[sdiy] Reliable MIDI recording app for PC.. Or my Sonar X3 Pro DAW is not set correctly..

[brianw]

Compact Cassette would have the same problem, but the design solves this with a capstan and pinch roller. With a cassette, both the feed and the take-up reels need enough tension to properly spool the tape, but not enough tension to stretch the tape. But neither reel is responsible for precise speed. The capstan and pinch roller accomplish precise speed by not allowing the tape to slip.

I have not studied your entire design, but it seems that your take-up reel is responsible for controlling the speed, and if the paper doesn't maintain constant tightness, then the speed varies. I hope you have room to install some sort of pinch roller between the spools - preferably near the reader element - so that the linear speed of the paper stays within musical timing.

Brian Willoughby


On Nov 8, 2025, at 9:48 AM, Jean-Pierre Desrochers wrote:
> I'm thinking about a slipery paper behaviour  getting worst at the end of a song.
> My machine has 2 paper spools:
> The top one is the 'giving' spool where I install a roll to be played.
> The second bottom one is the 'receiving' spool which pulls down the paper and accumulates it on its shaft.
>  
> The first 'giving' spool is the one that needs special adjustments around its mechanics.
> Let me explain:
> This spool has a small felt break that is applied on its shaft (only in playback mode) To create a paper 'tension' to keep the paper firmly on the reading brass bar and help the 'receiving' spool to accumulate a spool of 'correctly pressed' paper while on playback.
> The problem is that the 'giving spool' also needs to be constantly adjusted in its left/right position to keep 'alignment' of all the paper holes according to the brass bar reader. Hope I'm clear enough here..
> This adjustment is made with a stepper motor arm that push or pull the giving spool to keep it at the good position.
> But that's where the problem arises.
> Adjusting the felt break to tight keeps the left/right adjustment from being freely  done.
> The shaft sticks on the felt and the stepper arm cannot do it's job .
> But loosing that breaks helps the left/right adjustment to be light and easy but doing so that brings the paper tension too loose and the receiving spool accumulates a 'not enough pressed' paper
> -> And that loose paper accumulation shows slippery behaviours
> specially at the end of the roll when the receiving spool pulls the paper but the paper sometimes does not move but it's inner layers do.
>  
> Feeding a constant fast MIDI notes stream in my Sonar from my modular sequencer
> did not cause any lags in the MIDI recordings !
>  
> So... the lags in the MIDI recordings seems to be caused by the paper slips at the song end's and create small lags that can be heard.
>  
> Thanks anyway for your interest to reply my questionings..