JMK Mic Pres have features not found on most other mic pres:
Very high Input headroom: for a very wide Dynamic range, over 131dB for the JM-130, >128dB for the JM-530.
The Pad is on the output this has several advantages
- The pad does not affect the loading and sound on the mic
- Since there is no DC voltage going thru the switch (Phantom) like most mic pre pad circuits, there is NO pop when the switch is engaged.
- Being on the output allows the output transformer to be driven harder for a warmer sound.
- The Phantom switch: the phantom voltage ramps up to reduce the pop when powering a Condenser mic.
All switches on both the are the large Gold plated switch to provide very long life and improve the clarity of the signal path, and greatly reduce the probability of noise and static.
- Jensen JT-16B Input Transformer
- Operates at + & – 24 Volt for very high headroom & Dynamic Range
- Input Impedance: 1.6K @ 1Khz
- Output Transformer Option: Nickel or Steel
- Hand wired point to point
- THD+N: .006% @50dB Gain @ 1Khz
- .025% @-5dB In @ 50Hz
- .044% @ +5dB In @ 50Hz
- .0125% @ 0dB Input @ 100 Hz
- .025% @ +10dB Input @100Hz
- .007% @-10dB Input @15Khz
- 990 Op Amp Slew Rate: 18Vus @ 150 Ohm Load
- Frequency response: +- 1dB 10hz to 170khz ; +-.25dB 10 to 50Khz
- Max Gain: -3dB @174Khz.
- 990 Op Amp Only: +-1dB 5Hz to 500Khz
- Output clips at +35dBu
- Crosstalk: @20Khz below noise floor
- CMRR: 117dB @ 60Hz, 85dB @ 3Khz
- E.I.N. Noise: -128.5dB w/ 20 to 20kHz filter w/150 ohm load @62dB Gain
- -127dB W/20 to 20KHz Filter W/300 ohm load @62dB Gain
- Dynamic Range: >131dB; 20 to 20KHz filter w/150 ohm load min gain
- > 105dB; 20 to 20KHz filter w/150 ohm load max gain
- Maximum Input: +12dBu
- Gain: 62dB
- Hand selected .1% Phantom Resistors
- Superior grounding technique
- All Gold Input/Output Connectors
- Pad: 12dB on output, enabling the output transformer to be driven harder.
- Phantom switching: voltage ramps up to reduce popping with condenser mics.
- Laser Engraved lettering, letters will not wear off.
- Note: 20 to 20 kHz filter used; -10dB @ 38 Hz & 32 KHz, -20dB @ 90 KHz
Far wider than the typical Brick wall filter, which is -20dB @36Khz
JM-P130 Power Supply
The JM-P130 has been refined and upgraded to help even further from being as immune as
Possible from any noise, ticks, pops, spikes & surges on the AC Line as we can..
Components are over sized from 5 to 12 times normal, to allow for surges & spikes with no damage.
So the DC power is very clean and stable.
We oversized ground wires & ground bus to have a very low impedance.
We also incorporate several techniques we have not seen on any other power supply..
The traces on the PCB are extremely low impedance..
We also recommend a isolated AC circuit with very good quality AC outlets for all audio gear.
There is more noise on the AC line today than ever.