MBsid stepA report

[chriss]

hello all

first i want to give a small report of my MB SID so far. As for the moment i only tested the stepA and i am really exited. everething works apart from some minor problems.

(i will refer to them later on). But  this is all nothing in comparison to what it can. it is really outstanding. And everthing can made so simple. You just have to read the hompage several times and the forum every day und with some patience and smartness you are in the MBclub.

Big thanks to Thorsten!!!!

My way so far. build the jdm programmer and tested it on a win2000 desktop and win98 laptop. both worked even i didn´t get the 13,7 volt, but only 12,7 volt. And on the win98 laptop i also needed to switch into API mode. otherwise i got error 0000. wanted to put the mios on it but only had a keyboard with usb to midi out interface and only could get a 6n139 optocoupler from my local supplier. seemed not to work so i build the to com interface burned the modefied bootstrap loader (changed the baudrate) and everything went fine. had to change one mistake on my SIDpcb (solderplob) and bingo.

Know some little questions:

1. Why is there no Vss conection between core and Dinx1  on the  2x20_enc.pdf as well on the other pdf´s? i didn´t try it without because i thought it´s an mistake in the drawing? but i wanted to ask. maybe i am missing something.

2. can i seperate the ground from the core and the sid somehow? i am using two transformers one for the 5V, one  for the 12V so i have two seperate grounds available. might be better for the audio signal. (when i turn an encoder i can slightly hear  the movement.) that leads me to the next question.

3. i hear slightly some sound from the sid after i the hit the first note. (thats fantastic you might think, but i mean after i released it again.) its for sure the sound of the sid (it is just the last played note and when i transpose the oscillators for example i can hear the changing) and it stay present until i change into another patch. it is very small though but i as i used very good sennheiser i noticed it.

4. When i go into the envelope sektion, the first parameter shown is the number of the envelope. on my lcd everytime the default envelope number is 7! but there are only 2 envelops!

5. is it right that stepA sends no midi so far? as mentioned  i am using the to com interface and for fun i loaded  the TC application and could send mididata.

6. where can i change the direction of the encoders? (or what is the default setup? A=0;B=1 or B=0, A=1 on the shiftregister pins?)

7.one parts question. where to find knobs in europe (preferred in germany or austria) for the alps stecB16 encoder which don´t have a marking?

thats all i hope it is not to much.

Thanks a lot i am looking forward to MB SIDstepD!

chriss

[TK.]

Hi Chriss,

thanks for your input! :)

1. Why is there no Vss conection between core and Dinx1  on the  2x20_enc.pdf as well on the other pdf´s? i didn´t try it without because i thought it´s an mistake in the drawing? but i wanted to ask. maybe i am missing something.

This was my fault - sure, the Vss (ground) connection is very important, I just have fixed the schematics.

2. can i seperate the ground from the core and the sid somehow? i am using two transformers one for the 5V, one  for the 12V so i have two seperate grounds available. might be better for the audio signal. (when i turn an encoder i can slightly hear  the movement.) that leads me to the next question.

Unfortunately not, the SID chip doesn't provide an analog ground. On the other hand: I don't hear this effect... maybe you can improve the signal quality when you add an additional capacitor of 10 uF to the +5V domain of the SID module (parallel to the 100nF cap C8 )

3. i hear slightly some sound from the sid after i the hit the first note. (thats fantastic you might think, but i mean after i released it again.) its for sure the sound of the sid (it is just the last played note and when i transpose the oscillators for example i can hear the changing) and it stay present until i change into another patch. it is very small though but i as i used very good sennheiser i noticed it.

Thats one of the known SID bugs :-(

See also the interview with Bob Yannes, who designed the SID: http://stud4.tuwien.ac.at/~e9426444/yannes.html

What would you have changed in the SIDs design, if you had a bigger budget from Commodore ?

The issue wasn't budget, it was development time and chip size constraints. The design/prototype/debug/production schedule of the SID chip, VIC II chip and Commodore 64 were incredibly tight (some would say impossibly tight)--we did things faster than Commodore had ever done before and were never able to repeat after! If I had had more time, I would have developed a proper MOS op-amp which would have eliminated the signal leakage which occurred when the volume of the voice was supposed to be zero. This lead to poor signal-to-noise ratio, although it could be dealt with by stopping the oscillator. It would also have greatly improved the filter, particularly in achieving high resonance. I originally planned to have an exponential look-up table to provide a direct translation for the equal-tempered scale, but it took up too much silicon and it was easy enough to do in software anyway.

4. When i go into the envelope sektion, the first parameter shown is the number of the envelope. on my lcd everytime the default envelope number is 7! but there are only 2 envelops!

Congratulations, you've found a software bug :) Temporary fix: in cs_menu_exec.inc add to following line

CS_MENU_EXEC_GoToENV
        clrf    CS_MENU_PARAMETER_L; begin with first envelope

following call:

CS_MENU_EXEC_GoToENV
        clrf    CS_MENU_PARAMETER_L; begin with first envelope
        call    CS_MENU_P2R_ENV_Num

(similar changes have to be made for CS_MENU_EXEC_GoToLFO and CS_MENU_EXEC_GoToMOD)

5. is it right that stepA sends no midi so far? as mentioned  i am using the to com interface and for fun i loaded  the TC application and could send mididata.

yes, thats correct. Step B will send MIDI data

6. where can i change the direction of the encoders? (or what is the default setup? A=0;B=1 or B=0, A=1 on the shiftregister pins?)

The direction can only be changed by hardware modification (in order to save performance). If you are using ALPS STEC16 encoders, the correct wiring for channel A and B can be found here:

http://www.ucapps.de/mbhp/mbhp_dinx4_16enc_alps_stec16b03.pdf

7.one parts question. where to find knobs in europe (preferred in germany or austria) for the alps stecB16 encoder which don´t have a marking?

Good question! http://www.albs.de provides a good variety, but they are expensive $$$ :-( Does anybody know a better source?

Best Regards, Thorsten.

[ilmenator]

Hi all,

for good-looking, not expensive knobs I can suggest Canford: http://www.canford.co.uk/

Prices start at around 0,20€ or less, and you will find some knobs that are used in "professional" equipment. Problem might be that they don't do business with private users, but this would have to be checked out. You can order a catalog from them or print the relevant pages (pp. 348-35x) as pdf.

Best, ilmenator

[chriss]

hello

Thorsten:thanks a lot for the reply.

i changed the env sektion and it works. cool.

concerning the knobs i called www.albs.de and its quite cheap actually.

100 pieces of standard black knobs, 4mm flat type cost 26,90€ excl.Mwst.

you only need to purchase at least 30 €. so you must take 100 or more.

but if you take knobs from other companies like farnell or rs-components you pay1.50- 2€ a knob.

so if you get 100 pieces from albs you can build on MB64, one MBsid and one MB16E for 30€. thats fairly cheap.

chriss