Why not a ".TSX" Format for MSX Tapes???

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By Paulo Scheidegger

Supporter (12)

Paulo Scheidegger's picture

04-05-2017, 19:28

Thanks, RetroTechie.
I guess volume is an issue, but only for the recording operation. When playing back I can adjust output volume at the phone, unlike when recording, since the MSX volume knob only affects the sound sent to local speaker.
The cell phones I am using have a TRRS jack, the kind that accepts microphone equiped stereo headphones. I was able to record, I heard the whinning when played back on the loudspeaker. The problem, I think, is that my MSX sends almost directly the PPI output to the datacorder. There are only a simple filter to "unsquare" the wave form and a voltage divisor to adjust level. The whinning seems a bit distorted and there is a 60 Hz noise superimposed.

By RetroTechie

Paragon (1414)

RetroTechie's picture

04-05-2017, 21:22

Ah you're right, maybe TRRS jacks (with mic input) is more common these days. Tbh I'm not even sure about my own cellphones since I don't use microphone-equipped headsets... Wink

Anyway, if all you're recording is mains AC noise, this suggests that you may not be getting a mic signal at all. Check your cable, and have a look here: (top 2 lines)

en.wikipedia.org/wiki/Phone_connector_(audio)#TRRS_standards

(making clickable link didn't work...!?! grrr)

Maybe your cellphone has mic & ground swapped vs. what you expected for the cable you use? To check, you could wire up a cable with just the 2nd ring & sleeve connected on cellphone end (and maybe swap wires & try again). Other than that, only thing I can think of is software issues (mic input muted / not selected or whatever).

By Paulo Scheidegger

Supporter (12)

Paulo Scheidegger's picture

04-05-2017, 22:20

[Anyway, if all you're recording is mains AC noise...]
Actually, there IS usable signal on the record, perceptible by ear and on the scope screen. However I hear AC noise whenever the signal stops (between file name and content, for instance), and I presume it is superimposed to the signal and causing interference in detecting correct information on the receiving circuit.

I checked the plug connections by comparing to an actual mic/phone set and they are ok. The only difference is I shorted both channels of audio into a single MSX input pin. I also connected a standard loudspeaker in lieu of MSX input and was able to hear the recording. Perhaps your suggestion on using only one channel may do the trick, I'll give it a try!

Thanks!

By RetroTechie

Paragon (1414)

RetroTechie's picture

05-05-2017, 00:59

Paulo Scheidegger wrote:

Actually, there IS usable signal on the record, perceptible by ear and on the scope screen. However I hear AC noise whenever the signal stops (between file name and content, for instance),

That'll be automatic gain control on the mic input. When input level drops, sensitivity is automatically dialed up until a reasonable signal is recorded.

Very annoying indeed! In theory, to enable decent recordings with a wide range of input signal strengths. But in practice, this amplifies quiet passages so all you record is noise where quiet used to be. Evil Just give me a recording level that I can set manually as needed, and then don't f*** with that please!

Quote:

and I presume it is superimposed to the signal and causing interference in detecting correct information on the receiving circuit.

Well that's one function of the header parts in tape signals: to dial such AGC circuits back to normal recording level before the data bits come along. But as you found, sometimes such AGC circuits respond too slow or headers are too short. Not much you can do other than use recording equipment where you can disable this behavior.

Do you really need to record from MSX tape output? If not, you could just forget about that & focus on playback only.

By Paulo Scheidegger

Supporter (12)

Paulo Scheidegger's picture

05-05-2017, 04:21

Yes, AGC can be very annoying sometimes. But I love to defeat those stupid automated things, so I searched for an AGC disabler and, voilà! Downloaded "RecForge Light" from Google Play wich has an option to do it. Tomorrow will try it too.
I'll post the results.

BTW, while my floppy drive is down my only saving option is the tape port, but I won't care adjusting head azimuth back and forth as in the '80s anymore. That's why the cell phone instead of a tape recorder.

By manolito74

Paladin (814)

manolito74's picture

11-06-2017, 16:32

The version 0.6 of makeTSX is available. It includes several new features:

1. Option to do hex / ASCII dump [-c]

2. When generating a ".TSX" file automatically are generated also the following blocks at the beginning of the file:

-- Block # 30 with info about the version of makeTSX that has extracted this file.

-- Block # 32 with an empty info block in order that user can modify it to identify the Tape.

-- Block # 35 with the MSXLOAD key to indicate the load instruction of the Tape (RUN / CLOAD / BLOAD), provided the first data block be a standard MSX header.

3. Listing the blocks of a ".TSX" file now shows the start / finish / execution addresses of data blocks # 4B in case of having previously an MSX header that identifies it as binary.

You can found this new version here:

http://www.zonadepruebas.com/download/file.php?id=5200

Thank you very much to NataliaPC for her efforts creating the MakeTSX Program. ;-)

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