Hi.
How would one better this one?
Gyraf Audio - DIY Calrec EQ
Any input is welcome - most bang for the buck is more welcome of course.
Still this must be analogue so no dsp's are allowed in this one.
Regards
How would one better this one?
Gyraf Audio - DIY Calrec EQ
Any input is welcome - most bang for the buck is more welcome of course.
Still this must be analogue so no dsp's are allowed in this one.
Regards
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The Calrec has a large number of series elements, adding color... Try searching for info on the Massenburg circuit. It uses a single op-amp with nested filters in the feedback loop, so aside from an input buffer, and the buffers in the gyrator circuits, it is essentially a single stage. Parametric and Sub-Woofer Equaliser
I built that Subwoofer PAEQ from ESP's site and it is pretty much useless. Gain and Q do not stay consistent and vary with frequency. You can't dial in high Q values and it's a noisey design. It's a waste of time for a subwoofer or for any kind of application where you need fully parametric controls to dial in response for a room.
I'd be interested in finding a relatively simple solution to DIY Pa EQ but I was not successful in finding one online.
For PA you mostly need narrow high-Q cuts. The Massenburg and Calrec are not really suitable for that application. They are more for gentle tone control. The circuits as shown on Soundhost are elementary and use cheap hobby ways of doing things. There are several commercial examples of the Massenburg type, that are exceptionally quiet and low distortion, but they are built to far higher standards than the Soundhost examples. I mentioned it as a starting point to look at the theory of operation. There IS interaction in the adjustments, not so much a problem at low boost/cut and lower Q, which is what this basic circuit is really designed for. When constructed with low noise op-amp, and low noise discrete buffers in the gyrators, it works well AS A VARIABLE TONE CONTROL. Examples of this topology have been in use in almost every recording studio and mastering lab in the world since the mid 1970s.
If you REALLY want a narrow band cut only "anti-feedback" EQ box for sound reinforcement-PA, it may be far cheaper to just buy a commercial unit designed for the purpose. Sorry to lead you to a blind alley...I did not see the sound reinforcement aspects of you need, only the desire to have something with similar function to the Calrec....which is not suitable to your application either.
In my experience the 'DIY Calreq Eq' is pretty good. However my personal favorite is the old Valley People MAXI-Q EQ.
A copy of the users manual can be found here: http://umlsrt.com/wp-content/uploads/Studio%20Documents/Valley_maxiq_EQ.pdf A schematic can be found on the last page.
And finally just before Barry Porter died, he gifted a very nice parametric 'Net EQ' to the DIY community.
A copy of the users manual can be found here: http://umlsrt.com/wp-content/uploads/Studio%20Documents/Valley_maxiq_EQ.pdf A schematic can be found on the last page.
And finally just before Barry Porter died, he gifted a very nice parametric 'Net EQ' to the DIY community.
Send me a private message with your email address and I'll send you a Zip of the Barry Porter files.
I would like to point out that Rod Elliott's circuit only has two op amps in the signal path. The first one is an input buffer, which is necessary for the circuit to work properly with a wider range of source output impedances. The last three op amps are gyrators.
That being said, the circuit is very similar in operation to those built in graphic equalizers that were so popular in early 90s receivers. In fact it's better than most; those 90s circuits typically used a single transistor as the gyrator. And in my opinion, those graphic equalizers did terrible things to the sound and had very limited practical use.
That being said, the circuit is very similar in operation to those built in graphic equalizers that were so popular in early 90s receivers. In fact it's better than most; those 90s circuits typically used a single transistor as the gyrator. And in my opinion, those graphic equalizers did terrible things to the sound and had very limited practical use.
Don't take me the wrong way, I'm not hating it and I appreciate that Rod put it out there but he himself says that it's not an EQ for HI-FI applications. The noise floor is a deal breaker and the EQ controls are just not useful for targeting problematic frequencies to dial in a system to a room. As far as a broad band EQ I'd much prefer a Baxandall design.
By the way, thanks to audiowolf for bumping the thread and to Carl for the schematics!
By the way, thanks to audiowolf for bumping the thread and to Carl for the schematics!
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