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 Forum index » DIY Hardware and Software » Thomas Henry designs
The VCO-555
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mrmrshoes



Joined: Feb 19, 2011
Posts: 73
Location: Newcastle Upon Tyne
Audio files: 4

PostPosted: Mon Jun 24, 2013 5:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

C4 is the timing cap so a high quality polystyrene capacitor should be used to reduce drift.

here is a link
http://www.rapidonline.com/Electronic-Components/Polystyrene-capacitors-62504

you might be able to get away with a Wima Polypropylene cap.
http://www.rapidonline.com/Electronic-Components/Wima-Polypropylene-capacitors-62505

but Silvered mica or polystyrene capacitors will be a better choice.
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mosheen



Joined: Jun 19, 2013
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Location: NC

PostPosted: Mon Jun 24, 2013 6:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you. I couldn't tell exactly what it was for.
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elmegil



Joined: Mar 20, 2012
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Location: Chicago
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PostPosted: Mon Jun 24, 2013 7:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

usually I use polystyrene for those, but I'll be honest and say I'm not sure.
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codenamerofl



Joined: May 26, 2013
Posts: 5
Location: south carolina

PostPosted: Fri Jul 05, 2013 6:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

i have an interesting problem.

built one of these, got 6 octaves out of it.

i built another one, and used a different thermistor.

the first one used an NTC honeywell thermistor that i got from mouser.
this one uses an NTC thermistor from futurlec. i cannot get more then a couple notes out of it. if i play an octave up, it goes sharp, and an octave down causes it to go flat. from a tuned C an octave up gets a C# and an octave down gets a B. I have my v/oct trimmer maxed out.

Could it be due to the thermistor? timing cap?


thanks for any help.
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mosheen



Joined: Jun 19, 2013
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PostPosted: Fri Jul 05, 2013 6:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

Is it the correct type? The curve and rate are very important.
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codenamerofl



Joined: May 26, 2013
Posts: 5
Location: south carolina

PostPosted: Fri Jul 05, 2013 8:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

mosheen wrote:
Is it the correct type? The curve and rate are very important.


thanks for the quick reply. as luck would have it, i scrounged around and found an extra thermistor i had from the previous build. swapped em, and now i've got v/oct scailing on the entire scale of my x0xb0x. will get fine tuned for higher ranges once i get fresh batteries for my sh101.
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mosheen



Joined: Jun 19, 2013
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PostPosted: Fri Jul 05, 2013 8:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cool. Remember too that some thermistors are positive coefficient, while others are negative coefficient. Have fun!
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fuzzo



Joined: Nov 12, 2011
Posts: 4
Location: Lyon , France

PostPosted: Sun Jul 21, 2013 8:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi ,

I've decided to build a tiny analog synth and I highly consider this 555 VCO (for its simplicity). However, I'd like to know if there's a VCF better than the others to be coupled with it ?

it may be an odd question. Say , if you'll have to chose only one , what it will be ?

I though of a 24db ota's based (inexpensive and easy to build)
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mosheen



Joined: Jun 19, 2013
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PostPosted: Sun Jul 21, 2013 9:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Oh no! Not the "best filter" debate!
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fuzzo



Joined: Nov 12, 2011
Posts: 4
Location: Lyon , France

PostPosted: Sun Jul 21, 2013 9:45 am    Post subject: Reply with quote  Mark this post and the followings unread

oups. sorry !

Even in synth world there's this kind of silly debate ? the same that between fender and Gibson I guess Laughing) .

I'm not looking for the "best" (that doesn't make sense anyway) , juste idea and advices on what could be interesting to do and add. I just want directions to start my project and make the best of it.

anyway, I'll stick with the original idea and see how it sounds. Very Happy
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mosheen



Joined: Jun 19, 2013
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PostPosted: Sun Jul 21, 2013 9:55 am    Post subject: Reply with quote  Mark this post and the followings unread

You can't go wrong with a moog ladder clone. It's cheap, easy to build and sounds great. It's the sound you probably associate with a synth filter too.

I'm just ribbing you on the "debate" part. I don't think there will be any wars fought over here about it, but it's all a matter of taste. I think it's more of which one they love more, not which ones they hate. At least that's the impression I've gotten in my short stay here.
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mosheen



Joined: Jun 19, 2013
Posts: 19
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PostPosted: Tue Jul 30, 2013 11:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

I need a little advice. I have had my own boards made for myself and everything seems to work great except for the ramp wave. Does anyone have any suggestions as to where I should be looking in the circuit? I've swapped all the chips just to be sure, and traced all of the connections a good ways back through the circuit and everything seems ok. I know it's a very broad question, but any starting points would be appreciated. I'm a digital guy who dove off into an oscillator for my first ever module and analogue circuit. Silly me!

This is the Ramp wave paired with the triangle. Notice it's a 1vpp square wave. The Ramp Contour trimmer does nothing to its shape, but the trimmer is changing witrh the adjustment screw when I measure it with my meter.

The triangle wave is on the 2V scale, that's why it shows 5vpp right now.

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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mosheen



Joined: Jun 19, 2013
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PostPosted: Wed Jul 31, 2013 8:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

I figured it out. I accidentally nuked a single rat line when designing it.

Guess it's time to break out the 30awg....

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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Sony Crocket



Joined: Sep 27, 2010
Posts: 13
Location: Madrid, Spain

PostPosted: Tue Sep 03, 2013 7:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi!

Im populating the fonik´s PCB, and I am stuck on the 2k tempco.

So hard to find them, and the only one I found on a shop is 4 euros for a 1k tempco. Is it a critical component? I don´t need perfect tunning stability, but wonder if it will work and get the full oct range with a standard 2k 1% resistor.

I can´t figure how to solder it on the PCB. Q2 and Q3 does not give much room for it. Can I solder it on the back of the pcb?

Could someone show me a photo of the tempco mounted on the board?


Thanks a lot!
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oculus



Joined: Oct 30, 2011
Posts: 30
Location: Iceland, Reykjavik

PostPosted: Tue Sep 03, 2013 10:15 am    Post subject: Reply with quote  Mark this post and the followings unread

i have made both the TH Vco-1 and the XR-2206
just using regular 1% 2k resistors as i didn´t have any tempcos,
there´s a littlebit drift in much heat change
but they are completely usable , iv´e already made some songs with them,
but i plan on ordering tempcos and put them in instead.



Sony Crocket wrote:
Hi!

Im populating the fonik´s PCB, and I am stuck on the 2k tempco.

So hard to find them, and the only one I found on a shop is 4 euros for a 1k tempco. Is it a critical component? I don´t need perfect tunning stability, but wonder if it will work and get the full oct range with a standard 2k 1% resistor.

I can´t figure how to solder it on the PCB. Q2 and Q3 does not give much room for it. Can I solder it on the back of the pcb?

Could someone show me a photo of the tempco mounted on the board?


Thanks a lot!
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oculus



Joined: Oct 30, 2011
Posts: 30
Location: Iceland, Reykjavik

PostPosted: Tue Sep 03, 2013 10:20 am    Post subject: Reply with quote  Mark this post and the followings unread

i just breadboarded the core of the VCO-555, (first page of the schematic)
im currently not getting anything at the ramp and triangle output.

shouldn´t i be able to make it work without the waveshapers for the sine and square ? (so without breadboarding the page2 of the schematic)

nevermind, got it working, i had a broken LM13600

thanks kind regards
Oculus
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fonik



Joined: Jun 07, 2006
Posts: 3760
Location: Germany
Audio files: 23

PostPosted: Wed Sep 04, 2013 4:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Sony Crocket wrote:
Hi!

Im populating the fonik´s PCB, and I am stuck on the 2k tempco.

So hard to find them, and the only one I found on a shop is 4 euros for a 1k tempco. Is it a critical component? I don´t need perfect tunning stability, but wonder if it will work and get the full oct range with a standard 2k 1% resistor.

no problem at all (see comment above).

Quote:
I can´t figure how to solder it on the PCB. Q2 and Q3 does not give much room for it. Can I solder it on the back of the pcb?

Could someone show me a photo of the tempco mounted on the board?

don't have a good picure on hand right now, however, the tempco is supposed to be mounted ON TOP of the transistors. both transistors and the tempco PTC should be in a termal contact to each other. since you plan to use common resistors there is no need to mount it on top. you could mount it to the reverse side of the PCB instead.

anyways, here is a picture of a PTC mounted on top of a super matched pair for a 555VCO. i think you get the idea:

Posted Image, might have been reduced in size. Click Image to view fullscreen.


Thanks a lot![/quote]

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Posted Image, might have been reduced in size. Click Image to view fullscreen.
cheers,
matthias
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Sony Crocket



Joined: Sep 27, 2010
Posts: 13
Location: Madrid, Spain

PostPosted: Wed Sep 04, 2013 7:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for your responses.

Matthias, this is the photo I needed! Didn´t knew the tempco should be in contact with the transistors... yes, I´m a newbie...

Regards!
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flyweight303



Joined: Sep 04, 2013
Posts: 3
Location: Praha

PostPosted: Wed Sep 04, 2013 8:02 am    Post subject: Reply with quote  Mark this post and the followings unread

I cannot sleep i cannot eat can't stop thinking about the VCO 555.

Man i want 3 pcb's for the VCO 555. really bad.

Is there gonna be anothe run??

Thanks in advance,

Kindest regards,
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HansRL



Joined: Nov 17, 2012
Posts: 11
Location: Norway

PostPosted: Fri Sep 06, 2013 4:18 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
I still have PCBs and eurorack front panels ... Wink


Are PCB still available? If so, it seems I'm to stupid to find my way around your web site to find it.

TIA
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fonik



Joined: Jun 07, 2006
Posts: 3760
Location: Germany
Audio files: 23

PostPosted: Sat Sep 07, 2013 2:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

HansRL wrote:
fonik wrote:
I still have PCBs and eurorack front panels ... Wink


Are PCB still available? If so, it seems I'm to stupid to find my way around your web site to find it.

TIA

my DIY pages have not been updated for a long time... you will find all info in the fonik's place subforum.

anyways, the 555-VCO is currently sold out, however, i am running a waiting list. i could re-order any quantity of ciruit boards any time. it is just that some people like to get the eurorack front panel and front panel components PCB as well. and for the front panels i need at least 30pcs minimum of interest....

_________________
Posted Image, might have been reduced in size. Click Image to view fullscreen.
cheers,
matthias
____________
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widdly



Joined: Jun 25, 2007
Posts: 265
Location: singapore
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PostPosted: Wed Oct 16, 2013 6:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've built 3 of these so far and found that some LM13600 don't give linear tracking. I know the schematic specifies LM13700 but I didn't have any on hand.

One of the three I built could not be tuned accurately for more than an octave. I swapped the LM13600 with one of the properly working builds and the tuning problem followed the LM13600. I tried 7 different chips and 3 wouldn't give proper tuning. Interestingly these were from different manufacturers.

So if you have a lot of trouble getting this VCO to track properly then you should try swapping out a few different OTA's.


BTW. These are the best VCO's I've ever built. The tracking is great, the waveshapes and level are spot on and the frequency range is amazing. They cover your VCLFO needs too.
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mosheen



Joined: Jun 19, 2013
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PostPosted: Wed Dec 11, 2013 11:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

So...now that I've played around with this for a while, how do you tune it? I know to use a 1V CV difference and go back and forth until the slope is right, but how do the 1V/oct and HF trim pots relate?

What is a good octave to start and end with? If I tune across say 5 octaves, and the turn the coarse pot left or right will is skew the tuning?

If anyone has any input or a definitive guide I'd appreciate it.
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mosheen



Joined: Jun 19, 2013
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PostPosted: Tue Dec 17, 2013 1:02 am    Post subject: Reply with quote  Mark this post and the followings unread

Figured it out.

Turn the HF trim knob all the way to its stop whichever way lowers the frequency.

Turn the V/Oct trimmer to the stop and then turn it back 15 turns to center it.

Don't try and adjust the second reading to an absolute, just turn the trimmer one rotation at a time and go back to 0v and use the fine pot to reset the first frequency. Lather, rinse, repeat.
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jukingeo



Joined: Oct 24, 2007
Posts: 161
Location: The dark side of the moon

PostPosted: Sat Jan 25, 2014 10:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello All,

I just stumbled upon this thread today while looking into some ideas for module VCO's and VC-LFO's.

Up to now I been dealing with MFOS and I have bought some boards from them. I am currently constructing the DIY-Experimenter Synth. The thing isn't even built yet, and I am looking into more options.

For the LFO, I am completely nuts over the Variable Skew LFO on the MFOS site. The trouble is this isn't a supported project anymore and as such there isn't a PCB available. Not too much of a problem as I can try to strip board it. The problem with it is that it isn't a VC-LFO, but I do intend to build a couple anyway.

Now for the VCO, the issue I am having with the MFOS design is that I feel it is overly complex and it seems there is a fairly long calibration process. Naturally I am wanting to look for something simpler and less complex, but nearly offers the same features as the MFOS design.

After a quick search I came across this post on a 555 based VCO created by Thomas Henry. After reading through this thread, it seems that it is accepted that this is the arguably the best VCO out there currently. What I like it is that it uses quite less parts than the MFOS design, and a fellow in Germany is making boards for this. So I have a few questions:

1) Is this really the better picks of the VCO's out there and does it compare to the MFOS VCO or does this clearly blow the MFOS one away?
2) Is there someone here in the US that is distributing the boards?
3) One feature I liked on the variable skew LFO is the ability to adjust the waveform of the triangle wave to a saw or ramp wave and anywhere in between. Could this feature be added to the 555-VCO?
4) I would assume that changing out the timing cap could easily make this an LFO, correct?

Thank You,

Geo

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