I bought this for use as a small smartphone-controlled amp modeler / eq / reverb box. I play clean jazz exclusively, and I like to bring the smallest possible amp to gigs. I like the Mackie SRM150 a lot but it has no built-in reverb and sounds very hi-fi by itself.
Features on the Spark Go are all I need. In fact, I didn’t even need the built-in speaker but I figured it would be a nice bonus.
Modeling sounds and effects are all OK. The big issue, that made it unusable for my purpose, is the low output level from the headphone / line out jack. I didn’t get any decent signal level out of the preamp, no matter what guitar I used or what amp/ headphone / powered speaker I connected it to. Note that I only care about clean tones. Distorted tones seem to have a much higher signal level. Also, again for clean tones, the output volume from the speaker is a joke. It sounds like the tinny pocket radio I used to have as a kid in the 1970’s, both in terms of volume and sound quality. So, for clean tone seekers, it is a toy - at best. I returned it and got a Mooer Prime P2 instead (unfortunately not yet available from Thomann on a reasonable term) and this is just perfect for my needs. It has the added benefit of a 1/4 inch output jack over the vulnerable 1/8 inch mini jack from the Spark.
Some years ago, I bought the Bias Head amp, also by Positive Grid, and ended up selling it again for similar reasons. Clean tones came at a hiss level that made it useless. I guess Positive Grid are aiming for the rock or metal player, at least not the clean player. Too bad for me, will not buy PG stuff again.