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Re: echoplex or jamman?

At 11:34 AM 10/29/98 -0600, Chuck Zwicky vitriolically wrote:
>I have used both. The jamman sounds so much better it's shocking. The EDP
>is very noisy. The EDP uses pre-emphasis/de-emphasis in their converter
>topology, this means that any signals with a lot of high end, like from a
>fuzzbox, will overload or alias like crazy. The EDP sounds subjectively
>dull or cloudy compared to the jamman.

If you have this problem, it means you have the input level set too high,
and you are clipping the digital input. If you turn the input down a bit,
the problem goes away. Every person I've every dealt with who had this
complaint was happy after they knew how to set the input level right.
Personally, I use the echoplex with drum loops containing lots of cymbals,
and have no trouble with high end response at all. 

On older units, the problem was compounded by too much gain in the input, 
it was a little difficult to set properly. Most of the range of the input
volume knob was way too loud, and people tended to have it way too high.
That gain range was reset some time ago, so it's much easier to work with 

This has been covered here numerous times, and is also in the echoplex FAQ
on the website. If you have an older unit and want to change how the input
gain works, that mod is also in the FAQ.

>I really wish that they had done a better job with the EDP circuit board
>layout, so that the fidelity was higher. The seem to use a decent 
>in the EDP, but Lexicon has such a great design team when it comes to
>digital audio....

I measured the Echoplex's audio characteristics on an Audio Precision 
>From memory (sorry, I don't have the details with me...they all get ~):

Signal-to-Noise Ratio (A-weighted): ~88dB
Signal-to-Noise Ratio (unweighted): ~80dB
Freq Response (+0/-3dB): 18Hz - 19.5KHz

If you have the input signal too high, you definitely see the frequency
response roll off in the high end. That's why it is important to set the
input level correctly. I typically use the loudest signal with the most 
end I expect to use (typically a crash cymbal, or a loud/clean skank guitar
thing) in a loop to set the level to where it does not clip.

Kim Flint, MTS                 408-752-9284
Chromatic Research             kflint@chromatic.com