Poor Man's Pultec EQP1-A Build Support Thread

[salomonander]

can you measure the resistances on same value inductors.... which changes the Q

you mean simply measure resistance with a multimeter? sorry im a noob

 

[kambo]

yeap, with simple multimeter


edit: Ian has a great documentation on his web btw... all the formulas, tip and tricks... 
easy to understand language too! not full of technical jargons unlike some books!

 

[ruffrecords]

as i have said - im really no expert. but the none carnhill inductors look so much more heathy and are almost the same value. say id find a multitap inductor that has the necessary values and behaves more like the ones i have found at the surplus - would my q change? aaron at don audio does some great custom inductors for fair prices. maybe his work better.

If the inductance values stay the same then then there are no other changes to make and the Q would remain the same. Although it is affected by the resistance of the inductor this is usually  swamped by the overall circuit resistance. It would be interesting to see what Don comes up with. I use him all the time for mains transformers and his work is excellent.

In the meantime I may have found a fix. I have been looking for a way to counteract the rise above 20KHz. The problem is to do it without affecting the flat response. I think I may have a possible solution. To try it all you need to is a 5mH inductor connected  in series with 390pF capacitor in series with a 1K resistor. Connect this combination between the junction of the high boost/high cut pots and 0V. It is a series resonant circuit at about 110KHz. Its effect is to tame the tail end of the 10KHz boost. I have only simulated this and only with the 10KHz boost so I don't know if it will have any effect at the other frequencies.


Edit: 15mH should have been 5mH

Cheers

Ian

 

[salomonander]

as i have said - im really no expert. but the none carnhill inductors look so much more heathy and are almost the same value. say id find a multitap inductor that has the necessary values and behaves more like the ones i have found at the surplus - would my q change? aaron at don audio does some great custom inductors for fair prices. maybe his work better.

If the inductance values stay the same then then there are no other changes to make. It would be interesting to see what Don comes up with. I use him all the time for mains transformers and his work is excellent.

In the meantime I may have found a fix. I have been looking for a way to counteract the rise above 20KHz. The problem is to do it without affecting the flat response. I think I may have a possible solution. To try it all you need to is a 15mH inductor connected  in series with 390pF capacitor in series with a 1K resistor. Connect this combination between the junction of the high boost/high cut pots and 0V. It is a series resonant circuit at about 110KHz. Its effect is to tame the tail end of the 10KHz boost. I have only simulated this and only with the 10KHz boost so I don't know if it will have any effect at the other frequencies.

Cheers

Ian

thanks ian,

great to know that you are on it!  i do have one of dons multitap inductors that features a 12mh tap. but i dont have any finished pcbs here. can i test this with the inductor alone? otherwise we will have to wait until i built one of the units. or maybe jonas can try this with his unit?

 

[salomonander]

yeap, with simple multimeter


edit: Ian has a great documentation on his web btw... all the formulas, tip and tricks... 
easy to understand language too! not full of technical jargons unlike some books!

ill do this  and report back

 

[ruffrecords]

thanks ian,

great to know that you are on it!  i do have one of dons multitap inductors that features a 12mh tap. but i dont have any finished pcbs here. can i test this with the inductor alone? otherwise we will have to wait until i built one of the units. or maybe jonas can try this with his unit?

I made a typo in the previous post ; the inductor value is 5mH not 15mH.

Cheers

Ian

 

[salomonander]

no worries. i sthis something i can test with the inductor alone or will i need a finished unit in order to try?

 

[ruffrecords]

no worries. i sthis something i can test with the inductor alone or will i need a finished unit in order to try?

If you test the inductor into a 4K7 load and add the netwrok I desicribed across the 4K7 then you should  see the effect.

Cheers

Ian

 

[salomonander]

alright,
did not have a 5mh inductor so i could oly measure the resistance on the coils. for some reason die induction measured differently today (slightly)

so the siemens 166mh measured perfect 160mh today. it has a resistance of 76,2Kohms compared to 29,8K on the carnhill winding
the noname 250 measured 240mh today and has a resistance of of 36k as opposed to 47k on the 220mh winding on the carnhill.
dont know why my inductance is different today. maybe i did not calibrate yesterday.

 

[kambo]

your resistance measurements seems extremely high to me!
i think they should be in "ohm" range not in "K" kilo_ohm range  ???

 

[salomonander]

your resistance measurements seems extremely high to me!
i think they should be in "ohm" range not in "K" kilo_ohm range  ???

maybe i have misread. ill double check. if anything i invented the k by accident

 

[salomonander]

no. values are correct. at least thats what my lcr tells me. its a new one but i measured some resistors just now and they measured perfectly. so i assume my inductor resistances are correct. unless i somehow messed up the process. i simply measured the taps....


this was measured at 1khz. i can aslo measure at 120hz and get way lower resistances.... as ive said - im a noob

 

[salomonander]

my reguar multimeter gives me way different results:

for the 160mh siemens its 5 Ohms
carnhill 160mh is 33,2 OHms

carnhill 220 measures 41,3 Ohms
noname 250 measures 3,6 Ohms

maybe i do really not understand the resistance reading on my lcr properly. these would make a whole lot more sense and point towards the carnhills having a very high resistance. sorry that im of no better help. just trying my best

 

[kambo]

these measurements makes more sense.. even if u typed "K" by mistake they dont match with ur first measurements!

just curious... what "lcr" r u using ?

may be add a 1K  - 3k3 or something (measure it first) in series with ur inductor and re measure and deduct series resistor measured value from the reading... and compare to other multimeter readings....

 

[salomonander]

these measurements makes more sense.. even if u typed "K" by mistake they dont match with ur first measurements!

just curious... what "lcr" r u using ?

may be add a 1K  - 3k3 or something (measure it first) in series with ur inductor and re measure and deduct series resistor measured value from the reading... and compare to other multimeter readings....

i know.... i literally just swapped the probes to the other unit. my lcr is a bk precision 878b. akward thing is that it measured 5 resistors perfectly (and they were 1% ones). ill try around some more...

 

[salomonander]

alright .... im just swapping around now and values change slightly all over the place. but they are getting closer. i think im too dumb to read the lcr and the measurements done with the reguar multimeter are about right. not exact but about right. way more resistance in the carnhills.

 

[ruffrecords]

alright .... im just swapping around now and values change slightly all over the place. but they are getting closer. i think im too dumb to read the lcr and the measurements done with the reguar multimeter are about right. not exact but about right. way more resistance in the carnhills.

Way more resistance than what? What exact values are you measuring.?

Cheers

Ian

 

[salomonander]

ill try to sound less confudsing:

first i measured the taps resistance with my lcr meter which gave me the following readings (i measured the four coils i posted screenshots of. so one of each carnhill inductor compared to other inductors of similar value):

for the 160mh siemens its 76,2Kohms
carnhill 160mh is 29,8K

carnhill 220 measures 47k
noname 250 measures 36k

since kambo said that these look way too high i tried again with my regulat multimeter which gave me these readings:

for the 160mh siemens its 5 Ohms
carnhill 160mh is 33,2 OHms

carnhill 220 measures 41,3 Ohms
noname 250 measures 3,6 Ohms

so i assume that my lcr showed the "k" for no reason (or im too stupid to read it). if comparing these results, they are somewhat in the same ballpark (ignoring the "k") and when considering how low the resistance is it would also explain why my readings vary slightly each time i try (especially on my shitty multimeter). i hope this makes more sense. let me know if i still not made it clear. cheers

 

[ruffrecords]

The second set of DCR readings seem about the same as I meaure for the Carnhills. I suspect there is something wrong with your LCR meter.

Cheers

In

 

[salomonander]

The second set of DCR readings seem about the same as I meaure for the Carnhills. I suspect there is something wrong with your LCR meter.

Cheers

In

yeah i think so too. that aside is there anything you can tell from these tests? am i correct in assuming that we need as low of a resistance as possible for this circuit?