Metalizer effect and artifacts from buffer size.

I was mixing my project, no longer needed to track anything, so I raised the buffer size to lighten the load on my CPU.
Something sounded not quite right and I narrowed it down to metalizer insert effect I had placed on an fx track…

Changing the buffer size on my audio interface (Tascam US-16x08) changes how the metalizer effect sounds…I was under the impression that once everything is in the box, the buffer size should not have any effect on the sound?? (well, technically I know the buffersize is used by the vst effect code but the point is that it shouldn’t affect the sound if it’s coded properly)

I’ve attached an example:
1st segment original sound.
2ndst segment is buffer size @ 128 samples (oddly, this sounds ok here once I export the track but it sounds different/broken on live playback within project)
3rd segment @ 1024 samples
4th @ 2048 samples.

One can clearly hear the difference.

is it broken? Anyone have a good explanation as to the artifacts?

I tried to reproduce this issue, but the rendered audio was exactly the same when rendered with 128 or 2048 samples buffer size. There must be something else going on. By the way the attachment of your post is only a picture not audio.

Thanks for the quick response Arne! interesting that you are not reproing the same issue (did you use same settings as me? The sharpness setting exacerbates the issue I think).

I don’t seem to be able to attach audio files so here’s a link to the MP3 example (i’ll also attach inside a zip):

https://filebin.net/aps7npiwejpcttt5
badMetaliserExample.zip (231 KB)

It indeed sounds strange, but as I already posted I was not able to reproduce. Can you try to make a simple reproduction, maybe just removing all tracks but the source of your fx track and send it to us if it still exhibits this behavior?