listening test: inductors for the pultec eq

Hi,

I just tested some different inductors (27mh) in the hiboost section of the pultec eq.

I tested a

wilco inductor
one from toko
fastron
oppermann
and a self wounded inductor with epcos core

I've made 2 files with each inductor,
one with narrow and one with wide Bandwidth.

Hiboost is at its full maximum, the boost frequency is 8khz.


here you can get the zipfile containing all the recorded test-files:

http://www.cmaudio.de/lab-inductor-test.zip


please listen carefully and tell me, which inductor you like best...


thanks,
mat

A seems to have a little less peak, so is sounds less bad than the others.
I would choose A.

a and b have a very low resistance...

the inductor is connected in series with the bandwidth pot...

I think at sharp position the pot value is 0k, so if the resistance of the inductor is lower, the Q must be more shrap... if I'm right ???

otherwise, I could try to connect a resistor in series to adjust the imbalance??

Cool test Matthias.

I found them very distinguished at narrow Q but the differences were more subtle at wide BW.

I chose A as it sounded more even at either setting and was smoother. Some seemed to have severe phase issues, #E in wide BW especially.

FWIW I found both A and C nice at wide BW....maybe preferred C.

B was alright - pretty balanced at both wide&narrow.

D & E were harsh at either setting IMO.

Thanks for the interesting comparison.
Looking forward to knowing which was which.
-Tom

I liked A narrow, B wide the most.
Listened of my crapPC speaker that is...

Tony

I like A in the narrow width and B in the wide width most.
Somebody should invent a morphing function to choose between those inductors with respect to the bandwidth. -Jakob :?:

Nice listening test!
Thanks, Matthias
:sam:
Jens

Hi Mat,

Good initiative! :thumb:

You should try to verify if these inductors are actually doing (roughly) the same thing - they sound a bit too different for my taste? But it's really hard to judge high-end-content from MP3-files..

Try analyzing with e.g. AudioTester to verify if the freq and "Q" are approximately the same - and adjust the "Q" pot so the different inductors behaves alike. Then the "real" properties of the inductors will show rather than tolerances in specs giving slightly different frequency- and Q curves, some of which will sound better at a specific meterial..

I've been listening to inductors for some years now - and It's no easy matter at all...

Jakob E.

I just made measured the frequency response of each inductor...

here it is:




as you can see, inductor b differs a little bit in the frequency range... that's because its mh value is a little bit more as the others... (around 29,4mh)
all other inductors are 27mh +/- 0,5

I think the curves are close enough so that you can evaluate the sound of the inductor...


the resolution of the mp3s is 256kbps...
that should be really enough... If you can't hear a difference here...I would say that if there is a difference, it's so small, that's really not important...


mat

Hmmm, so then A is the best inductor. Which inductor is it?

Matthias, do you have a part # of that Wilco?

it's the bsl series...

Good work..! :thumb:

The A inductor seems to suffer from high stray capacitance - the high side of it dosen't roll off as it should - indicating a rather large shunt capacitance across the inductor..

A lot of the sonic difference probably comes from the 2dB difference at peak of the curves?

Jakob E.

A lot of the sonic difference probably comes from the 2dB difference at peak of the curves?

Click to expand...

that's really a weak point...

is there a way to solve the problem..???

Great idea to compare different inductors!

[quote author="matthias"]
b = epcos
[/quote]

What Epcos core have you used?
RM8 maybe?
And what material?

I've built the inductor for my Pultec experiments with
RM8, T38 material (the highest AL I could get).
Can't get T38 anymore, though. Experimenting with
N30 material now (also RM8 size), AL=5700nH.
With 0.14mm wire and this core I can make up to 2H,
with resonance at 27kHz. Haven't compared anything for
sound yet. Eager to listen to your examples tonight when
I'm at the PC with soundcard.

JH.

[quote author="matthias"] is there a way to solve the problem..???[/quote]

I'd adjust Q's with the different inductors so the max. peaking level matches the lowest-Q one. That way they'll "do the same thing" roughly, and selecting-by-listening will be easier.

:razz: I've done this a lot, can you tell? G14 was several months of this - and then they discontinued my favorite core. Had to start over.. But it ended happily - I eventually found material that works REALLY well for these very-high inductance filter coils, and that should stay in production.

Jakob E.

what do you mean by "boomy"???

do you know, if wilco sells some different coils in low quantity...???