signal to Noise) ratio deteriorates. Generally,
Dynamic mics and instruments without preamps will require more gain than con­denser mics and instruments that have a built-in preamp. If you should require more
signal out of the preamp for a hotter recording level, cranking up the gain should
provide all the signal that you'll need.
To obtain the best possible S/N (Signal to Noise) ratio and subsequently the best
transparent sound, keep an eye on the VU Meter.

- Drive Control (7):

The effect achieved by this control can be subtle to extreme, depending on the
settings being used. A "warming up" of the sound can be noticed at lower settings.
This desirable effect is especially good for microphones and on an electric bass
and the resulting sound is infinitely richer and sweeter.
An over-driven signal can be achieved by significantly raising the level of the Drive
control. This over-driven tube effect is extremely useful in providing cool guitar
sounds and way cool for use with harmonicas for that authentic "Blues harp" vibe.
The limits on the possibilities of the Drive control are up to you, your application
and your imagination.

3.2 The Rear Panel

OUTPUT INPUT

18VAC

~

POWER

MODEL

SERIAL

BALANCED UNBALANCED BALANCED UNBALANCED

a. Power Supply Connection

Please use the 18VAC AC/AC Adaptor provided by LTO to connect your Mini­Tube. Detail your can follow the illustration.

18VAC

~

POWER

MODEL

SERIAL

IN

18VAC

b. Analogue Inputs / Outputs

The output XLR connector is servo balanced and operates at +4dBu. The output

1/4" Phone jack is unbalanced and operates at -10dBv.

7

4. INSTALLATION & CONNECTION

4.1 Mains Connection

- Please ensure that the LTO Mini-Tube Preamplifier is connected to the correct supply
voltage before operating this unit.

- Only use the 18VAC AC/AC Adaptor provided by LTO.

4.2 Audio onnectionC

The presents with balanced XLR connectors and 1/4" TRSLTO Mini-Tube Preamp
phone jack and it can be interfaced by several ways to support a variety of app­lications without any signal loss.

a. Wiring Configuration

Either the 1/4" TRS (Tip-Ring-Sleeve) phone jack or the XLR servo connector can
be wired in balanced and unbalanced modes, which will be determined by the
actual application status, Please wire your systems as the following examples:

For 1/4" Phone jack

+

Tip

Sleeve

TS Type Unbalanced

Ring

TRS Type Balanced

+

-

Tip

Sleeve

Ring

TRS Type Unbalanced

+

Tip

Sleeve

For XLR connector

Pin1 ( )

Pin2 (+)

Pin3 (-)
(Linked to Pin1 manually, )

Pin3 (-)

Pin1 ( )

XLR Type alancedBXLR Type Unbalanced

Pin2 (+)

b. In Line Connection

For these applications, the Preamp provides XLR connector andMini-Tube
1/4" TRS phone jack to easily interface with most professional audio devices. Follow
the configuration examples below for your particular connection.

8

Balanced

Tip

TIPRING SLEEVE

3

21

TIPRING SLEEVE

SLEEVERING TIP

1

3

2

1

3

2

Sleeve

Sleeve

Ring

1
2

3

Tip

Ring

Unbalanced

TIPRING SLEEVE

TIPSLEEVE

1

3

2

TIPSLEEVE

TIPRING SLEEVE

TIPSLEEVE

TIPRING SLEEVE

1

3

2

SLEEVETIP

SLEEVERING TIP

1

3

2

1

3

2

1

3

2

Sleeve

Sleeve

Sleeve

Sleeve

Sleeve

Sleeve

Tip

Ring

Tip

1
2
3

Tip

Tip

Ring

Tip

Tip

Ring

1
2

3

4.3 Rack Mounting

The most secure mounting is on a "universal" rack shelf, available from various
rack manufacturers or your music dealer. The Mini-Tube Preamplifier's height conforms
to single-space mounting, and up to two Mini-Tube Preamplifier may be mounted
side-by-side in a standard universal EIA 19" equipment rack.

Tip
Ring

Sleeve

1
2

3

1
2
3

1
2
3

1
2
3

Cent er

Screen

Tip

Sleeve

Tip
Ring

Sleeve

Cent er

Screen

Centre

Screen

1
2
3

T

M

MONOTUBE PREAMP

LTO

3

6

0

10

3

20

5

50 10050 100

VU

LTO

POWEROUTPUT

MINI-TUBE

PAD

40 20

00

PHASE

LOWCUT

GAIN

LTO

3

6

0

10

3

20

+48V

80HZ

CLIP

DRIVE

50 10050 100

VU

LTO

POWEROUTPUT

5

MINI-TUBE

PAD

40 20

00

PHASE

LOWCUT

GAIN

+48V

80HZ

T

M

MONOTUBE PREAMP

DRIVE

5. APPLICATIONS

This section presents some typical applications of our LTO Preamplifier.Mini-Tube
Please reserve your time to well understand the application examples, so as to be able
to fully exploit this unit and its versatile features.

5.1 The as icrophone reamplifierAM PMini-Tube

It is the basic application for .Mini-Tube
Before you can use the LTO as a Mono Microphone Preamplifier,Mini-Tube
we recommend that you study the various functions of the unit first. The high gain
factors (+30dB) provided by the microphone preamplifier can produce extreme levels

9

CLIP

on the output side, which may damage subsequent devices, so you should turn
down all the level controls beforehand, or you can press the 20dB PAD (2) to
attenuate the incoming signal level about 20dB, then hook up a microphone to the
XLR or 1/4" TRS Input connector, and use either the 1/4" jack or XLR output connector
to connect the audio system.
Now, power up the entire equipment, if you wish to use a condenser mic requiring
+48V phantom power, please press the Phantom Power Switch (4) (to avoid electric
damage, please read Control Elements "Phantom Power Switch" carefully). After
that, please adjust your Input Gain Control and Drive Control to get the best result.

5.2 The as Direct-Injection ox (DI Box)ABMini-Tube

When audio signals produced by instruments such as guitars, keyboards, etc. are
transported over long unbalanced lines, the transmission quality may be affected by
Hum or other interference signals included in the cable. So called DI Box are used to
solve this issue: the DI Box converts the unbalanced signal coming from the instrument
into a balanced signal that is sent over the line. Interference included in balanced
cables is then eliminated by a subsequent balanced input stage.
Using the LTO as a Mono Microphone Preamplifier for this application isMini-Tube
very easy. Simply connect the line output of your instrument to the XLR or 1/4" TRS
Input jack on the rear panel of , then use the Mini-Tube'sMini-Tube balanced output
to send the signal to the next stage.

5.3 The as evel ranslatorAL TMini-Tube

Semi-professional appliances in home recording system are normally operated with a
nominal level of 10dBV, while the level used in studios and other professional application
is 0dBu or +4dBu. So, when you connect devices of both types to each other, you
should consider some kind of level translators of course.
The LTO Mono Microphone Preamplifier is pretty suited for this application.Mini-Tube
The Input Gain control allows you to raise or lower your input signal level by as much
as 30dB. The functions Phase Inversion is also enabled in this mode.

10

6. TECHNICAL SPECIFICATIONS

6.1 Block Diagram

4

3

D

Block Diagram

C

B

A

4

2

4

2

3

2

1

D

C

B

A

2

1

11

6.2 Specifications

General

Preamp Bandwidth

Number of Channels

THD+Noise

Performance

Output Level (MAX)

Noise Floor

Signal to Noise

Input

Connectors

Input Impedance, XLR

Input Impedance, Hight Z 1/4

Output

Output Impedance,
XLR Balanced

Output Impedance, Hight

Z 1/4" TRS Unbalanced

Panel Controls

Tube Drive

Gain

Phase Reversal

-20dB Pad

+48V Phantom Power

Metering

VU Meter

Clip Led

Power Supply

Input

Power

Physical Weight

Size

Dimension (W D H)

20Hz ~ 50KHz / 2dB
one

0.05% @ GAIN +0dBu (A-Weighting)

+22dBu

-88dBu( 2dBu)

>108dBu
XLR and 1/4"

1.3K Ohms
1Meg Ohms

51 Ohms

51 Ohms

0dB ~ +20dB

0dB ~ +40dB

-20dBu ~ +5dBu

+20dBu

18VAC/1000mA

12WATT

0.7Kg

1U Rack

210mm 93mm 44mm

12

7. WARRANTY

7.1

Warranty registration card

To obtain Warranty Service, the buyer should first fill out and return the enclosed
Warranty Registration Card within 10 days of the Purchase Date.
All the information presented in this Warranty Registration Card gives the manu­facturer a better understanding of the sales status, so as to purport a more effective
and efficient after-sales warranty service.
Please fill out all the information carefully and genuinely, miswriting or absence of
this card will void any of your warranty service.

Return notice

7.2

a. In case of return for any warranty service, please make sure that the product is

well packed in its original shipping carton, and it can protect your unit from any

other extra damage.

b. Please provide a copy of your sales receipt or other proof of purchase with the

returned machine, and give detail information about your return address and

contact telephone number.

c. A brief description of the defect will be appreciated.

d. Please prepay all the costs involved in the return shipping, handling and insurance.

7.3 Terms and conditions

a. warrants that this product will be free from any defects in materials and/orLTO

workmanship for a period of 1 year from the purchase date if you have completed

the Warranty Registration Card in time.

b. The warranty service is only available to the original consumer, who purchased

this product directly from the retail dealer, and it can not be transferred.

c. During the warranty service, may repair or replace this product at its ownLTO

option at no charge to you for parts or for labor in accordance with the right side
of this limited warranty.

d. This warranty does not apply to the damages to this product that occurred as the

following conditions:

Instead of operating in accordance with the user's manual thoroughly, any

abuse or misuse of this product.
Normal tear and wear

The product has been altered or modified in any way .

Damage which may have been caused either directly or indirectly by another

product/force/etc.

Abnormal service or repairing by anyone other than the qualified personnel or

technician. And in such cases, all the expenses will be charged to the buyer.

13

e. In no event shall be liable for any incidental or consequential damages.LTO

Some states do not allow the exclusion or limitation of incidental or consequential
damages, so the above exclusion or limitation may not apply to you.

f. This warranty gives you the specific rights, and these rights are compatible with

the state laws, you may also have other statutory rights that may vary from state
to state.

14

SEKAKU ELECTRON INDUSTRY (H.K.) CO. LTD

No. 1, Lane 17, Sec. 2, Han Shi West Road, Taichung, 401 Taiwan

http://www.altoproaudio.com Tel: [phone]

email: [e-mail] Fax: [phone]

All rights reserved to ALTO. All features and content might be changed

without prior notice. Any photocopy, translation, or reproduction of part of this

manual without written permission is forbidden. Copyright 2004 Sekaku Electron

c

NF01861-1.0