Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. New: view Recent Searches.
New: visit Schematic Hell!
The sunn still shines online!

Listen to great tunes streaming live right now!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  
previous: jimbo Hi there, I just received a Ross re... -- 1103763400 View Thread

Re: Ross/MXR tweak or not to tweak

12/23/2004 8:38 AM
Mark Hammer
Re: Ross/MXR tweak or not to tweak
First off, yes, many Ross products ARE virtual clones of their MXR equivalent. I wish I knew more about how that happened, historically.  
Second, though you can render any flanger nonfunctioning by mis-setting the trimpots, you won't destroy it.  
Third, the trimpots in flangers can serve any combination of the following functions:  
a) Biasing the delay chip. This feeds a DC voltage to the input of the delay chip, which is required for the delay chip to pass audio signal. If the bias voltage is wrong, the chip will either pass a very distiorted signal or none at all. Generally speaking, this can be set by ear. As you tweak it will go from no delay sound, to a dirty one, to clean, to dirty again and finally no delay sound.  
b) Clock trim. Achieving a characteristic flanging sound means producing the same range of minimum and maximum delay times. Some flangers will include a trimpot to adjust the delay time range for consistency across copies.  
c) Bbd balance. Some delay chips include a variable balance control to adjust the relative level of each of the two outputs found on the BBD. This helps to better cancel out clock noise that may come through. More flangers tend to use just a pair of matched resistors instead of a trimpot.  
d) Delay level. Maximum notching is achieved by a perfect 50/50 balance of dry and wet signal. What some flangers have is a slightly attenuated dry signal, and a trimpot on the output of the delay chip to trim back the delay signal for a 50/50 mix when it is combined with the dry signal downstream.  
e) Regen trim. Too much regeneration produces annoying oscillation. If the combination of components in the regeneration path does not keep regeneration under control, you can end up only being able to use maybe 80% of your regen/feedback pot's rotation before it becomes annoying. Consequently, many flangers (and phasers too) have a regen trimpot. During setup, the regen/feedback control is maxed and the trimpot is eased back just to the point where it stops howling, allowing the user to aim for as much regen as they can use.  
"Depth" in the flange can mean a lot of things. For example, it may be that the 50/50 balance to be aimed for is a little off and there is not as much notching as there might be. It may also be that the range of delay times is a little off, resulting in notches that never seem to sweep high enough or low enough.  
For a great many people, though, "depth" is really about how wide the flanger sweeps, and there you have a design issue rather than a trimpot or tweaking issue. Though it matters little for "bubbly" sounds, slow jet plane sweeps require a very wide sweep range and "sweep ratio". Conventional wisdom says that a sweep ratio of at least about 30-to-1 is needed for dramtic sweeps. So, if max delay time was 15msec, a minimum delay time of 0.5msec would be needed to get something that sounds really majestic. A sweep from, say 0.3msec to 14msec would be even better. Regrettably, the LFOs and clock circuits on many garden variety flangers don't permit much more than a 20:1 sweep. Unfortunately I forget what the swep ratio is on that one, though I suppose you could look it up somewhere on the net.  
All of this is the long way of saying that there may be some additional oomph you could wring out of your pedal with trimpot tweaking, but there may not be much else to squeeze out too.

jimbo Hey Mark..thanks. Thats quite the ... -- 12/23/2004 9:42 AM