Neovibe question

[fatt-one]

Hi Guy's,
I have a question, is the bulb brightness supposed to change as you turn up the speed control? or is it only controlling the rate at which it flashes? the intensity control will also control the brightness,but is this normal for the speed control to alter the brightness?
Thanks
Fatt-one

[R.G.]

is the bulb brightness supposed to change as you turn up the speed control? or is it only controlling the rate at which it flashes?

In a perfect world, no, the bright ness would not change with speed. In the real world, the bulb does not cool down fast enough between peaks to get really dim, so the average brightness goes up. The bulb is not fast enough to follow the LFO accurately.

[sfr]

Thing is, musically, it's part of the unique Univibe character.

[fatt-one]

Thanks for the replies,Well...I was fooling around with the bulb bias,I have a 200 ohm trim into a 100 ohm resistor......and bam the bulb is gone!!!! I went to the rat shack and grabbed a 1.5 volt 25ma and a 12v 25ma .I had the 1.5 volt in there this time I will try the 12volt.............I believe the problem I'm having is in the oscillator,the pedal sounded good,but if you went to high on the intensity control it doesn't sound right to me,theres a throb behind the sound that doesn't fit any ideas?
Thanks
Fatt-one

[SteveB]

Anything higher than 3 o'clock on the intesity on mine, & the bottom end throb gets a bit too heavy.

I have a 51 ohm resistor (instead of the 150ohm) to ground in conjunction with a 200 ohm trimmer. The most pleasing sounds to my ears are between 100-130 ohms which is within 1/16" travel on the trimmer. I am going to replace the 200 ohm trimmer with a 100 ohm, so I can hopefully fine tune the sweet spot a little easier. The lower the resistance is, the brighter the bulb, & also, the brighter the phasing sound is. If the resistance is higher, you get more throb, & less phasing, sort of like an amp's vibrato. If the resistance is too low, you loose the "body" & fullness, & get more upper frequency phasing. I like to try & find the perfect blend between throb & phasing.

Of course, all of this is just my opinion. 

Steve

[RedHouse]

Anything higher than 3 o'clock on the intesity on mine, & the bottom end throb gets a bit too heavy.

I have a 51 ohm resistor (instead of the 150ohm) to ground in conjunction with a 200 ohm trimmer. The most pleasing sounds to my ears are between 100-130 ohms which is within 1/16" travel on the trimmer. I am going to replace the 200 ohm trimmer with a 100 ohm, so I can hopefully fine tune the sweet spot a little easier. The lower the resistance is, the brighter the bulb, & also, the brighter the phasing sound is. If the resistance is higher, you get more throb, & less phasing, sort of like an amp's vibrato. If the resistance is too low, you loose the "body" & fullness, & get more upper frequency phasing. I like to try & find the perfect blend between throb & phasing.

Of course, all of this is just my opinion. 

Steve

I think that's got to be a bulb difference issue, I've been using some grain-of-wheat bulbs lately 14V/30mA and they like about 200-350 Ohms when run off a 15V power supply (I use a separate LM78L15 to power the LFO)

[Mark Hammer]

Virtually all modulation devices, whether chorus, flanger, tremolo, vibrato, or whatnot, insist upon a reduction in sweep width as speed goes up.  Or rather, the human ear inisists upon it.  Nervous systems are designed to take notice of rate/amount of overall change.  When the speed is slow, wide sweeps still present fairly modest change per unit of time.  As the sweep speed increases, the amount of change per unit time starts to become too distracting.  Consequently, we turn down the sweep width to compensate, such that things may be changing quickly, but not THAT much.

The characteristics of incandescent bulbs are such that quicker modulation speeds do not give the filament enough time to completely cool down.   Much like a fast-moving car that requires very little gas to get back up to faster speeds, the bulb doesn't get quite dark and quickly illuminates.  The shift in how much illumination change the bulb goes through at a different speeds is part of the character of the "classic" Uni-Vibe.  I suspect that if we were able to do tightly-controlled luminance measurements, we'd probably find that the shape of the illumination "curve" (i.e., how quickly it went from least to most brightness) would change with modulation speed.  Apparently, we like it that way.

[SteveB]

I think that's got to be a bulb difference issue, I've been using some grain-of-wheat bulbs lately 14V/30mA and they like about 200-350 Ohms when run off a 15V power supply (I use a separate LM78L15 to power the LFO)

I used a 12V 50mA on mine, so you are probably correct. I am also using a 12V regulator, not 15V.

This is the one I have in mine. Model: 272-1154

Steve