Anyone interested in some API 500 format projects??

[Family Hoof]

I'm pretty clueless when it comes to inductors, so bare with me here...

but shouldn't we be considering things other than just the 1H value? like well... uhhh... let's see... um... core material? winding pattern? Q factor? The "pure air" and other fabulous things that strangeandbouncy had to say about the 553 could disappear with the use of a different part. Anyone who's heard the difference between a cheap inductor and a good inductor in an EQ knows what I'm talking about. One is unpleasant to listen to while the other one sounds awesome, both possessing the same inductance value.

That said, I think we need to either A) shell out the cash for something that's guaranteed to sound great, regardless of how similar it sounds to the original A*P*I parts, OR B) get an original 553 and send the inductors to Jenrick for analysis so we'd then have the proper data to be shopping for a substitute.

If it's going to sound like it's cheap pricetag then why the f**k would want to build it? Because when it comes to coils you are almost always paying for performance. Just some food for thought. :guinness:

 

[MikoKensington]

I hear what your're saying. Component quality becomes crutial in a passive circuit. But there has to be a balance or a bargain.

 

[drpat]

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[Sammas]

"service unavaliable" :evil:


Anyway... I hear what you are saying F.H! I don't mind paying a more for inductors if its going to make it much nicer to use... I'm not very fussed about how accurate it is to the original either...


Last night in the dying stages of awareness I started thinking about push/pull & push/push Pots... you know, the ones with switches in them. They could be used for the LF & HF frequencies to get 2 different frequenies choices... It is probably just as easy and cheaper to do it with a simple toggle switch though. If we used the 1.2H from cinemag you could just switch cap values to vary the LF curve... same as the HF... (strangeandbouncey??)


I wonder how the Cinemag CML-150T would fair for the MF. Here's a diagram off there website indicating the tappings

The original value for the 553 MF inductor is 100mH isnt it?


hmmm im not sure. I think i might order a cinemag 1.2H inductor as well as there CMOB-2 output trannies (2 birds with one stone as they say)... Try and put the LF part together over the next week or two... as well as the HF...

 

[Family Hoof]

Isn't the all steel CMOB-2 their 2503 equivalent? If you get dimensions for the PCB holes for that thing please let me know.

 

[Sammas]

[quote author="Family Hoof"]Isn't the all steel CMOB-2 their 2503 equivalent? If you get dimensions for the PCB holes for that thing please let me know.[/quote]


yeah it is... SCA have started using it since the little Profile/Api dispute started...

Will do...

 

[Family Hoof]

[quote author="Sammas"]Last night in the dying stages of awareness I started thinking about push/pull & push/push Pots... you know, the ones with switches in them.[/quote]
I searched all the U.S. catalogues for a push-pull pot for my last project and could only find the linear Alpha ones that Mouser stocks. It was DPDT, which was great, but also a cheap piece of crap and pretty unusable in practice.

These folks can do custom push-pull CP pots to spec, but I'm not sure what prices would be like. Probably high. I got this in an e-mail -- "We can assemble most requirements within 3 weeks and we have no minimum order; $50.00 set up charge on less than 25 pieces"

[EDIT] It is a good idea, though! Certainly much cheaper than dual concentric. If you pick good frequencies then you only need two, i.e. 60 and 120Hz lo shelf, 10k and 16kHz hi shelf.

 

[drpat]

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[peterc]

but shouldn't we be considering things other than just the 1H value? like well... uhhh... let's see... um... core material? winding pattern? Q factor?

I must admit I have not tried Opamplabs stuff, but from what I have heard, it is quality stuff. It is healthily sized & has a good Q factor. Pity they do not give a DC resistance, but it looks like a good product.

The only way to be sure is to try one out :wink:

Isn't the all steel CMOB-2 their 2503 equivalent?

Anyone know the price of these units?

Many thanks
Peter

 

[Sammas]

Peter, I don't know the cost but I do know they are most expensive than the Profile 4804. I've sent an email about buying one so i'll let you know when i get the reply.


drpat, you're right... it is probably easier to stick closer to the original in terms of having fixed frequencies. There is a fair amount of space left on the PCB for people to modify there EQ to suit there needs. It will be a lot easy to just start with a working fixed band eq and add your variations then to try and create something that is going to suit everyone...

 

[drpat]

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[Sammas]

[quote author="drpat"][quote author="Sammas"]drpat, you're right... it is probably easier to stick closer to the original in terms of having fixed frequencies. There is a fair amount of space left on the PCB for people to modify there EQ to suit there needs. It will be a lot easy to just start with a working fixed band eq and add your variations then to try and create something that is going to suit everyone...[/quote]

I'm only talking about the HF and LF bands. I still think the selectable mid band would be a good Idea for the basic build. The extra Grayhill rotary switch is only $11, and there would be plenty of room on the panel for it. What do you think?[/quote]


Im keen as mustard... Just point me to a source of appropriate inductors and im there :wink: :green:

:thumb:

It seems it is the last remaining hurdle...

 

[Sammas]

Sowter has a few that could fit the MF nicely.

9815 Neve T1280 EQ Inductor
A 200mH inductor tapped at 160, 100, 80, and 50 mH

9858 Pultec MEQ-5 EQ Inductor
A 420 mH inductor tapped at 420/277/145/108/61/34 mH

9325 Pultec EQP-1A EQ Inductor
A 150 mH inductor tapped at 150/82/68/47/33/27 mH


But they aren't cheap

 

[drpat]

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[drpat]

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[Sammas]

the MEQ-1 EQ uses a 6 tap inductor in series with 11 different cap values to get the 11 different frequencies... In the MEQ-1 the 11 mid frequencies range from 200hz right up to 7khz. It covers quite some ground. You could use just 5 or 6 caps to get 6 different mid freq's.


Or there is the CEQI as you suggested if someone is willing to calculate some values?

 

[drpat]

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[Sammas]

[quote author="drpat"][quote author="Sammas"]the MEQ-1 EQ uses a 6 tap inductor in series with 11 different cap values to get the 11 different frequencies... In the MEQ-1 the 11 mid frequencies range from 200hz right up to 7khz. It covers quite some ground. You could use just 5 or 6 caps to get 6 different mid freq's.


Or there is the CEQI as you suggested if someone is willing to calculate some values?[/quote]

I've never used an MEQ-1. Are you talking about the MEQ-5?

Anyway, I calculated some cap values for the 9858 (MEQ-5) inductor and came up with the following.

420mH tap- 1.5mfd = 200Hz
277mH tap- 572nF = 400Hz
145mH tap- 357nF = 700Hz
108mH tap- 26nF = 3k
61mH tap- 17nF = 5k
34mH tap- 12nF = 8k

These are just suggested frequencies. Also, I may be waaaay off considering I've never done this before, so somebody may need to check my work.[/quote]


yes, yes... i mean the MEQ-5

There will be 6 caps spaces on the board anyway, so people could choose what they'd like to use.


Nice work! :thumb:

 

[Sammas]

Nice work indeed!

People can choose there values with this...

http://www.opamplabs.com/cfl.htm


:thumb:

 

[drpat]

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