neovibe power supply

[larsthestrat]

could I use this transformer to power up my neovibe build?
http://www.banzaimusic.com/Hahn-BVEI3042046.html

The neovibe uses 18V DC, 200mA at least.

schematics:
http://www.geofex.com/FX_images/vibeschm.pdf

[R.G.]

From a quick look, it ought to work OK.

Be *very* careful wiring the AC power into it, though. AC power line voltages and connections can be deadly.

[larsthestrat]

thanks, just connect the 18V wires to K and J on the PCB?

[R.G.]

The transformer shown puts out 18Vac. Yes, connect them to the pads for the AC power input.

[larsthestrat]

thanks,

one other option is this one (voltage doubler):

http://diy-layout.com/20

does this provide enough mA for the neovibe only?

[R.G.]

I always thought it would not, but there have been posts here where people reported using the LT1054 with success. It's worth a try if you have a source of lots of 9Vdc and want to experiment.

[larsthestrat]

I don't think so for now, because this chip is very expensive. Thanks!

[larsthestrat]

another qusetion. I bought a bunch of 5088's and 3 3904's. Is there a particular place where I should put the 3904's?

[Morocotopo]

OK, this post made me curious. Measured my Neovibe for current consumption. With status LED on (a super bright blue one, but kind of dim, so the limiting resistor may be high value. 10K? Don´t remember) it peaks at about 43-44 mA. So a LT1054 should work. Would require about 100 mA of 9V DC to power it. Hmm. It never was in my pedalboard because of it´s unique power needs. Hmm again.

EDIT: the current consumption would depend on the type of lamp used, right?

[R.G.]

EDIT: the current consumption would depend on the type of lamp used, right?

Yep.

Since you're set up to measure, it would be very interesting - well, to me at least  - to see what the current drain is with
(a) both LED and bulb disconnected, measuring only the analog circuitry current
(b) circuit plus lamp and knowing what kind of lamp you used.

I'd do this myself, but I don't currently have a running 'vibe.   

[Morocotopo]

R.G., I´ll measure those. Give me a couple of days, work gets in the way. Regarding the lamp, I built my ´Vibe some time ago, the lamp is a "grain of rice" type, very small, I´ll check my build notes to see if I wrote down the type I used.

[larsthestrat]

could you help me out with my Q a couple of posts before, about the transistors, thanks!

[R.G.]

The 3904s can pretty much go anywhere. I've built all-3904 neovibes. That being said, they're generally lower gain than the 5088, and as such better suited to the second transistor in a two-transistor darlington. And they're rated for higher current, so they're better than the 5088 for the lamp driver.

That being said, I've also built all-5088 vibes, too.

If you have to choose, make sure you put a 5088 in for the first transistor (Q11? as I remember) in the LFO darlington for the higher gain, and possibly the first input transistor for the lower noise and higher gain.

[larsthestrat]

thanks! I think I put the one 3904 in the lamp driver and the rest with 5088, see houw that works. soundwise it doesn't matter does it?

[R.G.]

Should make no detectable difference in sound. Perhaps noise, but this is not a high gain pedal where hiss-type noise is often an issue.

[Morocotopo]

OK, been fiddling with my Vibe and the LT 1054. No positive outcome, till I realized this:

The 1054 produces double V minus the diode drops and the internal switches drop etc etc, so not 18V from 9V but more like 17, using schottkys, I got 17,7V max unloaded. Loaded it dropped to 15,5V.

BUT, the Vibe has an internal 15V regulator, that needs 2-2,5V input voltage above the output to work. That´s 15+2,5 worst case: 17,5V. Not enough V!

So I added another diode/cap string to the doubler. Bingo!!! The Vibe vibes!!! Loaded, I get about 20,5V output. Unloaded, about 26V.

In the couple of minutes I had this running, the 1054 didn´t die. Now I´ll check currents to see if it´s too close to maximum.

Getting closer to a working solution!

Another path would be to replace the internal 15V regulator with another means of getting 15V. Zener?


More news to come.

[Morocotopo]

Current consumption:

Neovibe input: 45 mA

Charge pump input: 145 mA! Quite a lot...

[R.G.]

Some thoughts.

There are Low Drop Out (LDO) linear regulators which can live with input voltages only half a volt, or even less, bigger than their output. They're more finicky than regulator 7800 devices, though.

It is possible the vibe would vibe OK on only 12V.

The tripler is a good solution, though. Seems to work OK.

Another path would be to replace the internal 15V regulator with another means of getting 15V. Zener?

Possible. But I really don't like zener power regulators. They're prone to dying at light loads, where the zener has to eat all the "excess" current. I'd personally prefer an LDO or the tripler.

Current consumption: Neovibe input: 45 mA
Charge pump input: 145 mA! Quite a lot...

That's Mother Nature again. One of Her Rules is that you have to put in as much or more power as you take out. If you take out 45ma at 27V, and you're making it from 9V, then 27*0.45 has to be equal to 9V times the input current. Three times 45ma is 135ma. And Mother insists that you pay more than just breaking even. So 145ma sounds about right.

[Morocotopo]

LDO´s, eh? Never used them. Might investigate.

Listening to the thing, there´s a bit less of mod sweep range with the charge pump. Not super different, but...
Maybe it needs bigger caps at the charge pump? It might be as simple as reseting the lamp bias... or not. Not enough current for the lamp to swing from on to (sort of) off?
Also, the diodes I´m using for the charge pump are 1N4148´s and, ehh, BAT41 schottkys. So signal ones, not power ones. Maybe that is limiting my supply current?
All my testing so far has been without opening the vibe. Maybe it´s time to rip it apart and experiment. 12V regulator, rebiasing, etc etc.
More research ahead!

That Mother Nature character and its sidecick, Mr. Ohm will never go away... damn!

By the way, I´m powering this from a DIY regulated PS, LM317-powered if i recall correctly, adjustable Vout. The transformer is a 300 mA one, those chinese cheapos. I suppose it´s able to provide around 150-200 mA. Or am I wrong?

EDIT: A bit less volume with the charge pump, too.
EDIT 2: R.G, looking around my lamp stash from when I built the Vibe, I believe I used a 35 mA one, so if the thing uses around 45 mA, less the lamp, less the led, the circuit alone should use about 10 mA or less. Anyway, when I open it up I´ll measure what you asked me.

[larsthestrat]

this Hahn PT, it is so small I can build this inside the box, have to cover it very well because it's conected to 240V.