Slower Vibrato on Vibro Champ??

vortex · 11-13-2006, 09:16 PM

I am looking to get a nice slow vibrato on my Vibro Champ. I did this mod (Weber?)that I found online and it seems to have worked yet still I would like to get an even slower vibrato.

Quote:

2. Slow down the vibrato on your Vibro-Champ
If you want to slow down the vibrato speed. This can be easily accomplished by
changing a cap. On the board you will find three caps in a vertical row whose values are .01, .01, and .02 mfd.
Change one of the .01 caps to a .02 mfd for slower speed.

Could anyone suggest how I would go about doing this?
Here's a link to the schem.
http://www.ampwares.com/ffg/schem/ch...a764_schem.gif

Thanks again!

Tom Phillips · 11-13-2006, 10:35 PM

There are limits to how slow you can make it. You must be getting a pretty slow tremolo now. You can try changng the remaining .01uF cap to a .02uF cap. However, if you try to make it too slow the circuit will stop oscillating. Can't hurt to try though.

Enzo · 11-13-2006, 10:55 PM

I routinely replace the two .01 caps with .02. It oscillates fine. Most FEnders I encounter trem between not slow enough and way too fast at half way up. So with owners approval I slow them down. i wouldn't have a problem with going even larger than .02 if I had to. Make sure the cathode bypass cap is present and in good shape. Without it, the low freq gain of the trem tube suffers. it could be larger even. The poor tube has to amplify as low as one Hz. And of course the tube has to be good.

stokes · 11-14-2006, 12:58 AM

I've tried .047's in a similar circuit.Didnt like it,it had a lot of put-putting underneath.

vortex · 11-14-2006, 02:14 AM

I replaced both 0.1Uf caps with 0.02Uf. The vibrato range is excellent! It goes from a nice slow throb up to a fast shimmer. This is exactly what I was hoping for. Thanks again everbody for your help!

Another question: I find that the intensity pot has a small sweet spot that I like between 3 and 4 on the dial. I think it would be useful to widen that area. On the lower ranges of the dial the vibrato is fairly inaudible and in the area between 6-10 it seems that there is more than enough hard chop.

Does it make sense to swap out the 25K intensity pot with a 10K and perhaps a 5k resistor in series or is there a way to add a parralel resistor to the pot to drop the resistance to a better suited range? Perhaps it would be better to use a linear pot?

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11-13-2006, 10:35 PM	#2
Tom Phillips Senior Member Join Date: Jun 2006 Location: California, USA Posts: 676	There are limits to how slow you can make it. You must be getting a pretty slow tremolo now. You can try changng the remaining .01uF cap to a .02uF cap. However, if you try to make it too slow the circuit will stop oscillating. Can't hurt to try though.

11-13-2006, 10:55 PM	#3
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,263	I routinely replace the two .01 caps with .02. It oscillates fine. Most FEnders I encounter trem between not slow enough and way too fast at half way up. So with owners approval I slow them down. i wouldn't have a problem with going even larger than .02 if I had to. Make sure the cathode bypass cap is present and in good shape. Without it, the low freq gain of the trem tube suffers. it could be larger even. The poor tube has to amplify as low as one Hz. And of course the tube has to be good.

11-14-2006, 12:58 AM	#4
stokes Old Timer Join Date: May 2006 Location: NYC Posts: 1,305	I've tried .047's in a similar circuit.Didnt like it,it had a lot of put-putting underneath.

11-14-2006, 02:14 AM	#5
vortex Member Join Date: Jun 2006 Posts: 35	I replaced both 0.1Uf caps with 0.02Uf. The vibrato range is excellent! It goes from a nice slow throb up to a fast shimmer. This is exactly what I was hoping for. Thanks again everbody for your help! Another question: I find that the intensity pot has a small sweet spot that I like between 3 and 4 on the dial. I think it would be useful to widen that area. On the lower ranges of the dial the vibrato is fairly inaudible and in the area between 6-10 it seems that there is more than enough hard chop. Does it make sense to swap out the 25K intensity pot with a 10K and perhaps a 5k resistor in series or is there a way to add a parralel resistor to the pot to drop the resistance to a better suited range? Perhaps it would be better to use a linear pot?

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