NYD's passive EQ, ghetto edition

[analag]

Had to revive this thread. I just finished winding an EQP1A inductor with an added 70mH on top of the 150mH for a 2k frequency select (220mH total). I used a P-3622-77 pot core, from CWS Bytemark. A few minutes of experimental winding showed me AL=6665 not 7680 as they claim on the website. I calculated all my turns based off of this value and swept all the frequencies with the appropriate caps in place and only the 16k sweep was a few Hz off(capacitor related), everything else was dead on.

Total resistance is 2.3 ohms. It took me all of five minutes to do it by hand, with some #26 wire I had lying around.

analag

 

[Viitalahde]

Damn, I still need to wind my own some day.. Well done! :thumb:

 

[NewYorkDave]

Good info, Rowan. I was considering those cores, myself.

 

[alk509]

Good job, Analag! :thumb:

You gotta keep in mind that those pot cores are spec'd with a 20% tolerance. So, 7680*.8=6144. I'm going to be doing some winding as soon as I get a counter and a hand-drill I got off eBay (thanks for the inspiration, NYD! :thumb. My plan is to overwind using Al=6144, and then remove turns until I hit the sweet spot.

My EQ will have 10 bands - 1 band per octave, or 32Hz (shelf), 64Hz, 125Hz, 250Hz, 500Hz, 1KHz, 2KHz, 4KHz, 8KHz and 16Khz (shelf) - with selectable shelf or peaking response on the 64Hz, 125Hz, 4KHz and 8KHz bands.

I'll try to document the build for the group's perusal.

Peace,
Al.

 

[analag]

[quote author="NewYorkDave"] I was considering those cores, myself.[/quote]

It a damn good looking core too. Comes with a white plastic nut, bolt, washer and bobbin.
When winding, take all your taps from the same slot, including the begining and end.

 

[Viitalahde]

BTW, I just added some series resistance to the highest band, thought it was too sharp. I ended up with a 200ohm resistor, way better now. I reckon it took about 3dB away from the maximum boost. Didn't even bother to measure. :razz:

 

[NewYorkDave]

I drove right by the Fair-Rite factory the other day. If I'd planned ahead and left in some extra time, I could have stopped in and asked for some samples :?

 

[analag]

Hey Dave, it's better if you roll your own

to the required specification of what you're building.

 

[NewYorkDave]

Fair-Rite sells cores, not complete inductors.

 

[radiance]

Dave: Looking at your scematic I was wondering if it's possible to make a very simple version of your EQ, one with only 1 frequencie selector switch with 6 positions (2 X low, 2 X mid and 2 X high) and 1 cut/boost rotary switch.

I'm in the proces of "thinking of building" a 10 X stereo channel active summing box and a very simple passive EQ would be a nice addition.
It will be all stereo EQ's so I'll need some hefty rotarie switches.
(this "thinking of building" proces will be taking some more years :grin: )

 

[Viitalahde]

Then you'll feel pissed off when you need both low and high. :wink: I'd suggest that you make instead a 2-band version with fixed, wide frequencies. Same amount on knobs. Low shelf at, say, 100hz and a w i d e 12-14k peak?

 

[radiance]

Yeah, that would also be an option.On the other hand, this EQ will only be for mild coloring, not for hefty EQ tasks.
One thing that I want to get rid of is that 2 pole 12 position rotary (I don't think it's possible though) ...when building a stereo version it will be 4 pole 12 position and quite costly :sad:

 

[Viitalahde]

Well, if you're not going for heavy EQ'ing, you could go with less maximum boost/cut..? That would make the switch requirements simpler.

But the boost/cut switch only needs to be a two-decker for stereo material.

 

[radiance]

[quote author="Viitalahde"]
But the boost/cut switch only needs to be a two-decker for stereo material.[/quote]

Maybe I don't have the latest schematic, but mine sais that for the high bands (5k, 10k and 15k) I need a 2 pole 12 pos rotary for boost/cut and a 2 pole 3 pos for frequencie selection...(for a mono version that is)

 

[radiance]

Viitalahde: looking at your version of NYD's EQ I don't see any 4 deck rotaries. Your's is also a stereo version right?

 

[alexidoia]

[quote author="donnysparks"]i wish i had saved more of your scematics rather than bookmarking the threads[/quote]
I just thought the same eating my fingernails...

I understand NYD althought this a difficult decision to make. Having said that he said he would give it out to regular members of the forum, so no need to be sad.

NYD: have you thought about the GPL licenses ? Maybe that would be a good think to keep your work public.

I am very new here, but already love this forum. I took on a electronic course and bought some books. I always wanted to do DIY audio but did not think I would manage anything until I met you guys.

Thanks.

 

[Viitalahde]

[quote author="radiance"]Viitalahde: looking at your version of NYD's EQ I don't see any 4 deck rotaries. Your's is also a stereo version right?[/quote]

Yes. You only need one deck per channel.

 

[radiance]

[quote author="Viitalahde"][quote author="radiance"]Viitalahde: looking at your version of NYD's EQ I don't see any 4 deck rotaries. Your's is also a stereo version right?[/quote]

Yes. You only need one deck per channel.[/quote]

GREAT :thumb:

 

[NewYorkDave]

The two-deck switch on the high band is because I wanted peaking boost and shelving cut. If peaking boost AND cut is acceptable, you only need a single deck.

 

[Viitalahde]

Ah, now I got it - Radiance was referring to that pretty new schematic. :thumb: