Two years ago I had posted about this amp.  Not surprisingly, considering my memory lately, I completely forgot about that post until now. 

But Santa brought me the Positive Grid Spark 40. And actually I got the amp a few days before Christmas so I have had nearly a week to play with it and can report back with that amount of practice time.  What a great little amp it is.   I paid $239 (US) plus tax for it.  At that price I believe it is great value as just that, a practice amp.  Considering all that it will do, that I will try and relay to you, it is a steal at that price.  And maybe it can be more than just a practice amp.  It is so small and light there is no doubt it could serve at a jam.  I plan on using it for just that at a jam we are going to start up again very soon.  But I wonder, with its 40 watts of power, if this amp couldn't serve at a small gig?  @robert, what do you think?  

One can setup your sim amp and pedal board to get exactly YOUR tone!  Actually, here, it is almost counter-productive!  With 40 different amp simulations and I don't know how many pedal sims one can waste hours, as I have, trying to set up that perfect amp and pedal board.  🤔 😉 There are thousands of examples, they claim 10,000+, to download and modify or you can upload your perfect pedalboard to the cloud.

AutoChords . If there is a song that you are trying to learn, any song, you can download it to the app. And it will study it and within a very short period of time provide you with the chords to the song.  And then play the song with the chords on the screen for you to jam to. 

SmartJam: Play a little bit and the app generates bass and drums to jam with you.  

It has USB interface so can serve as guitar interface to one's DAW.  If I should ever finish Jingle Bell Blues my recording into Reaper will be with this.  

If you are needing a practice amp, with my limited experience thus far, I am really impressed with the Spark 40.  When one then considers the price I think this thing is a steal.