Preamplifiers · User manual

GP-2000 user manual

Full Feature Audiophile Preamplifier

Thank you for choosing the GP-2000 preamplifier. We appreciate your confidence in us for such an important purchase, and we built it to give you command over the sound your system produces.

Rev A · October 202614 chapters

View the GP-2000

GP-2000 Full Feature Audiophile Preamplifier, front panel

Specifications

As engraved on the unit.

G Pulse Linear · Audio SolutionsModel GP-2000Rev A

Phono response: ±0.25 dB of RIAA
Line response: 3 Hz – 100 kHz
THD: Below 0.1 %
Sensitivity: 3.2 mV phono · 350 mV line
Input impedance: 47 kΩ, RF filtered
Phono loading: 100–250 pF · 56–400 Ω
Output impedance: 100 Ω, XLR and RCA
Hum and noise: 74 dB phono · 88 dB line
Phono gain: Over 56 dB at 1 kHz
Phono overload: 80 mV
Volume tracking: Within 0.5 dB
Maximum output: 10 V RMS
Bass: ±11 to ±13 dB at 20 Hz
Treble: ±10 to ±14 dB at 20 kHz
Dimensions: 19-in rack, 5½ in high
Weight: 6 lb

Phono loading is set by DIP switch: 100, 150, 200 or 250 pF, and 56, 66, 80, 100, 200 or 400 Ω. Hum and noise: phono 74 dB below 10 mV, line 88 dB below 2 V, 20 Hz–20 kHz with the inputs shorted. Bass range depends on the 50 or 150 Hz turnover, treble on the 5 or 2 kHz turnover. Maximum output into a 2 kΩ load; distortion measured with an HP 334A analyzer.

Before you start

Connect first.
Power last.

Four things, in this order, every time you change your system.

Read before switching on

Make every connection before you switch on this unit and the rest of your system.
Never change connections while the system is on. Doing so can damage your equipment.
Always start with the main system volume turned fully counterclockwise, to off. Mishaps happen, so take care.
Attach your turntable's ground wire to the GND post on the GP-2000 and tighten it.

Connections

From the record to your amplifiers.

Main outputs: use either the balanced XLR outputs or the unbalanced RCA outputs. The inputs on the equipment you connect to decide which.

**Turntable**Phono input, or a line source

GP-2000 front panel — **GP-2000**XLR main outputs

Cable runs

Keep RCA cables short. Matched-length XLR cables can run more than 100 ft with no loss of performance. If a ground loop causes hum, move the XLR ground-lift switch up.

Front speakers

Front left and right go to your power amplifier's inputs for normal stereo.

Rear ambience

The rear left and right outputs go to a stereo amplifier driving speakers behind your listening position.

Set-up

Set the controls.

Before you listen, set everything like this.

Volume
Fully counterclockwise before you switch on.
Set to: off
Ambience
Fully counterclockwise. Bring it up slowly later.
Set to: off
Subwoofer level
Fully counterclockwise. A little goes a long way.
Set to: off
Tone controls
All four, bass and treble on both channels.
Set to: centre
Tone switch
Up, to engage the tone controls.
Set to: up
EQ switches
Left and right down, for no low-frequency boost.
Set to: down
Rumble filter
On. It removes the subsonic band that makes woofers flap.
Set to: on

At switch-onThere is a designed-in delay of about three seconds at switch-on, so the power supply and amplifier circuits can settle without turn-on noise. Always wait for the green light before turning up the volume.

Ambience and sound stage with rear speakers

Rear ambience.

The GP-2000 includes an ambience-recovery system that adds realism and sound stage. It recreates natural concert-hall acoustics from the way the material was originally recorded, so results vary from album to album. Mono sources produce no ambience output.

To run four speakers, connect your front speakers' amplifier to the main outputs and your rear speakers' amplifier to the rear ambience outputs.

Start with the ambience level knob fully counterclockwise. Choose your source, then slowly turn the knob clockwise until the rear ambience sounds right to you.

Tone controls and turnover

Tone controls.

Bass and treble can be boosted or cut independently on each channel. The turnover switches move the frequency at which each control starts to act; the exact range at each setting is in the specifications.

Bass turnover: switch down for 50 Hz; switch up for 150 Hz, for a stronger bass boost or cut.
Treble turnover: switch up for 5 kHz; switch down for 2 kHz, to extend the treble control further into the midrange.

Each control at its extreme, as the change it makes against the channel left flat, with the line-level inputs driven. Redrawn from the GP-2000 manual's measurement plot.

Rumble and tonearm-resonance filter

The GP-2000 includes a purpose-built turntable problem solver. A carefully designed notch filter attenuates the narrow band of subsonic frequencies, from 5 Hz to 12 Hz, where most tonearm resonances occur.

This is also the band of turntable rumble that makes woofers flap at random. If that subsonic energy is loud enough to start acoustic feedback, it can damage your speakers.

The filter was modelled in P-Spice, then built with custom-made toroidal inductors resonated with very high-quality, near-zero-leakage film capacitors. It is essentially transparent to the preamplifier's accurate RIAA response.

Take careWith the filter switched off, the response is flat down to 3 Hz. It can be thunderous, so take care.

Signal-to-noise ratio, phono input to line output, with the rumble filter on and off. The P-Spice simulation with the filter on matches the measured "filter on" curve to within 0.3 dB. Redrawn from the GP-2000 manual's measurement plot.

Operation

Subwoofer level and phase

Start with the subwoofer level fully off and bring it up slowly. Once set, it tracks the main volume control.

Use it sparingly: you do not want the room to sound boomy, and a little goes a long way towards rounding out the deep bass you hear and feel.

Try the 0° / 180° phase switch to match the subwoofer's bass arrival to your listening position.

Operation

Cartridge gain and loading

Start with every DIP switch down for a typical moving-magnet cartridge.

For more gain, begin with the top-left gain DIP switches, which raise the gain in 2 dB steps on each channel.

For a moving-coil cartridge, set the gain to high, then set the loading resistance and capacitance to the cartridge manufacturer's recommendations.

Take careChange these switches only with the volume fully counterclockwise, to avoid loud switching noise.

Operation

Source and loop switches

Phono / Line source switch: selects the phono preamplifier input or the line-level input. Turn the volume fully counterclockwise before switching.
Loop switch: brings in the external loop, so you can add other stereo components. Turn the volume fully counterclockwise before switching.

Be careful with your controls: you have more control over the sound than most preamplifiers provide.

Troubleshooting

Tuning the sound to your room.

Start with the subwoofer level fully counterclockwise, to off. Some of what you hear may come from your room's acoustics.

Boomy bass
Set the bass turnover to 150 Hz and turn both bass controls counterclockwise until the low end tightens.
Too much midrange
Set the treble turnover to 2 kHz and turn both treble controls counterclockwise to balance the midrange against the bass.
Lacking highs
Set the treble turnover to 5 kHz and turn both treble controls clockwise to bring out high-frequency detail.

Design notes

How it was built.

3: Active stages per channel, for the lowest noise, propagation delay and phase shift.
±0.25 dB: RIAA accuracy, phono input to line output.
56 dB+: Phono gain at 1 kHz, adjustable by DIP switch in 2 dB steps.

Design goals

The lowest distortion achievable.
A very accurate RIAA curve for vinyl.
Fully separate left and right controls for everything.
Delayed start-up to eliminate turn-on noise.
Sealed, replaceable relays for signal switching.
No noisy slide switches that wear out.
RF filtering, so no cell tower, CB or ham radio signal can enter the preamplifier.
True, fully balanced XLR connections as standard.
A ground-lift switch on the XLR output shields, as best practice recommends, to avoid ground loops and hum.
A 19-inch rack chassis with chrome handles.
Light weight: there is no heavy 60 Hz toroidal input transformer. A 65 kHz AC-to-DC switcher is better and far easier to filter, and linear regulators after it give the quietest possible supply.

Circuit and components

Only three active stages per channel, for the lowest noise, propagation delay, phase shift and group delay.
Every amplifier chip is a Texas Instruments SoundPlus device rated at less than 0.00003 % total harmonic distortion.
Every active and passive component in the signal path was modelled.
All capacitors are high-quality film types or special non-polarised, audio-grade high-value types.
All resistors are 1 % precision, industrial grade.
Every device is derated by more than 200 % in power dissipation, for very high reliability.

Measurements

Measured and simulated.

The engineering work behind the design, as live charts. Move across one, or focus it and use the arrow keys, to read exact values.

Total RIAA response, phono input to the last output stage. Accuracy within ±0.20 dB. Shown relative to the 1 kHz level.

Group delay: Phono input to XLR output: essentially zero out to 100 kHz, and 0.008 s at 20 Hz, referenced to 1 kHz.

Redrawn from the engineering plots in the GP-2000 user manual (Rev A · October 2026). Each point is traced from the original measurement image.

MaintenanceCare

Cleaning. Use a damp cloth only, never glass cleaners or alcohol-based products.
Surge protection. Put a surge protector on the power line, against a nearby lightning strike or a line-level overload.

Questions about your GP-2000?

Talk it through with us.

Tell us what is in your system and what you want it to do. We answer set-up questions before and after you buy.

G Pulse Linear Audio Solutions

GP-2000

Full Feature Audiophile Preamplifier

User Manual · Rev A · October 2026

Thank you for choosing the GP-2000 preamplifier. We appreciate your confidence in us for such an important purchase, and we built it to give you command over the sound your system produces.

1. Before you start

Read these instructions before you switch anything on.

Make every connection before you switch on this unit and the rest of your system.
Never change connections while the system is on. Doing so can damage your equipment.
Always start with the main system volume turned fully counterclockwise, to off. Mishaps happen, so take care.
Attach your turntable's ground wire to the GND post on the GP-2000 and tighten it.

2. Specifications

Frequency response	Phono: ±0.25 dB of the RIAA standard to line output, with tone controls off or centred and all filters off. Line-level path: 3 Hz to 100 kHz.
Total harmonic distortion	Less than 0.1 % at rated output, measured with an HP 334A distortion analyzer
Input sensitivity	Line: 350 mV · Phono: 3.2 mV
Line input impedance	47 kΩ, 100 pF, RF filtered above 1 MHz
Phono input impedance	47 kΩ, RF filtered. Capacitive loading 100, 150, 200 or 250 pF; resistive loading 56, 66, 80, 100, 200 or 400 Ω, set by DIP switch. An internal relay shorts the phono input to ground while the line input is in use.
Output impedance	XLR balanced: 100 Ω source, with shield ground-lift switch · RCA unbalanced: 100 Ω source
Hum and noise	Line: 88 dB below 2 V · Phono: 74 dB below a 10 mV input (20 Hz–20 kHz, inputs shorted)
Ambience signal	(L − R) to the left rear output and (R − L) to the right rear output
Phono gain	More than 56 dB at 1 kHz, adjustable by DIP switch in 2 dB steps, with options
Volume control tracking	Less than 0.5 dB tracking error
Phono overload	80 mV
Maximum output	10 V RMS into a 2 kΩ load
Tone controls	A rotary bass and treble control for each channel, with switchable turnover frequencies
Bass	50 Hz turnover: ±11 dB at 20 Hz · 150 Hz turnover: ±13 dB at 20 Hz
Treble	5 kHz turnover: ±10 dB at 20 kHz · 2 kHz turnover: ±14 dB at 20 kHz
Dimensions	5½" H × 19" W × 6" D, 19-inch rack mount
Weight	6 lb

3. Connections

Main outputs: use either the balanced XLR outputs or the unbalanced RCA outputs. The inputs on the equipment you connect to decide which.

Keep RCA cables as short as practical to avoid noise and signal loss. XLR cables should be the same length and can run more than 100 ft with no loss of performance. If a ground loop causes hum, move the XLR ground-lift switch up.

Front left and right: connect to your power amplifier's inputs for normal stereo.

Rear left and right (ambience outputs): connect to the inputs of a stereo amplifier driving speakers placed behind your listening position.

4. Setting the controls

Before you listen, set the controls as follows.

Volume fully counterclockwise, to off.
Ambience fully counterclockwise, to off.
Subwoofer level fully counterclockwise, to off.
All tone controls centred.
Tone switch up, to engage the tone controls.
Left and right EQ switches down, for no low-frequency boost.
Rumble filter switch on.

At switch-on: There is a designed-in delay of about three seconds at switch-on, so the power supply and amplifier circuits can settle without turn-on noise. Always wait for the green light before turning up the volume.

5. Ambience and sound stage with rear speakers

To run four speakers, connect your front speakers' amplifier to the main outputs and your rear speakers' amplifier to the rear ambience outputs.

Start with the ambience level knob fully counterclockwise. Choose your source, then slowly turn the knob clockwise until the rear ambience sounds right to you.

6. Tone controls and turnover

Bass turnover: switch down for 50 Hz; switch up for 150 Hz, for a stronger bass boost or cut.
Treble turnover: switch up for 5 kHz; switch down for 2 kHz, to extend the treble control further into the midrange.

7. Rumble and tonearm-resonance filter

This is also the band of turntable rumble that makes woofers flap at random. If that subsonic energy is loud enough to start acoustic feedback, it can damage your speakers.

Caution: With the filter switched off, the response is flat down to 3 Hz. It can be thunderous, so take care.

8. Subwoofer level and phase

Start with the subwoofer level fully off and bring it up slowly. Once set, it tracks the main volume control.

Use it sparingly: you do not want the room to sound boomy, and a little goes a long way towards rounding out the deep bass you hear and feel.

Try the 0° / 180° phase switch to match the subwoofer's bass arrival to your listening position.

9. Cartridge gain and loading

Start with every DIP switch down for a typical moving-magnet cartridge.

For more gain, begin with the top-left gain DIP switches, which raise the gain in 2 dB steps on each channel.

For a moving-coil cartridge, set the gain to high, then set the loading resistance and capacitance to the cartridge manufacturer's recommendations.

Caution: Change these switches only with the volume fully counterclockwise, to avoid loud switching noise.

10. Source and loop switches

Phono / Line source switch: selects the phono preamplifier input or the line-level input. Turn the volume fully counterclockwise before switching.
Loop switch: brings in the external loop, so you can add other stereo components. Turn the volume fully counterclockwise before switching.

Be careful with your controls: you have more control over the sound than most preamplifiers provide.

11. Troubleshooting

Start with the subwoofer level fully counterclockwise, to off. Some of what you hear may come from your room's acoustics.

Boomy bass: Set the bass turnover to 150 Hz and turn both bass controls counterclockwise until the low end tightens.
Too much midrange: Set the treble turnover to 2 kHz and turn both treble controls counterclockwise to balance the midrange against the bass.
Lacking highs: Set the treble turnover to 5 kHz and turn both treble controls clockwise to bring out high-frequency detail.

12. Design notes

Design goals

The lowest distortion achievable.
A very accurate RIAA curve for vinyl.
Fully separate left and right controls for everything.
Delayed start-up to eliminate turn-on noise.
Sealed, replaceable relays for signal switching.
No noisy slide switches that wear out.
RF filtering, so no cell tower, CB or ham radio signal can enter the preamplifier.
True, fully balanced XLR connections as standard.
A ground-lift switch on the XLR output shields, as best practice recommends, to avoid ground loops and hum.
A 19-inch rack chassis with chrome handles.
Light weight: there is no heavy 60 Hz toroidal input transformer. A 65 kHz AC-to-DC switcher is better and far easier to filter, and linear regulators after it give the quietest possible supply.

Circuit and components

Only three active stages per channel, for the lowest noise, propagation delay, phase shift and group delay.
Every amplifier chip is a Texas Instruments SoundPlus device rated at less than 0.00003 % total harmonic distortion.
Every active and passive component in the signal path was modelled.
All capacitors are high-quality film types or special non-polarised, audio-grade high-value types.
All resistors are 1 % precision, industrial grade.
Every device is derated by more than 200 % in power dissipation, for very high reliability.

13. Measurements

These views show some of the initial engineering and simulation work behind the design. The design goals were met with great satisfaction, and we hope you agree. Tone-control plots show both channels: one set flat with the EQ switch off, the other adjusted for comparison, with the line-level inputs driven.

Figure 1. Total RIAA response, phono input to the last output stage. Accuracy within ±0.20 dB. Shown relative to the 1 kHz level.

Figure 2. Signal-to-noise ratio, phono input to line output, with the rumble filter on and off. The P-Spice simulation with the filter on matches the measured "filter on" curve to within 0.3 dB. Solid line: rumble filter on. Dashed line: rumble filter off.

Figure 3. Tone controls. Each control at its extreme, as the change it makes against the channel left flat, with the line-level inputs driven. Solid lines: bass fully clockwise and counterclockwise. Dashed lines: treble fully clockwise and counterclockwise. Dotted line: low EQ switch on.

Group delay: Phono input to XLR output: essentially zero out to 100 kHz, and 0.008 s at 20 Hz, referenced to 1 kHz.

Charts redrawn from the engineering plots in the original GP-2000 manual.

14. Care

Clean the GP-2000 with a damp cloth only. Do not use glass cleaners or alcohol-based products.
Use a transient (surge) protection device on the power line, to protect the unit from a nearby lightning strike or a line-level overload.

GP-2000 user manual

As engraved on the unit.

Connect first.Power last.

From the record to your amplifiers.

Cable runs

Front speakers

Rear ambience

Set the controls.

Volume

Ambience

Subwoofer level

Tone controls

Tone switch

EQ switches

Rumble filter

Rear ambience.

Tone controls.

The rumble filter.

Subwoofer level and phase

Cartridge gain and loading

Source and loop switches

Tuning the sound to your room.

Boomy bass

Too much midrange

Lacking highs

How it was built.

Design goals

Circuit and components

Measured and simulated.

MaintenanceCare

Talk it through with us.

Connect first.
Power last.