How to Convert a Two-Oscillator Mix Ratio into Decibel Levels

For a linear mix, write the signal relationship as:

output = gA × oscillator_A + gB × oscillator_B

Here, gA and gB are amplitude multipliers. A ratio of 3:2 specifies their relative size, but leaves their overall scale open: gains of 0.6 and 0.4 have the same ratio as gains of 0.3 and 0.2. Multiplying a signal to control amplitude is the operation described in Miller Puckette’s Controlling Amplitude.

Consequently, a ratio alone cannot select one unique pair of gain settings. You must also choose a reference: keep one oscillator at its existing level, normalize the gains to sum to one, or apply another documented normalization.

A knob labeled “70%” needs interpretation too. VCV’s VCA documentation distinguishes linear gain response from an optional exponential response. A percentage of control travel therefore cannot automatically be read as the same percentage of signal amplitude. Check the control’s documented mapping before converting it. VCV Free Modules: VCA

For positive amplitude quantities A and B:

A relative to B, in dB = 20 × log10(A/B)

For a 3:2 ratio, the calculation is 20 × log10(3/2) = 3.52 dB. Oscillator A should therefore be 3.52 dB above oscillator B, provided the original oscillator amplitudes are equal. The factor of 20 applies to amplitude ratios; power ratios use a factor of 10. Logarithms and Decibels

If you want to keep oscillator A’s gain at −6 dB, set oscillator B’s gain to:

−6 − 3.52 = −9.52 dB

This produces the same 3:2 gain ratio as other pairs separated by 3.52 dB. It does not require either channel to sit at unity.

Keep the direction explicit. For 70:30, A relative to B is +7.36 dB; B relative to A is −7.36 dB. Writing the reference beside the result prevents accidentally making the quieter oscillator louder.

For a linear blend whose gains sum to one, divide each ratio component by the total:

gA = A / (A + B)

gB = B / (A + B)

Then convert each multiplier relative to unity:

gain_dB = 20 × log10(gain_multiplier)

Dome Music Technologies documents this complementary linear relationship in its Linear Crossfade user guide: one input’s multiplier is one minus the other’s.

For an illustrative 70:30 setting, the multipliers are 0.7 and 0.3. Their calculated gains are 20 × log10(0.7) = −3.10 dB and 20 × log10(0.3) = −10.46 dB. The difference remains 7.36 dB.

The following reference table uses that same sum-to-one normalization. Values are calculated and rounded to two decimal places; they assume positive amplitude weights.

Amplitude ratio A:B	A gain relative to unity	B gain relative to unity	A above B
1:1, or 50:50	−6.02 dB	−6.02 dB	0.00 dB
3:2, or 60:40	−4.44 dB	−7.96 dB	3.52 dB
7:3, or 70:30	−3.10 dB	−10.46 dB	7.36 dB
3:1, or 75:25	−2.50 dB	−12.04 dB	9.54 dB
4:1, or 80:20	−1.94 dB	−13.98 dB	12.04 dB
9:1, or 90:10	−0.92 dB	−20.00 dB	19.08 dB

At an endpoint such as 100:0, the zero component is muted. Its theoretical gain is −∞ dB; do not attempt an ordinary logarithm calculation with zero. Also, 0 dB gain means a multiplier of one. It does not specify the oscillator’s output amplitude. Units of Amplitude

The amplitude-to-decibel formula stays the same, but the gain multipliers can change. Applied Acoustics’ Multiphonics CV-2 manual, version 2.2.0, documents linear crossfading at approximately −6 dB per input in the center, constant-power crossfading at approximately −3 dB, and a full-scale mode at 0 dB. Those center settings all have equal input gains, yet different overall levels. Multiphonics CV-2 Manual: Crossfader

If your intended 70:30 means 70% versus 30% of the separate power contributions, equal-RMS sources require amplitude multipliers sqrt(0.7) and sqrt(0.3). Converting those gives approximately −1.55 dB and −5.23 dB: a 3.68 dB difference. This illustrative calculation follows the amplitude-squared relationship between amplitude and power. Logarithms and Decibels

That power split differs from a 70:30 amplitude ratio. To preserve a 7:3 amplitude ratio while making the squared gains sum to one, instead calculate:

gA = 7 / sqrt(7² + 3²)

gB = 3 / sqrt(7² + 3²)

The resulting gains are approximately −0.73 dB and −8.09 dB, still separated by 7.36 dB. These are a chosen normalization, not a prediction of where an unspecified crossfade knob should sit.

Equal gain settings preserve any existing source-level difference. If your goal concerns the actual oscillator contributions, measure both sources separately using the same amplitude measure—peak with peak, or RMS with RMS. Puckette’s Units of Amplitude explains that amplitude comparisons can use either measure.

Let SA − SB be the original source-level difference in dB, and let GA − GB be the difference between gain settings. Applying the logarithmic gain relationship gives:

output difference = (SA − SB) + (GA − GB)

Therefore:

required gain difference = target output difference − source difference

For an illustrative example, suppose oscillator A measures 3 dB below oscillator B, and you want A’s output contribution to be 3.52 dB higher—a 3:2 amplitude ratio. The required gain difference is 3.52 − (−3) = 6.52 dB. Setting A’s gain to −3 dB and B’s to −9.52 dB achieves that measured balance. This correction is a calculation from the stated inputs, not a measurement of a particular synthesizer.

The relative gains do not determine the summed waveform by themselves. For two sinusoids at the same frequency, phase affects whether their amplitudes reinforce or cancel. Puckette’s Superposing Sinusoids shows that the resulting amplitude can range from the difference of the component amplitudes to their sum.

For example, two identical, phase-aligned signals mixed at 0.5 each reproduce the original signal: 0.5x + 0.5x = x. If one is inverted, the same settings produce cancellation: 0.5x − 0.5x = 0. Neither outcome changes the fact that the two gain coefficients are equal.

Constant-power blending is useful under its signal assumptions. Dome Music Technologies explains that it avoids a midpoint dip for uncorrelated sources, while correlated oscillator waveforms can produce a midpoint increase. Treat constant power as a conditional mixing approach and check the actual combined signal. Linear Crossfade user guide

Use this sequence to turn a written ratio into repeatable settings:

1. Define the ratio. Specify amplitude weights, measured output amplitudes, or power contributions.
2. Check the controls. Confirm whether percentages represent linear gain and identify the crossfade law.
3. Choose the reference. Keep one gain fixed or use the sum-to-one conversion table.
4. Correct unequal sources. Measure each oscillator separately and account for its starting level.
5. Enter the gains. Use numeric dB entry where available; otherwise adjust while measuring each contribution separately.
6. Check the combined output. Confirm that the resulting level and waveform behavior suit the patch.

For a straightforward linear 70:30 blend of equally leveled oscillators, start at −3.10 dB and −10.46 dB relative to unity. Once the balance is established, adding the same dB offset to both gain settings preserves their ratio. Keep that relative balance separate from the final output adjustment, and the conversion remains easy to reproduce.

• Logarithms and Decibels — Mathematics of the DFT, Julius O. Smith
• Controlling Amplitude — The Theory and Technique of Electronic Music, Miller Puckette
• Units of Amplitude — The Theory and Technique of Electronic Music, Miller Puckette
• VCV Free Modules — Module Manuals
• Linear Crossfade from Dome Music Technologies — User Guide 1.0
• Multiphonics CV-2 Manual — Crossfader
• Superposing Sinusoids — Miller Puckette