API eq kits????

[strangeandbouncy]

:green: :green: :green: :thumb:

 

[Greg]

elco - Excellent work !!! Keep it going ! :thumb:

 

[synthetic]

I'm very glad to see this project back on track. :thumb:

 

[clintrubber]

[quote author="peter purpose"]I built a prototype 553ish dead bug, with simulated inductors.... sweet.[/quote]
This is now coming near the EQ-circuit of SWR bass-amps like the SM-400, -220 etc. and there'll be others of course.
The SWR-EQs do LF & HF shelving and have four semi-param. mid-bands (bell). They simulate inductors like Peter does and have continuously variable freqs.
Can post schematic if anyone's interested.

The big question if course is whether there is a difference between those 'real' & 'simulated/emulated' inductors, which might be an alike debate as the tube-vs-transistor-thing...

Bye,

Peter

 

[peter purpose]

Peter,
I tried a Toko 100mH inductor in that mid frq circuit and couldn't get it to sound good at all. Horrible ringing and really harsh.
So I used the 'braductor' version of the gyrator with 100nF for the cap and several switched caps that all sound really good to my ears.

peter

 

[clintrubber]

[quote author="peter purpose"]Peter,
I tried a Toko 100mH inductor in that mid frq circuit and couldn't get it to sound good at all. Horrible ringing and really harsh.
So I used the 'braductor' version of the gyrator with 100nF for the cap and several switched caps that all sound really good to my ears.

peter[/quote]

D*mn, that's exactly the one & only Toko-L inductor value of which I ordered one additional one when getting coils for G-Pultec... :evil:

Did you try adding some resistance in series with that 100mH ?

'braductor'

:grin:

Bye,

Peter

 

[peter purpose]

<<Did you try adding some resistance in series with that 100mH ?>>

If I had known anything about this game I would have tried, but I don't, so I didn't... :green:

BTW.... the 'paulductor' and 'braductor' are both fine gyrators.

peter

 

[clintrubber]

[quote author="peter purpose"]<<Did you try adding some resistance in series with that 100mH ?>>

If I had known anything about this game I would have tried, but I don't, so I didn't... :green:
[/quote]I see :thumb: Could imagine the Toko was harsh because of its high Q, but that's just a guess.
I've measured those coils but don't have the data here, will look.
Must say I was impressed by the accuracy though: I ordered an additional coil to be able to make two pairs for stereo-G-Pultec. For some reason I expected loose specs, but values were accurate to 1 or 2 %. I could probably have known this before if I had looked at the specsheet, but I hadn't.

BTW.... the 'paulductor' and 'braductor' are both fine gyrators.

peter

:grin:

Bye,

Peter

 

[gar381]

elco

I've been wanting to do a 553 project for sometime
now. I would be very interested in at least 2 ofyour PCB's.
Please keep this project ALIVE!! :grin: :grin:
Thanks for your hard work...lookin' GOOD!

GARY

 

[peter purpose]

Peter,
What would you suggest as a starting point for the resistor, if I were to fiddle with that Toko again?

And please post schems of that SWR.

peter

 

[clintrubber]

[quote author="peter purpose"]Peter,
What would you suggest as a starting point for the resistor, if I were to fiddle with that Toko again?

And please post schems of that SWR.

peter[/quote]

The idea is of course to bring the Q of the Braductor/Paulductor
and the Toko in the same ballpark. So we need to know more about those
emulated-Ls.
Or simply start with what the Pultec-EQ is using for its broad/wide-pot
(a 2k5 pot or something like that) and toy
around and see if it sounds more pleasant now.

Once that is made equal (say you really get things going by making EQ-graphs (with whatwasthat PC-program again, Rightmark ?- and adjust the series-L of the real-L to the emulated-L for same EQ-curves) the interesting question is of course which one sounds best. :wink:

I'll post the SWR-EQ this weekend.

Bye,

Peter

 

[clintrubber]

BTW, the EAR-EQ on Jakobs site uses this topology as well IIRIC: an amp with a bunch of pots across and all kind of L&C from the wipers to gnd.

 

[peter purpose]

Cheers Peter.. :thumb:

 

[NewYorkDave]

Here are some more examples of "swinging input", opamp-based L-C equalizers. These are from Opamp Labs.

Model 109

325 EQ amplifier application

Two-band EQ using 325 and 105P/106P control kits

425 general purpose opamp used in a tone-control circuit

 

[clintrubber]

Thanks for adding :thumb:

 

[clintrubber]

SWR-EQ ('Variable Graphic Equalizer' as they call it) is here:
http://home.hetnet.nl/~chickennerdpig/FILES/SWR/swr_studio220_preamp_schematic.jpg
http://home.hetnet.nl/~chickennerdpig/FILES/SWR/swr_studio220_sm400_preamp_settings.jpg

Busy schematic, EQ-section is in the lower left. (The filter in the middle is the Xover)

The section in the dashed box is there four times in total, with component values as in the table.

Bass & Treble-pots are also 50k I thought, and there's a mod to add the SWR-called 'transparency' knob, which is a second treble-section with a differently dimensioned R+C on its wiper.

Looks like you can keep adding pots'n'sections, but as I think to understand it it'll lower the max&min EQ-levels unless you do some redimensiong to compensate.

So here we have variable mimiced inductors, freq ranges of the four bands are something like:
31-160 / 80-320 / 200-800 / 400-1600 [Hz]

Regards,

Peter

 

[peter purpose]

Thanks Peter.... :thumb:

 

[MikoKensington]

Hey Elco, any news? I'm thinking about taking this project on. Just wondering how your BOM worked for you.

 

[gar381]

Hi Elco

What is the latest on your 553 pcb's??

Please keep us posted. :thumb:

GARY

 

[Guest]

I had some major money issues over the hollidays. Things are finnally starting to pick up arouund the studio.

The design is mostly finished and I'm actually going to be ordering most of the parts for 4 EQ's on on Monday. I'll keep ypu posted.

Cheers,

elco