Active EQ Circuits Anyone?

[vanessa]

Does anyone have any links to some active eq schematics. I was even wondering if there are even some simple tube active eq circuits out there?

[didier]

[toneman]

Have U discovered how to google 
It's easy to find "active eqalizer"   or "tone control active"   

[vanessa]

Me Googled long time...

Not really a whole lot out there about it or the science of it and I could only find a few complex Pultec active EQ's that used tubes. I really would like more info about tube and solid state as well as some simple circuits.

[toneman]

Hi V,
It helps if U spell equ-il-zer correctly   
I've googled "tone control schematic active" & "tone control schematic".
PM me with your eaddress, & i'll send U a few....

[RaceDriver205]

Lol, I don't know why anyone would want to do a tube EQ, but there is an active EQ project over at generalguitargadgets.com

[lovekraft0]

Here and here are a couple of great ideas (from our own stm), and here's a good overview, including a tube EQ (from headwize.com). HTH

[KMS]

Hopefully I can save you some time....and effort....as I have been through all this EQ stuff to the max.

It has been my experience that tube EQ is totally inferior to solid state......it sounds like crap with a load such as the load used in a live band.  I have no experience with tube EQ for home stereo use but I can't think of any reason why that would make it better just because it is inside the house.

It does however yield distortion with high loads......if that's what you looking for in your EQ.....not me....I get that out of my Tube amp.

The "warm SOUND" that some folks talk about with tube EQ is actually a slight amount of distortion.

If the science is important to you you should go to GEO and read all about it here http://www.geofex.com/Article_Folders/EQs/paramet.htm

The principles are fundamentally the same for both solid state and tube.

If you need an active EQ it will be quite a challenge to build for less than you could just buy one.  

If you build on specific for you need, then you have a one of kind just for your particular set up....which means it will not likely work for anything else...might as well call it an adjustable cross-over....and it will likely have controls such that it will take you 15 to 30 minuets to get what you think you want and then later change your mind and mess with it again and again (maybe)......until you eventually go buy one (maybe).

The one below is only $15 Buy-It-Now price at E-Bay...and it is not my sale.

http://cgi.ebay.com/LEGACY-7-BAND-200-WATT-CAR-EQUALIZER-SUB-BASS-ACTIVE-EQ_W0QQitemZ170041292137QQihZ007QQcategoryZ79841QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


Good Luck

[Meanderthal]

Lol, I don't know why anyone would want to do a tube EQ, but there is an active EQ project over at generalguitargadgets.com

It has been my experience that tube EQ is totally inferior to solid state......it sounds like crap with a load such as the load used in a live band.

Suppose you're building an amp. With a 'tube eq' you've got 90% of yer preamp. Might sound nice on guitar... or wouldn't it?  seems like the tonestack on all those marshalls, fenders, ampegs, etc. suddenly became obsolete.

[Gilles C]

Another tube EQ I Googled earlier today... but wasn't sure it was worth posting.

Well, maybe to read for info. There are so many schematics out there.

http://www.scopeboy.com/baxeq.html

Gilles

[lovekraft0]

It has been my experience that tube EQ is totally inferior to solid state...

And yet all those wonderful classic albums were recorded and mastered with those "inferior" tube EQs (and compressors, and preamps, and mixing desks), and that sound is still highly prized by recording engineers worldwide. To each his own, I suppose.

[RaceDriver205]

And yet all those wonderful classic albums were recorded and mastered with those "inferior" tube EQs

Indeed!

[vanessa]

I found this, it looks very cool:

http://www.angelfire.com/electronic/funwithtubes/Amp-Tone.html

I did not know it was that easy to convert from opamp schemo's to tube. I wish it had a mid range and just mono. Is that first tube acting as a preamp?

[donald stringer]

Here is the place for eq, [lots of choices] http://sound.westhost.com/site-map.htm

[Meanderthal]

Is that first tube acting as a preamp?

The primary function of the first 12AX7 circuit is to give a high input impedance for earlier stages to drive and the necessary low output impedance to drive the tone circuit.

It's more of a buffer.

This circuit should be very clean, even if it's a little complex... Good choice!

[Ben N]

It has been my experience that tube EQ is totally inferior to solid state...

And yet all those wonderful classic albums were recorded and mastered with those "inferior" tube EQs (and compressors, and preamps, and mixing desks), and that sound is still highly prized by recording engineers worldwide. To each his own, I suppose.

I don't know squat about vintage recording equipment, but might the eq on that stuff have been passive, like in a guitar amp?  From what I've read, engineers in the good old days used far less eq and more mike placement technique, and got their compression in the form of sag or saturation in their tube or germanium powered mixing desks or analog tape, rather than from the use of compressor circuits (although tube studio compressors certainly did exist).  But like I say, I don't really know...
Ben

[KMS]

If your building a tube amp...then tube EQ will work just fine with the low loading of your guitar signal.

My thoughts are about the top post of "active" EQ and  of course in a stompbox where your making a specifice device just for EQ which it will be getting the full load from your cranked amp......no need to make one like that given that you have already made the distortion you need from your amp and stompboxes.............would be best to make or perhaps buy and solid state "active" EQ...unless of course your trying to increase your distortion......but "active" EQ as a means for distortion is a motive all it's own........if EQ is what you seek....solid state does that with no extra massaging to the sound thereby solid state is superior "Active solid state EQ" compared to "Active tube EQ".  "Superior" meaning it does exactly what you want EQ without adding another function with no regard to your wanting that function or not....like distortion.

Compressors with tubes are some of the best.  Those are cool and a little distortion is what most are looking for with their compressor or at least that has been what I have observed......my solid state compressor that I built has no detectable distortion which I like very much......I seem to get all the tube distortion I need from my RP7Valve and my Club50 (more than I need and more than I will ever use especially with the RP7 set on Heavy Sustain or Grunge).....so for me I would not consider any other external devices that add more distortion of any kind.......as I would then have to re-do all the settings for each song in order to decrease distortion. Just trying to make the point here that I also love the sound of tube distortion and I use it.

Also, with active tube EQ in most cases your power output will be the same amount running through the EQ in order to stay mixed with the rest of the band.....so whatever "warmth" you get from it will always be there until you bypass it.  Depending on how you run your speaker cables this could become inconvenient when and if you ever need clean sound and when you by bass it you loose or also change your EQ setting......I suppose there could be a need for that...not run into it yet however.

Cheers

[Izzy]

Recently I am having problems with which resitors and which caps come into play for certain band ? I mean which  resistors and caps  become Hipass or loww pass.
I tried to find out using calculation, but still..

I would appreciate if anyone would explain me which caps and resistor come into play for those 3 band? If anyone could explain me using f=1/(2*pi*r*c)

I would seriously appreciate it!