+- 16v Virtual Earth summing ideas.

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

hans a

Well-known member
Joined
Feb 17, 2014
Messages
60
Im trying to setup my custom 16ch console for a recording session.
The board was bought unfinished with most of its funcionality (i would guess 😋). Its a 16ch board with two stereo subgroups and 2 stereo master strips where The master sections are missing (and with them The two echo send/returen masters).
All The infrastruktur is there, output connections, lundahl output trafos. But The Electronic are not. Also wiring is setup on what i would believe is a dB connector.

I have a female connector in my stash and also basic components.

Even an untouched ready lade channelstrip PCB. But im uncertain what to build. Firat thought of 2520 or equivalent. But im in a bit of hurry and IF there is a schematic People use often with basic parts i would settle for that.

Any ideas maybe?
I can research The xfo.
Br Hans
 
Yeah also, thought about The possibility to make near 30v glass a. The xfo i believe is not "DC-Rated" or cant be an active part in The circuitry like most Lundahls as ive read.

But that would be East enough maybe? Passive summing, a buffer and an output stage with four transistors? It would be Nice with AT least one of The four master strips to be sonically apart.
 
We miss some vital information there.
Are the bus balanced or unbalanced?
What is the value of the bus injection resistors?
What is the operating level before the bus?
What are the specs of the output xfmrs?
I suppose there are faders between the summing amps and the outputs...
 
Ok i went trough The documents i have. I Will photograph them and post. Im quite certain that The console is based solely on Steven Doves console design ideas from The studio sound article. Im missing The technical documents on The channelstrip and The master. But i have The subs and The limiter part of The preamp.
The preamp design is straight of The mic-pre tied to vactrol (dual rectifying detector) limiter design he proposed. The transformer balanced version with ll1538. NO line input as I can see.

The documents drawings show an input to The subs containing one bead to ground and a coil 150mh to an opamp, also passes trough a 10k attenuator first of. But i Will post...
 
You could do worse than copying Steve Dove... Last time I spoke with him (last century) he was living in PA, and had moved on to working with DSP instead of analog audio.

Look for schematics of respected designs and reverse engineer why the designers did what they did.

JR
 
Lol. Thanks Mr. Roberts. I guess that is called retirement then? 😊

Ive read that studio sound article a lot. This console has gotten me interested in op-amp design (by nescessity mostly. Right know theres NO time to fully invest in this hobby) so right know im looking at Dobkin's Op-Amp Circuit Collection. I actually found a PDF of your article too that i Will read. Theres a lot of stuff i've noticed that you can find if looking trough technical archives.

Im thinking of posting The documents i have in The technical documents section. It is a one of console but it Maybe someone else made a singular design? Br Alex
 
hans a said:
Lol. Thanks Mr. Roberts. I guess that is called retirement then? 😊
That was called consulting... by now a couple decades later I hope he is retired.
Ive read that studio sound article a lot. This console has gotten me interested in op-amp design (by nescessity mostly. Right know theres NO time to fully invest in this hobby) so right know im looking at Dobkin's Op-Amp Circuit Collection. I actually found a PDF of your article too that i Will read. Theres a lot of stuff i've noticed that you can find if looking trough technical archives.

Im thinking of posting The documents i have in The technical documents section. It is a one of console but it Maybe someone else made a singular design? Br Alex
There is a ton of reference designs out there, some are obviously better than others, but many are more than adequate.

JR
 
It seems there is. Just glad to have a console that i may (😋) be able to record on an learn from. It's also very Well crafted, and that makes it a Joy to use.
What i Will try to fix/continue where he left of:

> Dir Out is tapped at the Insert point before EQ section. I want The signal after fader to be able to adjust The signal when recording from externa pres. And also to be able to use The console for mixing to an interface.

> The limiter was, as read in Studio Sound, designed for more of a protection duty and it is not usable when recording and mixing right now. I'm reading up on this and atleast gonna try to make it more usable. It's hitting to hard and has too a long release. It seems the (home made) foto cell either is like that inherently, or maybe a timing cap that i can take away.

> Two stereo channels are missing

> Master section is missing

> Echo master (summing and send and return)

Br
 
image3A2606.jpg

image3A2605.jpg

image3A2604.jpg

image3A2603.jpg

image3A2601.jpg

image3A2602.jpg

image3A2600.jpg

image3A2599.jpg

image3A2598.jpg

image3A2597.jpg

image3A2596.jpg

image3A2595.jpg

image3A2594.jpg

image3A2593.jpg

image3A2592.jpg

image3A2591.jpg

image3A2590.jpg

image3A2586.jpg

image3A2581.jpg

image3A2584.jpg

image3A2583.jpg

image3A2585.jpg

image3A2577.jpg

image3A2574.jpg

image3A2575.jpg

image3A2572.jpg

image3A2573.jpg

image3A2571.jpg

image3A2568.jpg

image3A2569.jpg

image3A2570.jpg

image3A2567.jpg

image3A2566.jpg
 
If you are interested I have just posted the link to an Acrobat Pdf document containing the entire series of 14 articles "Steve Dove: Designing a professional mixing console", published on "Studio Sound and Broadcast Engineering" from September 1980 to January 1982, in the Technical Documents section of the forum.

Cheers
J.
 
Hey jacomarth. Thanks for letting me know😊

This is what i've got for the console if anyone is interested. I also posted it in the technical documents section.

Löhman LE 84 Mixing Console (Steve Dove design i mostly certain of) https://imgur.com/gallery/PbzyL3l
 
Seems to be inspired by Steve Dove, however significant departure using discrete mic pre instead of 5534.
TL071's in summing amps? I didn't remember Steve Dove advocating that, but yes, he did. 5534 was expensive at the time...
 
abbey road d enfer said:
Seems to be inspired by Steve Dove, however significant departure using discrete mic pre instead of 5534.
TL071's in summing amps? I didn't remember Steve Dove advocating that, but yes, he did. 5534 was expensive at the time...
A TL07x is not an obvious choice for a summing amp due to relatively high ein (3uV) and modest open loop gain @ 20kHz...  That said I resolved a bus rectification (radio station interference) issue inside a small Peavey mixer I inherited by using a JFET opamp. Not sure why the bus inside a steel chassis was acting like an antenna but swapping out the bipolar summing opamp for a JFET opamp cleared up the radio interference issue relatively simply.

I recall speaking with Steve at a trade show back in the 80s and he shared that he did some consulting work on broadcast mixers/consoles operating in high RF environments where a JFET opamp might make sense.

JR

PS: JFET opamps can tolerate a couple volts of RF superimposed on inputs before rectifying, bipolar opamps start playing radio tunes at roughly 1/2V of RF
 
Im there is two pictures of SR HB66 that slipped by when i uploaded. They are the discrete stuff.
The mic pre is a ne5534.
Br Alex
 
JohnRoberts said:
I recall speaking with Steve at a trade show back in the 80s and he shared that he did some consulting work on broadcast mixers/consoles operating in high RF environments where a JFET opamp might make sense.
That's correct. I remember having solved a similar problem in a FET compressor of mine located right under a 1kW FM rig, by replacing the 5534 make-up amp with a TL071.
Trading RF immunity for increased hiss.
 
The first time we recorded thru this console we used the master out to be able to use the eq and the hiss was really loud. The sound was rather nice tho. A couple of years later i tried it with a band using dir outs and i got bad distortion.
Maybe try to find a less noisy equivalent or replacement then.
Or try to put something more modern in the empty master sections.
There is a post eq tap that i did use on a few channels. But i think there is oscillation since the led level meter is stuck on overload. It might explain the distortion on the session. It sounded like a touch of high frequency modulation.
When i have a day of i will restore these channels and try to find a more decent place to tap if possible. Maybe the fader buffer?
 
Update. I found that it was built with a lot of functionality in mind. The dir out is marked jack in and out on the pcb pin header. It could be modified to be a line in i suppose with a switch.
The insert send did'nt work so i rerouted the dir out wich was pre eq to the send part of that jack and took tje dir out jack and put it on one of two empty pins, post-eq or post fader. Choose post fader. I suppose its a blend of two outputs on the pan buffer.

I found the echo sends bus lines. To the empty master slots. If i find the same lines for the master a and b routs it should be simple (no clue, first time 😋)  enough to buffer them and route the to the send and return jacks and route the back to the master a and b channels.
I guess this is just a log to keep the work realized. Or at least the intention.
 
Back
Top