RAVENFORGE / DESIGN METHODOLOGY RESEARCH LOG — A07

RAVENFORGE

Design Methodology Research Log

A07 — 9V vs. 18V: Headroom and Dynamic Range

Verification of bass onboard-preamp supply voltage · rail margin · gain structure · clipping · dynamic range through literature and published specifications

1. Research question — is supply voltage tone, or an operating envelope?

A07 does not ask, “Does 18V make a better tone?” The useful question is: “Can a given onboard preamp process the maximum signal swing required in real use linearly enough at 9V, or does it need 18V to increase rail margin?”

Doubling the supply voltage can ideally double the upper limit of a symmetrical signal swing, so the voltage ratio alone gives 20·log10(18/9) = 6.02 dB. Real usable headroom, however, is constrained by the bias/reference, input common-mode range, output-stage swing, load, device topology, internal gain distribution and battery condition. Therefore, “18V always equals +6.02 dB of usable headroom” is not a general law.

2. Definitions — separate Headroom, Dynamic Range, Noise and Output Level

3. Circuit theory — when does 9V→18V correspond to +6.02 dB?

If a single-supply circuit is biased near mid-rail and the positive and negative margins are symmetrical, its ideal peak swing scales with supply voltage. With the same topology, gain, load and clipping criterion, the result approaches +6.02 dB only when the usable 9V peak swing is exactly half the 18V swing and the rail margin expands proportionally.

Real circuits can be limited by input common-mode range and output swing independently of the supply rails, and even a rail-to-rail stage may not reach the rails cleanly when load current rises. If the bias point is not exactly centered, or positive and negative headroom are asymmetric, one side clips first. With a regulated rail, charge pump or DC/DC converter, battery voltage may also differ from the actual analog rail.

Figure 1. Idealized comparison of 9V and 18V rail/headroom. Doubling voltage can create a +6.02 dB ceiling difference under ideal conditions, but real usable swing is limited by bias, device swing, load and topology. Conceptual diagram, not product measurement data.

3.1 EQ boost and internal-node clipping

+12 dB corresponds to about 3.98× voltage, +15 dB to 5.62×, +16 dB to 6.31× and +18 dB to 7.94×. This does not mean that the output always becomes that much larger; it means that the circuit may be asked to provide that amount of gain in the affected band. When pickup/source peaks accumulate with input gain, mixing gain, filter resonance or EQ boost, an internal node can saturate before the final output jack does.

A07 therefore analyzes the full chain, not pickup output alone: Source peak → input boundary → input gain → per-source/filter processing → mixing → EQ/filter peak gain → inter-stage level → output gain → load.

Figure 2. Headroom-budget aid converting EQ/filter boost into voltage ratio. +12 dB is about 3.98× and +18 dB about 7.94×; the actual internal-node peak must also include source level and preceding-stage gain.

4. Configurator 11 candidates — comparison of published specifications

“Unknown” in the table does not mean the research was skipped; it means the value could not be established from the available primary source. Unpublished internal rails, op-amps and clipping voltages are not guessed.

Figure 3. Published supply-range map for the 11 Configurator candidates. Continuous lines indicate published operating ranges, 9V/18V option labels indicate selectable support, and gray labels mark products whose supply could not be confirmed from the current primary evidence. Fishman is interpreted from the Fluence Bass system-level statement [1–13].

5. Candidate-by-candidate evidence audit

5.1 Lusithand Double NFP MKII

The official product page publishes 9–27 V operation, current draw of about 2.9 mA, and per-pickup resonant-peak filters with +3 dB standard / +6 dB switched Q boost. The wide supply range is confirmed, but the manufacturer does not quantify how many dB of extra headroom 18V provides. The Configurator should therefore record the supported supply rather than force 9V, while the actual 9V/18V effect size belongs in C04.

5.2 Fishman Fluence Bass 2-Band EQ

Fishman sells the Fluence Bass 2-Band EQ as a separate product, while the 2026 OEM catalog lists the Fluence Bass system battery as 9–18 V and the 2-Band EQ current draw as 1.1 mA. This is strong evidence for a system-level Fluence Bass supply range, but it is not a claim that the standalone EQ module is an independent “18V upgrade.” The Configurator can retain 9V as the standard implementation, but should not label the system “9V only.”

5.3 Underhill Cali Dub

The official page documents BP buffers for two pickups, two FV variable-Q filters, an EPB parametric bass EQ, and active blend/volume. Filter Q is 0–13 dB, filter frequency 130–5300 Hz, bass EQ ±7.5 dB with a 30–200 Hz sweep, and idle current 2.4 mA. Because the public page does not establish supply voltage, the 9V/18V rule must remain Unknown.

5.4 Glockenklang 3-Band

The official electronics page specifies gain 1 (0 dB), input 1.5 MΩ, Bass ±14 dB @40 Hz, Mid ±9 dB @550 Hz, Treble ±18 dB @18 kHz, and 9/18 V power at 2.3 mA. 18V support is clear, but no manufacturer statement was found that recommends 18V or quantifies extra headroom at 18V. The Configurator may use 18V as a house configuration, but must not present it as a manufacturer requirement.

5.5 ZUTA Bass Core

The official page publishes 1 MΩ input, 1 kΩ output, recommended load ≥10 kΩ, nominal input level up to +20 dBu, Bass ±16 / Mid ±15 / Treble ±12 dB, 9–18 V supply, and a roughly 500-hour battery-life claim. “High headroom” and low distortion/noise are manufacturer claims, while the quantitative 9V↔18V delta is unpublished. A07 records +20 dBu and the boost range as important published boundaries; the actual extra margin at 18V moves to C04.

5.6 Noll TCM-4XM

Noll is one of the most useful quantitative cases. It publishes input >1 MΩ, output <10 kΩ, max input sensitivity 450 mV @9V, max output 4.5 V @9V, S/N 96 dB, ±15 dB four-band EQ, 9V base / +18V optional power, and 1.5 mA @9V. It also states directly that adding a second 9V battery (18V) provides “more headroom and longer battery life.” Because it does not publish an exact doubled max-output value at 18V, A07 does not automatically assign +6.02 dB.

5.7 Darkglass Tone Capsule

Darkglass officially publishes 500 kΩ input, 1 kΩ output, current ≈2.4 mA, Bass/Mid/HiMid ±12 dB, and 9–18 V operation. The official product page, however, does not quantify 18V as a mandatory high-headroom mode. An 18V Configurator default can remain as an engineering choice, but calling it a “manufacturer high-headroom requirement” would exceed the evidence.

5.8 LHZ-05 / HAZ-style 3-Band

LHZ-05 is the current three-band product combining the HAZ-style two-band circuit of the LHZ-04 with the MID-03. The manufacturer’s BAT-01 description states that both 9V and 18V operate normally and that the choice is a matter of personal preference. It also directly describes peak compression and high-frequency harmonic overtones at 9V under aggressive playing and boosted EQ, while 18V reduces peak compression and raises the ceiling/headroom of the nonlinear zone. The Configurator’s 9V “Classic HAZ Response” / 18V “High Headroom” distinction therefore has the most direct manufacturer support among these candidates. This characterization applies to the modern LHZ implementation and should not be generalized to every HAZ-style clone.

5.9 John East UNI-PRE 5

The official manual confirms completely separate active/passive paths, a Class-A FET input stage and 0–12 dB gain trim for each pickup, plus Bass ±18 dB, Mid ±14 dB and Treble ±18 dB. This amount of boost and trim matters to the headroom budget, but the current evidence set does not quantify a 9V/18V delta. The important UNI-PRE issue is to manage per-pickup gain calibration and internal processing headroom together, not merely to attach a voltage label.

5.10 ACG EQ-01

ACG’s official material confirms that the EQ-01 is a filter-style preamp with a variable low-pass filter and overshoot-peak level per pickup, plus a global high-pass filter or passive-tone variant. Unlike a conventional three-band ±dB EQ, filter cutoff and resonance peaks create internal spectral peaks. Because supply, current and maximum swing are not established in the current public evidence, A07 defines the worst-case peak for each filter state as a specification requirement and leaves quantitative results to C04.

5.11 Nova Dual Filter Custom

For a RavenForge/custom candidate with no published product datasheet, the correct status is “Custom / specification required.” At minimum, the specification must define supply range, current, Zin/Zout, filter cutoff range, maximum resonance/Q boost, input/output clean swing, noise floor, and bypass/reference state. No 9V or 18V default should be locked until these values are defined.

6. Reference cases — Bartolini, Aguilar, EMG

7. 9V vs. 18V — Headroom / Dynamic Range / Noise / Runtime

7.1 Headroom

If a circuit actually approaches a rail-limited condition, 18V can expand clean swing. If 9V already provides sufficient margin, there may be no audible change. More important than the manufacturer’s nominal supported voltage is how close the worst-case internal node comes to its limit at 9V.

7.2 Dynamic range

Dynamic range is the difference between the maximum clean signal and the noise floor. Even if a higher supply raises the maximum clean signal, the increase is not exactly 6 dB if the noise floor also changes. The DR effect of 18V must therefore be measured separately from headroom.

7.3 Noise

There is no universal rule that 18V automatically lowers the noise floor. In some circuits a higher rail changes device operating points, and battery/source impedance and decoupling also influence noise. Published “low noise” language is recorded as a marketing/specification claim and kept separate from bench measurements made at a defined bandwidth.

7.4 Battery runtime

With two identical 9V batteries in series, nominal voltage adds while Ah capacity remains roughly that of one battery. Stored energy (Wh) increases, but runtime depends on supply-dependent circuit current, battery chemistry, internal resistance, discharge curve and cutoff condition. Real examples such as the EMG BQC at 600 µA @9V and 740 µA @18V show why “18V = half the battery life” is false.

8. Configurator power-rule audit

Figure 4. Configurator power-rule audit. Revise the system so that “manufacturer-supported voltage range” and “RavenForge default” are separate fields, and every default carries a documented engineering reason.

9. Configurator replacement wording

10. Myth Audit

11. RavenForge Headroom Map / Power Specification Bundle

Figure 5. Documentation model overlaying the A07 Headroom Map on the B06 Signal-Flow Graph. At each active node, record nominal level, worst-case peak, published maximum clean swing, remaining margin and evidence source together.

12. RavenForge model application — verification requirements, not results

ASKR

In an active-source + onboard-EQ combination, the source’s own nominal/peak output and the EQ’s maximum boost jointly define the worst-case node. Do not treat 18V support as a “premium specification.” Compare the published source level with the onboard EQ clean-swing specification across the complete chain, and measure missing information in C04.

EMBLA

For passive pickup + selectable-preamp systems, define input loading and gain trim first, then record how large the internal peak becomes after blending and boost. If a three-pickup option is used, include summing conditions and simultaneous-source peaks in the headroom map.

EDDA

In a filter-centric architecture, a conventional three-band “maximum boost” number is not enough to identify the risky node. Define the worst-case state from each pickup’s low-pass cutoff, resonance/overshoot peak, blend ratio and global high-pass/treble state, then measure clean swing.

13. What A07 can establish vs. what moves to C04

Fix the C04 clipping criterion before measurement, for example 1% THD+N or waveform-defined clipping. Different criteria produce different “headroom” values, so the same criterion must be used across documents.

14. Integrated conclusion — voltage is a margin parameter, not a tone label

The most important result of this re-study is that the simple specification “supports 18V” means very different things across products. Noll directly describes 18V as a means of adding headroom and battery life, while LHZ describes intentionally different large-signal behavior at 9V and 18V. Darkglass and Glockenklang publish 9/18V compatibility without quantifying the 18V effect. The Fishman Fluence Bass system is documented as an integrated 9–18V system, so reducing the standalone EQ to “9V only” is inaccurate.

RavenForge supply policy should therefore move away from global rules such as “active = 9V” or “premium = 18V” and use three fields: product-specific supported range + RavenForge default + documented reason. An 18V default is valid when justified, but the documentation must say whether it is a manufacturer requirement or a RavenForge engineering-margin choice.

References — primary sources first

[1] Lusithand Devices. “Double NFP MKII (new attack feature).” Official product page. https://lusithanddevices.com/product/double-nfp/

[2] Fishman. “Fluence Bass 2-Band EQ.” Official product page. https://fishman.com/dp/fluence-bass-2-band-eq/

[3] Fishman. 2026 OEM Catalog — Fluence Bass Soapbar / Bass EQ Parts Kit. https://fishman.com/wp-content/uploads/2026/05/fishman-2026-oem-catalog_v2.pdf

[4] Underhill Bass. “Cali Dub — Dual Filter and Bass EQ.” Official product page. https://www.underhillbass.com/product-page/cali-dub-dual-filter-and-bass-eq

[5] Glockenklang. “Electronics — Bass Electronics / 3-Band.” Official specifications. https://glockenklang.de/en/electronics/

[6] ZUTA. “ZUTA Bass Core.” Official product specifications. https://zutagroup.com/products/zuta-bass-core

[7] Noll Electronic. “TCM 4 XM.” Official specifications and wiring. https://www.noll-electronic.de/bass-electronics/tcm-4-xm/

[8] Darkglass Electronics. “Tone Capsule.” Official product page/manual. https://www.darkglass.com/products/tone-capsule

[9] LHZ Preamps. “LHZ-05 Three-Band Preamp Kit.” Official product page. https://lhzpreampshop.com/products/lhz-05

[10] LHZ Preamps. “BAT-01 Adapter 18 Volts.” Official 9V/18V operating explanation. https://lhzpreampshop.com/products/bat-01

[11] East UK. “UNI-PRE 5 Knob User Manual.” Official manual. https://www.east-uk.com/2025/11/28/uni-pre-5-knob-user-manual/

[12] ACG / AC Guitars. “Electronics — ACG EQ01 Filter Pre-Amp.” https://acguitars.co.uk/electronics/

[13] ACG / AC Guitars. “Bass-EQ-01 Filter Style Active Preamp — Instruction Manual.” https://www.acguitars.co.uk/wp-content/uploads/2017/05/ACG_EQ01.pdf

[14] Bartolini. “NTMB+FL 3-Band EQ Preamp Module.” Official product page. https://bartolini.net/product/ntmbfl/

[15] Aguilar. “OBP-3.” Official product page. https://aguilaramp.com/products/aguilar-obp-3

[16] EMG. “BQC Control — Installation Information.” Official PDF. https://www.emgpickups.com/pub/media/Mageants/b/q/bqc_control_b245_0230-0203rk.pdf

[17] EMG. “BQC System — Installation Instructions.” Official PDF. https://www.emgpickups.com/pub/media/Mageants/b/q/bqc_system_0217rk.pdf

Source-status note: terms such as “transparent”, “high headroom” and “low noise” are recorded as manufacturer claims and are not treated as equivalent to C04 bench measurements. Product revisions may change; verify the current manual again immediately before a build.