recent poor mans and 500 peqs

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kepeb

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Joined
Sep 4, 2010
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without me treading on toes or disrespecting the very impressive recent efforts of both ruffrecords/Ian and mitsos here on the forum.
I have been following and I'm very interested In learning more about whats going on as my understanding improves.

Although I think I would like to sometime build myself a Tube version of the EQ, The idea of a solid gain make up stage doesnt really offend me... hope thats not blasphemy  :-X

I bought g-pultec boards ages ago now but never got started on them, i didn't even get a definite parts list together, there are just so many options.

what I was thinking was combining the new inductor-less design Ian has worked so hard on, with an IC make up for an even more cost aware project. preferably in 500 format to avoid psu's and cases.

although i kind of get the jist of whats going on in the circuits... impedance matching and correct approaches to designing something like that goes way beyond me.
is anyone on the same page here?

i can already envision cries for no more peq versions and scowls from other forum members, i really dont want to offend or steal any thunder, i have nothing to offer like your excellent projects, just questions.
maybe this would work with the boards already being made?
apologies in advance.



 
don't apologize, this is a DIY forum. If you can't quite design it yourself, that is ok--you can be here to learn. If you cobble something together on your own (without buying a readymade solution) than that is extraordinary.
 
I was going to do the same with the makeup, using good dual opamps, but I'm simply tired to making pcs for such simple circuits and I'm going vero for the makeup, p2p for the eq, transformerless all around. I just need a solid eq right now, I have plenty of color/flavor/dirt/whatever boxes already. Pier has designed a nice IC/DOA makeup and posted schematics, as well; as organizing a group pcb buy, maybe take a look at that for some inspiration, maybe just buy a pcb. I believe he allowed for all IC opamps.
 
In a reply to Ptownkid I said I thought perhaps the lowest overall cost por man's Pultec would use an NE5532, one half used as an input buffer and the other as a gain make up stage. A wall wart, a few connectors and a simple power supply and you are in business.

With the NE5532 acting as an input buffer and providing a nice low impedance drive to the EQ, you no longer have to worry about ensuring the EQ input  looks like at least 10K to the outside world so you could reduce all the pot values almost down to those of the original. The would make the EQ output impedance lower and hence less susceptible to crosstalk, hum and noise problems.

Cheers

Ian
 
ah, well i totally missed what pier was up to! :)
seems like its well on the way already.

strange place this forum, it was almost a ghost town over jan to mid-April and then all of a sudden switched a couple of gears on me :)

anyway sweet, i need some bang for the buck right now to get some hardware units and out of my behr*nger desk's eq!  :eek: was thinking maybe cram a few into a 2u case i have with some trs.. or 500 series ones. even better if i can use ne5532 and a wall wart!! no bank balance raping and still a damn sight better than my bellringer rubbish.

agree w/gemini but it would be great to have an all in one.(complete transformerless -inductorless capable pcb that is)
i'm ready to attempt a go on stripboard just to see if its worth it, how simple can i actually make this?
can someone explain the fet buffer stage to me as i thought the gain was made back up in the last stage.
 
kepeb said:
can someone explain the fet buffer stage to me as i thought the gain was made back up in the last stage.

I think is is basically that the EQ needs to look into a fairly high impedance - 470K or so - and a FET input op amp is the easiest way to do this. OTOH , using the non-inverting input of a 5532 should allow you do achieve this too. You could eliminate the pot I have at the front of the tube gain make up stage and set the overall gain by adjusting the 5532 feedback.

Cheers

Ian
 

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