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Thomas Henry VCO-1 for Eurorack
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page Previous  1, 2, 3, 4  Next [all]
Author Thomas Henry VCO-1 for Eurorack
J3RK
Currently the board is 3" x 4". (so 15-16 HP) However, I'm trying to squeeze it all into a 2"x4" PCB right now for fun. I'm not sure if I'll be successful, but we'll see. grin There are 12 ICs in this VCO and a lot of passives. Dead Banana

Edit: I've got the 2" x 4" version almost routed. A few areas are being a little less than... ...shall we say... ...cooperative. I think it will work though. I also had to do a couple of things that I'm not super-fond of. (like put a pulse output near a sine trim...) I'm going to see if I can resolve a few of these items, clean it up to acceptable levels, and we may have a 2x4 VCO. All IO is in-line, so a control PCB could be doable. More soon...
emmaker
Don't think the J3RK VCO will work as shown and needs to be verified and tweaked.

R4 is 100 ohms which would suck ~0.2 amps relative to -10V ground at +10V output. Can't find a spec on the output current relative to 'ground' (which is -10V) but for the positive/negative rail the max specs are 7.5ma/5.0ma.

???

J3RK VCO:
J3RK
You're correct. That needs to be changed. I'll post an update asap.

Edit: 2.2K for R10, 8.2K for R11, 10K for R4, might do the trick. I'm at work, so I'm unable to test this.
J3RK
I ordered some prototypes of this VCO. (actually more than the schematic posted as I included more wave shapers, sync, control/IO, FM, etc.) I've done some simulation, and done a bit more calculation around the comparator, and think I've come up with the right values. I'll give them a whirl as soon as the boards show up. Also, I did manage to squeeze it all into 2" x 4". w00t Sorry for the confusion around the comparator. That was based on some quick simulation while at work. Mr. Green On the Pico and Ultra VCOs I used the LM311 quite differently because I didn't provide reference voltages for the core in those ones. This was a bit new. Anyway, it will be tested in about a week or so.
Tombola
Great minds thinking alike...

I've been doing the same thing...

Mine is built almost exactly as the Thomas Henry Schematic, with a couple of small value changes. So far it seems to work beautifully - lovely sine, square is a bit wide range - dead patches on either end. I got about 5 octaves as close as my Dixie, didn't persist calibration beyond that.
10HP
Parallel boards - one for pots + a few resistors & one cap - one for everything else.
Through Hole
LM13700 + THAT 340 for the matched pairs

Happy to share the eagle files if anyone wants them. I haven't been able to contact Thomas Henry, not really planning anything with this.

VIDEO: https://www.instagram.com/p/_etQT6DmdM/

geecen
That looks great Tom!

Looking forward to seeing the J3RK boards too. cool
J3RK
Tombola wrote:
Great minds thinking alike...

I've been doing the same thing...

Mine is built almost exactly as the Thomas Henry Schematic, with a couple of small value changes. So far it seems to work beautifully - lovely sine, square is a bit wide range - dead patches on either end. I got about 5 octaves as close as my Dixie, didn't persist calibration beyond that.
10HP
Parallel boards - one for pots + a few resistors & one cap - one for everything else.
Through Hole
LM13700 + THAT 340 for the matched pairs

Happy to share the eagle files if anyone wants them. I haven't been able to contact Thomas Henry, not really planning anything with this.

VIDEO: https://www.instagram.com/p/_etQT6DmdM/



Nice!

You should be able to get rid of those dead spots on the PW controls by tweaking the summing resistor values. (R31 / R41) If I'm not mistaken the two will interact a bit, so you'll need to bounce back and forth a little bit.
Isaiah
J3RK
So, is this effectively like your UFO minus the VC-fader?
Will the boards have mounting holes (0.15" from the PCB edges)?
Will a control panel PCB be necessary?
J3RK
Isaiah wrote:
J3RK
So, is this effectively like your UFO minus the VC-fader?
Will the boards have mounting holes (0.15" from the PCB edges)?
Will a control panel PCB be necessary?


It's basically like the UFO minus VC-Fader as you've mentioned, but with the addition of reference voltages for the core and controls (something I've always thought about doing, but then this thread kinda pushed me into implementing.) I've lined up all IO in lines around the edges, so while I wouldn't say a control PCB is NECESSARY, it would be very easy to do. I haven't made anything with Euro-friendliness in mind in a couple of years now, so this seemed like a fun little project with that in mind. Also, I'm kind of going away from doing board runs now, so I can focus on my custom synth work, but something like this would be easy enough to do at some point. After I test the prototype, and make sure everything can stay where it is, I'll make a control PCB for it, and then if people want some, I can place an order for them. w00t Oh, and yes, the mounting hole spacing is the same as all my boards. .15" in from the edges, X.7" center to center. (so if it's a 2" x 4" board, the mounting holes are 1.7" C2C and 3.7" C2C.)
emmaker
J3RK
Quote:
It's basically like the UFO minus VC-Fader as you've mentioned


I'd like to see pins for a fine freq pot and expo/lin FM.

One thing that I was wondering if using the linearization diodes and boosting the voltages in the oscillator loop would make the oscillator better. Anyone done any looking into this?

Thanks
J3RK
emmaker wrote:
J3RK
Quote:
It's basically like the UFO minus VC-Fader as you've mentioned


I'd like to see pins for a fine freq pot and expo/lin FM.

One thing that I was wondering if using the linearization diodes and boosting the voltages in the oscillator loop would make the oscillator better. Anyone done any looking into this?

Thanks


Those are included. The final version will also have initial frequency trim, a switch for mor traditional hard sync as well as the indefinite reset sync thst the Pico and UFO have.

I kind of doubt the linearization diodes would help much. I do use them in my VCF and in the fader portion of the UFO.
J3RK
Ok, here is the final version. Putting in a not so readable image just for a quick visual. Attaching a PDF for proper viewing. The comparator is now completely correct with proper hysteresis. The prototype PCBs were ordered, and don't need any changes, just a few value tweaks (which are present in this schematic.) Feel free to use this however you like. The core obviously resembles the EN triangle core with some updates and improvements. Some of the suggestions for improvements came from Dave Brown (in the form of the Pico VCO and UltraFade) Thomas Henry, and a relative of mine helped tweak a few items as well. The sine shaper is OTA based. 10V reference voltages are fully implemented, so this can be powered by 12 or 15 volts, and will also be quite a bit more precise with tracking and stability. The matched PNP pair is an SMT footprint for SSM2220 or LS352.

Exponential and Linear FM are present. Initial frequency trim is in. Typical hard sync and an indefinite reset/hold sync switch is in place.

This should do the trick for a full featured, accurate and small VCO. (not that there aren't a million out there already hihi ) Still though, it was fun to do, and smashing things into 2" x 4" was interesting. (we need a smiley in a vice)

Oh, one other "SMT compromise" is that the bypass caps for the ICs are 0805. Otherwise all through-hole. While I'm waiting for the prototype I will try to come up with a control PCB. If a few people end up wanting some of these, I'm happy to do a small run of them. I know I could squash a few of them into a few projects.

More soon. I will open up another thread for that after the prototyping is done.



I'm making a few improvements to the board layout, traces, etc. Here's the prototype version:



sammy123
Very cool. I'd definitely be interested in a couple.
Grumskiz
Since I don't have a triangle core VCO in my european racks yet, this is relevant to my interests wink
sammy123
These will come after the dual mirror core. SlayerBadger!
J3RK
sammy123 wrote:
These will come after the dual mirror core. SlayerBadger!


You could actually use these with the dual mirror core control PCB instead of the MCVCOs if you wanted to. You'd get additional things like sync and exp FM, and a slightly easier build.
sammy123
eek! that's amazing. Maybe a Stroh Dual Mirror Core Special Edition in the future? wink

I am committed to finishing the DMC first. Been sitting on it way too long, just waiting on some parts.

edit: of course If I could get a second control board then anything is possible I guess. I'd probably need some help with the new wiring though.

J3RK wrote:
sammy123 wrote:
These will come after the dual mirror core. SlayerBadger!


You could actually use these with the dual mirror core control PCB instead of the MCVCOs if you wanted to. You'd get additional things like sync and exp FM, and a slightly easier build.
J3RK
Actually, I should just lay out a new, smaller control PCB to go with these. I've got better versions of all of the circuits now anyway. For example, for the phase detector, I'd just use an AD633 now instead of a CMOS XOR, as it would be WAY better and more flexible for detection. I'd also use the voltage controlled integrator/slew as it's better than the simple RC network. I think I could also make a smaller/better clock divider that still did half-steps maybe using a cheap readily available MCU. One control PCB for the whole set. Etc. Etc. That will need to wait a bit, but is definitely doable. I need to finish building my blue synth first though. (or I'll never actually get around to it lol )
Isaiah
Apologies in advance for going off topic...

J3RK
This looks fantastic. I'm interested.
While it's small enough for Euro and Frac, I'm glad you kept the integer inch dimensions and CGS mounting hole convention.

I very much hope that the new elements included in your most recent full panel project find themselves available in CGS/Serge-format, or this ?" X 4" size.
Seems a little more flexible than the (mostly) 3"x3" (?) Frac PCBs for use outside that format, maybe.
Maybe just ignore me, I always get a little giddy whenever I see you're releasing something new!
I'm just waiting for enough of your circuits to be available in one format so I can make a dedicated Stroh Modular voice.
J3RK
Isaiah wrote:

I'm just waiting for enough of your circuits to be available in one format so I can make a dedicated Stroh Modular voice.


Actually, just looking at the handful of things that are approximately this size that I've got whipped up right now, this would be quite possible. The main issue is that of time. All the circuits are designed, PCBs are all laid out in multiple sizes and shapes (I get bored late at night sometimes hihi ) etc. The only thing is, in no way am I in a position to pack and ship PCBs, and I can't really ask the distributors to order a whole line of PCBs at a time.

One possible solution would be to build a Voice PCB (like the one I did for the blue synth,) but maybe to make it accessible to more people make it a size that would fit inside a standard 84HP euro-chunk. Then it could really go behind any panel in any format, and I wouldn't have to worry about a ton of separate boards that all have to be shipped separately in multiple quantities. I'll start thinking about that a bit. I think I have everything needed to do a pretty good voice this size/shape.

Now we're way off topic though Mr. Green I'll work on the idea, and post a new thread.
emmaker
J2RK
Just a personal preference but I'd rather solder 0805 or 1206 resistors than vertical mount thru hole.

Thanks for the soap box.
dogfaceaudio
J3RK - That looks awesome, I'm sure if you went fully SMD you could squeeze it down to 8HP. What schematic capture/board layout software do you use?

Tombola - I would definitely be interested in seeing your VCO-1 schematics! I'm also working on an all OTA triangle core VCO based around the LM13700. I'll be starting another thread for that though.
Isaiah
J3RK
Is it possible to implement Linear Detuning with your design?
Could it be done by sending a small variable offset to pin 6 of op-amp U6B?
Tombola
dogfaceaudio wrote:

Tombola - I would definitely be interested in seeing your VCO-1 schematics! I'm also working on an all OTA triangle core VCO based around the LM13700. I'll be starting another thread for that though.


Email me and I'll send them over.
calaveras
emmaker wrote:
J2RK
Just a personal preference but I'd rather solder 0805 or 1206 resistors than vertical mount thru hole.

Thanks for the soap box.

I'd rather solder through hole because my peepers are shot. If I have to start using a magnifying glass to solder it's just not fun anymore.
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