OPL4 family

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By PAC

Guardian (5210)

PAC's picture

08-03-2013, 02:27

Once Wozblaster was announced, I was firmly decided to make my own cartridge but as might be expected, the OPL4 IC is almost impossible to find nowdays. After some contacts, the result has been unsucessful and although I'm going to keep searching, finally I'll buy an old PC board with the Yamaha soundchip.

Anyway during these days I have been collecting more information about the OPL4 and I noticed that the family didn't finish with the YMF278B. AFAIK it has two eldest brothers, the YMF704 (OPL4-ML) and YMF721 (OPL4-ML2):

Both are newer than "our" OPL4, the FM part is ovbiously OPL3 compatible but Wave table ROM is built-in and capacity only 1 MB. On the other hand they contain a MPU-401 UART and other features not available on the original OPL4. Anyway I don't understand why to decrease the wave table ROM to 1MB losing sample variety when you already had a functional 2MB ROM.

1. Does someone know more about them?
2. Are there more OPL4 family members?
3. General MIDI logo is clearly visible, so I guess these IC were used to be the soundchip of commercial MIDI modules. Right? Just an example. (Also included in this thread from MSX Village.)
4. Could they be adapted "easily" to be part of a clone of the original Moonsound?

That's all, just sharing it with you. :)

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By WORP3

Paladin (804)

WORP3's picture

08-03-2013, 10:01

Very nice chip but a bit outdated as they already develop the YMF754 and that was already 14 years ago !

Just found a short Yamaha lsi list, they already produced the YMF807 but also having the YMF825 and the 827 !

By msd

Paragon (1372)

msd's picture

08-03-2013, 11:18

1. Does someone know more about them?
The different ROMmakes it unusable. Also you can't connect external sram to it iirc.
2. Are there more OPL4 family members?
No
3. General MIDI logo is clearly visible, so I guess these IC were used to be the soundchip of commercial MIDI modules.
Well probably only to put on PC soundcards.
4. Could they be adapted "easily" to be part of a clone of the original Moonsound?
No, because of things mentioned in point 1.

By anonymous

incognito ergo sum (109)

anonymous's picture

08-03-2013, 13:16

Yes I know that there are some obvious differences related to HW so impossible to use
directly but they are almost the same. Adapting the existing SW woud be another issue.

By Colemu

Hero (531)

Colemu's picture

08-03-2013, 23:30

PAC wrote:

the OPL4 IC is almost impossible to find nowdays. After some contacts, the result has been unsucessful and although I'm going to keep searching, finally I'll buy an old PC board with the Yamaha soundchip.)

What about this: http://www.ebay.co.uk/itm/YMF278B-F-Manu-YAMAHA-Encapsulatio...

By PAC

Guardian (5210)

PAC's picture

09-03-2013, 00:30

Thank you Colemu, I would say is the same supplier I contacted. They told me there is a shortage of this IC in the market. Anyway I'll try. Smile

By msd

Paragon (1372)

msd's picture

09-03-2013, 12:23

Yes the opl4-ml is almost the same.. but you can't connect extern rom or ram. Having a different rom also means a completely different instrument patch table.

By JamesBurton

Resident (33)

JamesBurton's picture

09-03-2013, 17:30

PAC wrote:

Once Wozblaster was announced, I was firmly decided to make my own cartridge

I'm decided too but I've been reviewing the circuit design and the list of components and have a couple of doubts. I would like to ask the author but I cannot find his email address.

I'm a MRC newbie and don't know if private messages can be sent through MRC. Do private messages exist in MRC? If yes, how can I send one to the author of the Wozblaster?

Thank you in advance :)

By JamesBurton

Resident (33)

JamesBurton's picture

10-03-2013, 11:03

Me again Smile

I'm going to post my doubts here hoping that somebody with knowledge of electronics can help me instead of bothering the author:

1) The components listing indicates that capacitors C4 and C11 have a capacity of 0.015µF each but according to the schematics are not C4 and C11 but C4 and C2 the capacitors that should have that capacity because C4 and C2 have the same function, C4 for one audio channel and C2 for the other channel. Same thing for C12 and C2 pair: it should be C12 and C11. In summary, the pairs of capacitors should be C4 - C2 and C12 - C11

2) Capacity indicated for C12 and C11 (assuming point 1), that is, C2 is actually C11) is 0.33µF but in the schematics C12 and C11 have a capacity of 0.039µF. In Mediafire the schematics file was uploaded on 29/09/2012 and the components listing was uploaded on 17/02/2013 so looks like that the author introduced changes, thus correct capacity seems to be 0.33µF

3) I've seen photos published by the author with 3 different capacitors configurations:
- Capacitors C4 and C2 not installed and capacitor C22 installed
- Capacitors C4 and C2 installed and capacitor C22 not installed
- Capacitors C4, C2 and C22 installed
Again, in the latest component listing all three capacitors appear listed so I guess that the correct configuration is to have these three capacitors installed on the board.

Can anybody, please, have a look at these points and enlighten me?

Excuse me for this long (and probably confusing) post but I'd like to be absolutely right when assembling the cart, I'll be very disappointing to "fry" any of the ICs if the circuit is not electrically correct.

Thank you so much for your help Smile

By anonymous

incognito ergo sum (109)

anonymous's picture

10-03-2013, 12:30

JamesBurton, I didn't see your comments before. Let me pass your questions to him and if you want contact me (check my profile). Hablamos Smile .

By JamesBurton

Resident (33)

JamesBurton's picture

10-03-2013, 13:21

Great!

I'm really willing to see the Wozblaster inserted on my beloved FS-A1WX Smile

Thanks a lot!

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