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



Joined: Jan 14, 2013
Posts: 11
Location: Finland

PostPosted: Tue Mar 19, 2013 1:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Fonik,
it is Variable 0-32V 2A tripple channel psu.
No voltage drop noticed.
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fonik



Joined: Jun 07, 2006
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PostPosted: Tue Mar 19, 2013 2:18 am    Post subject: Reply with quote  Mark this post and the followings unread

so no problem here, unless you are powering a lot of modules....

does it still bleed when not mounted into the cabinet, but moved away from the other modules?
if no, then do not mount it side by side with your mixer module, or whatever you are using.
if yes, the it might be related to your distro buss.
try connecting it near the connection to the PSU.

or, just to try it, connect it temporary not to the distro at all, but to the PSU directly.

so far i never had any issues with crossbleed in my modulars at all, so i am no expert regarding this issue Very Happy

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MrZ



Joined: Jan 14, 2013
Posts: 11
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PostPosted: Tue Mar 19, 2013 2:25 am    Post subject: Reply with quote  Mark this post and the followings unread

i have no case yet.
i have only one VCO module and one filter module.
they both connected to the psu at the same point without any special distributor.
when the filter is not connected to anything except to the input of my monitors i can hear the VCO, it bleeds thru the power source.

i should mention that they both are stripboard layouts but i checked every jumper so all seems ok.

the bleeding is low at the lvl but it is strong enough to hear it when nothing is at the background.
i assume it is not normal.

Last edited by MrZ on Tue Mar 19, 2013 2:34 am; edited 1 time in total
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fonik



Joined: Jun 07, 2006
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PostPosted: Tue Mar 19, 2013 2:33 am    Post subject: Reply with quote  Mark this post and the followings unread

so yo built the 555-VCO on stripboard.

did you implement decoupling capacitors at the power the entry points of your stripboard builds?

since it is crossbleed, the frequency changes when changing the VCOs freuency? otherwise it would be hum (i.e. from the mains).

and triple check the grounding.

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MrZ



Joined: Jan 14, 2013
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PostPosted: Tue Mar 19, 2013 2:38 am    Post subject: Reply with quote  Mark this post and the followings unread

yes, i put the decoupling caps and ofcoarse i can hear the freq changes at the bleeding.

i disconnected all the panel wires and i am going to ground everything from beginning.

i'll post the results when time comes.
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MrZ



Joined: Jan 14, 2013
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PostPosted: Fri Mar 22, 2013 8:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Fonik, can the problem exist because i have wood panel ?
is it a must to ground all the pots and if yes in what way ?

Thanks
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elmegil



Joined: Mar 20, 2012
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PostPosted: Fri Mar 22, 2013 9:31 am    Post subject: Reply with quote  Mark this post and the followings unread

I have suspected this occasionally but never found it to be a final solution to the problems.

However, it is best practice to ground everything together on the panel.

In the US at our "big box" hardware stores you can get aluminum tape which is about the same size as "duct tape" but is more often used for ducts where you want to have heat shielding. On my wooden panels, I have put a layer of this tape on the back of the panel after I drill holes, cut out the holes for the tape, and that has provided grounding.

An example: http://www.uline.com/Product/Detail/S-7166/Specialty-Tapes/2-x-60-yards-Industrial-Aluminum-Foil-Tape?pricode=WU351&gadtype=pla&gclid=CJqOp7jfkLYCFaUWMgodFTYACA
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MrZ



Joined: Jan 14, 2013
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PostPosted: Fri Mar 22, 2013 10:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks man Smile

sombody already recommended me to stick it on my wooden panel.
my question thu is if it is a must and also if that can be the cause for the symptoms my poor vco suffer from.


so, what do you think ?
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elmegil



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PostPosted: Fri Mar 22, 2013 10:50 am    Post subject: Reply with quote  Mark this post and the followings unread

I honestly don't think lack of panel grounding is likely to be the problem.

On the other hand, it doesn't seem like it would be terribly hard to test. Another thing I've done with a plastic panel where I thought I had grounding issues was to use the same tape to set up a grounding grid between all the pot bodies. Didn't solve the problem there either, but took all of 20 minutes to check it.

Does the VCF also have appropriate bypass caps?

The only real bleeding issue I've troubleshot was internal to a Soundlab, I had Osc 2 and LFO signals coming through on the Noise channel. I fixed it by totally reworking the Noise channel with Ray's "improved noise" circuit. That doesn't really help with this type of problem though Sad
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MrZ



Joined: Jan 14, 2013
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PostPosted: Fri Mar 22, 2013 10:56 am    Post subject: Reply with quote  Mark this post and the followings unread

i did a new layout design which is much smaller (from 160x100 to 100x100)
i'll test it with this new design.
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MrZ



Joined: Jan 14, 2013
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PostPosted: Mon Apr 15, 2013 11:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

ok, it was just the ground between the modules.
nothing bad. Smile
now i want to put this vco on PCB.
is there anywhere a single sided pcb plan so i can etch it ?
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fonik



Joined: Jun 07, 2006
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PostPosted: Tue Apr 16, 2013 9:18 am    Post subject: Reply with quote  Mark this post and the followings unread

I still have PCBs and eurorack front panels ... Wink
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forbin



Joined: Jan 29, 2009
Posts: 118
Location: Fremantle, Australia

PostPosted: Tue Apr 30, 2013 5:14 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi MrZ -- i do have a press'n'peel layout that i used for myself but i will have to run it past Thomas before i post it. See pix: http://forbinthesynthesizer.blogspot.com.au/2012/08/02-thd.html
I don't want to undermine fonik's effot but there are people (weird ones like me) that enjoy making absolutely everything.
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fonik



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PostPosted: Tue Apr 30, 2013 10:51 am    Post subject: Reply with quote  Mark this post and the followings unread

forbin wrote:
I don't want to undermine fonik's effort but there are people (weird ones like me) that enjoy making absolutely everything.

great attitude. nothing to say against it! did it myself in the past... however, at some point i got tired of all that drilling and all the dust.

asking thomas is a good thing, since his name would go with your layout.

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MrZ



Joined: Jan 14, 2013
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PostPosted: Wed May 01, 2013 11:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, i got enough pcbs but in the future to have the option to do more pcbs would be great.

btw, thanks Fonik, the pcbs are fantanstic. Smile
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mrmrshoes



Joined: Feb 19, 2011
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PostPosted: Thu May 23, 2013 12:50 am    Post subject: Reply with quote  Mark this post and the followings unread

Hia all

I've just finished my own build of this great VCO. It sounds awesome like.
I built this from my own PCB design and is my first step into building up a real modular set up.

On the whole my build of the VCO seems to work pretty well. I'm getting good looking waveforms that are consistent amplitude on there respective saw,square,triangle and sine (before shaping) outputs. The course / fine tune as-well as PWM controls work as excepted. I've not tested the synch or FM inputs as of yet coz this is my first module so no modulation source to hand.

So in short I’m here for advice because I’m not sure if I got a build fault or maybe I’m getting lost in the calibration process because I’ve never really used 1V-OCT gear before just midi shit.


My pitch coarse control on my VCO build ranges from sub audio frequency to beyond the human hearing range. My DVM has a Hz function and I got readings 0.03 – 27000 Hz.
This lines up with TH measurement sheet, but is this normal behaver? I'm asking because when I breadboarded this circuit I got a different result. The lowest range of the coarse control was some were between 20-80 Hz depending on the 1v-Oct Trim. Also when testing the 1V-OCT input I have not been getting the expected Frequency's based on Control Voltages that TH listed in his measurement sheet.
0V – 40Hz, 1V – 80Hz ect

I'm thinking that they might be a problem somewhere in the CV summing stage. TH schematic IC3- a and IC3-b.
I can post my PCB schematic if anyone wants a look at it. I've checked it against the original one about a 100 time and I can't see any errors. Might be worth someone else having a look at it.

Anyway to sum up I was wondering if anyone could shed some light on on expected behaviour of the pitch coarse control and the HF-trim section of the VCO.

If possible could anyone post a list of expected voltage or test points that I can compare my board to a known working one?


Thanks a lot for any help

cheers

mrmrshoes
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fonik



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PostPosted: Thu May 23, 2013 2:28 am    Post subject: Reply with quote  Mark this post and the followings unread

mrmrshoes wrote:
My pitch coarse control on my VCO build ranges from sub audio frequency to beyond the human hearing range. My DVM has a Hz function and I got readings 0.03 – 27000 Hz.

sub-audio and above audio is normal for thomas' designs. this might look awkward at the 1st glance, but as soon as yo start mixing control voltages you might be happy to have enough control headroom to tune the VCO into the range you wanted.
and having sub-audio is a good thing, it makes your VCO becoming a VC LFO, w/o any additional switch Very Happy

Quote:
This lines up with TH measurement sheet, but is this normal behaver? I'm asking because when I breadboarded this circuit I got a different result. The lowest range of the coarse control was some were between 20-80 Hz depending on the 1v-Oct Trim. Also when testing the 1V-OCT input I have not been getting the expected Frequency's based on Control Voltages that TH listed in his measurement sheet.
0V – 40Hz, 1V – 80Hz ect

don't worry as long as you still get the 1V/oct. the overall tuning depends on the coarse and fine tune control, and on the 1V/oct trimmer setting anyways (as you already observed).

Quote:
Anyway to sum up I was wondering if anyone could shed some light on on expected behaviour of the pitch coarse control and the HF-trim section of the VCO.

the HF trimm comes into play after you calibrated your VCO for the lower range allready. this type of VCO tends to get flat on the high end, and the HF trimmer compensates this.

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mrmrshoes



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PostPosted: Sat May 25, 2013 6:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks alot Fonik.

Cheers for clearing this up for me.

I've just finished a Midi CV converter and found the coarse control setting the base frequency of the VCO a bit funny. I guess I’m used to playing a midi note and everything is in tune.
This stuff is a bit more involved.

A quick update

I tried last night to tune up the 1V/Oct of the VCO but couldn't even get a couple of lower Oct's in tune.
The best readings I could get from my DVM on the Midi 2 CV output were these:

0.00V
1.01V
2.00V
3.00V
4.00V
5.00V
6.00V
7.00V
8.00V
9.01V
10.01V

The DAC's I’m using have a 0.2% error value this is pretty close to Rays (MFOS) 0.1% error value on his 1V/Oct calibration tool. So should be good

I didn't use a matched pair for the Expo just two from the same batch.

I Think I've got a problem some where Not sure were. I'll have to breadboard the VCO Triangle core and see what differences I can find from there. I'm pretty sure it has something to do with the CV summing stage, But it could be anything.

I'll have one last go at tuning the VCO the afternoon, If this fails i'll hit the breadboard.

Thanks a lot for your help man.
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fonik



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PostPosted: Sun May 26, 2013 2:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

mrmrshoes wrote:
I tried last night to tune up the 1V/Oct of the VCO but couldn't even get a couple of lower Oct's in tune.
<snip>
I didn't use a matched pair for the Expo just two from the same batch.

the matched pair is needed together with a tempco resistor to manage the drift of the VCO, not the scale.
and i got the VCO calibrated to about 6 octaves within a minute.

for now i would say, take care that the HF trim is set to max resistance. try to get the lower octaves in scale (0V to 4V from your MIDI2CV interface).
then go for the higher octaves by adjusting the HF trim.

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mrmrshoes



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PostPosted: Thu May 30, 2013 12:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks alot for the tips Fonik.

I've managed to get it up and runnning with six octaves without the use of the HF trim. Very Happy

I bought a grt tuner and found the info on Yusynth's VCO page very helpful.

http://yusynth.net/Modular/index_en.html


I've got a bit of drift but that's to be expected when you overlook a decent timing cap (I'm using a cheap poly film for testing) and the tempco is not in contact with the expo pair.

I'll order Silvered mica or Polystyrene in the next couple of days.

Still it's only floating around a few cents +/- which ain't to bad.



Once again Thanks alot for your help man

mrmrshoes
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codenamerofl



Joined: May 26, 2013
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PostPosted: Tue Jun 04, 2013 5:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

hello folks,

i have been working on building this on pad per hole board, and while i have everything wired on the board, i do not have pots or jacks wired up yet. i hooked it up to my power supply, and my meter is reading 0 volts coming out of the supply. when i unhook it, it goes up to 15 volts like it should be at. why is that?

this is the first module i'm building for my small diy modular. any help would be appreciated.
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Blue Hell
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Joined: Apr 03, 2004
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PostPosted: Tue Jun 04, 2013 5:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

welcome codenamerofl

Looks like your power supply has a current limiter (short circuit protection) and you are shorting it ... or maybe reversed + and - ... or just overload it.

Or when it does not have over current protection .. its a damn hard short Shocked

Anyway, some wiring fault.

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codenamerofl



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PostPosted: Tue Jun 04, 2013 5:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

thank you for the quick reply!

it must be a real bad short then as this supply doesnt have any current limiting, as i'm building every aspect of this thing. nothing popped or burned or smoked though so i suppose thats good.

EDIT: Had a small solder bridge between pins 3 and pins 4 of a tl074. fixed that and it doesn't short anymore. time to wire up pots and jacks and see if it is doing what it should be doing.
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mosheen



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PostPosted: Wed Jun 19, 2013 8:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

Noob question: C4 is marked "Poly". Is that Polyester Mylar?
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mosheen



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PostPosted: Mon Jun 24, 2013 2:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Bueller?... Bueller?... Bueller?
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