Sammas

Anyone interested in some API 500 format projects??
« Reply #100 on: July 27, 2005, 06:07:31 AM »
Quote from: "drpat"
Quote from: "Sammas"


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


Nice work! :thumb:


It may be a good idea to put an extra cap space on each inductor tap for anybody who really wants to go there!

Do you have everything you need to continue, Sammas?



Will do!

Yup! Looks like we are set!  I'll put in an extra cap space or two if there is enough room for the LF & HF just incase people want to add a toggle switch for a little variation!

 :thumb:


drpat

Anyone interested in some API 500 format projects?? New
« Reply #101 on: July 27, 2005, 06:39:02 AM »
...
« Last Edit: September 17, 2010, 08:15:01 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

Sammas

Anyone interested in some API 500 format projects??
« Reply #102 on: July 27, 2005, 08:30:56 AM »
Guys, 2-3week lead time on the Sowter MEQ-5 inductors... It appears they are made to order...  Seem like a good bunch though. Real quick on the replies.


Still waiting for a reply on the Cinemag stuff but i'll let you guys know how much they are...

drpat

Anyone interested in some API 500 format projects?? New
« Reply #103 on: July 27, 2005, 08:58:33 AM »
...
« Last Edit: September 17, 2010, 08:15:13 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

Sammas

Anyone interested in some API 500 format projects??
« Reply #104 on: July 27, 2005, 09:26:14 AM »
Quote from: "drpat"
Hey Sammas,

Where are you located, and are you working on a BOM for this?

-Patrick



I'm in Sydney...

I was going to do a BOM as well...

I'm trying to find some appropriate, yet easily accessable switches for bypass and LF & HF frequencies so everyone can source them.

I was thinking these from digikey http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=401&M=PHA4UEE

I dunno... they are really cheap, but i dunno how good they'll be  :?

It appears the E-switch discontinued the ones that i wanted to use  :mad:

drpat

Anyone interested in some API 500 format projects?? New
« Reply #105 on: July 27, 2005, 09:55:32 AM »
...
« Last Edit: September 17, 2010, 08:15:26 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

drpat

Anyone interested in some API 500 format projects?? New
« Reply #106 on: July 27, 2005, 10:56:03 AM »
...
« Last Edit: September 17, 2010, 08:15:38 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

TomWaterman

Anyone interested in some API 500 format projects??
« Reply #107 on: July 27, 2005, 12:11:15 PM »
Coming along nicely I see guys.

I just thought I'd mention this as I didn't see it addressed from earlier on. I agree that different inductors will totally change the sound.  Matthias's excellent Pultec inductor test illustrated this nicely. Thats why I suggested the Wilco's as they came out best in his round up....seemed smoothest.

Anyway, someone was mentioning the 'air' that Andy was on about and how that could dissapear with different iron. The HF has no iron, its just RC filters, so that fabulous air should stay there no matter what inductor we use. Perhaps Andy's sounds so nice and airy as its the only filter network he has. No LF, MF networks to cloud the signal path? Maybe that increases the purity?

This clone will never sound just like a 553 but it may sound excellent in its own right.

-Tom

drpat

Anyone interested in some API 500 format projects?? New
« Reply #108 on: July 27, 2005, 01:21:11 PM »
...
« Last Edit: September 17, 2010, 08:15:52 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

strangeandbouncy

Anyone interested in some API 500 format projects??
« Reply #109 on: July 27, 2005, 03:19:36 PM »
Tom,

   I have so ay tht the Assumtion that my 553 HF is my only "filter" is a serious case of jumping to conclusions! - Helios, Siemens, Neve, Focusrite(Blech!), Maselec, SSL, Pultec, API, APSI, Sony, Avantic, Lang, Audix, Trident, etc, etc, etc. Not quite sure what impression I am giving off . . .
  For what it's worth, a while ago, I diconnected the LF and MF of my 553, and this makes no difference to the hf at all. And as for the iron, WHAT iron? the only thing that can possibly really affect the HF is the output tx, and since it is a Profile 2503, and has a repsonse from dc to ultraviolet light, and will handle +30dB, I cannot conceive any other "iron" having any effect. My original 553 sounds identical to my lash-up, providing that you put the same caps in each. The biggest difference for me is in the cap you use for the HF. Polystyrene pisses on anything else i have tried, and, since they are available in 1 percent tolerences, you can match channels with no phase diferences on the Slope regoin.


   BLah Blah B;lah


  ANdyP
. . . . RUH ROH . . . . .


TomWaterman

Anyone interested in some API 500 format projects??
« Reply #110 on: July 27, 2005, 05:23:34 PM »
Hey!

I didn't even think I was helping - just confusing myself and others!  :thumb:

Looking at the schemo again, I presume pins 6 & 7 actually go to ground? Has anyone determined exactly where they go - the info at Dan Alexander says NC but they have to go somewhere I reckon?

Also when using the online calculator from opamp labs I'm was surprised by the results....was wondering if it was something to do with the resistor to ground.

If you plug in 47uF and 1H for the LF, the freq given is around 23Hz....seems a little low for a 100Hz peak no?

Anyway, after looking in H&H, it appears to be a 'series LC notch' filter creating a 'trap' for signals at or near to the resonant frequency by shorting them to ground.

Formula is given as:

Resonant frequency = 1/(2pi(LC^0.5))

Which surprisingly gives the same values as the opamp labs calculator, 23.2 Hz for the LF with a 47uF cap and 1H inductor.

According to H&H its a sharp peaking filter with losses in the cap and inductor smoothing the peak out. I presume that the further addition of the resistor to ground adds a Q-spoiling effect which increases the BW of the peak.

So maybe you can play with the 'Q' of the filters by adjusting the resistor to ground, 1.8k and 680R respectively for LF and MF.

I know this goes against the front panel space of the 500-type idea here but maybe a 1/2k pot in place of the MF 680R resistor would allow for variable mid Q too......

Maybe I'm misunderstanding so someone correct me if I'm wrong.

Back to the 23.2Hz for the LF - it seems low to me, is there a chance that the 1.8k resistor makes it wide BW and work more like a shelf with its -3dB point close to 100Hz?

The Q can apparently be calculated by:

Q = (WoL)/R

where Wo=1/(sqr root(LC)) I think.....maybe thats a parallel filter. I'm afraid j and w numbers confuse the hell outta me, imaginary bullsh*t!!

With these calcs I get a Q of 0.08, thats pretty wide ain't it?

Might be wrong though...hope I'm fishing in the right pond

-Tom

TomWaterman

Anyone interested in some API 500 format projects??
« Reply #111 on: July 27, 2005, 05:34:17 PM »
Andy, woah nelly! :grin:

I meant that as you have not built the LF and MF parts in your '553' clone (as you don't have any inductors), the HF is the 'only filter' you have in that box.[/i] I was wondering if thats why your HF sounds so airy, as you've increased the frequency choices to get where the 'air' is and have no LF, MF 'iron' [read: inductors] to perhaps mess with the tone. Meaning the signal path is more pure.

Hence my assumption of the greater purity in your lashed up clone. I was in no way insinuating that the 553 HF clone is the only filter you've ever heard.....I was fully aware of your mahoosive collection!!!  :thumb:

Glad to know that disconnecting the LF and MF off the original makes no difference to the perceived 'air', thats a good sign that inductor choice in the lower bands will not Fcuk with the tone Family Hoof was wanting to ensure remained....which makes sense as the 'trap' circuits are in parallel with each other....

Very cool to know the original sounds identical to your clone!  :thumb:  :green:

-Tom

strangeandbouncy

Anyone interested in some API 500 format projects??
« Reply #112 on: July 27, 2005, 05:38:57 PM »
553 LF is a Shelf, with a HPF at whatever the frequency the cap is. Mine has a 470uF cap . . . i think that the cap has too low a value to make a bell shape with the inductor.

    jm1/2p'sworth,


      ANdyP.

   ps if you'd like to borrow my 553, yous would be very welcome, if you live in da UK.

    btw, my 553 uses cheap green, Mylar caps. I have put these back in 'cos i like the sound for some things. very agressive compared to phillips orange polyester ones, or the incredibly smooth sounding polystyrenes i've used in my lash-ups.
. . . . RUH ROH . . . . .

strangeandbouncy

Anyone interested in some API 500 format projects??
« Reply #113 on: July 27, 2005, 05:57:55 PM »
Tom,

   No offence taken, so, easy, now, jus' checkin' you are awake! - Arf Arf arf . . .

     I would have built some kinda LF, preferably switchable, but i can't afford it at da mo, at least that's what my wife says, and she IS the boss when it comes to money! I have an agreement with her not to buy anything new. This means i can build what I like, but £38 x 2 for Sowter iron is NOT acceptible at the 'mo, since we are negotiating for a house in Italy . . . .

   When i said "Identical", i have not yet tried swapping every single component!. swapping caps makes a big difference. i have to say that mine are sweeter. that is partly the styrene caps, and partly Fabio's Fab 2520's. i do not have any spare original 2520;s at the mo, and i haven;t got time to swap em from anything else. besides, i don;t think they like to be desoldered that much! I have many different types, and they all sound different. perhaps some have drifted, perhaps some have a different arangement. Anyhow, the one Ihave in my 553 does not seem to have the same hf extrension as Fabios. you are welcome to borrow it,  as i said.

    Keepin' it real fo' da People!


     ANdyP
. . . . RUH ROH . . . . .

TomWaterman

Anyone interested in some API 500 format projects??
« Reply #114 on: July 27, 2005, 06:01:49 PM »
Thanks for the offer Andy - I am in the UK - in Brum at the mo but moving in a two weeks....maybe I'll take you up on the offer at somepoint.

Could you explain how the LF network makes a shelf and then the HPF? I think we're both talking about the same thing essentially. In effect it is a very broad peaking response, rolling off smoothly towards 20Hz....

Are you sure you have a 470uF cap in there? Its listed as 47uF on the schem....that would put the resonant freq at 7Hz!!

-Tom

strangeandbouncy

Anyone interested in some API 500 format projects??
« Reply #115 on: July 27, 2005, 06:20:43 PM »
Tom,
 
   yes, I think we are talking about the same thing . . . i am no wizz, but i am certain that the LF respose is a shelf, not a bell . i suspect that the cap is to prevent instability at very low frequency - too low to really interact with the inductor. tomorrow, I;ll try to listen to the eq with the cap bypassed. that should show up something . . .

    I am certain that Op-amp labs circuit does not have a cap there.


     Blah,

     ANdyP
. . . . RUH ROH . . . . .

Sammas

Anyone interested in some API 500 format projects??
« Reply #116 on: July 27, 2005, 08:49:38 PM »
Hey Guys... hectic day today...


Just thought I'd let you guys know that Cinemag 1.2H inductors and the CMOB-2S (steel core will give a sound closer to API sound than the 50%/100% nickel trannies will - for better or worse) tranny are both a little under $22us a piece...  

Tom, I was thinking the same think regarding the 47uF cap being too big... but im not sure, maybe the resistor does have some affect on bandwidth. I Thought maybe 4.7uF was more appropriate...


Anyways... be back on in about 8 hours...  :thumb:

drpat

Anyone interested in some API 500 format projects?? New
« Reply #117 on: July 29, 2005, 05:04:40 AM »
...
« Last Edit: September 17, 2010, 08:16:09 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

Sammas

Anyone interested in some API 500 format projects??
« Reply #118 on: July 29, 2005, 06:31:45 AM »
yeah i'll give it ago...  

Most of the parts on are on there way now except for the Sowter inductor which is a few weeks off... hopefully most the stuff arrives during next week so i can put together the top and bottom frequencies...


Im having trouble finding a 5uF cap (for c9) though... I'll give a 4.7uf a go with and without a 300nf in parallel to see if there is a dramatic difference between the two...

Also can someone check R13 for me? Either looking at the schem (or an actual 553) is R13 a 10K? I thought it was 11K but think its just missing some ink... i think its ment to be the same as 614 which is 10K.


Hope you guys don't mind, but i'd like to build a working unit before posting the layouts? Just to make sure everything works, etc, etc before other people jump in on a potentially trouble riddled project. The Sowter inductor is still a few weeks away so it might be 2 weeks or so before i post the goods up...  Unless any of you are willing to be a ginea pig  :twisted:

drpat

Anyone interested in some API 500 format projects?? New
« Reply #119 on: July 29, 2005, 08:59:07 AM »
...
« Last Edit: September 17, 2010, 08:16:20 PM by drpat »
I use the LA2a on very hot signals like lead vocal.


 

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