Capturing a good recording of an Echorec drum delay unit can be a challenging task as the they exhibit a relatively poor signal to noise ratio in comparison to modern digital delay units. The noise floor is raised by several factors, including:
- hiss (white/pink noise) from the bias oscillator
- A.C. hum from the tube heaters
- motor noise
- earthing issues
When recording an Echorec direct you’ll more than likely hear an unpleasant hum which is a mix of the fundamental mains frequency plus harmonics which is very obtrusive and distracting. This noise is impossible to filter out once it is convolved with the audio signal because the harmonics are distributed all across the audio spectrum. The good news is that this hum can be completely eliminated by isolating the Echorecs’ output from the recording device (PC sound capture, tape player, etc) input using an audio transformer. Another method is by lifting the ground, however exercise extreme CAUTION if using this method. Ground-lift is achieved by disconnecting the ground from the mains plug, however be aware that the Echorec will only be grounded through the shield of the connecting signal cable. This is potentially dangerous if the signal cable is not connected as the chassis is ungrounded. If there are any live wires dangling around inside the Echorec (a not unlikely scenario with electronic equipment of this age) then the chassis could become live, exposing the user to a potentially lethal voltages. If in doubt consult a qualified technician. The first part of the following sound sample below demonstrates the characteristic hum and in the second part the hum is eliminated by ground-lift:
As for A.C. heater hum, there are modern rebuilds of Echorecs available from Marcello Patruni with D.C. powered heaters. Additionally, these machines are fitted with a manual bias adjustment which allows some control over bias hiss noise. The sound quality of these machines is a significant improvement over the original Binson Echorec. However, bias adjustment only has a marginal effect on the background hiss. Further improvements on the signal to noise ratio can be obtained by using a compressor between the guitar and the input of the Echorec. Compression has been used for decades in AM radio broadcasting and when cutting discs (records/vinyl) to overcome the limitation of recording or broadcasting a signal with wide dynamic range on these mediums. Compressing the signal will attenuate high level transients allowing the the overall signal level on the drum to be higher relative to the noise floor of any hiss and hum—it pushes the signal up another few decibels above the noise floor of hiss and hum. Technically, it is also feasible to design a photo-optical compander (compressor/expander) circuit to improve the signal to noise ratio of the recording medium. I can only imagine how incredible an Echorec would sound with such an enhancement!
I’ve also found that using a compressor with an Echorec has an additional benefit buffering the guitar pickup giving a substantial improvement tone. Binson Echorecs have an input impedance of 47KΩ—this will load your guitar pickup and suck tone. The following sound sample demonstrates this. The first four measures are with the Effectrode PC-2A compressor in bypass and the effect on the tone is very obvious when the pedal is engaged as it opens out the sound to let it breathe giving a very nice improvement on dynamics and clarity.