sphere 71636 boost fader amp questions

I'm hoping to confirm that this amp which replaces the 900 EQ does in fact get hooked up to the
fader via the 18 pin connector?  Also, does the input transformer feed this amp and then does this amp
next feed another buffer amp for the pan circuit?

https://groupdiy.com/index.php?topic=45864.msg783899#msg783899

Also, exactly which pins on the connector connect to the fader? I'd like to try this in my small
Sphere console which uses 10 pin connectors instead of 18 pin.

A sphere block diagram would be awesome, if anyone has one.

hitchhiker

Generally speaking the BST on the EQs both 18 pin (EQ900, 803) and the 10 pin (EQ 910,920, 823,813)
serve the same purpose ... the fader amp. This guy is generally set up for15db of makeup  gain post fader.
The 71636 card is the 18pin version and is strictly just the BST section.  Don't know if Sphere ever made
a 10 pin version  as I have never seen one but it wouldn't surprise me if they did.  It should be not
to difficult to design one however.  If you study the 10pin EQ pinout skitz....

https://groupdiy.com/index.php?topic=45864.msg783807#msg783807

You should be able to feed the "top" of the fader from the 22193 card pin # 28A  the bottom of the Fader (AGND) from  28B.
The wiper would feed the BST "IN" on the 10 pin EQ connector pin "H"
BST out  pin "B"  would feed Pin 40A on the 22193 Card.

Make sure that Pins 2, 4 , 7,and 10 are jumped on your new PCB.

This should place your fader after the "L" button on the 22224 Mic pre card.  Note that all Pan pots are down stream of the
BST... no more buffers needed.  Should be simple after a little detective work.  Got to find my 920 skitz to design a proper
DOA for this.  I have been wanting to design this card for a while myself.  I'll Share

GARY

Thanks Gary,  The pin outs all check out with my  console frame. Good to know that there is no buffer needed for the pan circuits.
My console is mono, so the outputs go straight to the 4 buss selectors. All I need is to do is insert a pan circuit before the bus selectors.  Do you have a pan circuit to share?  BTW, my bus sum resistors are 20k. I'm definitely looking forward to seeing your BST card design.

  It looks as though I could drop in 813, 823 and 920 EQ's (if I had the serious money).  My output cards are built on the
22745A  EQ cards which I have in pics to be the 920 EQ. For some reason they cut off a chunk where the eq, hi pass and thumb wheel switches attach.  Both the input and fader buffer amps are populated.  If I could find the inductors I could  get creative and add in the EQ sections. That would be cool!

Lance

Edit, my 4 bus out cards are  22745A and my one external mono feed is a 22745 C

hitchhiker

I have had a bit of down time today in the shop so I worked a bit on the
2x10 pin BST PCB to replace a 10 pin Sphere EQ in a Sphere Eclipse Desk.



working from this old skitz...
Inside the BLUE BOX is the 10 pin EQ of your choice

Pin "28A" from the  22193 monitor module (RED BOX) feeds the  EQ input on
Pin "L" of the 10 pin EQ connector.  On our New PCB we jump Pin "L" to pin "J"
to bypass the EQ section on the 10 pin connector.

Note the FADER (GREEN BOX) Pin "J" in the 10 pin connector feeds the top of the fader
The fader wiper feeds pin "H" on 10 pin EQ connector.  This feeds the input of the BST
(fader amp).  The bottom of the fader goes to a GND connection on the 10 pin connector.
The ground connection  could be on any of the following pins of the 10 pin connector
Pins... 2,4,7,9,or D.  These are all in common when a EQ is inserted in the connector.
Please meter the connections out to make shure they are correct in your desk.

The output of the BST is PIN "B" this feeds back to the 22193 monitor module at pin "40A"
and /or Pin "37A" depending on your console configuration.

On the 10 Pin EQs,  the phase rev switch is on the input to the BST... (old school) .  since we don't
have a front panel for our new little PCB this has been eliminated.  The new little PCB
has the input permanently wired IN PHASE.



Here is the Skitz of the new little PCB.  (I'll work on getting
a bigger better copy of this guy)



Note the the layout is based on the SPA-62 DOA and is set up for 15db of gain

This PCB pic is a bit big looking... its really about 3.8" x 2.7"



Also note that the fingers for the LEDs are not needed and do not exist on this PCB
to save Gold.


At this point This is only in the design stage and is untested.

All for now..

GARY

Wow!  Very nice looking pcb.

Thanks Gary for all the good info,  I'll check out my notes and schematics as soon as I get my file folder back. My brother took it by accident with his files, and he's out of town a few days.

Lance

Gary

  The pin outs you've given are a match with my console. The BST card should work great.

  I'm now wondering which would be the better wiring of the input transformers,  1:1  or  step down  2:1 ? 
My faders are 10k . What have done on your console here?

Lance

Hi Lance

Here is how Sphere did trafos on the Eclipse Desks...

The 7341PC mic trafo is wired 600:30k. ( M1200 and Eclipse "C"  mic pre cards)
Thats why it is now a custom wound Cinemag these days.  Wound to original
Reichenbach blue prints.

The 7393 output trafo (alias Jensen JE-123-SLPC  and JT-123-SLPC) is wired 600:600
( Tie pins 2 to 3 and Pins 6 to 7)

Hope this helps.

GARY

Hi Gary,

Interesting,  so the Eclipse had no dedicated line in transformers, only mic pre's and pads?  I saw a post by Duncan  at Orphan Audio  stating  that Sphere used a couple of different step down ratios for line in , but no specific console was mentioned.  I think I'll  go with 1:1 input so that if it's getting  input from the sound card there will still be enough gain to the sum bus with the added 15 dB gain on  the BST card.  Sound cards don't seem to put out quite like my 3M m56.

Lance

Lance

The channel line ins/tape returns were unbalanced at least in the Eclipse A and B. don't know about the C
The Echo returns used a 10k:10k transformer.... Sphere 76113.



I just helped Shirk Studios with 40 channels of Balanced receivers for their 32 channel Eclipse "A" for all
line ins,  2 track returns and Echo returns.

http://gar381interests.com/SPHERE_PROJECT.html

From what I understand about the 76113 transformer,  it was badly shielded and was subject
to noise problems. 

I can custom make up Dual or Quad receivers for you using gar6220 DOAs (used in the Shirk Desk)
which are SPA-62 ported to a 2520 pin format.

I am using these receivers in my desk as well using the single XLR version and they sound wonderful.


GARY

Gary,

That's really great that you've done the SPA62 in 2530 pin format! BTW a little aside, I was told by Steve Firlotte  that the SPA62 will run on up to bipolar 31 volts.

For my first try on this console I'd like to feed straight from the input transformer to the input fader to the BST card. That would  put my audio path through four SPA62's in total.  BST, Sum Bus, and finally the 2274F cards to output TX

On your design for the BST card is the gain set on the card?  My console has cut wires at 3 & C so it seems it likely at one time had gain switches of some sort.

Lance

BTW, I just edited my second post. I didn't know that my 4 bus cards are different than the fifth card which is a mono input that IIRC is wired to go straight out on it's own and  I'm not sure what it's purpose was.

The correction is that my 4 bus out cards are  22745A  and my one external mono feed is a 22745 C  .

Interesting !!

The original desk that my goodies came from was a 12 input 4 bus with a mono cue send.
I think it was an old broadcast desk.

The 4 bus out card in my desk is the standard 22404 bus card that contains 8 summing amp  SPA-62 slots and
8 line amp SPA-62 slots.  This card directly feeds the Sphere output transformers thru a 470/16 cap. 
This guy was only half stuffed to get the 4 buses out. 
Your 22745A card I have never seen, but Sphere was alway customizing to order.

My desk has the standard 22416 card  for outputs with 7 SPA-62s that are used for
L&R Program,  L&R Studio, L&R Control Room and MONO outs.  These all directly feed the Sphere output
transformers thru a 470/16 cap. 

Note that the line amp SPA-62s for Cue and Echo sends are on the 22190
card and directly feed the Sphere transformers thru a 470/16 cap

Here is a basic simplified Eclipse A & B flow chart.  This may help you some and may save
you a month of reverse engineering.



Have fun!!  Sphere stuff sounds  wonderful but the control logic and signal flow is
like no other desks ever made.

BTW... I will be testing the 10 pin BST cards late next month in a friends console
while I work on a couple on of his 920s

GARY

Well you have the luxury model with all the options and I have the plain Jane model. When I found this one all the transformers were gone as were all the input EQ's.  Also the original shell was gone.  So it was just the bus switch bank cards and connectors, the framework with the input and output 10 pin connectors, the faders and face plates in a greyish off white and the VU panel with wiring and connector, (minus 4 VU's which I have yet to find).

I've done all the reverse engineering but have yet to do a detailed all on one page schematic.

Here is a quick sketch of this consoles simple signal flow as I believe it was originally.

I can't remember where I found these pics of the same 22745 A EQ cards but the poster claimed
that these white EQ's were 920's.  Did they do the 920 in a 10 pin  version?

That looks like a 920.  Yes 920s were 10 pin.  It was the 900 that was 18 pin.
Never knew 22745 was the pcb # of a 920....  Thanks for the info.
An unpopulated EQ section of the 22745 could be used as a BST fader amp but could also be used as a line amp.

GARY

An unpopulated EQ section of the 22745 could be used as a BST fader amp but could also be used as a line amp.
[/quote]

Yes, if I take 2 of the 22745  bus cards and insert them into the input slots the console works as a 2 input  2 bus.

I should have 10 pin BST cards available sometime in Feb!   That should get your desk
back to full size!!  Meanwhile you can use your 22745 cards for the R&D of your project.

GARY

gar381 said:

I should have 10 pin BST cards available sometime in Feb!   That should get your desk
back to full size!!  Meanwhile you can use your 22745 cards for the R&D of your project.

GARY

Click to expand...

Awesome!  I was just about to ask you if I could get a dozen from you when you get some made. 

Lance

Gerbers are at the board house for 20 protos  

Just put your name on 12 of these if they work out!!
These are protos without gold fingers....  But then Sphere never used gold either.   
BTW.. I added a gain trimer  to fine tune +15db.

I'll keep you informed as to progress.

GARY

gar381 said:

Gerbers are at the board house for 20 protos  

Just put your name on 12 of these if they work out!!
These are protos without gold fingers....  But then Sphere never used gold either.   
BTW.. I added a gain trimer  to fine tune +15db.

I'll keep you informed as to progress.

GARY

Click to expand...

Sweet!! Love that you added the gain trim. I couldn't make sense of the gain set with pins 3 and C  and
so  I was hoping to  decide on the gain  with the SPA62 on the BST card (56 k I think )  and hopefully forget it.

Lance