1084+API=B@stard child EQ

[glazer56]

Hey all. I know the 1084 build has been done to death around here, everybody is familiar with it by now, but I thought i'd post some pics of my latest project anyways.. Since i'm not really interested in building another clone, these boards are basically 1084 filters, (sans HP and LP) with 2520 opamps in the filter sections. The IO is handled with opamps, choosing to leave the color, and cost of transformers to my preamps. I've got four of these guys going in the tracking room, and a pair headed for mastering. Got the front panels done through FPE, and have sent it to a local guy to be silk screened. $50 is a far better deal that paying for the engraving! The prototype sounded pretty cool, hopefully these will too!
Cheers!

 

[spase]

wohaaa great project!We Need Better Pictures ))) and of course some samples )

 

[glazer56]

Ill try to snap some better ones tomorrow
SG

 

[nielsk]

I take it you are using a 2520 instead of a BA284 section on each EQ band? I have been wanting to play with different op amps in this application, what gain are you configuring? Inverting?
Pretty please post your schematic!

 

[glazer56]

Nielsk, Here are the schemetics I have. Keep in mind, these weren't meant for 'public consumption'! I never planned on making more than a few of these for the studio, so they look a little rough. Basically, it's just the 1084 filter sections, with a few extra EQ points using the 2520's instead of the BA284's. The I/O section was a schematic I had stashed from my searches at one point. If anyone knows who the designer is I'd certainly give him credit in the post! I also added a relay bypass to the boards.

I've spent 15+ years building equipment, even reverse engineering the 1272 before the internet days, but I don't consider myself a designer. I just like hacking stuff together!  If you see anything that might cause problems, please let me know.
Cheers!

 

[glazer56]

Page 2

 

[glazer56]

FPE panel silk-screened locally.  ;D

 

[dissonantstring]

hi SG,
nice build!  i'm in SJ and I'm interested in the business you were using for silk screening your panels?  they look great.  do they accept FPE files or do you convert to another format?
thanks!
-grant

 

[glazer56]

I had the film made by a company called

Advanced Graphics and Circuits
(408) 744-0590
1270 Lawrence Station Rd
Sunnyvale, CA 94089

I had the panel silkscreened By

Advanced Metal Finishers LLC
1291 Oakland Road  San Jose, CA 95112
(408) 885-9445

I'm finishing up the EQ this weekend, will post pictures!
SG

 

[nielsk]

Question: I have been cross referencing to the Neve 1084 docs ( I do not know if there is more than one version) and it seems like the point you have labeled as "C"  should be "J"?
They also show a 620 Ohm from the common of the H/F switch section "B" to point "H" on the 205 card (A3 on yours) and a second 620 Ohm to point "H" in the 205 card, you show only one?

 

[glazer56]

Question: I have been cross referencing to the Neve 1084 docs ( I do not know if there is more than one version) and it seems like the point you have labeled as "C"  should be "J"?
They also show a 620 Ohm from the common of the H/F switch section "B" to point "H" on the 205 card (A3 on yours) and a second 620 Ohm to point "H" in the 205 card, you show only one?

Hi, I'm not exactly sure where you are seeing point "C". I don't have a connection listed as C above. Did you confuse it with a capacitor? On my 1084 schematic, the HF selection switch ties into point H and F on the 205 card through two 620R resistors. My schematic has both. I'll post the 1084 schematic i'm referencing

 

[nielsk]

Ha! I think I figured out the "C" is an sideways  "J"! 
Trying to decipher between the two, on the 205 card there is a 22n cap and a 620 Ohm resistor between points N & H. Point H goes to the "b" side H/F switch common through a 620 Ohm resistor, and N goes to the op amp (284) output. I am going to try a 12K in there instead of two 620 in series.
I think the 205 point "H" corresponds to the "A3" on the H/F switch on yours (that ties directly to the op amp output), correct?
Are you using a 10K pot on the Bass as shown instead of the 50K?

 

[dissonantstring]

thanks for the graphics and screening info SG.  good for future reference.
best regards,
grant

 

[glazer56]

Ha! I think I figured out the "C" is an sideways  "J"! 
Trying to decipher between the two, on the 205 card there is a 22n cap and a 620 Ohm resistor between points N & H. Point H goes to the "b" side H/F switch common through a 620 Ohm resistor, and N goes to the op amp (284) output. I am going to try a 12K in there instead of two 620 in series.
I think the 205 point "H" corresponds to the "A3" on the H/F switch on yours (that ties directly to the op amp output), correct?
Are you using a 10K pot on the Bass as shown instead of the 50K?

Hi Nielsk, I am trying to locate my schematic for the 205 card, my computer died a little while back and I have to search through my backups. You are correct, point H is A3, and I am using a 50K pot in the bass, not a 10K, that is a misprint on the schematic. My apologies! I've built a prototype of the EQ and it works great; Let me see if I can pull up the 205 schematic and get back to you about specifics. Thanks!
SG

 

[glazer56]

The finished EQ... or Four! Sounding good so far! ;D ;D ;D

 

[warpie]

excellent stuff.
well done!

 

[wolfgang]

Cool Project!!!!!

Wants me one too!!

regards,
Wolfgang

 

[okgb]

Good spirit & skill for a  " hacker  " nice job

 

[glazer56]

It was a good project, but I tell you, next time i'm using PCB mounted switches.. the money I saved using lorins wasn't worth it. Those buggers were a pain in the arse to wire up! The unit sounds really nice, a little goes a long way, and I even like the way they sound just running the audio through them. You can really hear the low mid boost from the gar2050's I put in it. I tell you though, after being stuck using plugin's for years it's so nice to use a good outboard EQ. I don't care what they say, nothing touches the sound of 'real' gear!

 

[rafafredd]

Really nice project. I was trying to follow the schematics thought, but I don't see what J, K and C poits are connected to. Is it the complete thing?