Gyraf Pultec EQ curve

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nacho459

Well-known member
Joined
Jul 20, 2004
Messages
339
Location
Pasadena CA
OK, I ghetto rigged the passive section of the pultec together, point to point style on my bench, and ran it through my X-Y plotter. Here's the results.

The scale on the chart is off. Where it says +5 it's actually +10. -5 is actually -10 etc...

http://www.459audio.com/Pultecres.jpg

I used the same values as the Gyraf schematic. Someone that's built one before let me know what you think. There's this weird dip around 4k in some of the low cut curves, anyone have any idea why? Everything else looks relatively ok.
 
Cool graphing software!
Which is it?
You might have had the high cut turned on slightly, or there might be a little interaction from one filter section to the next.
I put a groung lift on mine also, which is cool, as you can go 1/4 inch cable. balanced or unbalanced.
 
Cool graphing software!
Which is it?

Software!? it's an old UREI X-Y plotter!

ploter.jpg
 
Kev's GroupDIY-page once had a couple of plots of the frequency response of the pultec clone. But I can't find them now..

Somewhere i have the complete set of plots from the original pultec manual. I'll see if I can find them for you.

I don't think the bump in low-cut is an error.

Jakob E.
 
hmmm, the eqp has a low mid dip when bass boosting and cutting the same time. but the dip on graph looks too hi, frequencywise...

steff
 
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