The VCO-555

[fonik]

professional manufactured PCBs are available from THONK (he even sells just the main PCBs w/o the euro adapter and stuff), and synthCube.

[elmegil]

You can buy VCO-555 PCBs from Fonik, who Thomas has licensed this design to. Otherwise, it's perfboard....

[fonik]

i just placed a re-order, so all thomas henry diy projects via fonitronik will be available again, soon.

[Cfish]

I think he has them listed for sale on THONK DIY. Only had the board and euro face plate kit last time I looked

THONK is a great company to work with, plus they have tempcos in stock at a great price.

[Cfish]

Oops you posted as I did Fonik

I yeald the floor to the man who knows

[wackelpeter]

I would like to add that i guess the small 250mA PSU had fuses for it's Output voltages, if that's correct and furthermore if These where fast fuses they can affect the voltage at some minimal current changes... which in turn would result in unstable pitch of the VCO...

I have experienced similar behaviour because i always put fuses on the Output of my PSU to protect it and my builds when i first power them up and start with small ones and once the cabinet is finished drop in a 2A slow 1,5 or 2A fuse...
One advice too before you connect your circuit to a PSU measure the resistance between gnd and both power rails, maybe turning the pot's that are connected to the power rails each direction once, so you can be highly sure that there is no short in your circuit and you have minimal chance to blow something up...

[alanwilder81]

thanks chaps,

i mean i dont need pre made PCB but rather the black and white drawing of the circuit. Sorry but, how is it called in english?
I attached a Yusynth drawing for the ARP 2600 filter to give an example

i have the possiblity to etch my own PCB s at home, but obviously i'd need that drawing for the 555 VCO, if it's available at all

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[elmegil]

There are no press-n-peel / foil layouts for this circuit that I'm aware of.

[alanwilder81]

thanks elmegil
so,they are called press and peel or foil layouts? good to know. And you confirm there's none for the Thomas's 555 VCO, like i feared.Never mind. Perfboard will do the job.
Another question is, are the pulse-sawtooth-triangle-sine signal available at the same time?
cheers !

[wackelpeter]

yes, of course they are...

[alanwilder81]

wow.it's excellent to have all 4 waveforms available simultaneously and mixable to taste

[dillydally]

I'm thinking to use the VCO-555 as a replacement for the PCO in my DIY Serge system. It seems like it would be easy enough to use maths and an extra op-amp to scale and offset the triangle and sawtooth. After doing that will any change need to be made to the sine shaper circuit?

[alanwilder81]

hello chaps.

this post is about 555 VCO tuning.

i am trying to tune it by ear, which is playing octaves ( e.g. C1-C2). it kind of works but if i play the entire keyboard,I dont get a equally tempered scale at all. Also, what's the CV keyboard circuit role in VCO tuning? I see in it two trimmers in the upper left section ,one of which does a lot, while the other simply sets the initial frequency (10 k and 1 k respectively)

thanks for any advice !

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[fonik]

be sure to have an increase of 1V per octave from the keyboard.

when tuning the VCO start with the lower octaves (1-6), using the actual scale trim of the VCO. the higher octaves will be a little bit flat. use the HF trim to iron that out.
use matched transistors for the VCO expo!

[alanwilder81]

thanks
so i first set up the keyboard trimmers? then,once i get 1 V per octave output, i go on trimming the VCO . Hoping it works

[fonik]

[alanwilder81]

cheeers

[alanwilder81]

it worked ! that keyboard only has 3 octaves,so it was fairly easy to get it a decent tuning.
i measured the voltage at the lowest resistor,pointed out with the red arrow( 0.60 V). then, i measured the voltage 12 keys (resistors) further up on the keyboard and i got 1.60 V, which is 1 V increase , right what i was expected to get, i do believe.
and i can now fine-tune it with the 555 VCO 1 V oct trimmer.

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[alanwilder81]

another simple question is ,whats the difference between linear and exponential FM ? they sound fairly similar to my ears.

[fonik]

[alanwilder81]

thanks,
i need to experiment a little more to full exploit the 555 VCO potential

[bonzai]

Hi there!

I couldn't find an answer in the search function, so I am throwing in the question here: I don't have the 2N390x types available, but some BC549 and 559 (C types) instead. Now I am worried whether they would work anyways? Wikipedia lists them as (more or less) equivalent parts. Any one tried it out yet?
First problem I've just found out: the pinout of the BC types is apparently reversed (CBE instead of EBC), but what if I just flip them around? I.e the BC559s would be aligned "belly-to-belly" like this: |)(|

Same goes for the TLC555 - I have some UTC555 types laying around in the junk bin and I'm not sure whether they are CMOS or TTL, the DS does not tell anything... (not such a big problem though, as the chips are socketed anyway)

Any hints?

Cheers,
Chris
PS: I'm using fonik's PCBs btw...

[elmegil]

The transistor subs should work, but be aware that the pinouts are opposite (I believe) on the BC* transistors compared to the 2N39* transistors. Double check the data sheets!

As for the 555, if it's not CMOS it won't work right. Not sure the best way to ensure that.

[JovianPyx]

[bonzai]

Thanks guys!