Assembly instructions for Ambika

Dear Mutable’s,

i’m start to soldering now and i go step by step through the assembly instructions.
I’m not really understand this:

The 10k resistor just above the resistor network RN1 determines the gain of the final mixing stage. A value of 10k might cause clipping if the level of all voicecards is set to the maximum value. To prevent this, a lower value of 6.8k or 4.7k is recommended.

What do this mean if i have 6 cards?
I have soldered now a 10 KOhm resistor.
Is this wrong?

Thank you very much for your help.

All the best,

waldemaR

It means that it can cause a harsh sound output if you crank the volume on all voicecards to maximum volume :slight_smile:

10k should work ok with 4P voicecards. The only time I have had to change it was with 6 SVF voicecards. Best way to find out is to crank the volume pot up and hit all 6 voicecards at the same time. If it clips, change the resistor.

As you know the Ambika is capable of playing six voices at once. Each of the voices is controlled by the motherboard and is implemented by a separate card (PCB). So you have a mother board and six voice cards, seven pcb’s total. When you play all the voices at once, in a chord for example, there is a chance that they will overload the output circuitry and cause distortion. By lowering the resistor value you mentioned, this distortion will be prevented, but at the cost of lower overall volume. It is a good compromise; personally I would go with 4.7k and make up the volume on the mixer. Hope that helps!

  • cross post ! *

Dear V`cent, qp and mmarsh,

thank you very much for the fast response and help.
I forgot to write that i have 6 SMR.
I think that i prefer mmarsh answer and change the resistor to 4.7k.
Can i take this one?
http://de.farnell.com/multicomp/mf25-4k7/widerstand-0-25w-1-4k7/dp/9341951?Ntt=9341951

Thank you once again for you help.

All the best,

waldemaR

That should work fine.

It should be possible to change the volume level of the individial voicecards, so if you just lower the volume on the voice cards (or keep it from maximum), you shouldn’t experience any clipping, even with the 10k resistor :slight_smile:

One question more, regarding in this picture “Adjustable resistoris Ref 5K R47”,
in the BOM list is this R36.
It is correct that R36 is like same regarding in the picture?

Thank you once again for help.

All the best,

waldemaR

Yes, R47 got renamed R36 in later revisions of the board. Sorry!

Dear Olivier,

thank you for the answer, no problem. This will be good for any body else in the fututre who has the same question.

All the best,

waldemaR

One more :wink:
For C5, C22, C24, Mouser Part 75-1C10C0G220J050B
If you look at Mouser this will be a 22pf insteaf of 18pf.
Can i use this also?

All the best,

waldemaR

Yes, I use 22pf all the time, works fine

For C5 yes… for C22 and C24 you have to look at the datasheet of the 20Mhz crystal. It needs 2 caps that match it’s specifications.

Dear altitude, shiftr,
thank you very much for the quick reply.
What does it mean for the specifications regarding the two caps and the crystal.
Which are the important values.
Sorry that i ask for, i will learn something not only solder togehter.

@ altitude,
you use the 22pf for three mentioned above with this crystal:
http://de.mouser.com/ProductDetail/TXC-Corporation/9B-20000MAAJ-B/?qs=%2Fha2pyFadugh%2FD3LPoOATHoMdXTTKe2a5GTFaz0tfFNYHT9JIDY5veIdadZ1jMlW

This is the crystal what i used.

All the best,

waldemaR

it says:
Load Capacitance: 18 pF

I don’t know maybe it will work with 22pf too but i wouldn’t recommend it.

This is part# for 18p 594-K180J15C0GF5TL2

Dear shiftr,

thank you once for comming back.
This part that you mention is not on stock for the next 7 weeks.
Do you know an equalent part from Reichelt?

All the best,

waldemaR

Go with 22pF.

+1 for the 22p. I’ve built about 8 or so Ambika’s using the 22p without any issues.

Its not that Quartzes are overly picky with the Cap. For a “normal” Quartz anything from 18p to 25p will work. Reichelt sells some that need 33p, here 22ü is not enough - as i can tell from experience - but with the proper Cap everything is just fine.

Dear Mutable’s,

really thank you very much for the time to post and help someone who is new in this kind of material.
I think is not normal everywhere but here this is normal, GREAT!

All the best,

waldemaR