LA2A - DECONSTRUCTED INTO BASIC BLOCKS

[chrissugar]

Hi all

I had this idea for a while. In fact I had it since I started that thread about adapting the 1960 comp into a new circuit.

Let's take every popular project, like the LA2a, 1176, SSL9k, etc. and redraw the schematics in a way that would make for newbies easyer to understand the building blocks and how they work.

Unfortunately most of the available schematics are drawn in a way that is understandable for someone experienced, but for a newbie they look mostly like a bird nest. I hope this will help people not just to build blindly the projects, but to open their curiosity to understand how they work, and maybe at a next stage to start improvising.
When I say improvising I think about playing with these projects like if it would be a puzzle.
Be creative and change/adapt the building blocks for your needs. Change the balanced input receiver from transformer to opamp circuit, change the makeup gain circuit from solid state to tube or jfet (any topology that you like), change the PSU, change the metering or any other element. Have fun, listen and learn.

The first project I redrawn is the LA2A, and it is not a construction reference ( I intentionally omited the metering switch, to avoid complicating the schematics, and I put the accent on the gain reduction metering circuit to be easyer to identify - Wheatstone bridge) , but a guide for a beginner to understand how simple is in fact this compressor/limiter.

http://www.twin-x.com/groupdiy/albums/userpics/LA2A-deconstructed.jpg

Probably the next project will be the SSL9k
Hope you will find useful this series. :grin:

chrissugar

P.S. Picture is large, 300dpi and it can be printed to A3 at high resolution. If you can identify any mistakes I would be glad to correct them.

 

[ruairioflaherty]

This is a fantastic idea Chris. As a newbie I'd secretly hoped for something like this but figured it wouldn't happen. I'm thinking that if beginners like myself could get their heads around the basic functions of the various blocks in a circuit i would make understanding the intricacies a lot easier.

I spent a couple of nights recently pouring over Fred Forsells eq pdf and schemos of various passive eqs to try and understand the basics - you could hear my brain grinding from 20 paces.I've got so many fundamental questions that I could keep the forum going on my own :grin: Trying to connect the dots using online info, books and sheer will power can be tough but loads of fun.

Major kudos for a great idea Chris,

thanks,
Ruairi

 

[[silent:arts]]

great idea :thumb:

 

[Gus]

I am not sure of this.

The path to learning is important, it might be better for people to redraw stuff on their own.

Most old audio schematics like the la2 are easy to read with practice.

Wait till you chase down a problem in a book of schematics for a system or circuit, analog and digital signals jumping from page to page.

That posted, that is a good redraw.

One minor thing the arrow directions going into the makeup and sidechain are pointing out

 

[sintech]

Thank you, this is most helpful. :thumb:

 

[KingKai]

Great idea Chris.

I've thought for some time now that the ultimate dynamic processor would be modular in a card slot rack. One could have a separate card for each component. One for the input circuit, one for the detector, one for the side chain processing, one for the gain cell and one for the output / makeup gain. This would allow total flexibility for customization. You could change the character of the unit by just poping in a different component. Of course I was not thinking hollow state at the time but why not? Tubes would just increase the rack space a little for bottles and some cooling stuff.

Perhaps this could lead to a new group project, The Chamelion Project, Yeah that's it. I was in cleveland I did'nt do it, You don't have pictures and you can't prove it.........

Peace - Out, Irv

 

[Mbira]

I'm thankful for this!
:guinness:

 

[lovekraft]

Thanks, Chris, this is exactly what many of us noobs need to understand these classic circuits more completely - like anything I suppose, it's so obvious as soon as it's been explained completely, but the schematics can be pretty difficult to follow for those of us who aren't as familiar with the conventions (I still don't get the comp/limit switch function, but I'll work it out eventually). I'll be eagerly looking forward to your next installment!!

 

[chrissugar]

Thank you all. I'm glad most of you like the idea.

[quote author="Gus"]The path to learning is important, it might be better for people to redraw stuff on their own.
[/quote]
Gus, I agree with you that people should start redrawing stuff on their own, but everyone should start somewhere. I think this is the kind of thing that can produce the declick in the newbie to do the next step. If you are a beginner, and you start to look at the original schematic and the deconstructed one, everything starts to make sense, and a schematic will not look anymore just like a bird nest.
[quote author="Gus"]Wait till you chase down a problem in a book of schematics for a system or circuit, analog and digital signals jumping from page to page.[/quote]
I know what you mean. I remember 15 years ago I was a student, and I had to do some kind of repair/reverse engineering of a device containing 15 eurocards with tons of digital chips. It was a nightmare.
[quote author="Gus"]One minor thing the arrow directions going into the makeup and sidechain are pointing out[/quote]
Yes I know, my idea was not to make them show the signal flow, but to act as terminations for the blocks.
But you are right, it is more intuitive to show the signal flow. So I edited the schematic and now the arrows show the signal flow.
I also added the block that shows the negative feedback network in the gain circuit. Hope this will help newbies to identify it easyer in other similar circuits.

chrissugar

 

[tonwerker]

I think it is a great Idea - working on the same for a Pultec in the moment,
but later more...
BR
Stef

 

[L@urent]

I have redrawn la-2a CJ mod, if someone could check it before I design a PCB...

new LA-2a PSU
LA-2CJ SideChain
LA-2CJ Signal Path
LA-2CJ VU

 

[alk509]

Holy ****, are you kidding me?! That's so immensely helpful for a newbie! Boy, I wish I'd had that back when I started looking into the LA2a with Jansen's book and not a lot of know-how...

I see Gus's point, but I like the fact that, at least for some eager-to-learn newbies, it will clarify things enough for them to go in and try to understand the building blocks themselves.

Great stuff, Chris! :thumb:

Peace,
Al.

 

[syn]

This is great.Thank you very much.
m

 

[tony dB]

great info!
Thanks a lot!!
Tony

 

[Mlewis]

this is such a fantastic idea. there's such a gap between building something using a blueprint and understanding why each component was needed or why certain values were chosen.

looking foreward to the 9k deconstruction, well done.

 

[radiance]

Thanks a bunch :thumb:

 

[Kingston]

:shock:

Brilliant! I'm just at this stage of figuring out buklding blocks of schematics I'm looking at. I recently taught myself the LN1176 design in a similar way, trying to break it into discrete blocks. Luckily the gyraf schematics are very well draw in light of this.

This is a nice evening read for me. Thank you. :guinness: :guinness:

 

[chrissugar]

I'm really glad you find this helpful. I'm already working on the SSL9k preamp.
I also had the idea to do the same with the LA3A, LA4A, to see the evolution and where are the differences compared with the LA2A.

If you have other ideas about schematics that worth to be deconstructed you can leave here your sugestions. :grin:

chrissugar

 

[laitue5]

:thumb:

 

[John Peacock]

Chris or anyone else, do you have the decstructed files? They don't seem to be posted at the original link any more. Thanks.

-Jp