1 – Read and keep these instructions.
2 – Heed all warnings and follow all instructions.
3 – WARNING: To prevent fire or electric shock, do not expose this equipment to rain or moisture. Do not use this apparatus near water.
4 – Clean only with a dry cloth.
5 – WARNING: To prevent excessive temperature rise, operate product only in free air with unrestricted ventilation. Do not install in confined spaces or near heat sources such as radiators, heat registers, stoves, or other apparatus that produce heat.
6 – Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other. A grounding type plug has two blades and a grounding prong. The wide blade or third prong are provided for your safety. If the provided plug does not fit your outlet, consult an electrician for the replacement of the obsolete outlet.
7 – Protect the power cord from being walked on or pinched, particularly plugs, convenience receptacles, and the point where they exit from the apparatus.
8 – Unplug the apparatus during lightning storms or when unused for long periods of time.
9 – The appliance coupler (or attachment plug) is the mains disconnect device and should remain readily accessible when amplifier is in use.
10 – Refer all servicing to qualified service personnel. Servicing is required when the apparatus has been damaged in any way, such as power-supply cord or plug is damaged, liquid has been spilled or objects have fallen into the apparatus, the apparatus has been exposed to rain or moisture, does not operate normally, or has been dropped.
11 – This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.
12 – Changes or modifications made by the user that are not expressly approved by the manufacturer may void your authority to operate the amplifier.
The Bass Block V803 provides exceptional power and tonal versatility, combining for the first time the power of modern Class-D amplification with the warmth of vintage tube amps. The proprietary Quilter Labs power section provides over 800W for full performance from any speaker, with a quiet, variable-speed fan for heavy duty use. A 3 band EQ with sweepable midrange provides “pinpoint” control of bass tone. A three position Voice switch selects “MODERN” “WARM” and “QTUBE” offering three distinct amplifier modes. In addition, flat and “scooped” inputs, FX Loop, headphone and XLR Line Out with integral cab-sim and grounding switch round out the feature set.
The GAIN control regulates drive and sensitivity. Four ACTIVE EQ controls, TREBLE, MIDRANGE with sweepable FREQUENCY, and BASS regulate key frequencies for expanded bass voicings. The MASTER controls the overall peak power delivered to the speaker, to match any size and speaker rating.
Below the controls, an expanded jack bay provides full system connectivity. Dual high impedance INPUTS, Flat and Scoop, provide two “starting points” for setting up your tone. The FX LOOP Send and Return jacks support easy insertion of modulator effects as well as a tuner, and the FX Return can be used as a “stealth input” for backing tracks. The HEADPHONE output has automatic Cab-Sim on the WARM and Q-TUBE positions, with volume controlled by the Master.
On the left side, the MUTE-ACTIVE-PASSIVE switch is located well to the side to avoid accidental adjustments, with a bright red LED signaling the Mute condition. Above this switch is our exclusive three position VOICE selector. MODERN duplicates the performance of the Bass Block 802, combining our “bottomless” limiter system with a “solid state” amp output for tight speaker control. The WARM position uses the same limiter system but converts the amp to a tube-like output impedance, letting the speakers “loosen up” for lush old-school response. The Q-TUBE position replaces the limiter system with a tube-like clipping stage, providing the snap and overdrive associated with vintage high power tube amps.
On the right, the AC POWER LED also acts as a thermal warning light, “winking” if the amplifier is limiting power due to thermal overload. The XLR grounding switch provides three positions to minimize ground loops in different venues.
The rear panel provides dual SPEAKON™ COMBO connectors, for compatibility with all popular bass cabinets. The XLR LINE OUT is “preMaster” for fixed signal level. A LOCKING AC CORD ensures uninterrupted service. Please consult this manual for further details on these features, to obtain the best results.
Quilter Labs uses the latest high-current Class-D power technology to maximize warmth and dynamics without the weight and drawbacks of traditional technology. We receive advice from musicians far and wide, but our constant goal is to make products that we ourselves are proud to use. The result is a serious professional tool with performance that meets or beats handmade amps costing several times as much.
We hope you enjoy your new amplifier. May it give you many years of flawless service and provide a source of inspiration and creativity.
This setting duplicates the performance of the Bass Block 802, Our exclusive dual limiter prevents lower strings from bottoming out, even on high BASS settings, without choking or gagging the upper strings. Dynamic range is optimized, with a feeling of “grunt” or “effort” replacing the usual breakup at peak power. The power amp is “tight” with a high damping factor that keeps the speakers under control. Power delivery depends on speaker impedance, with up to 450W into 8 ohms and over 800W into 4 ohms.
The Modern setting works well for clean “bottomless” bass tone especially with 2-way speakers. Because this setting is basically an “FRFR” setting, the headphone and XLR Out signals are also full range with no added EQ shaping.
This position retains the dual limiter system for “bottomless” bass performance, but changes the amplifier impedance to “loosen up” the sound of most speakers, producing a warm “old-school” bass response normally associated with vintage tube amps. The rated power varies from 450 to 500W into either 8 or 4 ohm load, but due to the added voltage swing into resonant frequencies, the overall volume level sounds as big as the MODERN setting.
The Warm setting works well for clean “bottomless” bass with a warmer coloration, especially on vintage style all-cone speaker cabs. This setting engages a cab-sim circuit in the headphone and XLRout, duplicating the typical change in speaker response on the WARM setting.
This position uses the same amplifier character as WARM, but replaces the limiter system with a tube-like clipping circuit, providing a smooth transition from clean to breakup, similar to classic tube amps. Power at breakup ranges from 450W to 500 W into 8 and 4 ohm loads.
The Q-Tube setting works well for “heavier” bass playing when some grunge and breakup is desired, with about 10 times the power of a 50W Bassman and almost double the power of a 300W SVT head. This setting engages a cab-sim circuit in the headphone and XLRout that duplicates the typical change in speaker response on the WARM setting.
This position has 10dB more gain to match typical passive pickups.
This position is padded 10dB relative to PASSIVE, to balance the volume of an active bass with average control settings.
This position blocks the signal prior to the SPEAKER and SIG-OUT jacks, for noise-free instrument changes, with a bright red LED to remind the user that Mute is engaged. The FX LOOP is still active, so a tuner may be used on the MUTE position.
The GAIN control regulates the overall input volume to the preamp, along with the ACTIVE-PASSIVE switch settings.
On Modern and Warm settings, increased Gain will drive the signal into limiting, as indicated by mild flashing of the MUTE LED. You will hear the signal develop additional overtones or “grunt” rather than harsh breakup
On the QTube setting, increased Gain will drive the signal into overload breakup, just like classic tube amps.
To get the feel of how these interactions occur, set Master very low so you can explore these dynamics at a reasonable volume, and then run the Gain up and down on all three Voice settings. Once you find your “sweet spot” set the Master to obtain the overall volume you need to match the rest of the band,
The Bass Block V803 starts with a flat response curve with the EQ knobs on “0” (straight up). Up to 15dB of cut or boost is available, as shown on each knob.
A shelving filter boosts or cuts frequencies starting above 500Hz, reaching full swing at about 2kHz. This controls the “snap” or plucking overtones of the bass strings.
A selective midband filter boosts or cuts a band of frequencies centered at about 250Hz to 1kHz, depending on the Frequency setting. This can cut or boost the “twonk” or “bark” frequencies. Boosts can be used for emphasis, and cuts could help control midrange feedback howl on acoustic bass instruments.
A selective 4th order shelving filter adjusts frequencies below 100Hz, acting mainly on the lowest strings of the bass guitar’s range. Boosting BASS will produce a deep rounded tone. If pushed into limiting (on the Modern or Warm Voice), the low frequencies are limited separately, allowing the overtones and higher strings to “catch up” with the bass foundation, preserving a sense of effort without bottoming out or choking off the upper strings.
After adjusting your Gain and tone as described above, use the MASTER control to match the overall output power to your speaker's capacity. The wattage markings will provide initial guidance, but if you hear any popping or other signs of speaker overload, reduce the Master wattage until the speaker is operating comfortably. This allows the amp to be matched to a wide range of speaker ratings. On full Master, the amplifier can be driven to mild clipping on MODERN and WARM voices by using a lot of Gain, although limiting will begin to cushion the peaks at about 80% of full power. If you are unable to achieve the desired bass output with only one speaker, consider adding an additional speaker for more capacity.
A high impedance input matches both passive and active bass signals with no frequency shaping. All frequencies are treated equally, revealing the natural sound of your bass instrument.
This input produces an initial tone that is similar to classic “tone stack” EQ sections which have an inherent mid scoop. This input has full bass, leaner midrange, and silkier highs.
The two inputs are not designed to support two instruments at the same time. The Flat input disconnects the Scoop input. However, a second instrument could be connected to Scoop, and become active when unplugging Flat.
This output sends the final preamp signal, including all tone, limiting, and breakup dynamics, to external effects, at 1K impedance and 1V peak. Long cables may be used with no signal loss. FX Return impedance is 47K, which should be compatible with all pedals and processors. The resulting composite signal goes to the XLR-Out, and to the Master to adjust speaker and headphone volume.
External effect processors should be adjusted so there is no net change in volume when FX Return is inserted. Otherwise, the power markings on the Master control will not be accurate.
“STEALTH INPUT”: To practice or play with backing tracks, insert your signal into FX RETURN. The preamp signal level will drop about 4dB to provide some headroom for tracks. After dialing in your preamp level, use the external device’s volume control to match the track volume to your bass volume. The Master will control the combined mix as usual
Connect a quarter-inch stereo plug to the HEADPHONE jack located on the front. Standard 32-ohm headphones will work best but other impedances can be used, possibly with reduced peak level. Volume is controlled by the MASTER.
It is OK to run the amp without a speaker connected, for headphone or silent recording
Due to space limitations, Quilter BassDock cabs use short quarter-inch cables to connect amps that are “docked” in the rear compartment.
The amp performance is optimized for 8 and 4 ohm loads. Lower impedances can usually be driven with some precautions to avoid extreme volume levels. The amp is protected against overloads, and if pushed too hard, you may hear harsh breakup on peaks and/or a gradual power reduction accompanied by the Power LED “winking” to indicate thermal protection. Reduce Master somewhat to mitigate these behaviors.
The XLR Line Out on the back is pre-Master, and therefore the level is regulated only by the Gain control on the amp and guitar. To set console level, turn Master well down, dial in your intended preamp settings, and have the sound operator adjust their input gain for a good level. The amp Master may then be adjusted on stage as desired without changing the peak levels to the console. Signal level is approximately -6dB, and will contain all the preamp’s tone and breakup (if used).
The power cord that comes with your amplifier is designed to lock into the AC inlet to prevent it falling out during use. Press the yellow button on the cord to release it. Any normal 3-prong IEC cord may also be used, with a non-locking friction fit. Always ensure that the ground contact is intact on both the cord and receptacle.
The Bass Block can be used on all known worldwide AC voltages (100-250V), which allows you to play just about anywhere on the planet. There is nothing to change but your AC cord type.
Dual quarter-inch and Speakon outlets allow one or two speakers to be connected.
Clean the outer surfaces with a clean, damp cloth or vacuum with a soft brush. Never use any abrasives, harsh cleaners or solvents, and keep moisture out of the amp. The Bass Block V803 amplifier is manufactured with high quality components using modern industrial processes that greatly reduce production defects. Each amplifier goes through an intensive testing process before it leaves the factory ensuring that your amplifier will give you years of f lawless service. There are no user-serviceable parts inside the amplifier. Any repairs should be performed by a trained service professional. Always use the amplifier in a well-ventilated environment and protect from external heat sources such as furnaces or direct sunlight. Prolonged high-volume playing causes heat buildup in the speaker which reduces its working lifetime. If you f ind it necessary to consistently use the amp at full volume, we recommend using an extension speaker to prolong speaker life and improve sound coverage.
| Amplifier Module Specifications | |
| Power Output (MODERN): | 250W-16 ohm, 450W-8 ohm, 800W-4 ohm |
| Power Output (WARM/QTUBE): | 250W-16 ohm, 450W-8 ohm, 500W-4 ohm |
| AC Power Req.: | 100–240Vac, 50–60 Hz, 250 W typical, 1000W peak. |
| Input Connections: | ¼" mono, 2 meg, 4Vpk Passive, 12Vpk Active |
| LINE INPUT: | XLR 10K balanced, 1V full scale. |
| FX Loop: | ¼” mono, 1V full scale, 1K out, 47K inp (with FX Send lifted) |
| XLR Out: | Balanced, 600ohms, -6db. Ground lift switch |
| HEADPHONE OUT (POST MASTER): | ¼” TRS, 39 ohms each side. |
| Speaker Output: | 4-8 ohms, 90V, 25A peak |
| DIMENSIONS | |
| H x W x D: | 3” (76mm) x 8.5” (218mm) x 7.8” (200mm) |
| Weight: | 4.5 lbs (2kg) |
| Symptom | Action |
| No power, no lights | • Ensure that the AC cord is fully seated and connected to a live source. • Check the AC source by trying another device such as a lamp. |
| POWER LED on, but no sound | • Confirm the speaker is connected • Try headphones to see if preamp is active • Check the Mute switch • Confirm the Gain and Master are turned up • Check the guitar and cable by pluggin into another amp |
| Volume level slowly reduces. | • Thermal protection may be activating. The Power LED will be “winking”. Confirm fan is running at full speed, and that side vents have full air flow. • If amp develops harsh clipping, check load impedance and possible cable shorts. |
| Background hum | • Ensure the guitar plug is fully inserted. • Try using a different guitar cable. Make sure it is properly shielded. • Connect AC powered accessories to the same receptacle as the amplifier to avoid ground loops. • If hum goes away when guitar is turned down, Single coil pickups can be a source of hum, especially if near RF sources like light dimmers or neon lights. • Check that the guitar’s cavities are well shielded. |
| Bass is too thin or thick | • Adjust the BASS control. |
| Harmonics or high notes don’t sound right | • Adjust the MIDRANGE and FREQUENCY controls |
| "Twang" not right | • Adjust the TREBLE control • Try the SCOOP input |
| Sound is breaking up on peaks | • This is normal at high gains on QTUBE. Try voices WARM or MODERN. |
| Can't get breakup on peaks | • This is normal on WARM or MODERN. Try QTUBE. |
| Sound is garbled at all levels | • Speaker could be bad, especially if tone is clear in Headphones. |
| "Razzy" clipping on peaks | • Impedance is too low - reduce Master volume • Speaker or cable is partially shorted. Try another speaker. |
| Headphone image not centered | • Headphone cable not inserted fully. • 1/4-inch to 3.5mm adaptor may be defective |
| XLR Line Out distorted in console | • If connected to a mic input, set mic trim all the way down, or use a Line Input |
| ** Amplifier Requires Service** | If any of the following occur, immediately unplug the amplifier and refer to a service technician: • Amplifier or AC cord emits smoke • Amplifier is dropped or chassis is dented or bent • Liquid has been spilled into the amplifier • Loose parts inside the amplifier are heard • AC service breaker trips |
For warranty and service information, visit our support website at support.quilterlabs.com
Note: This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following measures
• Reorient or relocate the receiving antenna.
• Increase the separation between the equipment and receiver
• Connect the product into an outlet on a circuit different from that to which the
receiver is connected.
• Consult the dealer or an experienced radio/TV technician for help.