TomWaterman

Anyone interested in some API 500 format projects??
« Reply #60 on: July 26, 2005, 09:51:06 AM »
Hey sammas thats nice and quick. I'm wanting to do a layout for a pre/eq on one board but yours sounds cool.

I think you are correct, concerning the inductors and switching. If you used wilco inductors you could have separate ones for each freq, as opposed to having a tapped job. I think this would allow for more closely matched curves at all freqs....maybe, maybe not a good thing.

As andy said originally, the Sowter LF Neve inductor has three taps and should give something like 50, 100 and 180Hz on the LF. Its expensive at approx 35 quid.

The cinemag is cheaper but not tapped I think just 1.2H? So different caps will be switched for the freq and the curves will change slightly I think(?).

Wilcos will take up more board space and I'm not sure about purchasing from them but they would have enough values for both the LF and MF....

3 LF freqs
6 MF freqs
3 HF freqs

would be cool and require two 1 pole 3 way rotaries and a 1 pole 6 way...lorlins would do.

-Tom


TomWaterman

Anyone interested in some API 500 format projects??
« Reply #61 on: July 26, 2005, 10:12:44 AM »
Two Sowter inductors for LF:

T1230 - 9805. 2H, tapped at 1.2H and 0.7H.
T1530 - 9312. 2H, tapped at 1.1H and 0.45H.

With PCB pins they both cost 39.83 GBP....a lot of money. I expect three Wilco inductors would cost less than that. They would also allow more scope for tailoring freq choices as the board space would mean builders are not forced into using the expensive tapped iron on the PCB with only one set of values.

-Tom

Sammas

Anyone interested in some API 500 format projects??
« Reply #62 on: July 26, 2005, 10:22:15 AM »
hmmm... the only problem i can see is the lack of real estate. The card is only 115mm by 130mm one you take into account the edge pins. Plus the DOA and Tranny or two...

It might be a tight squeeze on the front panel to fight 3 rotary swtiches and 3 pots.

I'll have to ponder it for a bit... the best thinking i do is when i am about to go to sleep which is shortly.

I'll chime in tomorrow morning... (well in about 8 hours or so).

TomWaterman

Anyone interested in some API 500 format projects??
« Reply #63 on: July 26, 2005, 11:14:50 AM »
The largest Wilco appears to be 1H BSL series and I'm not sure if that will be a good match. Its 74ohm DC which is similar to the Sowters at the largest tap but it only handles 56mA if I understand right.

Is that good or bad?

Also inductance is measured at 1kHz. Is it likely that it will be higher or lower at lower freqs such as the 100Hz in this EQ. Anyone know, CJ?

-Tom

drpat

Anyone interested in some API 500 format projects?? New
« Reply #64 on: July 26, 2005, 11:35:51 AM »
...
« Last Edit: September 17, 2010, 08:26:10 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

TomWaterman

Anyone interested in some API 500 format projects??
« Reply #65 on: July 26, 2005, 12:28:28 PM »
Sorry yeah I wasn't thinking about the 500 series format when I suggested lorlins....however you can get small Elma's and Grayhills (which API uses) in those configs direct from Farnell.

Trouble is a $1 switch just became a $10 one....

Tekay had some Neve EQs which used toggles, and its a good plan if only a couple of freqs are used I guess.

-Tom

drpat

Anyone interested in some API 500 format projects?? New
« Reply #66 on: July 26, 2005, 01:16:06 PM »
...
« Last Edit: September 17, 2010, 08:26:27 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

Family Hoof

Anyone interested in some API 500 format projects??
« Reply #67 on: July 26, 2005, 01:32:35 PM »
Quote from: "drpat"
Can you get us a part number on those switches?

I'm not sammas, but I believe he's talking about Elma type 01 and Grayhill series 50 or 56

..or if we wanted right angle PCB mount it would be Elma type 08 and Grayhill series 71

drpat

Anyone interested in some API 500 format projects?? New
« Reply #68 on: July 26, 2005, 01:59:27 PM »
...
« Last Edit: September 17, 2010, 08:26:38 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

TomWaterman

Anyone interested in some API 500 format projects??
« Reply #69 on: July 26, 2005, 02:01:17 PM »
Yep dems the ones.....just checked they are almost $20...

Actually a way to save cost would be to have 3pole toggles on LF and HF and a 1pole 6way Elma 01 series for 6 MF freqs. That would be a good compromise of features and size / cost.

BTW are those linear 10k pots centre detented for 0dB cut/boost or what? I can't seem to find any centre tapped pots.

-Tom


TomWaterman

Anyone interested in some API 500 format projects??
« Reply #70 on: July 26, 2005, 02:07:03 PM »
oopps I mean the elmas and grayhills not the digikey part you picked above.

You would need the 2 pole switch for MF I think if you only use a tapped inductor and needed to switch taps and caps at the same time. With one inductor and switched caps only, a 1 pole switch would work after the inductor switching a diff combo (cap / resistor) to ground (I think).

You'd need a 2P3T toggle for 3 LF positions and a 1P3T toggle for HF as I understand it.

-Tom

Family Hoof

Anyone interested in some API 500 format projects??
« Reply #71 on: July 26, 2005, 02:21:36 PM »
DP3T can also cost close to $20

drpat

Anyone interested in some API 500 format projects?? New
« Reply #72 on: July 26, 2005, 02:31:10 PM »
...
« Last Edit: September 17, 2010, 08:26:53 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

Anyone interested in some API 500 format projects??
« Reply #73 on: July 26, 2005, 02:33:11 PM »
I like the idea of fixed HF and LF with a selectable mid.  It still keeps it simple and relatively cheap.  My enthusiasm for the 553 idea, was based on two factors.  Cheap and simple.

drpat

Anyone interested in some API 500 format projects?? New
« Reply #74 on: July 26, 2005, 02:50:00 PM »
...
« Last Edit: September 17, 2010, 08:27:06 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

TomWaterman

Anyone interested in some API 500 format projects??
« Reply #75 on: July 26, 2005, 02:55:35 PM »
I believe it is 100Hz, 3kHz and 10kHz for the 553 original.....

May as well go for the Cinemag 1.2H inductor if you want a fixed freq LF.

-Tom

drpat

Anyone interested in some API 500 format projects?? New
« Reply #76 on: July 26, 2005, 03:08:22 PM »
...
« Last Edit: September 17, 2010, 08:27:18 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

TomWaterman

Anyone interested in some API 500 format projects??
« Reply #77 on: July 26, 2005, 03:33:32 PM »
Not exactly, the original has a 1H inductor for 100Hz. It will be trial and error a little due to the fact the inductance will differ at 100Hz compared to the value given by manufacturers (taken at 1kHz).

1.2H and an appropriate cap will make 100Hz with a diff. curve I think...but don't quote me on that I'm a noobie!

Tom

peterc

Anyone interested in some API 500 format projects??
« Reply #78 on: July 26, 2005, 04:10:08 PM »
What about an Opamp labs inductor. 800mH should get you close.

http://www.opamplabs.com/87.htm

Cheap too.

Peter
If opportunity doesn't knock, build a door.

Anyone interested in some API 500 format projects??
« Reply #79 on: July 26, 2005, 04:19:54 PM »
Quote from: "peterc"
Cheap too.


I like your style.


 

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