The Glensound Atomic Helium 2 Feedback Destroyer works by rapidly varying the audio output by down-shifting it by about 4Hz over a short fluctuating cycle. This variable frequency shifting is sufficient in a speech/voice PA system to largely suppress risks of feedback and even 'ringing'. Such a unit should not be used with music (especially live music) because it noticeably alters the sound of some instruments, e.g. for keyboards the effect shows up most. But for spoken voice the frequency shifting effect is not noticeable other than that feedback is ‘magically’ suppressed. This method of ‘Feedback Destroying’ is generally much more effective with speech than can be achieved by any of the conventional notch filter effects units, e.g. Sabine or DBX (and certainly enormously more effective than Behringer’s product!).

The pitch shifting effect itself can be subtle to hear and is difficult to demonstrate, but see video (where steady tones have unfortunately been somewhat suppressed by the camera on the phone). In the video the Helium 2 is fed with a steady 400Hz on i/p 1 and its o/p 1 is connected to i/p L of a stereo speaker. Input R of the stereo speaker is connected directly to the same steady 400Hz tone. The Helium is then toggled between ‘Freq shift’ and ‘Bypass’. When the freq-shifted o/p is heard mixed with the clean tone there is a warbling effect, but when the bypass button is pressed the warbling ceases, hence the demonstration shows the unit does its job.

The unit is in excellent condition for its age, with the only marks and slight scratches being on its upper- and under-sides, from being rack-mounted.

Audio quality is to the usual Glensound level of excellence, see spec sheet for details. Line level balanced inputs and outputs are on gold-plated XLRs. Metalwork finish is hard-wearing black anodised with silver text showing through.

Perfect for use in public speaking situations, e.g. church, town hall, lecture theatre, etc. where spoken word intelligibility will be increased.

All packed carefully ready to ship with included insurance to a UK address now. Free postage to UK destinations. I’m prepared to take offers – contact me through eBay if you’d like to discuss.