IGS Audio DTL User manual

DTL
USER'S MANUAL
IGS Audio Igor Sobczyk
3 Maja 76d, 1- 00 Mysłowice, Poland
e-mail: [email protected] ph: + 8 601 597 592
www.igsaudio.com

Please read all of the following instructions and save them
for later reference before attempting to connect the unit to the mains.
EARTH
This unit is connected via its power cord to the mains safety earth.
NEVER OPERATE THE UNIT WITH THIS EARTH CONNECTION REMOVED.
COVERS
DO NOT remove the covers. Refer servicing to qualified personnel only.
VOLTAGE
Equipment is set to operate only at the voltage indicated on the back of the unit.
CHECK that the correct voltage is selected before connecting the AC mains supply.
FUSES
CHECK that the fuse fitted is the correct type for the local mains voltage.
ALWAYS replace fuse with the correct type.
MOISTURE
DO NOT expose the unit to rain or moisture. If the unit
should become so exposed REMOVE the mains power immediately.
CABLES
PROTECT the mains power cord from damage though impact or abrasion.
HEAT
ALWAYS site the unit away from sources of heat including direct sunlight and ensure
adequate ventilation around the unit.
Copyright 201 . All rights reserved.
The information in this document is subject to change without notice.
IGS Audio makes no warranty of any kind with respect to the material in this document
and shall not be liable for errors contained herein or for incidental or consequential
damages related to the use of the material.
Manual revision: 1.0 (December 201 )

Thank you for buying this IGS Audio product.
Please read the information provided below very carefully before using your IGS unit.
Unpacking
Your DTL has been carefully and meticulously tested and inspected before dispatch. Please
chec for any signs of transit damage. If any signs of mishandling are found please notify the
carrier and your dealer immediately.
Your DTL pac ing should contain an DTL with IGS Audio tag and power cord and this manual
with the Warranty and RoHS/CE/WEEE Declaration attached.
Compatibility and Power
There is a fuse soc et near the power cable connector on the on the bac of the unit. Ensure
that the correct fuse is being used before plugging the DTL to the power outlet.
➔For US area (115V) use 2A Slow Blow (Type T).
➔For Europe and rest of the world area (230V) use 1A Slow Blow (Type T).
Always check the voltage selector on the back of the unit to ensure that it is set to the
proper voltage available in your country.

IGS AUDIO DTL – dual microphone tube preamplifier
The Double Triode Limiter (DTL) is an expanded version of the Double Triode microphone
preamp.
The design was upgraded with a opto-limiter. The limiter is based on classic solutions used in
the 60’s and 70’s. The component in charge of compression is a IGS Audio custom designed
photocell. It consists of a electroluminescent panel and a photo resistor. This panel illuminates
the photo resistor that attenuates audio signal. Wor ing of the limiter is indicated by a LED
labeled “Limit” on the front panel.
Audio path of the preamp is a two stage tube amplifier with individual drive of both steps. The
saturation at the first step depends on the input signal level (with possibility to use Pad -20dB).
The saturation of the second step is dependent on the Output regulator. Inputs and outputs are
balanced with Sowter and Edcor (USA) transformers. The anode voltage is set close to 300V
DC.
For each of the channels Output and Limiter threshold can be regulated smoothly. The featured
switches are: GAIN, +48V, Mic/HiZ, Phase, Pad -20dB. Hi-Z inputs are located on the front
panel. The meters show output signal level.
Usage:
The DTL is a typical tube microphone preamp. It is adapted to wor with any type of
microphone. A wide range of amplification ma es it possible to record drums as well as the
quietest ribbon microphone. The Pad -20dB ma es it possible to wor with line signals as well.
In this case the DTL does a great job of recording trac s from external devices such as
synthesizers or drums machines (li e A ai MPC). Great results are achieved with reamping
trac s from DAWs. The DTL adds a nice tube saturation to the sound. The high impendence
inputs (HiZ) allow connecting a electric or bass guitar directly into the grid of the first step of
amplification (Typical HiZ solution).
Additional device capabilities are activated by the Limiter section. This can be used to limit pea
levels of the input signal. The wide range of Limiter settings goes from slight compression to
hard limiting. This is especially useful in vocal recording where the wide range of signal
dynamics is controlled. The limiter controls the louder parts and prevents from the digital
clipping at the inputs of you ADC. Another tric could be using the DTL as a drum compressor or
mix buss compressor. It can improve the overall dynamics of the mix and give it a brighter
sound. This is a very versatile device for audio processing.
Block diagram

VU METER Big VU meter showing the level of output signal.
GAIN KNOB Preamplifier gain setting.
LIMITER Allows to adjust the amount of limiting applied to the signal.
HIZ INPUT High impedance guitar input.
INPUT SELECTOR Choose between microphone or Hi-Z input
PAD and PHASE PAD switch allows to attenuate the microphone input by 20 dB.
PHASE switch simply flips the signal phase.
OUTPUT Output signal level.
LIMITER
INDICATOR
LED glows when the limiter is wor ing.
VU METER
LIMITER INDICATOR
HiZ INPUT
GAIN KNOB
LIMITER
OUTPUT
INPUT
SELECTOR
PAD &
PHASE

DTL technical specification:
–Inputs: 2 Mic/Line XLR and 2 Hi-Z Jac s on the
front
–Outputs: 2 balanced XLR
–Tube Only audio path
–Meters read Output VU
–Soft Start Power Tube Timer
Operating Level +4dBu
Maximum Output +22dBu
Input impedance 300 ohm (MIC), 1Mohm (Hi-Z)
Output Impedance 600 ohm
Tubes Used 6N1P-EW, 6N2P-EW
Max Gain Reduction 18 dB
Max Gain 60 dB
Frequency response 20Hz - 20 Hz
THD+N @0dBu 80 dB (A)
Power consumption 40 W
Shipping weight 7 g
Dimensions 19" 2U, 230mm deep

Troubleshooting
My unit doesn't light up (the VU meter is dark):
–Please chec the power cord and the switch at the front of the unit is in ON position
–Chec the fuses
The signal plays thru when i plug a microphone in:
–Please chec the input selector switch
–Please chec the +48 switch (if you are using condenser microphone)
–Please chec the gain and output nob
No signal plays thru the unit, regardless the settings at the front panel:
–Please chec the cables connecting the rac .
Limiter doesn't work:
–Please turn the Limiter nob to adjust the limiter threshold

Warranty:
This device is declared to be free from defects in material and workmanship for a period
of three years. Any device found defective within three years from the delivery date and
returned to the factory, will be repaired, adjusted, or replaced and sent to the customer
with no charge. The customer always pays the shipping cost to us. This warranty does
not cover expendable items such as tubes or fuses. If the defect has been caused by a
misuse or abnormal operation conditions, the repair will be billed at a nominal cost. The
product should be returned in its original package, if this is possible, or packed in such a
way that it is not damaged during the shipment. We are not to be held responsible for
any damages during the shipment. 19" units shall always be packed in a box with
support for the rack ears. All 500 series modules need to be secured in ESD bag and
protected with foam. We will charge the customer €20 + VAT if the packing material needs
to be replaced. If we find that the product works perfectly, the customer will be invoiced
€50 + VAT to cover our costs of examination and handling plus the cost for returning the
product to the customer.
www.igsaudio.com