gary o

CCA LA 1D Vari Mu limiter..any info on this ?????
« on: March 28, 2006, 01:36:00 PM »
Anyone know much about this over on the Sowter sight, he has the 2 irons, circuit looks simple, anyone know what these sound like was thinking of building one perhaps, uses a 6386 tube tho, I read the company was formed by previous RCA folks, heres the link to schematic.

http://www.sowter.co.uk/schematics/CCA_LA1D_Limiter.gif


Cheers........... Gary O.


gary o

CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #1 on: March 28, 2006, 01:48:56 PM »
Ah silly me should have did search first little bit info already here wouldnt mind bit more tho.

Cheers............. gary O.

audioforge

CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #2 on: March 28, 2006, 02:22:10 PM »
sowter had done thoses irons for my clone.
if you can wait untill end of may i will post pics and layout for this one.
can t say anything about how it sound as i need to repatch my studio but looks very promising on the oscilloscope.
audioforge

B-A-R

CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #3 on: March 28, 2006, 03:16:25 PM »
I have one, scored it off ebay last year. It's amazing. Crushes things in a good way. I use it in my vocal chain.....as well as on drums....build it!!

gary o

CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #4 on: March 28, 2006, 06:33:41 PM »
Yeah look for forward to those pics, mr Sowter done some iron for my BA6A too, was thinking of borowing them to test this project before I buy, but I think irons for each are bit different, glad to hear it crushes nicely tho

Thanks guys......Gary O.

rlaury

CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #5 on: March 28, 2006, 07:30:31 PM »
Very similar to the Collins 26U-1 without the interstage.
Seems somewhere along the line they decided they didn't need
the interstage. I would think the interstage would be much
needed to block the DC imbalance from the 6386. Otherwise
you may get a "thump" on high transients.
Anybody have any input on having or not having an interstage??
Any change in the sound between them?

RonL
When all you have to work with is a hammer,
everything looks like a nail.

gary o

CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #6 on: March 29, 2006, 04:58:00 AM »
when I was DIY ing my BA6A I didnt have my interstage so I coupled the 2 stages with capacitors & resistors like in this circuit, and got it to work but yes the control voltage came thru, then when I finally got the interstage in there it all came good, but this circuit has been designed not to have an inter so I suppose it must work nicely B A R likes it, I dont quite understand the theory side yet but the RCA guys must no what there doin, I wood love to hear this thing, heres a thought maybe silly one so please forgive me, could we make hybrid vari Mus say this circuit with input stage of BA6A thats 2 S6SK s or say input part of AM864/U to avoid using the 6386 ?? and if it worked I spose that would change its compression sound ??

audioforge

CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #7 on: March 29, 2006, 06:28:05 AM »
the LA1D is a GATE STALEVEL (compare the schem.)with minors variations
  one 12 bh7 for output  diodes inpsu to avoid 5v and 5y3gt valve and a more variable release time. off course diff. traffos.(utc ha100 and chicago BO2).
BAR (thanks again man for your help building my clone:thumb: ) said he like it much than his gate stalevel. i can t confirm as i do not have a gate
but i choose building this one for that,then i had some 3686 and nobody had done it before...
As soon as i can i will post pics and layout as i said before...
It will be my "contribution" to the forum as aknowledgment for all the things i ve learn at RO and here..
audioforge

ciminosound

CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #8 on: March 29, 2006, 01:46:56 PM »
Quote from: "gary o"
could we make hybrid vari Mus say this circuit with input stage of BA6A thats 2 S6SK s or say input part of AM864/U to avoid using the 6386 ?? and if it worked I spose that would change its compression sound ??


Don't forget M*anly uses the 6BA6 pentode wired as a triode to sub for the 6386tube. Supposed to give the same curves. The 6BA6 is a mini version of the 6sk7. Appears to be the closest anyone has found to the 6386tube.

Look at THIS Thread

gary o

CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #9 on: March 29, 2006, 06:22:15 PM »
Yeah thats the only way I could do this limiter with 2 x 6BA6s, I cant lay my hands on 6386s sadly, I no a man who has some 6BA6s tho, but in theory could stages of different limiters be bolted together just to make a sound thats not been heard before perhaps, thinking as I type I suppose the thumping would be one problem.

Cheers .........Gary O.


emrr

Re: CCA LA-1D and AGC-1D Vari Mu
« Reply #10 on: November 24, 2010, 09:24:45 AM »
I have the variant, the AGC-1D, on the bench and just finished up the electrical work.



Someone had moved the threshold control to the front panel, and added a release pot.   I hate it when people drill new holes in antique audio, cause they think they need some new control, like they are smarter than the original designers.

 If you have a look at the schematic, you will see the limiter and the AGC only differ in side chain timing.  

One cool thing is the date of manufacture, and the radio station it was made for, are on the model # tag.   This one was made in early '69.

HA-100X input, Chicago BO-2 output.

Was surprised to find the B+ is very high.   395VDC after the rectifier, 378VDC on the 12BH7 plates; beyond the ratings but no metldown.  310-0-310 coming from the power transformer.  

The original AGC timing had been altered, and was a single 0.68 cap with 4M7 in parallel with a 5M pot with a slug resistor, so release R ranged 250K to 2M5.    This timing didn't really work correctly.   It had a tendency to let too much by and distort, it thumped a lot, and there seemed to be oscillations at certain settings.

I took this timing network out, and put a DP6T rotary in using the 5 fastest limiter timings, and the original AGC timing in position 6.  I put the AGC timing parts back in the original position, and all the limiter timing parts on the switch.  This brought the unit around to proper operation.  It acts a lot like a sta-level, but with a lot more options in the timing department.  The AGC is different from the limiter settings, and I felt almost no one today would use the slower limiter settings on their own.   The AGC will cover that territory when needed, and better.  





I then noted the threshold pot caused the meter to shift downward when set to 0 volts.  Adding 3k9 to the bottom of the threshold pot kept this meter consistent across all settings.  As with almost all limiters like this, threshold is also ratio.  A 0 volt bias gives lowest ratio and lowest threshold.  Highest bias here is 72 volts actual.  I have not seen official spec for these amps.  

I still need to relabel the faceplate.  

EDIT:  done here

guts before

guts after
« Last Edit: January 01, 2011, 10:35:18 AM by emrr »
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounded g

dustbro

Re: CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #11 on: November 24, 2010, 06:50:01 PM »
wow  :o
pics please!

emrr

Re: CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #12 on: November 25, 2010, 10:58:00 PM »
pics added to earlier post
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounded g

pH

Re: CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #13 on: December 13, 2010, 02:14:46 PM »
Nice work Doug. Do you have a schematic available for the AGC version?  I've been interested in building a Sta-Level for a while, but I like the output of the CCA version better on paper (do we really need a 6v6 push pull output stage?!?).

-Paul

emrr

Re: CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #14 on: December 13, 2010, 03:17:21 PM »
The schematic that's out there is both versions. 

We do need a PP 6V6 output stage to get the higher levels necessary to reach high ratios for limiting. 
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounded g

pH

Re: CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #15 on: December 13, 2010, 04:40:40 PM »
Ah, now I see on the schematic, LA-1D or AGC-1D.

What do you think of this unit? I'm looking to add some more vari-mu color in my rack, something hopefully more flexible than the Federal.

emrr

Re: CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #16 on: December 13, 2010, 04:49:59 PM »
It's not hard to be more flexible than a federal.    This one sounded great.    The iron is a big piece of that.  Definitely nothing special about the guts of the thing.  Will do most of the Stalevel thing, but more clearly due to the transformers used. 
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounded g

pH

Re: CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #17 on: December 13, 2010, 05:28:04 PM »
Quote
It's not hard to be more flexible than a federal.

No kidding!
Looking into suitable iron for this one. Think this one might work for the output?

http://edcorusa.com/products/367-xpp1-600-15k.aspx

emrr

Re: CCA LA 1D Vari Mu limiter..any info on this ?????
« Reply #18 on: December 13, 2010, 05:40:18 PM »
response isn't too great there. 
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounded g