Conference napalm::commusic_v1

    Well, let me try. Parametric eq allows you to control the gain at
    a certain frequency range as well as the mid point of the range.
    So I would guess that the MID SWEEP pot controls the center freq
    of the midrange level pot.
    
    dave
    

    Standard ole "graphic" eq's let you vary the amount of gain/cut
    centered on a *predetermined* frequency. Parametrics let you determine
    the frequency (within bounds) you want to cut/boost.
    
    Frinstance...
    
    If you want a 5db boost at 200hz and your graphic eq has bands on
    either side of that (say 100 and 300hz) your going to have to play
    with either or both of those to get the requested 200hz boost, and
    you'll end up boosting all the other frequencies covered by those
    controls. (Some by more than 5db!) You may find yourself with a
    worse response then when you started.
    
    A parametric will allow you to center the boosted frequencies either
    right on or closer to the 200hz. If you can center it, nothing else
    should have over a 5db gain. If you can't choose the exact center
    frequency you want, at least your closer.
    
    The range of frequencies covered by any single control is an inverse
    function of the number of said controls. (On a graphic, that it.)
    I believe on parametrics you may also be able control the width
    of the effected frequencies. That is, if you have a narrow range
    of frequencies selected, the slope leading up to and away from the
    center frequency will be closer to vertical than one leading to
    the center frequency in a wider band.
    
    Some audiophiles swear by parametric. (Others swear AT any type
    of eq!) I have 12 band stereo with center frequencies about an
    octave apart. I find this satisfactory.
    
    Clear as mud, right?
    
    Edd 
    

	Was just snoopin' around the old notes and found this one...

	I've been wondering about parametric EQs;  Do they have some 'memory'
function that allows you to cut/boost one frequency band and then go to another
one and cut/boost...  Or is this something that more expensive ones have and not
all?  Otherwise, would this scheme be handled by more than one Parametric EQs
used together?

	PAIA has a four-channel parametric EQ. in their catalog.  Is this a 
common arrangement?  It says they are completely independent and can be used
for separate channels (like for a 4-track) or in any combination.

	Dan

    PAIA... (chorus of groans from the experienced)
    But I sometimes wax nostalgic for my 1972 "2720" modular system.
    
    Don't bother.  The low-seeming prices can't possibly make up for
    the lack of enclosure (I'm serious) on the rackmount stuff, and
    the general poor parts-quality.  About a year ago I decided maybe
    they had improved their act.  Nope.  The Quadrafuzz came with odd-sized
    pots that wouldn't take the knobs without shimming, etc, etc.
    
    To answer your question, unless an eq states that it is multi-channel,
    and programmable, "what you see is what you get," there is only
    one channel per set of knobs on the front.  The PAIA unit is a bit
    unique in my experience in that they only give you one section of
    eq per channel, a rather flexible arrangement, but I expect that
    you would normally cascade at least two sections.  If they put a
    box around their stuff, and upgraded the parts quality, they might
    have something.  But building the quadrafuzz, I became quite certain
    that the time saved by doing the assembly myself was
    reverse-cost-effective.
    
     	Eirikur
    
    
    

RE < Note 345.4 by DSSDEV::HALLGRIMSSON >

>    Don't bother.  The low-seeming prices can't possibly make up for
>    the lack of enclosure (I'm serious) on the rackmount stuff, and
>    the general poor parts-quality.  About a year ago I decided maybe

	To carry this idea on... Is there any reason why adding an enclosure
wouldn't prove effective?  Is there more to it than just finding a case that
fits (I've seen such things at U-DO-IT Electronics)?  What does the 'open' 
arrangement do?  Add noise?  Would it be more advantageous to simply find a
better unit to begin with?  The PAIA unit sells for $60 (and remember, it's
4 parametrics, not one), so it seems to be quite a bargain...

	I've wanted to buy some of the PAIA kits for some time since I'm
becoming more and more of an electronics hobbyist.  I can't seem to find
enough projects to work on to satisfy my hunger to learn more about the
subject, especially as is has to do with music.  I've all but mailed the
application for the compressor, the 6-channel stereo mixer, and various
other projects that are described in the book Electronic Projects for
Musicians by Craig Anderton.  It seems that many of the parts for these
projects are simply not available at most places (no longer produced?).
I've not been able to find a single electronics distributor that sells the Op 
Amp used in most of the projects in the book.  

	Anyone know of other companies that supply reliable kits for
electronic musicians like the kind PAIA sells?

	Dan    

    RE -.1 by AKO76::EATOND
    
>    I've not been able to find a single electronics distributor that sells the Op 
>    Amp used in most of the projects in the book.  
     
    What Op Amps are you looking for....
    
    I got some of the older types.

    If I don't have what you need, I can at least point you to the right
    place to get it.
    
    -TomR-

RE < Note 345.6 by AKRON::RATASKI "Tom Rataski - SWS Akron,Ohio" >
     
>    What Op Amps are you looking for....
    
>    I got some of the older types.

>    If I don't have what you need, I can at least point you to the right
>    place to get it.
    
	Thanks, Tom.  I don't have the book here at work, so I can't post the
type 'til tomorrow.

	Dan

RE < Note 345.7 & 345.7 

	O.K., got the book.

	The one op amp that comes up in almost every project is the one it seems
hardest to locate - RC4739 or XR4739.  They do suggest an alternative IC, the
4558, but it requires a re-design of the curcuit board.  There may be other
substitutes as well, but I'd like to avoid changing the board layout (again, 
inexperiense compells me).

	Another part I've been unable to locate is a part used in the compressor
limiter - an opto-isolator CLM6000 (manufactured by Clairex).  Anyone have any
suggestions for that as well?

	Dan

    By a Roland SRV-2000 reverb and you get a 3 ?band? parametric EQ
    as well (plus a damn good reverb).
    
    I'm not sure how useable the SRV-2000 is as a "parametric EQ" but
    it's an experiment I plan to make.
    
    	db

    RE < Note 345.7 & 345.7 & 345.8
                   
     RC4739 or XR4739 Equates to a 739. Very common. But sorry to say,
    I don't have any . You should be able to find these critters at
    any mail order house. Check out a copy of Byte or other PC type 
    magazine for a number of these venders. (Jameco comes to mind). 

    I can get you addresses, phone numbers and prices if you need them
    but not for a couple of days since I'm going out of town to a remote
    customer's site.
    
    As far as the Clairex part - Is it really a solid-state opto-Isolator? 
    Or is it one of the old fasion ones built from a photoresister and
    a light bulb inside a piece of heat shrink tubing. I can't picture 
    Clairex building anything solid-state, but they were known for the 
    older type I described above. Also this part was used frequently
    in older guitar amps for tremolo and in Wah pedals for varying the
    pitch. I can look up the part in a catalog if you wish.
                                      
    -TomR-

re < Note 345.10 by OVDVAX::RATASKI "Tom Rataski SWS Akron,Oh." >

>    I can get you addresses, phone numbers and prices if you need them

	Sure, I'd appreciate anything you find.
    
>    As far as the Clairex part - Is it really a solid-state opto-Isolator? 
>    Or is it one of the old fasion ones built from a photoresister and
>    a light bulb inside a piece of heat shrink tubing. 

	It is the latter (non solid-state).  There's a description in the book 
that pretty well compares with yours.  Again, I'd appreciate anything you can 
find on it.

	Dan

    re .9 - the SRV-2000's EQ is "quasi-parametric".  The low and high
    Eq are shelving with adjustable slopes; the mid EQ is peaking with
    adjustable Q.  Given these "limitations", the EQ is still quite
    capable.
    
    len.
    

    I suppose we just turn off alllll the reverb.
    
    expensive eq.......why not.
    
    a feature!
    
    The clarex parts that come to mind to me were the ones that
    had MULTIPLE drivers/detectors. A really wide phase shifter
    could be built from 1 driver and 4 to 6 detectors cause they
    tracked fairly well AND the resistance changed from Megs to
    100's ohms....whew.
    
    da good old daze.