GHR Audio

Sidechain
viewtopic.php?t=16

GR Meter
viewtopic.php?t=15

Power Supply
viewtopic.php?t=14

Main Board
viewtopic.php?t=13

Assembly
viewtopic.php?t=19

Testing
viewtopic.php?t=20

Front Panel
viewtopic.php?t=21

-
GroupDiy thread for the build
https://groupdiy.com/threads/transforme ... ead.78043/

Schematics

Main Board -

Sidechain -

Rotary Sidechain -

Power Supply -

GR Meter -

Compression Curves and THD @ 1kHz
-
Output noise at max gain (19 dB), 0 dBFS = +20 dBu
-

Specifications:

Input impedance ≈ 12k ohms, balanced line-to-line, *

THD < 0.25%, +20 dBu, 20-20 kHz, unity gain, no compression, **

S/N = 80 dB re +4 dBu, 22 kHz BW, unity gain, ***

Crosstalk = -60 dB, 20kHz, +4 dBu, channel-to-channel

Frequency response = 20 - 20 kHz, ±0.5 dB

Maximum gain = 17 dB or 19 dB, ****

Output impedance < 300 ohms, balanced line-to-line

* INA2137 Internal resistors are ratio matched but have ±25% absolute value

** Will heavily depend on the tubes used

*** Should be better than 80 dB unless the tubes are very noisy

**** Will depend on the tubes used and plate resistor value used. 19 dB with 5.5k plate resistors, 17 dB with 4.99k plate resistors

If the output is connected to unbalanced input do NOT ground xlr pin 3. For unbalanced connections output XLR pin 3 should be left floating, this will result 6dB loss of output level.

Mastering modifications