adding a transsformer to input or output of racked eq's ?

[antoniosolo]

I am interested in adding an old set of transformers to the in or out of a pair of eq's I am racking.  I am wondering if anyone has any suggestions and advice as to what and where to put these. I plan to have dpdt's to switch them in or out of the circuit.  All of your help is greatly appreciated.

 

[CJ]

1) what kind of eq
2) what kind of xfmr?

don't be shy...


maybe even post a schemo

 

[antoniosolo]

EQ's out of a mitsubishi westar console, 4 band parametric +- 18v that were supposedly designed by Quad8.... maybe LO2567 vintage.....or old rca or altec or utc or ??? Won't worry about the IC's so much at this point unless someone starts some crap about the originals...

 

[antoniosolo]

Basically looking for spec's like 600 and line level ? 

 

[CJ]

we need a schemo that can be expanded out,
so we can show you where to operate on the victim.

right now, we would be operating with a very dull scalpel.

 

[dissonantstring]

we need a schemo that can be expanded out,
so we can show you where to operate on the victim.

right now, we would be operating with a very dull scalpel.

dull scalpel?!  C'mon CJ you're used to operating with a hacksaw!!
hope your doing well CJ!
best regards,
grant

 

[antoniosolo]

Of course I can strap across the output anything really as long I show the next device 600...but I was hoping someone might suggest something that came out of that console......

 

[CJ]

we need a bigger schematic

 

[antoniosolo]

Thanks CJ, guys, I will have to search or ask the seller.....I thought it might be easier but again with the myriad laws I should have known.... ???

 

[CJ]

ok, i thought you had a bigger image and just resized it too much

no biggy, lets move on

i would say that any ol 600:600 on the input, unless you want a little gain,

the output is a bit more tricky, as i do not know what level is coming out, and what it needs to be changed into.

most good opamps will drive a 600:600 , but not very hard

you just have to be careful not to stress the output transistor pair in the last chip.

start with a 10 uf cap in between the output xfmr

and gradually work your way up to 1000uf/35 vdc.

if the opamp does not complain,
try a direct out into the winding.

be ready to kill the power if you see flames come out the sides of the chassis.

wear Nomex gloves and cary a sharp branding iron for this test.

if you somehow miraculosy get away with this,
Congrats!
you will have a killer sounding board with nice fat bottom end.

i think i have a Valley People wired direct, and i like it for its detail with transformer.
usually it is tough to get both.
but itis a lil shakey, if you know what i mean.

if for some reason the opamp locks and rails out, you will wish you left the cap in.

ask a propeller head how to stabilize an opamp.

 

[antoniosolo]

I think I will be safe  :-\ and settle for a 600:600 on each input and count on the nice sound of my pre's to cover the rest.  I just want to add some EXTRA umph to it the situation if I can.  I don't have the whole board, just a pair of the eq's.....Thank you for the guidance and comedy....

 

[CJ]

we can then narrow it down to some ideas on input only,

size: vary the size of the transformer-Beyer to UTC Large Can series

core:
a)vary the material-Superpermalloy, 50/50 (radiometal), 4% Si Grain Orient
b)vary the shape= C core, E-I, ribbon...

age:
earliest: Western Electric 111C
low mid:UTC black series 600:600 Keyon signal eater series-black can
upper mid:triad hs 600:600 or UTC Gray series
new: Jensen/Sowter/Lundah/Tab-Funkenwerk/Insert your favorite brand here

grab a bunch of samples, 1 from each category,
then line them up on a tag strip with  wafer switch 12 POS stackhouse wafer switch
(the stackhouse does not have a stop, therefore you will never know which xfmr you are hearing, good for blind testing,
just spin the bottle and strap on the phones...

i mean stackpole.

stackhouse was a stella player.

???

you Must use the blue torquoise style,
other colors do not have the same midrange.
;D

besides, it matches the headers on the Triad HS series used in the 670.

 

[antoniosolo]

I guess I can use my pair of LI 1366 Neves for 600:600.  I really want some old US tranny though......

 

[antoniosolo]

Anyone have the input and output impedances?  Should they be on the schemo?

 

[CJ]

pretend the input resistance of the opamp is almost infinite ohms,

so if anything, you will need to add a little resistance to the sec of a 600/600.

the dcr is low, so that is a stiff source that always needs a little resistance to sound nice.

 

[strangeandbouncy]

Hi,

  with the greatest of respect, I suggest that you try them out as is, unbalanced, first before you go the bother and expense of acquiring some iron for these. I used to work at a studio that had 8 Mitsubishi Westar eq's in a rack, and I have to say that they really weren't anything to write home about. They never got used. I don't know if they are the same model, but . . .

  They might be exactly what you want, so I hope I am not being a downer, but I would suggest you see if they are worth adding expensive iron too. Adding expensive iron is NOT going to turn them into  awesome eq's. They should be awesome first, naked and un-adorned . . . . the rest is just gravy, or somesuch.


    Good luck!


      ANdyP

 

[antoniosolo]

S&B, I appreciate the input and I hope that mine is not one of the four different models that you reference.  Also, many people love some things that other find repulsive....I am not afriad to put in line something that can be switched in and out of the circuit, just for choices.  I hope they are good and yes, I should listen first as you suggest.  You know how we like doing things extra to make something better, I hope it helps....

 

[antoniosolo]

....and since I really didn't pay anything for the pair I may as well invest in them.  Flavor almost always comes from transformers and all of my other gear attests to that.

 

[CJ]

exactly, and you can never have too many transformers laying around the house.

for instance, the peerless 15067 makes a great door stop. 

 

[lassoharp]

Yes and a Freed 17672 PT makes a hurricane proof paper weight.

I agree that iron can add character and I don't mean to be stating something you're probably already aware of, but to guard against putting all your eggs in one basket regarding transformer contribution to 'color' - I'll point out that circuit design can be an overriding  bottom line factor.  A 6G6 Fender Bassman's cathode follower circuit will do the heavily colorful things that makes it such a well liked guitar amp when overdriven with Humbuckers regardless of what brand of OT it uses.  Likewise as pointed out above, a circuit with 'poor ears' may not allow the full characteristics of the transformer to be realized in a satisfying way.

Cheap way to start would be Edcor of course.