peterc

Anyone interested in some API 500 format projects??
« Reply #120 on: July 29, 2005, 10:24:24 AM »
Hi all

With all this interest in this API project, anyone want to get some original style input transformers?

Any one remember this post (thaks Adrian)?

Quote
The Altran C-3402-2 (standard transformer in sheilded can with pin on bottom)
http://www.altrancorp.com/
Is probability the cheapest route


& again (thanks again, Adrian):

Quote
Did anyone read my last post!
I dangled a carrot in your face and no one even read it??????

I think the Altran are in the low $20's


from this thread

http://www.groupdiy.com/index.php?topic=242&postdays=0&postorder=asc&highlight=altran&start=0

I emailed Altran the other day, & the transformers are $27 each (qty 30) or else $20 ea (qty 75).

Anyone interested in doing a Group Buy? I cant coordinate a group buy from South Africa, 'else I would do it.

I would take 8 at least if it were to happen....


 :wink:  :wink:  :wink:

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


Sammas

Anyone interested in some API 500 format projects??
« Reply #121 on: July 29, 2005, 10:47:17 AM »
Quote from: "drpat"
Quote from: "Sammas"
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...


I'd buy the closest value above that too just in case.

Quote from: "Sammas"
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.


Looks like 10k to me from the schematic.

Quote from: "Sammas"
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.


Good plan, sounded like that was what was happening anyways. BTW: What is the final format that you're shooting for? IE: what mid band frequencies are you shooting for? Are you switching the hi and low bands? Are you adding an input tranny? Ice dispenser? etc...

Great work so far Sammas!



Hopefully it will tie my shoelaces too  :wink:

This is what i've planned for the first one

- sowter meq-5 inductor with 8.361k, 5.261k, 3.265k, 728Hz, 367Hz, 201Hz selection (drpat's suggestion)...
- cinemag 1.2h inductor on the LF with switchable 80hz & 120hz
- switchable high end frequencies (haven't calculated those yet...)
- cinemag cmob-2 tranny
- JLM 99V DOA (gotta support local products ya know  :wink: )
- and find out what the flippin' deal is with the "gain trim" pins... what the hell that 47uF cap is doing on the LF inductor... Find out if 1.8K and 680R  do adjust the Q... see if it all actually works  :wink: (perhaps add another resistor space or pot place if it fits for people to adjust the Q).


I don't plan on adding an input tranny but i'll definately try and squeeze the pin configurations in for one  :thumb: The CMOB-2 is 49mmx41mm and the Sowter inductor is 34mm in diameter... haven't got the dimensions of the 1.2H inductor but they take up a fair amount of room... I'll try my hardest to make it all fit with some input tranny options :thumb:

All the deallies and stuff should be posted in a few weeks... detailed parts lists, schem, layout, photos of a working unit (touch wood), etc, etc...

drpat

Anyone interested in some API 500 format projects?? New
« Reply #122 on: July 29, 2005, 11:46:55 AM »
...
« Last Edit: September 17, 2010, 08:11:22 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

Anyone interested in some API 500 format projects??
« Reply #123 on: July 29, 2005, 12:02:46 PM »
Hey guys little side tangent here, but one of the reasons this thread is 9 pages long is because you're quoting entire posts that are already quoting entire posts.  It gets hard to follow.

I'm done, sorry.   :thumb:   I like the parts list I'm seeing.  Except that Sowter price tag.  Maybe I'll just quit smoking and used my saved earnings to buy the Sowters.  

Sammas I'll be knocking on wood and crossing fingers.   :guinness:

drpat

Anyone interested in some API 500 format projects?? New
« Reply #124 on: July 29, 2005, 12:31:16 PM »
...
« Last Edit: September 17, 2010, 08:11:40 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

CJ

Anyone interested in some API 500 format projects??
« Reply #125 on: July 29, 2005, 02:37:47 PM »
Quote from: "drpat"
Quote from: "Sammas"

- sowter meq-5 inductor with 8.361k, 5.261k, 3.265k, 728Hz, 367Hz, 201Hz selection (drpat's suggestion)...
- cinemag 1.2h inductor on the LF with switchable 80hz & 120hz
- switchable high end frequencies (haven't calculated those yet...)
- cinemag cmob-2 tranny
- JLM 99V DOA (gotta support local products ya know  :wink: )
- and find out what the flippin' deal is with the "gain trim" pins... what the hell that 47uF cap is doing on the LF inductor... Find out if 1.8K and 680R  do adjust the Q... see if it all actually works  :wink: (perhaps add another resistor space or pot place if it fits for people to adjust the Q).


I like the whole configuration that you're planning on using. I'll probably build the original 2520 from Fabio's boards, and socket the pins for experimentation. I'm excited to try out the CMOB-2 tranny too.

As far as the HF selection goes, I'd stick with the original 10k and have it switchable to 12k or 16k or 20k... whatever strikes your fancy.

I wouldn't bang your head too much about the 47uF cap. Stick to the schematic and worry about it if it's not working as expected.

I believe, earlier in this post, somebody mentioned that the gain trim pins are not connected according to information on Dan Alexander's site, which I couldn't find.

According to 500 series rack specs, pin 11 is labeled as "gain adjust" 550b and 560b. I'm not sure what this means, as I don't see any type of external adjustment on the rack. I would just leave these floating and see what happens.

Another thing to take note of. I had the pin numbers reversed in one of my earlier posts. I've gone back and edited it to correct the error. So...


THE NEXT GUY WHO QUOTES GET'S SHOT BY ICE TEA! WE HAVE BRAINS, PEOPLE. BRAINS CONTAIN A SECTION CALLED MEMORY. NOT TO MENTION THE SCROLL BAR ON THE RIGHT.:razz:

Seriously, though. Sometimes all this quoting is harder to follow than just backing up a few posts/pages.

cj
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

soundguy

Anyone interested in some API 500 format projects??
« Reply #126 on: July 29, 2005, 04:51:07 PM »
Quote from: "Sammas"

- JLM 99V DOA (gotta support local products ya know  :wink: )
.


I havent read this whole thread but would remind folks thart api lunchboxes have +/- 15v supplies, the 99v wants twice that.

dave

chips are good with dip...

peterc

Anyone interested in some API 500 format projects??
« Reply #127 on: July 29, 2005, 06:34:13 PM »
Here is some data on the Altran transformer:



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

drpat

Anyone interested in some API 500 format projects??
« Reply #128 on: July 29, 2005, 06:41:55 PM »
Actually, they have +/-16V power supplies. Also I agree with Jimney, those bridge rectifiers are going to be a little hard to source. Maybe we could use the ones that Charles suggested instead.
I use the LA2a on very hot signals like lead vocal.

Sammas

Anyone interested in some API 500 format projects??
« Reply #129 on: July 29, 2005, 08:34:27 PM »
Quote from: "soundguy"



Hey Dave,

I spoke to Joe and he said he has used the 99v in the output of 550B's with good results before  :thumb:


drpat

Anyone interested in some API 500 format projects?? New
« Reply #130 on: August 01, 2005, 02:19:31 PM »
...
« Last Edit: September 17, 2010, 08:12:10 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

peterc

Anyone interested in some API 500 format projects??
« Reply #131 on: August 01, 2005, 03:24:12 PM »
Pat

What I left out of my post was the "mic pre input transformer" part   :?  I was enivisioning people building racks of mic pre's....

Got a bit lost within the whole thread, but the Altran  can be wired as a 1:8 mic input pre, that's what I was thinking of.

I assume you're referring to a line input transformer (1:1)?

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

soundguy

Anyone interested in some API 500 format projects??
« Reply #132 on: August 01, 2005, 04:59:08 PM »
finally had some time to read through this whole thread which is really interesting.  Just to point out the obvious-

the 553 used an air core inductor.  I think that unless you find a similar inductor you arent going to have a similar sounding band.

We should just design our own damn thing and free ourselves from trying to conform to that design since its going to sound different no matter how hard we try.  I see a lot of decisions being mulled over trying to get this to sound close to some old thing.  Since we'll never (Im assuming) find that exact part, seems like it woudl be way cooler to think out of the box and just do something cool as opposed to just doing what some other people did 20 years ago.

If we build one up with the cinemag pultec inductor, hows that not gonna sound cool?

The advantage of this project is so far as I see it:

a) not having to build a power supply

b) fill up empty spaces in your lunchbox

I have been wanting to build some stuff for my empty lunchbox slots but my whole motivation has been to build something that sounds DIFFERENT than from what I can go and buy, which commercially speaking, is all API inspired stuff, which is cool and all but Id rather be building something cool instead of something that we can just go and buy, doesnt make much sense to me.

cinemag inductor is not impossibly expensive, think it will fit, is readily available, and leaves us LOTS of options for designing something cool.

just some food for thought.

dave

chips are good with dip...

drpat

Anyone interested in some API 500 format projects?? New
« Reply #133 on: August 01, 2005, 05:29:54 PM »
...
« Last Edit: September 17, 2010, 08:06:51 PM by drpat »
I use the LA2a on very hot signals like lead vocal.

peterc

Anyone interested in some API 500 format projects??
« Reply #134 on: August 02, 2005, 01:50:09 PM »
Quote
Family Hoof and I are working on preamp PCB's in PM land. I'll buy one of these and try it, on your word that it's a good sounding x-former.


Ok, I must warn you that I've never tried these transformers......

Adrian intimated that these are the original part, might be worth contacting him & getting some more background from him.

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

Anyone interested in some API 500 format projects??
« Reply #135 on: August 02, 2005, 03:22:00 PM »
FWIW Altran is used by Old School Audio.

udo

Anyone interested in some API 500 format projects??
« Reply #136 on: August 03, 2005, 12:22:33 AM »
Quote from: "TomWaterman"
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 believe you're right. looks like something similar (the 2K2 pot in series with some resistors) is used in the 'hi boost Q' control of the pultec circuit:
http://members.nuvox.net/~zt.robgrow/circuits/pulteceq.html
Quote from: "TomWaterman"
The Q can apparently be calculated by:
Q = (WoL)/R

i get the same result (0.08) using:
Q = inductive reactance / R
=> Q = (2pifL)/R

bandwidth is defined as  BW= f res / Q   = 23Hz/0.08 = 287Hz

therefore the -3dB points should be 287Hz apart from each other with the resonant frequency 23Hz in their center. as the lower cutoff frequency is not in the audio band this looks like a shelf even though a resonant LCR circuit is used.

somebody correct me if i'm wrong, please!
udo

TomWaterman

Anyone interested in some API 500 format projects??
« Reply #137 on: August 03, 2005, 06:50:05 AM »
Awesome udo!

Thats what I was getting at - nice to see the other formula gives the same result. Thats a damn big LF BW...this is going to boost at up to 300Hz+.

Being able to change the Q could be a good addition to the EQ, especially the MF.

-Tom

strangeandbouncy

Anyone interested in some API 500 format projects??
« Reply #138 on: August 03, 2005, 12:43:24 PM »
Soundguy,

    My 553 doesn't have seem to have air-cored inductors . . .


    ANdyP
. . . . RUH ROH . . . . .

Anyone interested in some API 500 format projects??
« Reply #139 on: August 03, 2005, 01:23:32 PM »
On page 2 of this thread there are some pics of my 553 - aren't those air-cored toroidal inductors? Unless I'm misunderstanding the terminology, which is very possible.
Seth

The definition of insanity: "Hey, this thing could be really cool - if I had the money to fix it up, which I don't, but if I did it could be really cool - if I had the time, which I don't, but


 

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