The Inspiration

Have you ever noticed that your guitar sounds great when it's plugged straight into a combo with just your volume pedal in-line? Yes….. Then you add a delay or reverb pedal…. At first you're impressed with the fat, full sound that's produced with the added effect. Then you go to a gig….. Things don't work out how you expected! That great sound you had in the practice room isn't there!

After several years of playing guitar and steel guitar through many different amplifiers, effect units and combinations of equipment, in the repair workshop and in a gigging situation one simple fact became clear. The best guitar sounds are often produced using a classic design of amplifier (in good original working order) with no effects. Adding almost any effect in-line deteriorates the basic sound. I started to consider, why? And could there be a solution that would preserve the basic sound while allowing room simulating effects to be added?

Without doubt a good quality reverb and delay effect can greatly enhance the sound of the guitar or steel guitar; if adjusted correctly. Modern digital delay and reverb effects units are capable of producing very controllable and high quality effect emulations. Ironically, the more modern nicer sounding effects often introduce latency (a small delay) into the signal chain. Latency is insignificant in terms of its affect on the delay or reverb, but appears to degrade, as perceived by a musician, the dry element of the sound. For this reason some musicians use older low quality effects units that don't introduce latency and accept the compromise of a lower quality effect. Adding effects in series often compounds the latency in the signal and remains present even when the effect is bypassed.

The Steel Mixer was designed to make any deterioration in the raw guitar signal negligible, to introduce absolutely no latency, while enabling delay and reverb effects to be integrated into the sound. By using the Steel Mixer you really can have the best of both worlds, a great dry sound, combined with high quality modern digital reverb and delay.

 

How Does It Work?

The Steel Mixer circuitry uses around 200 carefully selected components. The fundamental principal and signal flow is relatively simple. But to make the unit work in a way that is useful to the musician, and integrates with the steel guitar and effect pedals, required some careful consideration during the design process.

Normal Mode

The block diagram Figure 1 (click) shows the circuit arrangement and the signal flow when the unit is in Normal (N) Mode. This mode is designed to mimic the traditional arrangement where a volume pedal, delay pedal and reverb pedal are connected as a series chain. i.e. Simply daisy-chained together, with the volume pedal first in the line and the reverb at the end of the line.

Important *** It is essential that the delay and reverb effects units are configured / adjusted so that they ONLY output the effect. The unaffected or dry sound must be completely removed from the effect output.

How to set up common effects units.

With the delay and reverb level controls set to zero, a guitar signal will pass straight through the Steel Mixer without being amplified, with no latency and with negligible frequency / phase modification. By rotating the delay or reverb controls clockwise, the selected effect will be added to your guitar sound.

In this mode the signal sent to the delay pedal is purely the dry guitar sound; this is delayed according to the settings on the delay pedal. However, the signal sent to the reverb is a combination of the dry guitar signal and delay pedal output. Hence the reverb pedal output is a reverb applied version of this. This combination of signals would be created when effects are simple daisy-chained together. The main difference is with the daisy-chained connection the summation of the effects pedal latency is added to the dry signal; whereas, by using the Steel Mixer absolutely no latency is added to the dry signal.

Although Figure 1 shows the reverb return as a mono return, the reverb return on the Steel Mixer is stereo. A reverb effect is normally enhanced by using a stereo amplifier configuration. The Steel Mixer therefore has two main outputs allowing two amplifiers to be driven with the stereo signal. When using a mono reverb, only one reverb return is used and the associated main output fed to the guitar amplifier (marked "MONO").

Note:- With reference to Figures 1 / 2 / 3:

A "Buffer" is a device that allows a signal to be fed to multiple circuit paths.

A "Cond." is short for Conditioner; this modifies a signal to make it more suitable for the circuitry it's feeding.

A "Summing Point" is a point in the circuitry where signals are added together.

Pre-delay Mode

When high levels of reverb are added to a guitar signal the attack of individual musical notes can become "cluttered" with the reverb sound. In this situation if the reverb is significantly delayed, the attack of the sound can be preserved. When a delay is placed before a reverb effect this is referred to as Pre-delay. Using a normal pedal arrangement the pre-delay effect is not practical as it requires some rewiring and significant re-adjustment of the pedal controls. This effect is normally only used by players with rack based effects units. Using a clever switching system the Steel Mixer automatically re-configures the pedal wiring and levels so that this mode is available at the flick of a switch.

The block diagram Figure 2 (click) shows the circuit arrangement and the signal flow when the unit is in Pre-delay (P) Mode.

In this mode the delay level control is not used and will have no effect on the sound. The reverb level control will function as normal.

Double Mode

Using a delay pedal it is possible to create an effect that makes a player appear to be picking at double the speed he or she is in reality. To create this effect does require practice and its practical use is limited. But as a special effect used once or twice during a performance it can really add the "Wow  factor". Under normal circumstances significant re-wiring of the pedals is required and issues of overloading the delay pedal input are often associated with this configuration.

Using the Steel Mixer and pressing just one button completely reconfigures the volume pedal and effects pedals so this effect can be achieved. User adjustable preset controls allow the repeat level and Double Mode volume to be set. The player only has to adjust the delay time to suit the song. A footswitch on the Steel Mixer floor box allows fast access to this mode, and when engaged overrides all other modes. The reverb operates as normal when this mode is engaged.

The block diagram Figure 3 (click) shows the circuit arrangement and the signal flow when the unit is in Double Mode.

Typical delay settings used to achieve this effect. 

*A video clip demonstrating this mode will be available shortly.

Added Value!

Having built a device that allowed the player to configure effects in a practical way it was logical to add the finishing touches that make the difference in a live situation. Easy access to the reverb and delay levels was an essential requirement identified during the design process. For this reason the Steel Mixer has two parts: A Floor Box that sits near the volume pedal and a Remote Box that clips to the leg of the steel. The two boxes are connected by a fixed cable. Splitting the Steel Mixer into two boxes increases the production cost but makes the unit more practical for the musician.

A 9VDC power supply with three outlets is included so the pedals interfaced into the Steel Mixer can be powered up without requiring additional power supplies or batteries. This reduces on-stage wiring and ensures the pedals have a steady supply.

A 24VDC (+/-12VDC) isolated supply outlet is provided for use with compatible devices. This may be used to power up volume pedals and other equipment that can be used in conjunction with the Steel Mixer.

A tuner output is provided that is tapped off before the delay and reverb effects are added. A normal guitar tuner may be plugged into this socket. Since this is a buffered output any loading that the tuner has will not affect the guitar signal through the Steel Mixer. In Normal and Pre-delay modes the volume pedal is in circuit before the tuner is tapped off. In Double mode the tuner is tapped off at the guitar input. The tuner output is a high quality output similar to the main outputs and therefore may also be used as a dry signal only output for recording purposes.

The Steel Mixer is supplied with a power supply that can be connected to a wide range of mains voltages. The normal DC plug fitted to this supply has been replaced with a more rugged connector that twist locks together.