ALTEC 436C compressor amplifier modification

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mata_haze

Well-known member
Joined
Dec 20, 2005
Messages
819
Location
Back in London!
HI everybody
I just thought it could be interesting to modify (following the SSL line) my altec 436 C in order to implement some sort of hi-pass filter on the sidechain. this is where I think it should be placed.




between PIN 2 of the 6AL5 and R12 which are responsible for the gain reduction
anyone would like to throw their 2 cents in?!
All the best,
Mattia.
 
[quote author="clintrubber"]While looking for something else I stumbled upon this:

Altec 436C Comp-Amp w/ Mods
(8.9MB)[/quote]

FWIW, i have talked to "recording the beatles" co-author brian kehew on numerous occassions and he is adamant that those mods are *not* the EMI mods...i'm not sure if he's right or not.
 
Interesting .....Im currently modding my BA6A vari mu limiter {similar to 436C type limiter} Im adding attack release ratio and threashold controls ...dont really no what im doing just plug and play and ask questions. Have just upped the side chain caps values myself ...just seems to work better.
Anyway theres more over on the Chiswick thread if any1 wants to throw there pennies in id love to read yr thoughts.

Mata, RE yr original post the Chiswick seems to be a tarted up version of the Altec 436C ...there could be some modds there for yr 436 if like me yr a serial fiddler.


Cheers .............................Gary O.
 
http://www.groupdiy.com/index.php?topic=10280

schematic is gone now unfortunately.

however- i printed it out before it disappeared. i dont have a scanner but i will describe the mods, refer to stock 436c schematic-

(i hope nyd doesnt mind. if its not cool with him i will take this down)

250 ohm balance trimpot between 6bc8 cathodes- wiper goes to gr meter

resistor across meter replaced with 100 ohm trimpot

33k resistor in sidechain replaced with 27k in series with 100k 'attack' control

resistor in series with 'release' pot changed to 180k

variable 600 ohm bridged t atten between output transformer and output terminals

a guy i work with tried these mods on his 436 and he likes em alot.
 
here is a thread over on pro sound web about the altec and the EMI modded ones, which were called model RS124:

http://recforums.prosoundweb.com/index.php/m/189323/0/

here's hoping that mr. hinson shares over here again in the future like he has in the past! :grin: :thumb:
 
he had a pretty good description of the real emi mods posted either here or on his webpage- it wasnt paint by numbers detailed- but was thoro enough to satisfy the idle curious. but he removed it.

but whatever! no compressor or preamp or vintage flux capacitor is going to make you or me or lenny cravitz sound like the beatles. people get really stupid about this shit.
 
guys..
I am just speechless to see all these answers...
many many thanks to everyone !
really appreciate it.
I'll try all the suggestion you gave me!
cheers,
Mattia.
 
I have the schematic for the Altec A-322-C if anybody is interested.
I believe it pre dates the 436, so it might be fun to study the "upgrades" and try to project from there. (integration in calculus) (or trig idenity for you AS guys.
 
errr, that means i need your addy also.

this has the manual also.
it tells you how to get rid of the thump.

"shout into the mic connected to the A 322, the words that rhyme with thiump, like pump, hump, rump,....."'' :razz:
 
it used to be posted in this thread-

http://www.groupdiy.com/index.php?topic=17355

looks like schematics disappeared in the twin x groupdiy server crash, tho'
 
[quote author="solder_city"]

but whatever! no compressor or preamp or vintage flux capacitor is going to make you or me or lenny cravitz sound like the beatles. people get really stupid about this shit.[/quote]

well, i suppose that true but i have been and will continue to be, VERY interested in recording techniques of the 60's and i, for one, want to learn as much as i can about the nuts & bolts of all the great studios of the 60's and i must confess, i find it more than a bit frustrating that the info is out there but not widely shared, at least in this case. but that's just me! :oops:
 
ok, they had my website partitioned into two parts, 10% here, 90% there, so depending on my pass used, i had two diferent disk quotas, long story short, an hour on hold at ipower web, only to find out that my new credit card did not jive, so call the next day, re submit credit info, transfer to tech dept. wait another 1/2 hour, then get it straightened out. :twisted: :twisted: :twisted: :twisted:

Anyway, I am back in, so here is the 322 file in "right click save target as" form.
my site is lighteneing fast if you have the bw to match up.
Enjoy!
3.4 smegabites
Props out to the fridgid north.

http://vacuumbrain.com/The_Lab/TA/Altec/altec_322_compressor.pdf
 
Wow thanks CJ :grin: I love these old limiters its similar to a BA6A, when you said shout thru the mic to tune out the DC volts, I thought you were jokin...well if its good enough for miami dog track its good enough for me,voice of america liked these then.....wonder where they put there rubbish. Whats going on with that interestage tranny.....I dont get that and whats tha 6sn {I think }tube doin ????...is it to drive the diode tube ???? for faster attack maybe ???...I feel some experiments coming on and ive just put the BA back together, typical.


Thanks once again CJ.......................Gary O.
 

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