18 Jul

Subtle Tape EQ for Analog Sound

Written by Wendy Dunham.

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Features white noise test signal, an additional Hi Shelf EQ for comparison, and a spectrum display

Sometimes people say that digital is too harsh compared to analog. In fact, some musicians record their DAW songs to tape to get that warmer sound, while others use plugins that emullate analog gear, valve warmers, or tape saturation and compression. In Reason, Scream 4 offers TAPE SPEED and COMPRESSOR for analog sound. Digital can sound harsh or brittle. It's not that something is really wrong with digital's accuracy – it's probably that we prefer that smoothed sound and EQ curve you get from tape. Also well known is how tape saturates pleasantly when you overdrive it versus digital distorion, which is intolerable.

Design Analysis:

I analyzed Scream 4 to see what the controls did exactly. In listening tests, I compared how various settings contoured the sound, then I visually compared them using spectrographs in iZotope RX. I found that by using "0" Damage Control, "127" SPEED and "0" COMPRESSOR, the sound passes through the Scream 4 and the spectra looks close to BYPASS, except for a slight bump in hi EQ (which I corrected in my combinator). It's pretty close to OFF with those settings, but not quite (see animation, below). Best to use BYPASS if you are not using it.

Learning that the Damage Control (which is really Input Gain) does not have to be above zero for the various effects to work, I set that to "0". Indeed, you still get full P1 and P2 control on the TAPE effect. I call this a "Subtle Tape EQ" because Damage Control remains at 0, while still getting the "analog sound" benefits without gain-related artifacts.

I was mainly interested in the Tape Speed as an EQ control, but I've included the Tape Compressor, which works remarkably well at reducing peaks, as verified in various spectrographs. Nice!

Using various combinations of P1 SPEED and P2 COMPRESSOR, I found that the output volume level would change undesirably. So I programmed a Line Mixer to increase/decrease output levels slightly to maintain a more constant output level when adjusting P1 and P2 controls. It's not perfect because it's dependent on the input source signal, but it helps a little. (To keep it simple, I did not want to manage this one-time volume change by adding a compressor or limiter. You can easily correct the volume elsewhere in your rack.)

tapeeqcontrols

User Controls:

Tape Speed: default is 127 ("fast"). Lowering decreases upper frequencies. "90" or less yields decent analog sound.
Tape Comp: default is 0 (off). Raising increases tape compression. It does not affect frequency, just peak reduction.
Phase Inverter: Inverts phase to compensate for Scream 4 inversion. (Only required if used as Send effect)

Test Controls:

For Test Purposes Only!

Hi Shelf Freq: Varies Hi Shelf roll-off.
Hi Shelf On: Use to compare Hi Shelf vs. the superior Tape Speed.
Noise Level: White noise amount.
Noise Test: Enables white noise to aid in setting your Tape Speed frequency roll-off preference.

The Noise Test signal makes it easier to hear the roll-off range as you set up Tape Speed – barely noticeable around "110" ("90" or less = decent analog sound). It also reveals the difference in sound character between Tape Speed versus Hi Shelf. Tape Speed rules, IMHO!

Tape Speed: Decrease to roll off the highs for that silky smooth tape-like analog sound you seek!
Tape Compressor: Increase to compress the peaks only (it has no effect on the frequency content).

The Tape Comp (peak compression) effect is best noticed on an external MClass Maximizer using Peak meters. Great for compressing transients to squeeze more out of drums and bass!

Performance Analysis:

P1 Values versus Frequency Roll-off

View Chart comparing P1 settings versus the frequency roll-off to be expected.

Spectrograph

According to spectrographic analysis, a Scream 4 using these default "OFF" settings (Speed=127 / Comp.=0) exhibits a negligible bump in EQ centered around 13K or 14K with high Q. To compensate for this subtle anomaly, I reduced with an opposite EQ curve at -1.4. There's still a slight bump present (see animation, below), but it's probably inaudible. Of course, once you begin to reduce Tape Speed and roll the highs off, it is not a factor.

Below is a spectrograph comparing BYPASS versus Enabled (at the default settings), then Tape Speed at "55". The first two frames shows that there is little difference between BYPASS and Enabled, which is good to know. Of course, when you decrease Tape Speed, as seen on 3rd frame, the highs can be rolled off just like analog tape. Nice!

tapeeq-ani

Notice the discrete notes in spectra - almost like MIDI Analysis performed using iZotope RX.

You do not need this combinator to achieve analog sound! If you prefer, simply use a Scream 4 set to "TAPE", Damage Control = "0" (or higher if you prefer grit), P1 = "127 to 0" (roll-off highs to suit), P2 = "0" (or more to compress like tape). My combinator just keeps your hands off Damage Control to keep the artifacts away, adds a white noise source for set-up, and provides a phase inverter which is needed if used as a Send effect
(see the excellent article Peff's Phased Aligned Tape Comp Combinator).