Visual Sound H2O "chorus mod"

[Alex C]

Hello, the following is from the Visual Sound website:

"As of June 2004, the H2O chorus channel will have an even sweeter sounding chorus, and a faster leslie speed potential.  If you would like to have your H2O pedal upgraded to include these mods, and have the new Visual Sound BBD chips, just send it to us with a money order or VISA/MC info for $29.95..."

Does anyone know about this?  "Sweeter sound?"  Sounds like they're just using a different BBD chip and changing whatever resistor or capacitor sets the chorus speed.

I searched the forum and Google and didn't come across any information about it.

Alex

[Mark Hammer]

First off, with the exception of headroom differences (that result in limits to how much signal you can push at it before significant clipping, and consequently how good the noise specs are), different BBD's don't have a sound.  

IF one uses a higher capacity BBD (e.g., a 2048-stage BL3208 in place of a 1024-stage BL3207), and clocks/samples at a higher rate to achieve the same delay range, then the overall design permits one to achieve a different quality of sound, but the quality difference is in the design not the component.  That being said, using a different capacity BBD permits sonic improvements.  Using a different batch of the same amount of storage capacity will not yield ANY audible difference, especially after all the filtering imposed to keep clock noise out of the way.

Okay, with that needless berating out of the way ( :roll:  ), the way the mods are described suggests that two simple things are done:
1) They change the LFO range-determining cap to a slightly smaller value (my guess is that consumers said "I have no use for the slowest speeds, and I wish it could go a little faster at the fast end"; solution? make the LFO cap a bit lower in value).

2) A "sweeter" sound can mean a number of things (Damn inarticulate musicians!!).  In many instances, people use "sweet" to imply the opposite of "harsh".  What is "harsh"?  Often an excess of annoying upper midrange, and sometimes harmonic distortion.
Here's a wild guess.  If a BBD-based effect does not use a compander to maintain optimum signal levels, one of the tricks often adopted is the use of a simple soft-clipping circuit, such as a back-to-back pair of diodes in series with a resistor in the feedback loop of an op-amp.  While that will keep the input signal from ever being to excessive and overloading the BBD, it also runs the risk of delivering a fuzzed (albeit softly) signal to the BBD for delaying.  Just exactly HOW fuzzed may depend on the diodes chosen, the series resistor value chosen, and whatever feedback cap is in parallel with that.  Changing either the resistor or cap value could effectively reduce the amount of undesirable clipping introduced at that point.  Of course, if the H2O unit uses a compander, then ignore my comments.  This suggestion is offered up simply because, for $30, the mods are going to have to be something that is worth their while to do, because they involve replacing 2 or maybe 3 inexpensive components.  More than that and it starts to become less than a break-even proposition for them.

As for replacing any chips, I honestly can't see them swapping BBDs, for both sonic or cost reasons.  If there are any key op-amp chips that are "budget" quality, and are socketed, then maybe I can see them yanking out a 4558 and popping in a BiFet or other chip.  These are the sorts of things you *can* stumble onto post-release, and if the chips are socketed, you get to keep the inventory for recycling another day.

Seem reasonable?