Hero and Sidekick VCOs

[analogoutput]

Hero VCO module

[Bpbby]

Really nice !!

[Sussmayr]

I ordered two sets a week ago. Just waiting now.

[analogoutput]

Heading to the PO tomorrow. There are a few sets still available (and a few other modules) if you want to get in on it.

[analogoutput]

Sidekick VCO module

[Sussmayr]

Nice Demo
Now I need to have the bandwidth to build mine!

[TL1A]

Dear analogoutput,
I am trying to put together the BOM for your HeroVCO. The LM4040BIZ-5 is hard to find/expensive. However, the LM4040CIZ-5 is no problem. I think the difference is the precision (BIZ - 0.2%; CIZ - 0.5 %). What is your opinion on the impact of this difference? Would one hear it?
Thank you and best regards,
TL1A

[Riggidyboo]

Digikey has them in stock now
https://www.digikey.com/en/products/detail/texas-instruments/LM4040BIZ-5-0-NOPB/363989?s=N4IgTCBcDaIDIFkAsAGVAhAkgLQLQFYA6FAegDkB5ABXVzJAF0BfIA

[analogoutput]

Good question. tl;dr: CIZ is probably okay, and in the worst case there’d be a workaround that’s probably more than good enough.

The voltage references are used, among other things, for the octave switch, which is a voltage divider of 10 resistors between ±5 V refs. With ideal voltages and resistances the octave steps are exactly 1 V.

If you bought two CIZs and one happened to be 0.5% high while the other was 0.5% too low, then for instance the two end voltages would be +5.025 V and -4.075 V. Then the voltage differences (with ideal resistors) would still be exactly 1 V. But if both were 0.5% high the end voltages would be ±5.025 V, the total voltage difference would be 10.05 V, and each step would be 1.005 V — 0.5% too large. That means what’s supposed to be an octave would actually be an octave plus 6 cents, or an octave plus about a sixteenth of a semitone. That’s quite good, 5 cents is often said to be about the threshold where two pitches can be discriminated, obviously varying for different listeners but 5 is close to as low as it gets. Though smaller differences can have audible consequences (beat frequencies) if you play two simultaneous notes a few cents apart, so 6 cents might really be marginal. Depends on what you’re doing, and on how pitch sensitive your ear is. Then again, 6 cents is pretty much the worst case for CIZ references, likely you’d get better results than that.

With BIZ references that 6 cent error would become 2.4 cents.

That assumes perfect resistors. If the resistors vary at the 1% level that would add similar size pitch errors, which could add up to something easily audible to most people. That’s why you’re instructed to match those resistors at the 0.1% level.

But that suggests a possibility if you’re (for instance) stuck with two 5.025 V regulators and 6 cents isn’t good enough for you. You could use hand selected accurate 10k resistors for the octave switch except for the first one (the one next to the -5 V rail) which you could make 10.5k — either by selecting a really off resistor or by putting a 10.03k in series with a 470R. Then (according to a spreadsheet I just did) all the octaves would be exactly accurate except the first one which would be 60 cents too wide, more than half a semitone painfully out of tune… except you probably won’t use that octave very often and when you do, it’s pretty much in LFO territory and who cares if it’s out of tune if it’s too low frequency to hear very well as a note anyway?

[TL1A]

Thank you very much for your elaborate answer analogoutput!

So I will measure the LM4040CIZ-5s and decide which of the options you discussed I will apply. You analysed the impact of CIZs being “one high - one low” and “two high ones”. An octave plus 6 cents appears acceptable when comparing the bigger challenge to put together your HeroVCO. Accumulating the error in the LFO range seems to be an even better solution.

Now my order list is complete. Your HeroVCO will get a journey for me, because I want to built it in Eurorack format. At first without PCB (Perf- or Stripboard). Most likely I won´t implement every feature (sine wave, link to sidekick) at the first try because I guess it will get a sandwich with at least 2 layers.

By the way, thank you very much for making your high quality projects accessible to everybody! I am sure that enriches the lives of many DIY colleagues.

Greetings and best regards from Vienna

[Vampyre]

@analogoutput in the BOM of the Hero it specifies 100nF Film Capacitors. Can I use Poly instead of Film?

Thanks
Chris

[analogoutput]

Is there a difference? I used these 100nF 0.1uF 100V 5% Polyester Film Box Type Capacitor. Does “Poly” not mean “polyester film”?

Anyway I don’t think it’s critical. Could probably get away with a good quality ceramic too. The one cap that’s specified as polypropylene should be that or other “low leakage, low tempco capacitor, such as mica” as the datasheet says, though mica’s pretty expensive. I used https://www.digikey.com/en/products/detail/wima/FKP2G011001D00HSSD/9370220.

[Vampyre]

I am not sure if there is a difference. The box type at your first link is the ones I have. Thanks.

Chris

[Arie]

I’m trying to get this fabbed at JLC.
They replied with a comment about the holes for the jacks in the panel. Weirdly, they do not have a similar complaint about the sidekick panel

'The plating hole in your file is bigger than 6.3mm, there is the possibility of tin blasting holes when using HASL.

Would you please select one of the following options?

1.Proceed with HASL and accept the risk wihtout complaint

2.Switch from HASL to ENIG surface finish to avoid defective plated slots.’

Since its the panel I’m sure it wont affect functionality, but honestly I have no idea what this might mean. I guess I should tell them to just go ahead, but what do you think @analogoutput?

[Vampyre]

That’s strange I got some Hero VCO’s done by them not long ago. AnalogOutput should be able to shed some light on the issue.

[Arie]

I did add a comment that this is a faceplate and has no circuit as per the instructions in the ‘how to order PCBs’ video by AnalogOutput

[Vampyre]

Yeah I did that as well.

[analogoutput]

There’s a whole topic about this.

Plated through panel holes

I submitted a JLCPCB order today including some front panels, and was quite surprised to get an email saying they can’t do plated through holes larger than 6.3 mm diameter. And sure enough, now that I check, that’s what it says on their website. Which hasn’t stopped them from putting 10 mm PTH in all my previous (FR4) panels with never an issue raised. Anyone else had these holes rejected before?

Short version: Those footprints with large plated through holes technically do not comply with JLCPCB capabilities but usually they do them anyway without comment. Usually, but sometimes they hold up the order for them. I have since switched to different footprints that specify unplated holes with vias.

I haven’t switched older design Gerbers to the newer footprints but the Hero’s popular enough that maybe I should.

[Arie]

Good morning Rich, thanks for the quick reply. Now that you mention it, I did read that topic a while back, but didn’t realize that it was this same issue.

I’ll tell them to just make em as is and not worry too much about it.

Thanks again!

[analogoutput]

Plated through panel holes

@Arie had the same problem with the Hero VCO: I haven’t gone through the process of changing over all my older designs to the newer footprints, but I’ve now changed the Hero and Sidekick VCOs. If you’d like me to convert another project please let me know. (I can’t guarantee to do it immediately though.) And if there are any problems with the new Hero and Sidekick versions let me know that too.