Blinds Gain Knob Curve


#1

What’s the response curve of the big knobs on Blinds?

I’ve been pressing mine into service as an audio mixer, and it seems difficult to set a low volume, and near impossible to mute the channel completely.

I realise Blinds isn’t designed to be used this way, of course, but I’m just curious.

a|x


#2

It’s linear.

The big knob goes through the same path as the CV input (in fact, it’s just an offset on the CV input), and you really need a linear circuit for ring-modulation applications!


#3

Ah, thought so. So the response on Veils is logarithmic, presumably. Good to know.

a|x


#4

The response on Veils is knob-controlled.


#5

Doh, yes it is, sorry. I knew that. I’m at work, so don’t have it in front of me right now.

a|x


#6

Does the curve control on Veils effect the Gain CV input alone, or both CV input and Gain knob?

a|x


#7

The gain knob is actually an attenuator for whatever goes through the CV input, and the CV input is normalized to 8V. The resulting sauce goes through the linear/exponential response generator.


#8

I see.

a|x


#9

I’m a bit in the same boat.
I “upgraded” my Shades to Blinds but am missing a center detent regularly.

On a side note and even if i think i may know why already, i’d be curious to hear about the reason you didn’t implement this detent center. Was it in order to prevent any weird shifting when the pot is at mid point in feedback/AM/RM applications and so offering perfect linearity ?

By the way, @toneburst, you should be able to use Blinds as a simili-standard VCA using channel B offset to completely mute Channel A one.


#10

I’m not too worried about not being able to completely mute the audio with Blinds. It’s not really designed as an audio mixer, anyway.

As you say, Shades works pretty well as an audio attenuator in uni-polar mode, but in that scenario, the centre detent is actually a hindrance.

I think the issue with using the centre detent in Blinds was that the detent wouldn’t necessarily line up exactly with an exactly 0V output. There’s a warning in the Blinds manual to the effect that the 0V point isn’t necessarily in the exact centre of the pot’s travel, so it makes sense not to have the detent.

I agree it would be handy though, if the detent could be guaranteed to always correspond to 0V.

a|x


#11

The minibrute has an interesting technique to overcome the problem of center detents not being accurate. The bipolar dials that control the LFO amounts for the filter, pitch and waveshape have an additional circuitry that creates an artificial deadzone in the center of the pot by muting the signal in the center area (window comparator + mute switch). The zone is wide enough so that the detent is guaranteed to be within the zone. The big drawback is that once you leave the deadzone, your output signal jumps up and that makes it impossible to apply small amounts of modulation.


#12

Wait… Shades doesn’t have a center detent! Are there really Shades out there with a center detent? Prototypes? DIY builds? Assembly mistakes? I want to know the truth!

Mechanical center detents create more problems than they solve, because of mechanical backlash. The detent “traps” the potentiometer in a position that is not always 12 o’clock exactly (sometimes it can be 11:59, sometimes 12:01), and then there’s no possibility of adjustment.


#13

Yes, this kind of “fish-eye” response curve can be obtained with diodes on the wiper of the potentiometer.

I considered it for Blinds, the downside was that each channel would have required a trimmer to make sure that the “blown up” region near the center of the potentiometer corresponds exactly to the offset that nulls the input signal.


#14

Oups ! Sorry for the misinformation.
It’s been put outside my setup since months now and was certain it does. My bad really. Or maybe i’m lucky enough to have a special, enhanced factory one* ?:sunglasses:

Yes, it makes sense Olivier.
Interesing to hear about this Minibrute technique though !

*just checke and indeed, no center detent. I wish it have it though…


#15

My Shades Is a pre-production unit, in fact.

I’m also not in front of it right now, so can’t check, but I thought it did have a detent. Perhaps I imagined that though.

I’ve never been 10% sure the LEDs operate as they should on my unit (something I didn’t notice while I was testing the unit, but has nagged at me since), but it’s still a super-useful module.

a|x


#16

No it’s not a “fish eye” response. It’s a window comparator and a dg444dy that mutes the signal when the pot is in the artificial deadzone. It’s not a good solution IMO, as I said, it makes it impossible to dial in a small amount. The schematics are available: http://hackabrute.yusynth.net/MINIBRUTE/analog-board/schematics/MiniBrute-12-LFO.pdf


#17

Huh that’s weird! I’m pretty sure I’ve seen diodes on the wiper of a modulation pot somewhere. Maybe in the Microbrute?

I agree that completely muting the modulation below a certain threshold is not a good thing.


#18

I learned attenuating using Blinds.

Up in this patch with cv via Blinds to Maths.

Attenuating the attenuator, that’s me.


#19

CV attenuation… While I get enjoyable use from passive atten’s, I’ve been thinking replacing with a Blinds. From my previous comparison, the voltage differential hence dynamic influence seems better than my comparison via my MN attenuverter. Am I correct in that assumption?! From what I read/hear, there is less sweep change on the blinds potentionmeter…