Two problems left. Volume and disappearing sound

[renepela]

Hi everybody,

It took a lot of time (it's the first project I ever soldered) and I made a lot of stupid mistakes, but thanks to this great forum I now have an almost working 4 sid midibox sid.

I have two small problems left which I can't tackle so maybe this forum can help me out once again.

Problem 1:

All 4 sids give sound, however the volumes differ a lot. The first sid has a medium volume, the second and third are very loud and the fourth has a low volume when it works (take a look at problem 2). I'd like to have volumes which are the same.

All 4 sids have there own audio out.

Problem 2:

Sometimes when I play a note on my midi keyboard it sounds through all 4 sids, but only the first note.

After playing one note sometimes one of the others sids stops working. When I do a program change (choose another sound) it works again and I can hear them all four.

Especially sid number 4 has this problem. After one note of sound it stops working in 99% of the cases.

The first sid always works.

Only the first core has an optocoupler. I removed the optocoupler IC on the other other cores. Is this all I need to do, or do I need to make some more changes to the slave cores?

Sid 1 and are 6581's and sid 3 and 4 are 8580's. I know they operate on different voltages and I believe I made all the adjustments for that.

Hopefully with the help of this forum I can finally finish my midibox sid and start working on the control panel.

Rene

[TK.]

Only the first core has an optocoupler. I removed the optocoupler IC on the other other cores. Is this all I need to do, or do I need to make some more changes to the slave cores?

no, other changes are not required.

Currently I've no idea how this effect could happen, can you try out more? What does "stops working" mean - no sound anymore, or an holded note? What happens, if the slave PIC is controlled directly from the PC/keyboard via MIDI (and not from the master core via Link)

Best Regards, Thorsten.

[renepela]

I have tried a few things, but so far I have not been able to fix these last issues.

I have swapped the sid chips and the Master Sid is still a lot lower in volume. So the chip itself is okay and it's a problem on the sid board.

The disappearing sound problem is also still there.

It's really strange.

The first sid always works perfect (except from the lower volume).

The second sid works most of the time, but after a few notes it just stops working. The sound is not "hanging"but is completely gone.

The third sid has the same problem, but it occurs sooner than on the second chip.

The fourth chip only works for one note and than all sound is gone.

So it looks like the problem gets worse downwards.

The forst works great. Second disappears after few notes, third even sooner and the fourth stops working after one note.

When I choose another sound, it all starts working again.

Really strange isn't it?

When I send the midi signal directly to one of the four boards, everything works great. So it only goes wrong when they are connected to each

other.

I hope someone can put me in the right direction.

Rene

[TK.]

Hm... volumes are lower at the slave side, MIDI (or PIC) doesn't work stable - could it be a voltage problem?

Have you measured the voltages at the Vdd/Vss pins of SID and PIC? Note: don't measure the +5V/+12/+9V voltages against the common ground, probe them directly on the pins - because it could also be a ground problem!

Best Regards, Thorsten.

[renepela]

Today I checked all voltages and they all turned out to be okay.

The 5V pins are slightly to high (5.13V), the 12V pins measure 11.76 so are a little to low.

The 9V are 8.98 so almost correct.

I think those values are okay.

I did a little more testing.

When some of the sids stop working, the sound disappears.

When I listen very close I can still hear a little sound, so the sid's don't stop working !!

They just have a huge drop of volume. It's seems to be happing quite random (except for sid 1, that one always works and sid 4 never works).

Sid 2 and 3 just drop there volume to almost zero after some time.

Could this be a heat problem?

TK you  mentioned in your previous post that my volumes are lower on the slaves. But it's the other way around.

The volumes on the slaves are higher than on my first sid.

Could it be that those volumes are to high and because of that the sid stops working?

Wat is a normal volume and how can I measure this?

Thanks in advance,

Rene

[TK.]

They just have a huge drop of volume. It's seems to be happing quite random (except for sid 1, that one always works and sid 4 never works).

Sid 2 and 3 just drop there volume to almost zero after some time.

Could this be a heat problem?

don't know. Does the volume drop very fast, or slowly? The effect could also be related to the SID envelope bug, what are the ADSR settings of the sound you are testing?

The volumes on the slaves are higher than on my first sid.

Could it be that those volumes are to high and because of that the sid stops working?

Wat is a normal volume and how can I measure this?

I would propose to measure the volume amplitude with a sampler. Just record a sound and check the dB settings in the waveform window of your sampling program. In order to 100% ensure, that the audio in of your soundcard doesn't falsify the results (who knows...), always take the same audio input.

Thereafter swap the SIDs and record it again - this should give you a good comparison.

Btw.: you could send me the samples in .mp3 format, I will upload them to the midibox server so that everybody can get an impression.

For the "missing sound" problem, there is also another good test which ensures that the slaves are working independent from the software. Currently the J11:MI lines of the slave are connected to J11:MO of the master. When you connect these lines to J11:MI of the master instead, the slaves will receive exactly the same MIDI data like the master.

This isn't a useful setup (because slaves won't receive patches from the master anymore), but it gives some important input for finding out the root cause

Best Regards, Thorsten.

[TK.]

Important question: do you notice the same problem with missing notes, when the MIDI Out of the master is not connected to any MIDI device? (only to the slaves)

Best Regards, Thorsten.

[renepela]

The volume drops very fast. Like it goes from the maximum volume to the lowest volume. It's gone in a blink of an eye.

The sounds that demonstrates it is for instanstance preset sound number 52.

When using this sound the sounds plays for a while and suddenly it's gone. Especially the 8580's have this problem.

Maybe I forgot to use replace some parts for the 8550's?

I didn't change a thing on the cores. All 4 are the same. On the 8550's I used a 78L09 and replaced C! and C2 with 6.8nF.

I believe that's all I have to change?

I don't think it's the ADSR bug but maybe you can tell.

Maybe the problem isn't midi related. Could I have made it mistake in the soldering of the output on the sid board?

I have also grounded the input on the sid board by placing a jumper on it. The input isn't used so it seemed logical to ground it with a jumper.

Can you tell me how I can check if the output parts are working the way they should.

I have also removed the midi out cable, to prevent loppbacks (although I'm sure midi throug is disabled on my pc). The results are the same. The problem is still there.

Tomorrow I go the the USA for a few days so I won't be able to make the suggested mp'3.

I will do that next week.

I really want to thank you for all your help. It's really appreciated.

Rene