Thank you Tom, I had a listen and it was very helpful!
Barbeque, it's not the waveform I was trying to get smooth, I was trying to get more of a smooth filter envelope, but I think I'll have to give up on it
And Shintarou, great idea, I like it

i say embrace the clicking ¯\_(ツ)_/¯

hand draw a triangle wave. is that smooth enough for you ?

I tried to create a housetrack with two synced dmg-01. It's 'EP +' on my actual release Gleichtakt: www.daheardit-records.net The track 'Gleichtakt' also contains some smooth bass- and BD-sounds. Both from wav ch, manual and sinelike waveforms.

So, try not to use frame changes then? Yeah, I did pick up on that, but thank you very much anyway!

It's hard to smooth out the WAV channel.  Definitely keep it on manual so that you're only working with one frame.  Also, don't know if you've noticed it or not yet, but some of the horrible popping & clicking will disappear if there are other things playing at the same time.  For instance, the clicking that comes from stereo panning left & right will be somewhat diminished if there is another channel playing music at the same time.

Jellica, thank you very much! I'd tried with manual mode but I still get the clicking noise, but keeping it in time with percussion, brilliant idea thank you! And, yes, I am a noob, but not too noob-ish...
Bitjacker, I'm not a huge fan of modding my gameboy as I only have one... I'd like to not go to extreme, but thank you nonetheless.
Still open to any other ideas as well...

Put it on manual. It should smooth it out.

look for a ltc 1799.  mod your gameboy. get an idea of what an oscillator does to a synth. The half clock mod is good too, but if you use a variable resistor, you will have the means to tweak sounds. there are sweet spots where i have gotten nice bass even with the noise channel. if you want a good bass, set a pulse instrument you like to pan left, set another to play at the same time panned right. put your wav instrument to right and your noise to left. use all four channels, and if needed get another gameboy and another lsdj.
Just experiment.

if you want a smooth bass sound turn off the frame changes - put the wav channel on manual (i think it is manual mode? off mode in some older versions?)

from there just experiment with the frame volume and cut off settings for nice smooth deep bass.

if you use high speed frame changes or volume envelopes you will most likely get distorted and clicking and crackling sounds.

you can learn to use these as percussion or to keep them in time with percussion so they are less noticeable but best keep it simple for now if you are a noob

im pretty sure you got to draw frames and put the speed high

So, after going out and watching some deep house dj's spin tracks for a couple of hours, I came home inspired to have a crack at making a deep-house style track in LSDJ. I started messing with the wav channel, but I could never get the sound right, it always seems to be very distorted with frame changes, crude volume envelopes, and not quite as smooth as I would like... :S Any suggestions? Or do I just have to suck it up, buy nanoloop 2.6 and move on...? And yes, I am quite new to this...

Edit: I'm a n00b...