Ambika "Pioneers" board run [all seats reserved]

I plan to order the boards for the “pioneers” run tonight. There are 25 seats, 2 already taken.


Individual outputs behavior

One “too bad…” I got from two people is that plugging a cable into an individual out does not take the signal out of the mix like on some drum machines. I hadn’t thought about that one. My thinking was that the serious guys would be using only the individual outs anyway because it’s awesome to pan each polyphony voice independently, so the “mix out” was just there for my testing and fooling around. I am changing my mind about it. Either I do a production run of the “proven” design ; or I do a run of an alternative design with the 808 behavior. What’s your opinion about it?

SVF voicecard DAC thing

The SVF voicecard will have one new bit of circuitry to fix an occasional envelope / VCA clickiness the protos had. It’s an extra 470R resistor and a 1uF 5mm pitched cap (can be film or ceramic). You can short the resistor and not populate the cap to get the “original” behavior. I have never built the circuit but it’s just a passive RC filter dammit!

LCD footprint

I have made the cutout for the LCD as large as the PCB layout allows, which seems to make it OK for the Optrex part. I cannot guarantee anything - a 1:1 print of the Optrex drawing seems to fit in a 1:1 print of my board. If you want to verify, grab the brd files.

Please send me a private message indicating your email address and the mix of voicecards you are interested in. If you are put off by the idea of beta-testing these new bits, let me know and I will postpone the whole cycle by 3 weeks. Note that it is not uncommon for me to directly do a production run of boards with this kind of modifications without checking them with a proto (4PM v0.2, digital board v0.7, SVF v0.2 were directly ordered in volume).

Good idea. I’ll take a day in the next 2 weeks to do the few updates to the Ambika code mentioned here…

Just an idea. The layout of the voice LEDs on the top panel appears to be:
IMHO it would be more practical to have
as this mirrors the physical layout of the voicecards. I thought this could help avoid confusion in systems with different voicecard types installed where, say, the user has disabled the card LEDs or the card LEDs can’t be seen because of an opaque case.
If this would be impractical or difficult to implement then please feel free to disregard it.

ooook! this is a bit less surprising :slight_smile:

Oups, just realized I didn’t take into account the time for the MOBO, so total time spent is 10h, not 7h30 (this was for the 8 Voicecards only).

I spent about 15 hours to get motherboard plus 4 SVF cards done, but I probably should have taken time to organise my parts better before starting. Did the same thing here with a production line for the voicecards which was faster, but found it easier to make mistakes due to my brain switching off. Now for the 4x4P cards (I hedged my bets…)

Regarding the overall time spent on it, after building and testing the first Mobo + 4P Voicecard without any real trouble ( except for the AC power supply trick), I decided to build the 5 other 4P Voicecards simultaneously and this was quite efficient actually. I did miss a few components so I first ended with a 3 voices Ambika and resumed the the 2 remaining 4P VC the following day quite quickly (I only missed 3 resistors and à set capacitors).
The SMR4 and SVF board were done in slightly less time than the first 4P voicecard.

And the most time spent now after a few days is already playing it rather than building it …

The SMR4 was designed before I realized that printing resistor values would make the boards a bit less sexy but much easier to troubleshoot through the web…

no, he’s speaking about labels.
you can read resistor and capacitors names on the 4P and SMR voicecards, but not on the SVF voicecards where only values are visible on the silkscreen.

7h30 for everything seems very fast for me!

No resistor silkscreen on the PCB? sound like a dud or perhaps they got damaged in transit?

They’re all labelled on every board I’ve had and I’ve got all three types.

If the Polivoks filter was an option we could be called “Young Pioneers”! :slight_smile: PM’d!

I’d appreciate feedback on this new variant of the output stage.

Each individual out is straight form the voicecard with a (bigger) protection resistor in case some voicecards in the future have some funky output stages. The unconnected individual outputs are routed to an inverting mixer (right side of the op-amp) and a gain of -1 to recover the same phase as the individual outputs.

" Either I do a production run of the “proven” design ; or I do a run of an alternative design with the 808 behavior. What’s your opinion about it?" I thought about this and it would be nice to have voices removed from the mix out when they are routed through their independent out. It would be nice to be able to use the mix out for poly stuff and each independent out for mono stuff simultaneously. Doubt I would ever do this, but I do know a lot of people like to use the Tetra like this.

Looks like it should work OK-just that if you are keeping the master volume pot at 100K then the 10K input to the final opamp stage will load it a lot-either change the resistor pair across the last opamp to 100K each or reduce the value of the master vol pot, or maybe both…

What QP said-it would give people a lot of incentive to have hybrid Ambikas ie one channel SVF for drones and 5 channels of 4P for melodic stuff, and only need 2 lines to the mixer.

Edit: you could probably put the output resistors up to 1K without much hassle-that’s standard in modulars, and better safety margin for accidents…

+1 for 808-like individual output behaviour.

To be honest i think the ambika deserves a stereo output on a stereo jack. Three voices panned left and three voices panned right. That way you could use 2 mono channels on a mixer and use the pans to set the width of the stereo field. I imagine using the ambika in a live setup with a
small mixer. Having to use 6 channels takes up a lot of mixer space.
This together with 808 output behaviour.
Just don’t wait for me as i’ll probably wait fot the kit version.

Taking individually connected Voicecards from the Main Mix seems to be the common behavior. As not everybody has the luxury of a big console (and maybe even wants to take the Ambika on Stage) it looks like a good idea to implement industry standard 808 behavior.
Maybe theres the additional possibility to implement in Jumpers to solder for options with the 808 behavior as standard? (Its common for big Consoles to have Routing Options by internally wired jumpers)

Better to get it perfect, then there’s nothing a reviewer can complain about?

i agree with shiftr that a stereo mix output would be immensely cooler than mono - but i imagine that individual panning for 6 voice cards might make things rather complicated.

yes, that’s why i proposed the crude stereo option of 3 left 3 right. This should relatively easy to implement.