Wellspring // The Sweet Spot Machine // Review and Demo

video upload by Starsky Carr

"The Wellspring from Teaching Machines has blown me away. I'm generally not a fan of spring reverbs but this one sounds great and is only a small part of the whole system. To me it feels like an analog multi-FX unit, and you can get textures I didnt think would be possible from an analog unit.

I did wonder what was going on and why it sounded so warm... and received this info from the designer:

It uses 2-pole VCFs based around two LM13700 for shaping the delay, and an analog switching system to control the type and frequency of both VCFs at the same time. There are some other filters in the path around the delay too, a gentle high pass, some shaping and a quite steep 8 pole lowpass around 8K, as that makes the delays behave better. So there is always some other filtering going on. There is also some diode based saturation and filtering, to try and soft clip more before the delay if things get really loud.

Having the VCFs in the feedback path of the delays is where a lot of the fun stuff is, as when swept with the LFO they also change the feedback character and length, so you can get these really interesting evolving sounds.

The delays are based on PT2399, though with a slightly unusual implementation, avoiding using some of the filtering on the chip. These are just dirty in general, especially at longer times.

There are some more straightforward uses of the delay. One of the reasons for having the delay is just to add some predelay to the springs, or to act like 'early reflections', or full wet with short times and a bit of delay time modulation to try to break up the fixed resonances you get with spring lines."