anyone built a GM- eL type 8200 EQ

as per topic really, was going to embark on my second project and make a calrec EQ however i really like the GM- eL 8200 and thought that maybe making this may be better and probably shouldnt be much more work or tricky.

pretty much at a loss ref schematics etc so was wondering if anyone here had built one or had any experiences to share.

anyone make PCBs for this, anything to worry about etc.

thanks

This guy sais that he's got the schematics of the device:
http://www3.telus.net/public/vintage1/record.htm

i think thats 'pat'

from everything i have heard, you do NOT want to deal with that guy!!

anyone got any views on the actual build. are these things super complex inside (probably since its george lol) or relatively straightforward?

You should have a look at the Sontec EQ that Fabio cloned...

thanks, ill have a search for it.
that may be a nice alternative, especially if theres boards up etc as they are really nice EQs. troublesome in the original form these days tho which is sad.

The Sontec and the GML don't differ in any radical way, even some of the R/C values might be the same. Go for the Sontec, sounds good. :thumb:

how hard is it to build compared to the others? i mean the sontec. i got ssl's, 1176 and a g9 under my belt.

[quote author="Viitalahde"]The Sontec and the GML don't differ in any radical way, even some of the R/C values might be the same. Go for the Sontec, sounds good. :thumb:[/quote]But Fabio's site is still down :sad:

[quote author="EEMO1"]how hard is it to build compared to the others?[/quote]

Way more difficult in the sense it's not a finished project at all (like the Calrec EQ is). Just a bunch of PCB layouts well done.

Mine turned in to a grounding hell, but after a weeks work I tamed the fucker. :twisted:



Fabio's site is up, at least I visited it 2-3 days ago..? :?

ok thanks. think im going to pass this one for now... looking mighty sweet btw!

maybe a bit OT but i have some nice inside shots of an GM 8900 compressor. If the 8200 is build the same way - no fun to DIY. A lot of IC, SMD.....
Maybe i can post some pictures...

toby

toby,

thanks for that, ive got a GML here in my studio and its pretty much as you describe the 8900 inside too.

i had just thought that given its fame, it may have been morphed into a nice DIY project already and if so i would have quite enjoyed building it.

im going to look at the sontec now instead as its pretty much the same as the GML and doesnt look too much work if i dont go stepped at first.

i think ill use regular pots then put in stepped switches at a later date if in happy with the sound to give good control.

forgot to add,
id followed your sontec on the other thread J. its looking really nice.

But Fabio's site is still down

Click to expand...

http://www.thediypill.phx.com.br/

And the Sontec...

http://www.thediypill.phx.com.br/diy_sontec.htm

Go knock yerself out!

:guinness:

fabios site working fine over here. :thumb:

very flattering to read the thread.

i've really be interested in seeing what folks do with clones of the gear that i've designed. the GML, and to a lesser extent the Sontec, kit will be pretty difficult to copy without retro-engineering the GML op-amp (currently a 9202D). the 990 is way too slow, due in large part to medium-scale output devices and the severe compensation required to stabilize it, and the 2520 doesn't have enough clean open-loop gain.

i learned alot from studying other folks' designs - still do - and would appreciate anyone sending me what they're working on for comment.

George Massenburg
[email protected]

p.s. note that the netcom mail system has a validation procedure that you'll have to go through, where i need to approve your domain before mail gets to me. sorry.

Mr. Massenburg,

nice to see you here again. :thumb:

Personally, the Sontec MEP250A seemed like a nice scheme to work on, it caught my eye at an instant when I saw the schematic. Radically different from most parametric equalizers I've seen - simple filters in parallel. Very nice!

My EQ is done with Forssell op-amps, 992's in filters, 993's as summing amps with Burr-Brown OPA604's as servos and DLR-1 at the input.

The grounding hell I was talking about was causing parasitic oscillations at high Q settings. Really odd stuff. Now it's completely stable after arranging the grounds differently.

I am very happy with the equalizer and I use it every day. There's no way I'm building another, not for me, not for anyone. Too much sweat, too much money. I got what I wanted and I'm happy with it.

Honestly, I do feel a little embarrassed to present this EQ to you. I quess it does feel a little like stepping on your toes. Luckily, an EQ like this would pretty much be a financial suicide to manufacture commercially. GML has its name & reputation, as does Sontec (whatever the situation is with Burgess.. does he or does he not make these anymore?). A new guy in town with a similar scheme and zero reputation would be a fool, nasty bastard and a man of no respect.

So I'd say you and your intellectual property is completely safe. There are a few DIYers who want to own a good EQ, and the Sontec scheme is a nice way to have it. Plenty of possibilities to tweak to your taste, too - and way better than the basic string-of-filters-in-series EQ.

:sam:

Word.
I'm trying to talk myself into doing the Sontec; anyone wanna be BuildBuddies?? Or something less gey? :wink:

I'm thinking it will give me something to do during my 9 days off at Christmahannukwanzika. I imagine it will be a long, grueling process, but I'm not in a big hurry. I'll just have to use software EQ's in the meantime. And sorry, I'm too much a bum to buy a GML.
I think I'll go ahead and buy the boards and resistors; maybe the switches, and see if I can get that much figured out. Prolly start with cheap IC's to get it working and then go with Forssells if I get that far.

I may chicken out and try the Calrec..... Is it pretty decent on the stereo buss, or is it mainly a tracking/mixing tool?

(BTW, I should have my appreciation thread up for my working GSSL soon. It kills drums. Just need to get a drill to redrill 4 chassis holes that hold the main PCB. Need to move it back so I can get my sweet front panel on. Whatta dummy )

george,

very nice of you to join in. your comments made for a good read too.
DIY for me is more of an interest, i enjoy the process of understanding that comes through building and the satisfaction when/if it works. in some masochistic way i also enjoy the figuring out of the issues that appear, though sometimes it doesnt seem it while its ongoing

after modding my SSL with some of the comments from here to address some areas i felt could be adjusted to serve me better, ive built a very nice passive mastering transfer console for my studio.

i decided an EQ would be a nice project to embark on next but wanted to try out something i though was an interesting design and a good sound rather than a more standard type or valve classic.
it was this that brought me on to the GML , i love the 8200 i have in my mastering room. a great sound and headroom, and then moved me on to the sontec from here.
a similar type it seems in many ways which would keep the interest factor for me but be much more accessible in terms of people to discuss with on here, schematics etc.

your point ref the discrete opamp is very interesting. it wasnt too much of a stretch to assume that these would be critical to the sound, especially given the high regard of the GML versions.

are there more stock 2520 type opamps that you feel would be better suited for this sontec type build? reverse engineering the 9202D i feel is beyond me at this stage though may be something i will try in the future.

anyone used the sc25?