Eagle Files - VCO, Filters, Touch, and SeqSw

[AlanP]

The Wave-Ctl and Sine-Trim trimpots are interactive, to a degree -- you'll need to adjust both at once to get the best sine wave. Make sure the panel pot is set to Sine before doing so (I don't wanna talk about it...) and flick it back to the other waveform after trimming the Sine to check how the other waveform for that oscillator works out. You're probably going to have to either settle for a compromise, or sift through a load of different jfets to get a good sine that also gives a good square/ramp (it's not a particularly good sineshaper, but it does do morphing between them.)

For v/oct and freq, it's pretty much as normal.

[skautkurt]

Make sure the panel pot is set to Sine before doing so (I don't wanna talk about it...)

I feel you there hehe

Thanks for the discription, the 258 and the 291 will be my holiday-leisure-projects.

[bcitral]

Afternoon all, can I query res pot. Its 5kb right?

[skautkurt]

Afternoon all, can I query res pot. Its 5kb right?

Should be, yeah.

I built one of the 291s tonight, but have not tried it out yet. Will do tomorrow night. Is there anything hacky or specific to look out for?
Cheers
T

[egilegilegil]

I built a 291 today. Such an incredibly juicy filter! It's got that wonderfully gurgly smooth vactrol response, also love the narrow bandwidth for picking out overtones without selfoscillation. Thanks AlanP for doing this!

I have a question regarding the response of the frequency CV potentiometer. Mine is incredible sensitive in the middle of the travel, it's almost an all CV off or on type situation where all the action of the travel happens very close to 12o clock. I suspect this is due to the vactrol nature of the circuit? Is it worth experimenting with different vactrols for a more even response, or is there some other solutions? What's your experience, how does your modules behave? I used a linear 10kb potentiometer btw.

Furthermore I’m getting some self oscillating at low (40hz ish) frequencies when the bandwidth is at its most narrow (with the filter cut off in this low range). Is there any remedy for this?

Cheers!

[skautkurt]

I built a 291 today. Such an incredibly juicy filter! It's got that wonderfully gurgly smooth vactrol response, also love the narrow bandwidth for picking out overtones without selfoscillation. Thanks AlanP for doing this!

I have a question regarding the response of the frequency CV potentiometer. Mine is incredible sensitive in the middle of the travel, it's almost an all CV off or on type situation where all the action of the travel happens very close to 12o clock. I suspect this is due to the vactrol nature of the circuit? Is it worth experimenting with different vactrols for a more even response, or is there some other solutions? What's your experience, how does your modules behave? I used a linear 10kb potentiometer btw.

Furthermore I’m getting some self oscillating at low (40hz ish) frequencies when the bandwidth is at its most narrow (with the filter cut off in this low range). Is there any remedy for this?

Cheers!

Huh, just tested mine, I think my vactrols work so well... the freqency pot does nothing at all, similiar to the q. Only the Bandwith really changes anything, and I think it only overdrives the signal. Which vactrols did you use? Xvive? Aliexpress ones (mine are)? DIYed ones?

Cheers,
T

[egilegilegil]

I built a 291 today. Such an incredibly juicy filter! It's got that wonderfully gurgly smooth vactrol response, also love the narrow bandwidth for picking out overtones without selfoscillation. Thanks AlanP for doing this!

I have a question regarding the response of the frequency CV potentiometer. Mine is incredible sensitive in the middle of the travel, it's almost an all CV off or on type situation where all the action of the travel happens very close to 12o clock. I suspect this is due to the vactrol nature of the circuit? Is it worth experimenting with different vactrols for a more even response, or is there some other solutions? What's your experience, how does your modules behave? I used a linear 10kb potentiometer btw.

Furthermore I’m getting some self oscillating at low (40hz ish) frequencies when the bandwidth is at its most narrow (with the filter cut off in this low range). Is there any remedy for this?

Cheers!

Huh, just tested mine, I think my vactrols work so well... the freqency pot does nothing at all, similiar to the q. Only the Bandwith really changes anything, and I think it only overdrives the signal. Which vactrols did you use? Xvive? Aliexpress ones (mine are)? DIYed ones?

Cheers,
T

I see, too bad :( , I used xvive vactrols from thonk. Hope it get's sorted!

[skautkurt]

Ups, I meant: I think my vactrols DONT work so well*

[skautkurt]

Some more testing happend, and I am quite sure, that my vactrols are at fault. I have some very limited response on the frequency and the bandwidth pots, meaning they only show effect in the first few degrees of turning. I now ordered some LDRs and LEDs and will try to experiment with those. And if that does not work... well. I might need to bite the (really quite sour, as they are super expensive here in germany) apple of buying some VTL5c3s.

[egilegilegil]

This thing can deliver some serious acid bass lines

[Bamboombaps]

Sounds awesome

[bcitral]

thanks for the info. Mine is built now but not passing audio. I think I bought a batch of fake TL072's.

[1WILDTHING]

Hi guys, I'm about to start this Buchla VCO project using the 0.1 brd layout. Suddenly I've realized that I miss the Tempco resistor required in R55. Could you please tell me which one you have chosen or you can recommend for this build?

[AlanP]

The ALT resistor locations can be used instead. If you later get a tempco resistor, you can remove the ALT resistor and place the tempco.

[SphericalSound]

If anybody has 291 spare PCBs I would gladly pay for the shipping plus a pair of beers.

I would go for homebrew vactrols. Any tutorial on how to match them?

[1WILDTHING]

The ALT resistor locations can be used instead. If you later get a tempco resistor, you can remove the ALT resistor and place the tempco.

Thanks Alan, but I have to admit that I don’t know what a ALT resistor is. Could you be so kind to explain what kind of resistor is?

[skautkurt]

The ALT resistor locations can be used instead. If you later get a tempco resistor, you can remove the ALT resistor and place the tempco.

Thanks Alan, but I have to admit that I don’t know what a ALT resistor is. Could you be so kind to explain what kind of resistor is?

Not Alan, but I think the ALT just means ALTernative. So, if you chose against using the Tempcos, you have to put an equivalent "normal" resistor there, meaning just a normal 2kohm resistor.

[skautkurt]

If anybody has 291 spare PCBs I would gladly pay for the shipping plus a pair of beers.

I would go for homebrew vactrols. Any tutorial on how to match them?

I will try some tonight, or tomorrow, and will experiment with GL5539 and GL5549 LDRs plus some different LED colors and strengths. I will report my success or failure here

[AlanP]

Not Alan, but I think the ALT just means ALTernative. So, if you chose against using the Tempcos, you have to put an equivalent "normal" resistor there, meaning just a normal 2kohm resistor.

Bingo.

[1WILDTHING]

Not Alan, but I think the ALT just means ALTernative. So, if you chose against using the Tempcos, you have to put an equivalent "normal" resistor there, meaning just a normal 2kohm resistor.

Bingo.

Thanks guys!

[romain]

Thanks a lot

[skautkurt]

If anybody has 291 spare PCBs I would gladly pay for the shipping plus a pair of beers.

I would go for homebrew vactrols. Any tutorial on how to match them?

I will try some tonight, or tomorrow, and will experiment with GL5539 and GL5549 LDRs plus some different LED colors and strengths. I will report my success or failure here

Tried the 291 with GL5549 and green LEDs. Works, but only reaally sluggish. Not really fun. Looked into the datasheets again and saw my mistake. GL5549 have a rise up time of 20ms, the VTL5c3 only need 2.5ms for that Stupid me. Well. I think I'll lay it to the side for now.

Cheers.

edit: driving the leds more by chaning R20 and R25 to 750R made it a bit more fun. Will experiment further and share my results.

[skautkurt]

Okay. Now I tested the GL5549 with ultrabright, clear, flattopped LEDs. And its way better. If I calculated correctly my LEDs with the 1k resistor are driven at around 8mah, in Scott Stites schematic the LEDs of the Vactrols get up to 11.8 (again, if my calcs are correct). I will try to reduce the resistors R20 and R25 to get a similar result.

[1WILDTHING]

Hi all. I’m trying to populate the 258’s 0.1 board. I’ve found almost all resistor values but I can’t find value for resistors called IP1 and IP2 (close to power socket). May be have they to be omitted and wired over (like r25, r34, r72 and r79)?

[skautkurt]

IP1 and IP2 are input/power protection, I think, and should be either a 10 Ohm resistors or ferrite beads (I think!!) Maybe AlanP can comment on this?

Edit: as AlanP stated on the first page of the thread, the omit resistors should be left free, and not be wired over. So no connection instead of 0 ohms.