Ambika voice card help

I have 3 Ambika voicecards but only one is working. The top one has the data and note LED mixed up but it does work. The bottom one made a held note sound in the second voicecard position when I powered it on so I pulled the plug and tried it in the first position. The data LED lights up slightly but no sound. I also should mention at first I was using a power supply marked as 9vac but which actually put out 12v. Anyone have any ideas? Hoping I didnt mess up the ICs. I’ve tried swapping them with the ICs from an unbuilt voicecard and that didn’t work either. I also just realized I had posted this in the wrong category and have moved it.

It is hard to see from above, but not all ICs seem to be pushed in far enough (into their sockets) … do you have an image from an angle ?

You have both voice cards jumpered to the same channels. If you stack them, one must have the jumpers set to A and one set to B.

I’ve checked that the ICs were pushed in far enough and the one in position 2 was jumpered correctly at the time. It doesn’t work in position 1 either which is why it is jumpered to A in the image.

OK. Maybe check the 10k resistor above D1 (next to the trimmer) - that one looks wrong on the upper board (but pictures are a bit blurry).
Other than that I can only advise to check for bad solder joints/resolder.
I can spot at least two almost unsoldered IC legs.

Well I’ve narrowed it down to the ATmega chips. Can anyone recommend an ISP programmer? I tried using an arduino as the programmer but no luck so far. So close…


an arduino should definitely work though… if you have an uno/due you can take the original atmega328 right out and replace them with the ones you want to program

Possible mistakes. Sometimes the arduino headers give no contact.
Test the +/-8V rails.
Than , it looks like you have some cold solder points on the board.
If nothing helps TubeOhm can fix it.


Cheers, well I received a new AVR programmer in the mail and all the voicecards are now at least responding to MIDI input. 4 of them are now working great. The last two voices still have issues. One of them is either too loud or too quiet depending which of two TL072s I put in. I think the quiet one is faulty since putting it in a working card results in quiet ouptut there too. But a known working TL072 sounds overdriven on one voicecard. And the last voicecard isn’t making any sound. It does show notes being sent but no sound. I’ve tried switching out the ICs with a working voicecard and swapping positions. All the joints look fine as well as caps and resistors appear to be in the right place. Could it be the clock? I guess the note LED wouldn’t be lighting up if that were the case. Any debugging suggestions would be welcome.

check your resistors, 4.7K and 47K look really similar (same goes for 220R and 2.2K)

Hi altitude. The resistors are correct. I’m going to replace the 2n3906 Q1 once rat shack opens tomorrow. It’s the only thing related to the gain I haven’t checked yet.

Looks like I put in RN1 backwards on the motherboard. Thanks everyone.

Well, it wasn’t RN1. Now I’ve got one silent one and with no filter response. These are SMR-4 voicecards. I’m about ready to just order some new boards and components and start over. I’ve been over both of them multiple times.

hmm filter response seems to be working now so I’m just troubleshooting a silent SMR-4 at this point. So close!

Now it’s down to the voicecard is in position 6 is quieter than the rest when mixed. Everything sounds even coming from the direct outs so I think it’s something about the way the mix is functioning. I’ve tried replacing the TL072 just before the output but that didn’t help. I thought that RN1 was in backwards but it’s been replaced as well. I didn’t have any 10k networks with 7 pins so I cut down a 10 pin bussed resistor. Maybe that’s the problem. Any other ideas?

Can anyone explain how the mixer works a little more? The technical documentation says each voice “is routed to an inverting mixer with a gain of 1, then through the volume pot, then through an inverting mixer with a gain of 1 (to get the original phase) – this yields the “mixed” output.”

I’m assuming that inverting mixer is the TL072 right next to the mixed output. Is there anything else other than the resistor network and the TL072 that an individual voice goes through after the individual out and before it is mixed? Thanks.

In the end it was the damn resistor network again. Just because you have replaced a component doesn’t mean the new one works. I am now happily in Ambika land