sound engineering
STEREO SUMMING AMPLIFIER
down-mixing with tubes
SSA 2A
The SSA 2A is the sound solution to the bottleneck problems arising when down-mixing digital
recordings on DAW’s. Our 8 stereo + 4 mono -> 2 channel down-mixing unit directly targets the
critical mastering process. Sonically it easily outperforms the quality of digital audio
workstations and even betters the performance of mixing amplifiers built into the most high-end
analogue consoles.
Product Description
The TUBE-TECH SSA 2A Stereo Summing Amplifier
features two very low noise / low distortion summing
amplifiers with a very wide frequency response.
The inputs are transformer balanced and the circuits
are symmetrical from input to output. The inputs are
capable of handling extremely high input levels.
The Outputs are balanced and have fully floating
transformers with a static screen.
The power supply is based on a solid-state circuit.
With the exception of the output stage all DC voltages
are stabilised.
Product Features
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8 stereo+4 mono inputs - 1 stereo output
23-step gold plated output gain control
Master Output Gain: -10 dB to +10 dB
Fully symmetrical circuitry from input to output
Zero field transformer balanced inputs
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Maximum input > +30 dBu
Low noise: < -85 dBu @ all inputs terminated
Two large VU meters showing output level
Frequency response 5 Hz – 100 kHz
Distortion < 0,05 %
SSA 2A technical specifications
Impedance
Input:
Output:
50 kohm
< - 60 ohm
Frequency response @ -3 dB:
Max. output:
Max input:
dBu
dBu
dBu
dBu
< 0,05 %
< 0,05 %
1%
1%
Noise Rg=200 ohm
Output Gain @
0dB
+10 dB
Inputs used
1
4+8
1
4+8
22Hz-22kHz:
< -90 < -85 < -80 < -75 dBu
CCIR-468-4:
< -80 < -75 < -70 < -65 dBu
CMRR @ 10 kHz:
Gain:
0,5dB steps
1 dB steps:
2 dB steps:
2 pcs.
2 pcs.
4 pcs.
5 Hz to 100 kHz
Distortion THD+N @ 40 Hz
0
+10
>+26
>+30
Tubes
ECC 82
ECC 83
ECC 88
Dimensions
Height: 2 units
Width:
Depth:
88 mm
483 mm
205 mm
3,5"
19,0"
8,1"
5,4 kg
6,5 kg
11,9 lbs.
14,3 lbs.
Weight
Net:
Shipping:
Power requirements
@ 115 V/230 V, 50-60 Hz:
< -60 dB
+/- 0-3 dB
+/- 3-6 dB
+/- 6-10 dB
Gain tracking
Between channels
< 0,1 dB
Notes
All specifications @ RL=600 ohm
Lydkraft reserves the right to alter
specifications without prior notice
Crosstalk @ 10 kHz:
< -70 dB
Dealer
LYDKRAFT
40-55 W
Mose Allé 20 • 2610 Rødovre • Denmark • T +45 3871 0021 • F +45 3879 0091 • www.tube-tech.com
TUBE-TECH SSA 2A
Stereo summing amplifier
Description:
The TUBE-TECH Stereo summing amplifier SSA 2A is aimed for use where extreme high
quality summing of several signals into two channels is the target.
It has 4 mono input (hard wired to CH1 and CH2) and 8 stereo inputs, which is summed
together into two outputs.
The SSA 2A consists of a summing amplifier at the input, a 23 stepped attenuator with a
range of +/- 10 dB and an output stage.
Two large VU-meters show the levels on the XLR output sockets.
To avoid the distortion introduced by the VU-meters when connected directly to the output
XLR sockets, symmetrical configured OP- amps buffer the VU-meters.
The summing amplifier is a symmetrical two-stage amplifier, designed around two dual, low
impedance, and high transconductance triodes. The input transformer is part of the dual
feedback configured as a so-called zero field transformer.
The attenuator is a heavy gilded 2x23 position switch with steps of +/- 0.5, 1, 1.5, 2, 2.5, 3, 4,
5, 6, 8, 10 dB.
The output stage is designed around two dual triodes in push-pull and an output transformer
(with a static screen).
Both the summing amplifiers and the output amplifiers are symmetrical.
Summing-amplifier:
All inputs are balanced by two zero field transformers (one for each channel).
What is zero field transformer?
In the zero field transformer configurations, the transformer is part of the feedback circuit.
There are several benefits for this:
1. The voltage across the transformer is reduced substantially whereby a much
smaller transformer is needed for the same specification.
The reduction is of the same magnitude as the feedback applied.
2. The distortion at low frequencies is reduced substantially.
2. Frequency response in both the low and high range is extended.
3. Phase response in both the low and high range, is also reduced
(050320)
Lydkraft ApS
Mose Allé 20, DK2610 Rødovre
Denmark
1
To avoid a reduction of the crosstalk between the channels, it is important that all four mono
inputs are terminated, either with a shorting plug or by a signal source.
2
Lydkraft ApS
Mose Allé 20, DK2610 Rødovre
Denmark
ADJUSTMENT PROCEDURE:
CAUTION:
Before making any adjustment let the unit heat-up at least 10 min.
Always check the DC voltages at the power supply.
1) The DC voltage in TP201 shall be +280V (265-295V).
2) The DC voltage in TP202 shall be +240V (238-242V).
3) The DC voltage in TP203 shall be +15,0V (14,7-15,3V).
4) The DC voltage in TP204 shall be -15,0V (14,7-15,3V).
5) The DC voltage in TP205 (across C211) shall be +12,0V (11,5-12,5V)
6) The DC voltage in TP206 shall be +238V (236,5-239,5V)
ADJUSTMENT OF PSU:
1) The DC voltage in TP202 shall be +240V.
Adjust with P202.
ADJUSTMENT OF BASIC GAIN:
1) Set the “OUTPUTGAI
N”on “
0”.
2) Apply a signal of 1 kHz, 0,0 dBU to the input, either one mono or two stereo (one for
each channel).
3) Adj
ustt
hepr
eset“
Gai
n”P1 (P101) (on amp/psu PCB) to an output
reading of 0,0 dBU
(041124)
Lydkraft ApS
Mose Allé 20, DK2610 Rødovre
Denmark
3