SammichSID Distortion on Left Socket

[Param1]

Hi guys,

I have a question.

As stated in the topic, the SID in the left socket distorts very early. The one in the right socket basically not at all and it can be very loud.

Distortion level depends on:

- Filter needs to be on

- Amount of notes I play at the same time

- Global Volume

- Sustain Level

- Amount of waveforms selected

Please note: This is NOT SID related. If I change SIDS the problem remains in the same sockets.

I made two sound examples:

A small loop with

- d-minor chords

- triangle & saw at the same time

- Sustain 10

- lfo sweeping activated Lowpass

- Manual sweeping global volume from around 50 - 127

Of course the question is: How come?

:question::shocked::question:

p.s. I got actually two Sammichs and on the other one it is exactly the other way around :turned:

Sid Location Left.mp3

Sid Location Right.mp3

Edited September 17, 2011 by Param1

[m00dawg]

Hmm that sounds to me like something going on with the filter section perhaps? Have you tried making a simple patch that sweeps along the filter range on both L and R? Also how about a patch that doesn't use the filter at all to see if that sounds clear. If you swapped your SIDs out than it probably isn't that so maybe a bad solder join on your filter caps? Sort of thinking out loud so I could be off-base but can't hurt to check.

[Param1]

Without the filter it sounds OK and with just one waveform selected it sounds almost normal. The filter cap sockets seem to be soldered well. I swapped the filter condensators and it did not change anything.

Can condensators actually saturate? Maybe it's the transistors T1L or T1R ? But I soldered them with caution. But maybe I broke them?

Edited September 17, 2011 by Param1

[Imp]

If it isn't the filter caps, I'd check the supply voltage on both sockets, with and without sids.

Maybe the sid needs more power when the filters are switched on.

Did you disable "Ext" (filter menu) on both channels? You can also pull the external input to ground with J4R/L.

Also check the row of caps below the audio sockets for bad joints.

Those transistors could cause the distortion, but as the sound passes them regardless of the filter, i don't think they do.

Caps can only store a limited amount of energy. If they get too much, they explode or short out. While explosion is obvious, you have to check for short circuits with a multimeter.

Edited September 18, 2011 by Imp

[Wilba]

Just a note on what Imp said: external input is already grounded by the audio in socket so there's no need to ground it more.

Since you swapped SIDs and the problem stays with the left socket, it could be either the solder joints for that SID and audio buffer, or perhaps something wrong with the firmware - i.e. the ensemble's filter range for the left SID is different to the right. So check the ensemble for anything different between left and right SID.

You say you checked the filter cap sockets, but check also the SID pins they connect to.

You could try routing the left SID's output to the right SID's audio buffer - remove the right SID and connect a wire between IC1L pin 27 and IC1R pin 27. Thus the left SID's audio output will go through the right SID's audio buffer and you should get identical sound on both outputs of the audio socket. If they don't sound identical (i.e. left channel distorts early, right channel does not) then you've isolated the problem to the audio buffer. You can then try taking out the left SID and inserting the right SID, do the same wire to test the right SID with the left SID's audio buffer. (I bolded the "taking out" part because you don't want to directly connect SID audio outputs!)

[Param1]

You could try routing the left SID's output to the right SID's audio buffer - remove the right SID and connect a wire between IC1L pin 27 and IC1R pin 27. Thus the left SID's audio output will go through the right SID's audio buffer and you should get identical sound on both outputs of the audio socket.

Thanks for chiming in Wilba. Well I did this interesting test and it brought up an interesting result:

Both channels sound the same BUT DISTORTED. I expected that if they sound the same that they sound right because the left Socket was used.

After the test I removed the bridge and testet Socket Left (IC1L) solo and it sounded ok again.

So I have not isolated the problem to the audio buffer? I am not sure what the audio buffer is anyways :-(

edit: Or should I also remove the Filter Caps of socket IC1R when doing this test?

@Imp the voltages seem to be OK

editedit: The ensemble shows me (via Editor) that the Filter Range is the same for both sockets.

Edited September 18, 2011 by Param1

[Wilba]

Thanks for chiming in Wilba. Well I did this interesting test and it brought up an interesting result:

Both channels sound the same BUT DISTORTED. I expected that if they sound the same that they sound right because the left Socket was used.

After the test I removed the bridge and testet Socket Left (IC1L) solo and it sounded ok again.

So I have not isolated the problem to the audio buffer? I am not sure what the audio buffer is anyways :-(

edit: Or should I also remove the Filter Caps of socket IC1R when doing this test?

@Imp the voltages seem to be OK

editedit: The ensemble shows me (via Editor) that the Filter Range is the same for both sockets.

OK so if you routed left SID socket to right SID audio buffer (that's the caps and BC547 between the SID and the audio socket) and both channels sounded the same (distorted), the problem is to do with the left SID socket only.

I don't understand what you meant by "it sounded OK again", I thought the problem was always with the left SID socket???

My best guess at the moment is that the filter caps, the machine pins for the filter caps, or some other solder joint in/around the left SID socket is the cause. You could try replacing the machine pins just in case the contacts with the filter cap leads are poor... maybe something got stuck inside them, or they are faulty, tarnished, etc.

[Param1]

OK so if you routed left SID socket to right SID audio buffer (that's the caps and BC547 between the SID and the audio socket) and both channels sounded the same (distorted), the problem is to do with the left SID socket only.

I don't understand what you meant by "it sounded OK again", I thought the problem was always with the left SID socket???

My best guess at the moment is that the filter caps, the machine pins for the filter caps, or some other solder joint in/around the left SID socket is the cause. You could try replacing the machine pins just in case the contacts with the filter cap leads are poor... maybe something got stuck inside them, or they are faulty, tarnished, etc.

Wilba, I think I mixed the Sammichs. One has distortion on the Left and one on the Right.

I fixed one of my Sammichs tho. Seems like it was related to the Resistors R2L R3L R4L on the one Sammich and R2R R3R R4R on the other.

The pins 27 of the distorted SID Sockets only had about 2.8V instead of 5V. By moving the resistors with my finger nails I was able to change the voltage lol...

I resoldered them and one Sammich is now working. The other however not but I will work on that again and report back, also when successful.

[Param1]

I am not able to fix the problem on my 2nd Sammich. And I am totally out of ideas and totally disapointed about the overal time invested into this.

And it does not make sense to me why I can't fix the 2nd one by fixing the resistors. It had the problem on the opposite socket and it showed

the low voltage on the opposite resistor row. I fixed it, yet the problem is still there, opposed to the other Sammich.

I checked 5000 connections with the continuity tester and I measured voltage at 5000 points on Sammich 1 and 2 to check for differences but there are none....

The sockets sound the same now but they are both distorted when the Sustain Level is about 10 (and volume 127), filter on and two waveforms.

[m00dawg]

For what it's worth, I had an issue with my sammichSID that took me a few weeks to track down, including cutting traces on the board, to find the problem. Turns out it was a bad solder joint that looked like a perfectly good one. Wouldn't think it could hurt just reflowing solder around the audio pipeline for the affected SID. In my case, the short was in the Bank Stick section but I can't imagine that affecting this. Just pointing out the fact that it may not be where you think it is.

[Wilba]

It looks like you're in Germany... so I recommend posting the "distorting" sammichSID to nILS (also in Germany). I'll pay the return shipping. I think a second pair of eyes will help in this case. It certainly sounds like it's a fixable problem, just what to fix is elusive. Email me to discuss the details.

[Param1]

It looks like you're in Germany... so I recommend posting the "distorting" sammichSID to nILS (also in Germany). I'll pay the return shipping. I think a second pair of eyes will help in this case. It certainly sounds like it's a fixable problem, just what to fix is elusive. Email me to discuss the details.

Thanks for the offer. You don't have to pay the shipping cost lol... the only one who transfers some money will be me.

[Param1]

A little update. I try to keep it as short as possible.

Situation before Thread:

Sammich 1: Distortion Socket L

Sammich 2: Distortion Socket R

Sammich 3: No Distortion

Situation Now:

All Sammichs and Sockets Distorted.

(when playing 3 notes at the same time (chords), Filter on (Lowpass is worst), and 2 Waveforms selected)

The reason why Sammich 3 is distorted now is unbelievable. I wanted to resolder some joints on Sammich 1 or 2 to see if it helps but took the wrong pcb and resoldered 3. (where are the facepalm smilies?)

Now, of course this is a strong hint that the soldering points are the cause but even after resoldering some more nothing worked.

I resoldered with care, especially the transistors. I measured lots of continuity tests, voltage tests with and without SIDS and everything looks OK (to my noob eyes).

I once found some anomalies but they were actually related to the SID that was in at that time. (had higher voltages at some pins compared to the others)

But what I find strange is: Why the exact same issue on all three Sammichs? Why not for example: Sammich 1 - receives no midi in , Sammich 2 - can not store data , Sammich 3 - no Sound at all

Possible Reason for all of this:

1. Most likey Me.

a. Maybe everything is soldered badly so it sums up and the Sammichs distort? Reason would be a regular mistake.

b. If only some joints don't work corectly, why at the same positions leading to the exact same issues? Unregular and unlikely cause?

2. If it is something else, it could be

a. A central part because the issues are always the same.

A central part would be the power supply. In fact my power supply is sub optimal. It only delivers 11.5V max although specced 12V. If I want to have 9V at the 8580

I have to bypass the bridge Rectifier.

b. Specific components in the audio path (and communication path with the main processor?).

But these would be many parts. For instance: transistors. 6 transistors need to malfunction. Or filter caps: 12 filter caps need to malfunction. - unlikely imo.

:-(

Edited September 27, 2011 by Param1

[m00dawg]

Distortion when playing multiple notes using a filter tends to happen even with normal SIDs so that might not be anything to be overly concerned about. I think you were on the right track with sticking with non-filtered polyphonic sounds in your testing.

Your PSU modifications don't seem out of the ordinary - if you are supplying DC current, you could bypass the rectifier. I would, however, recommend you simply get a power supply that works well with your Sammiches instead of trying to work around that problem. How much is a new wall-wart? How much is a SID chip? Exactly.

[Param1]

Distortion when playing multiple notes using a filter tends to happen even with normal SIDs so that might not be anything to be overly concerned about.

Any chance you can record some chords with your Sammich?

- Init patch with two Waveforms

- Sustain 15 , Volume 127

- Filter on, LP set somwhere into the middle

- Chords with 3 Notes

Would be great to hear whats going on!

[m00dawg]

I would but I'm actually in the middle of packing and will be moving this Friday so my rig is in shambles right now. If you can wait until next week I can get that for you though, sure. In the interim, can anyone else help him out?

[Param1]

I would but I'm actually in the middle of packing and will be moving this Friday so my rig is in shambles right now. If you can wait until next week I can get that for you though, sure. In the interim, can anyone else help him out?

Next week would be great, sure !

[Param1]

I am still interested, can you please help me ?

[m00dawg]

I wasn't totally following your patch configuration so, instead, I used the Filtered Poly patch (#16) from the standard kit, which uses a lowpass filter; and my own polyphonic patch, which doesn't use a filter.

SIDTest.wav.mp3

[Param1]

Thanks. I got the same results actually. I assume you get more distortion if you use more than one waveform in the polypatch?

[m00dawg]

That's correct and is a "feature" of how filtering works on the SID. There is a post about that somewhere on the forums (though it may be rather old by now). If you want to have a nice filter on top of polyphonic sounds, you may want to look at the SSM2044 stuff. I assume that behaves better with the addition of multiple notes. Disclaimer: That is raw assumption - I have not finished (or really even started) my own SSM filterbox so I don't have any proof :)