Bringing the Vocoder to life

jhaible

This will be your thread for exchanging information about building / optimizing / debugging.

I rely on the group to self-organize, and won't take any leading role here personally. Smile

JH.

The Bad Producer · Joined: Mar 08, 2009 Posts: 282 Location: The Manhole

If I may be so bold as to ask the first question!

How hard/pointless do you guys think it would be to hand-match all the caps, as opposed to getting 1%? Would this even be viable in this situation?

(I've got a fair amount of time on my hands at the moment!)

Charlie

/mr · Posted: Wed May 11, 2011 4:25 pm Post subject:

diablojoy · Posted: Wed May 11, 2011 4:31 pm Post subject:

150 each of 10n + 47n to within 1% you would need to buy thousands
of each at 5% values with no guarantee of complete success i guess it depends on what value you rate your time at but cost wise probably wouldn't work out that much cheaper
you could check out rush on line capacitors presently at 0.75 GBP each for both values or 225.00 GBP + postage the price only recently went up from 0.47 Sad

doh! they also have the 10n value in polystyrene in a 'd' tolerance 0.5% at 0.75 GBP though not certain they will fit the board at 7mm x 7mm x 13 mm

cheers

/mr · Posted: Wed May 11, 2011 4:48 pm Post subject:

diablojoy · Posted: Wed May 11, 2011 8:07 pm Post subject:

decaying.sine · Joined: Aug 31, 2009 Posts: 92 Location: New Haven, CT, USA

Would there be any appreciable benefit of sorting and matching specific 1% resistors into identical ohm groups and using those in certain areas of, say, the 8 pole filters (or other places)? In other words would this improve performance?

StephenGiles · Joined: Apr 17, 2006 Posts: 507 Location: England

/mr · Posted: Fri May 13, 2011 12:47 am Post subject:

jhaible · Posted: Fri May 13, 2011 2:56 am Post subject:

The design is relatively insensitive to component tolerances - that's why 1% is good enough.
That was EMS's method. Sennheiser achieved similarly steep filters with only 6 poles, but required much better component tolerances.
Synton used a similar approach - higher filter order, lower Q of individual stages.
The LPF is quite unique ineed - I've never seen it usesd othe rthan from EMS.
BTW, a single LPF stage is a resonant, 2pole, 6dB/Octave filter.

JH.

/mr · Posted: Fri May 13, 2011 11:07 am Post subject:

jhaible · Posted: Fri May 13, 2011 11:19 am Post subject:

/mr · Posted: Sat May 14, 2011 9:20 am Post subject:

decaying.sine · Joined: Aug 31, 2009 Posts: 92 Location: New Haven, CT, USA

I got my 1% caps from Newark already. They shipped very quickly. The 47nf shipped with part blue and part gray color. Now this just upsets my delicate sensibilities. Wink

jhaible · Posted: Sat May 14, 2011 12:15 pm Post subject:

jhaible · Posted: Sat May 14, 2011 12:21 pm Post subject:

BTW, the Korg MS-20 HPF is just the same principle. But here you want equal resistors (for changing them equally), and thus set the Q by capacitor values. So you get a 6dB/Oct slope, but still a resonant and even self oscillating HPF.

JH.

decaying.sine · Joined: Aug 31, 2009 Posts: 92 Location: New Haven, CT, USA

I wanted to let folks know that I am building a bill of materials to check against Oscar's BOM. I believe that I saw Jürgen post that this would be a good idea. I am almost done at this point. I'll also work on mouser order codes (or other sources) for the parts as well. This would probably only work for United States builders.

I started typing out all the parts from the schematics and quickly fell asleep. Then I opened up the PDF's and copy every bit of text, pasted it into a text document, and then just adjusted the spaces with tab delimits. It takes about 3 minutes per schematic (about 27 of them if I recall). I am sure everyone else already had this figured out long ago, but it was a Idea

moment for me!

The Bad Producer · Joined: Mar 08, 2009 Posts: 282 Location: The Manhole

Nice one decaying.sine, seeing as you've done the hard work Very Happy

I'd be up for translating your BOM into a UK friendly one with parts number from Rapid/RS/Farnell etc...

Charlie

(not sure whereabouts all ten peeps are based, I'm in UK)

decaying.sine · Joined: Aug 31, 2009 Posts: 92 Location: New Haven, CT, USA

This may have been mentioned before but I'll post anyways. I apologize if it has already been reported. These duplicate resistor identifiers came up when making my BOM to compare to Oscar's work.

The duplicates...
Synthesis Amp, Compander, Noise, and S-Generator Schematic
R2663 1k
R2663 1k

Synthesis Amp, Compander, Noise, and S-Generator Schematic
R2634 10R
R2634 100K

Slew Freeze Schematic
R2521 10k
R2521 27k

Silence Bridging Filterbank Control Schematic
U2402 is CD4016 on schematic. On Oscar's BOM there is a CD4066 but no CD4016. They're both Quad Bilateral Switches so either is okay, but 4066 better for audio switching? This may have been addressed earlier, if so, nothing to see here Smile

jhaible · Posted: Mon May 23, 2011 9:50 pm Post subject:

4016 and 4066 will both work. They are used as switches (B, D) and as Inverter (A) and Schmitt trigger (C) in the AR envelope generator of the Silence Bridging.

JH.

JoeMorris · Joined: Apr 26, 2009 Posts: 161 Location: Brighton

The Bad Producer · Joined: Mar 08, 2009 Posts: 282 Location: The Manhole

JoeMorris · Joined: Apr 26, 2009 Posts: 161 Location: Brighton

prefer the usability of their website to farnell's too... (auto-BOM import etc..)

/mr · Posted: Tue May 24, 2011 6:48 am Post subject:

decaying.sine · Joined: Aug 31, 2009 Posts: 92 Location: New Haven, CT, USA

I have all the resistors done for the BOM Mouser order. I included an extra column that recommends buying the number of pieces specified for the project or the next available price break--depending on the one that is cheaper. As you might guess sometimes it is cheaper to buy at the next available price break than the actual amount that you need.

I am working on caps now, but I'll wait and post everything together.

Also, my BOM of materials is identical to Oscar's original BOM. However, I am not 100% done checking yet. My suspicion is that his is accurate and it also has lead spacing for caps and that is awesome!