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This is a custom Built 1176 Rev A. The main board is the mnats. The beauty of this unit is that it has the UTC a20 transformers, which is an common updated done to vintage 1176s, and it also has the extremely rare and original UREI transformer that all original 1176s Pre Rev F have. The transformer can also be found in 1108 UA vintage preamps. The input knobs is also an original UERi knob to make sure the threshold compression would be accurate. This is an incredible opportunity to own an 1176 blue stripe with original parts, for a fraction of price. It was serviced by vintage king in 2013, before we added the original transformers.
An original REV A. Costs more than 8k, and it carries lots of collective value, he you have the sound without having to pay for the extra gold.
1. circuit board components revised to conform to 1176 version A, sn 125-216. larger heatsink installed on output transistor.
2. power transformer re-located to side panel.
3. attack control replaced with original type including limiting off-on switch.
4. VU meter lamps replaced. original type pilot lamp installed.
5. UTC A-20 input transformer installed, wired 500:200. 300 ohm A-B audio taper input control installed.
6. 250k A-B output control installed.
7. ratio switch board resistors revised to conform to 1176 version A.
8. output transformer from UA 1108 installed on rear panel.
9. all wiring replaced. grounding revised per text-book. single point to chassis at input XLR (no pin 1 problem).
10. rear panel power switch wired in series with front panel interlocking power/metering switch.
11. unit calibrated. meter tracking set at -6 VU.
Checkout Test Conditions
600 ohms source Z
600 ohms load Z
117 VAC 60 Hz
unless otherwise stated, -10 dBu input
input set at threshold of limiting, limiting switched off
20:1 when limiting
AC leakage to chassis 2.5 uA
Input Impedance: 950 ohms
Maximum Gain: 49.1 dB
Minimum Level for 1 dB of limiting: -27 dBm
Minimum Level for 10 dB of limiting: -17 dBm
Amount of Limiting with +4 dBu input: greater than 20 dB
Un-weighted Noise: -45 dBm (level controls CW)
Weighted (400 Hz and 30 kHz filters) Noise: -50.5 dBm (level controls CW)
Weighted (400 Hz and 30 kHz filters) Noise: -86 dBm (level controls CCW)
Total Harmonic Distortion @ +4 dBm (10 dBm input)
100 Hz: .08 %
1000 Hz: .07 %
10 kHz: .3 %
Total Harmonic Distortion @ +4 dBm (+4 dBm input)
100 Hz: .1 %
1000 Hz: .095 %
10 kHz: .35 %
Total Harmonic Distortion@ +4 dBm, 3 dB limiting
1000 Hz: .28 %
Maximum Output, 1000 Hz:
600 ohm load: +24 dBm @ 0.15 % THD
bridging load: +26 dBu @ 0.15 % THD
Frequency Response @ +4 dBm output
10 Hz: +1.1 dB
20 Hz: +0.3 dB
100 Hz: +0.1 dB
1000 Hz: 0 dB (reference)
10 kHz: -0.2 dB
20 kHz: -0.7 dB
30 kHz: -1.4 dB
Frequency Response @ +4 dBu output (unterminated)
10 Hz: +1.6 dB
20 Hz: +0.4 dB
100 Hz: +0.05 dB
1000 Hz: 0 dB (output rises 1.4 dB relative to terminated condition)
10 kHz: -0.2 dB
20 kHz: -0.4 dB
30 kHz: -0.8 dB
this 1176 does NOT require a 600 terminating resistor.
Phase Integrity
Input XLR pin 3 in phase with Output XLR pin 3
Input XLR pin 2 in phase with Output XLR pin 2