Vintage CX-1 decomposed

[Denyle]

While I'm waiting for a few pieces to complete my rack, I thought I'd post this.

A while back, I added some Jensen transformers to a pair of CX-1 compressors that weren't getting used. Now they play nice with everything else in the lunchbox.

http://www.denyleguitars.com/images/cx1s

[gm5k]

what kinda character do these babies have? lovin those guts :)

[Denyle]

They go from fairly transparent at modest settings to gritty and trashy at extremes. I like them on edrums to add a bit of hair. The manual has suggested settings to emulate classics like the LA-2A but I think that might be a stretch.

[pan60]

While I'm waiting for a few pieces to complete my rack, I thought I'd post this.

A while back, I added some Jensen transformers to a pair of CX-1 compressors that weren't getting used. Now they play nice with everything else in the lunchbox.

http://www.denyleguitars.com/images/cx1s

i have been jonesing for at least one of these for some time :D
buts i can not seem to find the finances to keep up with the new stuff i want, so i always seem to have to pass on these when they come up.
was adding the tranny a major pain?

[Denyle]

was adding the tranny a major pain?

It wasn't bad at all. It requires 2 or 3 component changes and a few 1/4 & 1/8" nylon spacers. And a $10 desoldering tool from Radio Shack to make life easier. One of these days, I'd like to try better op amps in the signal path.

[LunchBoxHero]

Now they play nice with everything else in the lunchbox.


Denyle, what were you experiencing before installing the jensens?

and did it improve the sound character? My (transformerless) CX-1's are now feeling very jealous! :(

what's the model number of what you installed? oddly enough, I think I have a set of those transformers that I pulled from an old broadcast console we scrapped years ago. I recognize them. (Finding them in studio storage is quite another matter :eek:)

[pan60]

It wasn't bad at all. It requires 2 or 3 component changes and a few 1/4 & 1/8" nylon spacers. And a $10 desoldering tool from Radio Shack to make life easier. One of these days, I'd like to try better op amps in the signal path.

you should give us all a descriptive lesson as to what you re doing their?
at least i would like to know. :D

[Denyle]

The transformers are Jensen JT-123-A, -ALCF is the current replacement. I didn't notice any difference in sound but Jensen's are all about transparency. The spec sheet says the output is increased to +30dbm with the transformers. I suppose you could go with a steel core if you want more color.

I had an issue with an OSA pre where the led's would all light up and another pre (forget which) would glow dimly. It got worse with both CX-1 in the rack and went away when they were pulled. Decoupling the output solved the problem.

[Denyle]

Pan60, Here's what I did.

R114-change to 470K.
C110-change to 0.33uf. I used a tant but schematic says "S" (stacked film).
FB201-? fb201=R236=150R for NON-transformer version. I believe it's just a ferrite bead. I can't tell from the CX-1 schematic how it's incorporated but on the EQ2, it shows FB-2 in series with a 10R resistor, followed by the high side of the xformer. Jensen still sells the FB-2. Presumably, it's a 2 hole ferrite core and I'm not sure if you use one or both.

Now, match up the wiring of your transformer to this:
http://www.denyleguitars.com/images/cx1_output

Mounting the transformer (Jensen style):

Remove the upper standoff and press in stud. Tip: unscrew the standoff almost all the way then give it a tap to pop out the stud.

Use 1/4" spacers b/t the bottom pcb and xformer. Use a 1/8" spacer b/t the xformer and edge connector pcb. Use 4-40x1.25" screws to bolt it all together.

[LunchBoxHero]

well I finally unearthed my jensen transformers that I wonder can be used in my Aphex Cx-1's...:confused:

What do you think?

They are steel core (hence the "s") i believe.

[Denyle]

well I finally unearthed my jensen transformers that I wonder can be used in my Aphex Cx-1's...:confused:

What do you think?

They are steel core (hence the "s") i believe.

IIRC, The 123-S is physically smaller than the 123-A. Better check with Jensen for the specs, specifically the mounting hole spacing. Besides, the A is a 3:1 and the S is a 1:1.

[pan60]

i seen these on ebay?
http://cgi.ebay.com/Jensen-JT-123-A-Output-transformers-Dual-pri-sec_W0QQitemZ290309715033QQcmdZViewItemQQptZLH_Def aultDomain_0?hash=item290309715033
maybe they will help?

[Denyle]

i seen these on ebay?
http://cgi.ebay.com/Jensen-JT-123-A-Output-transformers-Dual-pri-sec_W0QQitemZ290309715033QQcmdZViewItemQQptZLH_Def aultDomain_0?hash=item290309715033
maybe they will help?

Yup, that's who I bought mine from too.

BTW, I updated my previous post 9.

[LunchBoxHero]

thanks for the eBay lead (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290309715033) on the "A". Someday I will find something to do with my "S". :cool:

For reference:

Jt-123-s Specs
http://www.jensen-transformers.com/datashts/123slcf.pdf

Jt-123-a Specs
http://www.jensen-transformers.com/datashts/123alcf3.pdf