YM2413 - HAAG - noisy

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By dublevay

Supporter (5)

dublevay's picture

13-07-2020, 01:55

Hi,

I have some YM2413 chips which I am trying to use with a Dragon 64 computer. I already have the YM2149 and V9958 running from the cartridge port, and would really also like to add the YM2413.

I have purchased several YM2413 from AliExpress, and I think many have been faulty or fake. However, I do have some which are marked HAAG, which do seem to be genuine.

The problem I am experiencing is noise. I am using a BA14741 op-amp and have essentially recreated the output circuitry from the Sanyo PHD-70FD/70FD2 with fixes - as per this page.

The YM2149 sounds great. The YM2413 initially does nothing, but for some reason, after about a minute, background noise builds up and the YM2413 can actually be heard to respond, despite the background noise.

This is my circuit...

Are the YM2413 chips generally noisy - or is it likely these are still faulty chips?

Thanks

John

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By sdsnatcher73

Paladin (997)

sdsnatcher73's picture

13-07-2020, 12:39

Hi John. I don’t think YM2413 chips are all noisy. I have several (built inside MSX2+ machines, MSX turbo R machines, FM-PACs and 1 clone) and none of them are particularly noisy. All these (except for the clone FM-PAC) where all made in Japan at the time and were likely sourced from Yamaha directly. The clone I have was made by repro factory in France, but also 8bits4ever in Spain still produce FM-PAC clones with real chips (whether they are true original Yamaha is always hard to be certain about, but these carts do not use an FPGA is what I mean).

By Meits

Scribe (5897)

Meits's picture

13-07-2020, 13:00

You can spot a fake by rubbing aceton on the print. If the print stays it's genuine.
Getting parts from china can be risky. They like to fake. Sometimes even put a wrong print on it. Better try to source some genuine pull-offs.
Though, it is possible that circuitry causes noise. Eventhough all my MSX Musics sound good, some sound better.

By dublevay

Supporter (5)

dublevay's picture

13-07-2020, 16:28

Thanks both.

I tried rubbing acetone over the chips I had. The HAAG ones didn't change at all. Some that had really obvious fake markings rubbed away to nothing underneath at all. I then rubbed with ultra fine abrasive paper, but there seemed to be nothing there.

I have read somewhere about putting an octal buffer in between the data bus and the ym2413 to stop noise. But should that really be necessary?

Also, I am using the clock from the V9958 into XIN of the YM2413, with XOUT left unconnected. Its that fairly standard?

By Grauw

Ascended (9181)

Grauw's picture

13-07-2020, 16:55

It doesn’t seem a fake is the problem, or it wouldn’t work at all. It could be defective though, of course. But I think it may be more likely something wrong with the circuit. As for the circuit, you could try asking l_oliveira (@leo__oliveira on Twitter), he knows a thing or two.

By sdsnatcher73

Paladin (997)

sdsnatcher73's picture

13-07-2020, 17:57

Not an expert but according to the Ym2413 application manual the clock oscillator has to be connected between XIN and XOUT. So leaving XOUT disconnected might be an issue. This video (in Dutch) shows a guy using YM2414 in cooperation with an Arduino, may help you or not.

By jltursan

Prophet (2288)

jltursan's picture

13-07-2020, 18:27

Just in case, here're the FM-PAK schematics: FM-PAK schematics. They used LM1458 and it sounds pretty clear.

Btw, really nice work!

By lintweaker

Champion (266)

lintweaker's picture

13-07-2020, 19:33

sdsnatcher73 wrote:

Not an expert but according to the Ym2413 application manual the clock oscillator has to be connected between XIN and XOUT. So leaving XOUT disconnected might be an issue. This video (in Dutch) shows a guy using YM2414 in cooperation with an Arduino, may help you or not.

FYI. If you use a clock oscillator feeding it's output to XIN is all that is needed. If you use a crystal then you need to use both XIN and XOUT.
I have experience receiving fake YM2413s from China. These were clearly fakes as the lettering did not even look a bit like the original. Of course the seller kept on saying these were the real deal. I did not bother trying them.
Nb getting the amplification right while mixing in the PSG and keyboard clock is an art (for me at least). I'll stay with digital logic.

By Grauw

Ascended (9181)

Grauw's picture

13-07-2020, 21:17

lintweaker wrote:

I have experience receiving fake YM2413s from China. These were clearly fakes as the lettering did not even look a bit like the original. Of course the seller kept on saying these were the real deal. I did not bother trying them.

If you did not test them then I am giving the benefit of the doubt to the seller. Remarking happens a lot and it’s stupid and pointless, but it does not mean you don’t have an authentic functional Yamaha part. Of course used and perhaps not treated well, but still usable, and in the end I think we should be happy that they’re still available in the first place, even if that often means dealing with crap like remarking. I don’t see European parties even bothering to recycle these chips.

A few years ago I ordered a bunch of YM2608’s and YM2610B’s, all of them with a cleanly filed surface and remarked. All eight of them work perfectly. The latter were even real YM2610Bs even though those are actually often remarked YM2610’s (without B).

PlgDavid made a very nice video about the subject, where he also ordered a whole bunch of chips online and tests all of them. About 50% of them were remarked, 10% were non functioning.

By Eugeny_Brychkov

Paragon (1153)

Eugeny_Brychkov's picture

14-07-2020, 22:47

Circuit built using IC14B (IC1B in the Fabio's circuit) may be subject to oscillation.
Please explain the sound you hear. Anything heats up on the board?
What is Vcc in your circuit? What voltage op-amps are powered from? Fabio's circuit has no data on it.
What dielectric type and rated voltage capacitors you use in this circuit?
Are you sure in correct values on your real board?
Is the noise present on the IC14C output pin 8?

In overall the circuit is not of the best. Op-amp is expected to work in split-supply mode, and creation of the virtual ground may cause problems (I can not see input leakage currents in the datasheet, thus can not assess how inputs affect each other).

By dublevay

Supporter (5)

dublevay's picture

17-07-2020, 02:21

Thanks all for your responses. Sorry for my delayed response.

I've done some additional testing tonight, having now disconnected the V9958 and used a standalone oscillator for the YM2413. I am seeing some strange things. When I use the register settings from this page: https://www.smspower.org/Development/YM2413ReverseEngineerin..., I am seeing some rather odd oscilloscope outputs from the chips. No matter what the markings, some don't work at all, but those that do 'work' look like the attached image... The sine wave seems to be missing for 110ms!

Eugeny - I agree with you that the op-amp circuit is not the best. It seems to be very prone to picking up noise. Sad I confess I do not even understand what the split feedback is doing in IC14B - and furthermore, I am not sure whether C304 & R309 are forming a low-pass filter of 4KHz? That would seem incorrect.

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