hey vero guys... brazillian edition of elektor "octave up"

[pinkjimiphoton]

i found this looking for CDDB/os mutantes style stuff earlier... it was a simple one chip octave up, that required a bipolar 9v power supply...
this is the schematic i found:



anybody ever build this?

i worked up a vero for it incorporating a charge pump for the power supply... could probably make it a wee bit smaller, but
pretty lazy....
it's set up where black wire from batt/power supply is labeled 9v batt - and the red wire goes to 9v batt +

green ground is to chassis ground, the rest in black are for the pots etc... not really necessary, but nice to know where ground is when wiring the box.

the blue wire "to ring" is to turn the effect on when a battery inserted, ala RG's suggestion for something else a couple years ago.
i believe the rest is pretty self explanatory.

anyways, here's the vero:



i've gone over it a bunch to see if it's ok, i believe it's true to the schematic (other than the charge pump and associated circuitry)

would be JAZZED if someone else could peep it to make sure there's nothing wrong they can see. i know vero is a pain in the ass to most people, to us guys that
like it it's really not that bad, just check nodes against the schematic pretty much.

anyways, do you think this will fly?

has anyone else built this thing? if so, is it worth having a go at?

appreciate your comments brothers and sisters!!
thanks so much!
peace

[psychedelicfish]

I wouldn't bother with a charge pump, it would probably be fine to return all the grounds in the schematic to a VREF, with the exception of R11. You might want to include a 1M anti popping resistor on the input too. Another thing you could do would be to get rid of P2, and replace R9 & R10 with a 500k pot.

One problem with your layout is that the output and input traces are right next to each other, if this circuit has much gain it will oscillate. I would suggest moving them further apart if possible. If it makes your layout any easier I would use two dual op amps instead of the quad.

[pinkjimiphoton]

I wouldn't bother with a charge pump, it would probably be fine to return all the grounds in the schematic to a VREF, with the exception of R11. You might want to include a 1M anti popping resistor on the input too. Another thing you could do would be to get rid of P2, and replace R9 & R10 with a 500k pot.

so..... you're saying just run it at 9v (vref being half voltage)? and run all the grounds to that? why the exception with r11?
yah, i can see running a 1m anti pop resistor, if need be i can mount it on the switch. there IS a 1 meg anti pop resistor on the input  from pin 12 of the quad to ground.

wouldn't it be kinda redundant to have a dual stacked 500k pot  feeding another 500k pot? why not just go with a dual stacked 1m if doing that? or do you mean just use a single 500k pot there?

One problem with your layout is that the output and input traces are right next to each other, if this circuit has much gain it will oscillate. I would suggest moving them further apart if possible. If it makes your layout any easier I would use two dual op amps instead of the quad.

that one's easy. just gotta add a jumper. i did notice i missed one track cut too, at e13.

thanks for looking ed.

[duck_arse]

he means (I hope) connect the new, single gang 500k between C4 and C3/P1, and take the wiper to C6, so you have like a pan-pot. drop the dual gang and the 2 x 220k. the R11 is connected to the output, so it grounds. you don't want V/2 on your output socket.

[psychedelicfish]

I wouldn't bother with a charge pump, it would probably be fine to return all the grounds in the schematic to a VREF, with the exception of R11. You might want to include a 1M anti popping resistor on the input too. Another thing you could do would be to get rid of P2, and replace R9 & R10 with a 500k pot.

there IS a 1 meg anti pop resistor on the input  from pin 12 of the quad to ground.

The 1M resistor (R1) is for biasing, like the one from the + input of the op amp to a VREF in the MXR dist+. An anti pop resistor provides a connection to ground for the input capacitor to discharge through when the pedal is in bypass.

You might want to fiddle with some of the capacitor values, lots of them are quite large (the input capcitor has a corner frequency of 0.5Hz!). I'd suggest breadboarding it and swapping out the capacitors to get a sound you like before committing it to vero.

[R.G.]

The central part of it is an opamp-base precision full wave rectifier. There are other examples of this.

Take a look at the octave section here: http://www.hollis.co.uk/john/omnidrive.jpg in John Hollis' omnidrive; layout and redrawn schematic here:
http://www.geofex.com/PCB_layouts/Layouts/omnidrv.pdf

[GFR]

The picture is not from the brazilian magazine, the captions are not in Portuguese.

But I do remember similar designs on the brazilian magazine. I have a bunch of brazilian Elektors from the 80's, I can look for octave circuits like that if you want (and check if they have a pcb, or just the schematic).

[pinkjimiphoton]

my bad, i found it on a brazillian site i was surfing around in, google translate said the site was portugese, i guess the pdf wasn't tho.

thanks for the other suggestions guys.

one more dumb question... if using a charge pump, should you use power supply filtering before the pump? or is that stuff built into the chip?
when i revised my vero, i had some space so added some power supply filtering... probably will have to re-do the vero again anyways... definitely will socket the caps and experiment some. gonna try it with more standard values, too... thinking 10k instead of 12k maybe...

anyways.... this was the last revision i cobbled together (pre suggestions)

[StephenGiles]

I'm sure this was in the UK Elektor, what's wrong with using 2 x 9v batteries?

[greaser_au]

I expected the vero to be very narrow, maybe six columns...   

david

[tubegeek]

OK, I always forget this one: how many is a brazillion again? And - while I'm asking anyway - what color code goes on a 1 bohm resistor?

[pinkjimiphoton]

I'm sure this was in the UK Elektor, what's wrong with using 2 x 9v batteries?

the pdf i have is definitely not english, it's either portugese of brazillian, i got it from munky's site, tho i may have had to hack the wayback, i don't remember.
i can't tell the difference.

stephen, i don't wanna have to run anything on batteries, it kinda defeats the purpose of my present pedalboard. if i can't run it off my power supply, it don't live there.
i have still 5 unused 18v taps, and 7 9v ones, so it would be plenty of power... it would be really inconvenient to use batteries.

[pinkjimiphoton]

this is where this came from, before extracting it from the CHM file it was in:

http://wayback.archive.org/web/20040226072053/http://www.gfrhpg.hpg.ig.com.br/CCDB/oitavador.chm

definitely a brazillian site. it was on a page listing all of the CDDB stuff made for mutantes by cesar dias, so i downloaded it.

spanish? portugese? beats me, i can barely speak english.

[petey twofinger]

forgive me for beeing a weenie , but this is really cool what you are doing here jimi .

[Lurco]

I'm sure this was in the UK Elektor, what's wrong with using 2 x 9v batteries?

Originally published in Elektor Germany December 1979. In the UK probably either at the same time, or +/- a month or two.

[tubegeek]

Hey pinkjimi:

1. I too am thankful for your amazing skill at digging out cool (and eminently buildable!) circuits - can I call you "El Justiciero"? ("The Judge.")

2. If you have 18V available there may be a slicker way to do this. An LM386 chip will bias itself to 1/2 supply. Connect the LM386 +V and -V pins to +18 and 0, and *I THINK* it gives you 9V on the output pin. Then connect the +9, 0 and -9 nodes of the circuit above to +18, +9 and 0 respectively. The circuit is cap-coupled input and output so I believe (as in, haven't breadboarded it so I'm not 100% sure) this will work.

You might need a pair of caps to filter the DC (one between high and middle, and one between middle and low voltage) but I think that's ALL you'd need.
Hopefully someone smarter than me will jump in and tell us what to do with the other LM386 pins to get it to behave in this application. While we'ree waiting for that. I'll do a forum search to see where I got this idea - someone else suggested it before (John Lyons maybe?)


EDIT:

well, of course, it was RG on GEOFEX who gave me the idea:

http://www.geofex.com/circuits/biasnet.htm

"Many commercial opamp circuits with more than a few IC's need a more solid reference than the sloppy 10% we assumed. (Worse, actually. Did you notice that I didn't even calculate the variation in the reference voltage that happens because the reference resistors have a +/-5% tolerance, let alone end of life and temperature drift?)

In that case, they will make a resistor divider for ONE opamp, tie it to the + input, hook the output to the - input, and use the output for the reference voltage. Now, the opamp sources and sinks current to the rest of the circuit. The resistor reference has a low and constant load, and things have the potential to be much more accurate.

Recently, an even simpler way popped up in my head. The LM386 power amplifier chip comes in an 8 pin DIP package, is quite cheap, and self biases to half the power supply. With no input signal, its output sits at half the power supply and sources/sinks current to keep the output nice and quiet at that voltage. You don't even need biasing resistors or caps, since its inputs are self-biased at ground."

[pinkjimiphoton]

i DO have a couple 18v taps available on my pedal board, but don't have any free 18v ones other than the unregulated piece of suck i got on ebay to power my clone theory clone (which was unuseable from all the noise, but isn't now).

i want to be able to just run it off a battery if i have to, that's what's nice about the charge pump. the batt may not last long, but sometimes it's the way to go if possible. i don't wanna hassle with two batteries or a proprietary transformer if i can just add a couple pieces to a simple vero. at the huge size i posted, i think it'll still fit in a smallish box, and all the power supply crap will be onboard so it should be real stable and noise free if i like it enough to put on my board.

thanks for the lm386 chip trick... i will try and digest the post when slightly less stoned.

i really know a lot less i think than you guys think i do. i'm becoming a slightly more talented chimp, but i've got a long way before i graduate from typewriter to word processor!! lol

[Lurco]

Fig.19 here: http://www.ti.com/lit/an/snaa086/snaa086.pdf shows another possible candidate for power supply splitting.

[pinkjimiphoton]

thanks lurco!

[Mark Hammer]

I built this some 30 years ago, a little while after it appeared in the English Elektor.  Still have the photocopied article.  Of course, I didn't know 1/100 of what I know now, so there is no guarantee I made appropriate choices of components where they might have mattered.  But I did build it using the components indicated (all that TUP-TUN-DUG-DUS stuff that was common in Elektor at the time; I think I may still have the dual ganged pot it called for), got it working and have to say I did not feel the slightest qualm about cannibalizing it for parts afterwards.  The Anderton Octave Up is in the same league and is also "interesting", but not nearly as much fun as an Octavia or Tone Machine.