NewYorkDave Style Passive EQ

[owel]

>An inductor for low shelving, a capacitor for high shelving, or an inductor and capacitor in series for peaking

Ok, so it's in series. Thanks! Got it now.

 

[bluebird]

Hey thanks again everyone.

I have to say I think the SRPP stage works great for this. it actually has a bit of a boost compared to the bypass.

I wanted to have little adjustable pots for the 1K (600 ohm in Daves version) right before the tube. But there is absolutly no more space to put one. It would let you adjust the gain a bit. using a 600 ohm resistor would probably be unity gain...

Once again there is a small hum, its not noticable unless I really crank the monitor. it gets louder when I boost or cut the low. when I unplug the power cord it stops even though signal still passes for at lest 30 secs. as the caps unload and the heaters die down.
I was very careful with my star grounding scheme but I must have done something wrong.

its just going to have to stay that way I guess because I'm not tearing it apart.

I'm just worried if I'm using all six eq's in a mix it might have some effect. we'll see.

 

[peter purpose]

"I'm just worried if I'm using all six eq's in a mix it might have some effect. we'll see".

Hit record?

 

[bluebird]

:grin: :grin: :grin:

 

[toby]

hey bluebird,

i had the samething with the hum, and not continueing when the power was turned off, and it turned out i hadn't rectified the anodoe voltage sufficently ( i'm stingy with big expensive capcaitors) .

does giving the heaters DC actually make that much of a difference, i noticed that all the gyraf designs use it.


Toby

 

[bluebird]

Hey Toby, I'm sure I have enough capacitance on the B+ in multiple stages. and raising the heater winding didn't help a bit. I raised it to 30v and no change in hum.
I'm going to try an all together seperate heater TX. if that dosen't work I'll just have to live with it. I really can't hear it in normal recording.

As I learn and learn and learn...... :grin:

 

[ijr]

Try to figure out what is the hum source.
I guess it is power trafo inside of box and/or
ac on heaters.
All this stuff with a lot of trafos/inductors is better
build with PS out of box. And never put heatter wires close to
audio. Some old Telefunken equippment done so, that ac for heatters
goes inside of twisted pair shielded cable, with two resistors to ground-
truly like audio differential lines....
BTW:
If you use 6 12au6's, you need only 2.5A(roughly)/12.6v
DC power supply for it...
Plug an oscilloscope to eq out (before makeup gainstage)
and figure out the noise with and without power supply ON.
Maybe you have a hum from inductors or input trafos
(they love to pickup hum from power trafo.)
Simplest solution in this case is put out PS from box.
Also, check out star grounding for gain makeup stages.
Here is a sample of grounding schem.:
Roughly:

grid and cathode resistors, shield of input cable
is one point and it goes to PS star point with its wire.
Output trafo's "-" (load return path) goes to PS star point with its wire.
Provide also bypass cap. between B+ and ground for each
amplifier.
Ground shield of input wire only at "tube's" side.
You used input trafos, so, here is less problem with ground
interactions. Simply wire each "filterbank's" ground with individual
wire to starground too.

Hope this helps.
Good luck,
Igor.

 

[bluebird]

Thank you Igor.

I have already followed most all those rules. I have star grounded very carefully.

the transformer is outside the box and far from the inductors.
heater wires are tightly wound.

the actual heater hum is negligable. it is barely there. the hiss of the tubes is louder. and is only heard when I switch my monitoring set up to MIC in and turn up the gain. an audio signal would be crazy loud at that point.

the tube grid and cathode resistors are grounded to thier respective supply cap which is star grounded seperately from the main power star ground with transformer CT and main caps.

The main problem is with the low and mid frequencys boost/cut switches.
when in center position it is just the very light hum I spoke of earlier.
when I cut or boost the low more hum is injected.
when I cut the mid hum is injected.
the hum sound changes depending on the orientation of the mid and low in relation to eachother.
The hum sound also changes as I change the frequency.

I also noticed that this behaviour continues when I unplug it, as the caps drain.

So there is obviously a ground situation within the filters.
I have all the resistor strings (see daves schematic above) star grounded to the same point next in line after the tube star ground.

I also have the shield from the secondary of the input TX grounded to this point. THIS COULD BE A PROBLEM.

should I have grounded these to where the input TRS ground is???

Thanks again Igor :grin:

 

[Mark Burnley]

Hi Ian,

Glad your tour went well...

Wow, what an awesome project!

Great wiring and layout- it's all there!!
Hope you sort out the little problems too.

Grooovy DIY

:thumb:

Mark

 

[ijr]

I also have the shield from the secondary of the input TX grounded to this point. THIS COULD BE A PROBLEM.

Not sure.
You can try to ground the shield to shassis, if it has separated pin,
but maybe it will help like vitamine C to someone dead.
Maybe the problem is in interaction between unit plugged into EQ
and unit after?
I had same problem with my oscilloscope/oscillator setup
in Russia 6 years ago ))
Try to disconnect eq input and short + and - legs of trafo prim.
If hum still remains, the problem is in eq.
BTW, how much hum do you have in db?

 

[bluebird]

HI MARK!!!

Igor:

I never got the hang of testing the db thing...all I have is a VOM right now at my girlfrieds house. Something about a sign wave and testing the voltage at input and then at output? then a formula for db?

The input is the sound card from my computer and monitoring is through a little midiman mixer.

I'll experimet with the ground as best I can. I'm not un packing this thing and all the wires. way to much work, it might never get back together again!

Thanks again for all the advice Igor.

 

[Moby]

WOW! Looks great... :shock: Hope you will find hum source soon :thumb:

 

[CJ]

Man, you work fast!
Congrats!
Sheeesh, he writes the songs, he sings the songs, and he even builds his own studio!
What next?
Awesome, dude!
cj

 

[helterbelter]

Well, I just dug this up,and this is something I really want to build.... I hope the info is still here....

 

[mac]

hey Helterbelter,

Me too! I was just reading this thread the other night. Always sad when all the old links dont work....

Mac

 

[hobiesound]

wayback people.... that's all i'm gonna say.... i just found the schematic 10 min ago. using wayback....

 

[nielsk]

Oh, come on.... how about just a little link to it?

 

[substitute]

wayback people.... that's all i'm gonna say.... i just found the schematic 10 min ago. using wayback....

wow, skills!  I can't find this schematic for the life of me.  All I've come up with is discussions about it being unavailable.

 

[mac]

I had no idea about this....really awesome thanks

http://www.archive.org/web/web.php


Mac

 

[mac]

hey guys,
I only just stumbled upon this post from NY Dave FYI...

As for the schematic... Here's the thing:

My ongoing financial problems came to the fore again today, and that got me thinking about some things. What this means, with regard to the matter at hand, is that I've put a lot of time into this circuit and I'd be very upset if it turned up in some ripoff product. While the circuit itself is certainly not rocket science, with all the present mania for "passive EQ", it's feasible that some bottom-feeder manufacturer could go fishing on the web for designs. And since there just ain't much out there beside the Pultec circuit, mine could definitely pop up on the short list.

Besides, I might choose to exploit the design commercially myself, someday. And you can't sell something if you've already given it away.

Therefore, I've removed all diagrams relating to this EQ from the web. For those of you who've downloaded them, I ask that you extend me the courtesy of not sharing them with others, or utilizing the design for anything outside non-commercial personal use. I'll be removing material related to a couple of other designs as well, and I request that you observe the came courtesy regarding those. Outside of "gadgets" and other little tossed-off stuff, I'll no longer be posting publicly any circuit which I believe to have commercial potential worth pursuing.

However, I will share schematics (including the latest revision of this EQ) under certain conditions. If you're a regular contributing member of the Lab and you agree to observe the "no sharing, no commercial use" policy, I'll email it to you. Write to electronic_dave *at* y*hoo dotcom and be sure to identify yourself by your Lab handle. Sorry, but requests from lurkers will be ignored.

I apologize if this seems weird, but I really gotta start looking out for myself more.