Cinemag CMMI-8-PCA vs. EA2622 (vs. AP2622)

Hey, first post here.  The forum has been a great help.  Thanks!
Has anyone compared these three transfos? I'm doing four 325 > 312 conversions and have narrowed it down to either the CMMI-8-PCA or EA2622 for input.  I want to stay true to the original AP2622 sound.  Thanks!

Any thoughts on this?

waterloo said:

Any thoughts on this?

Click to expand...

I haven't said anything since I may be a little biased.  ;D

But Ed's whole deal with the EA2622's was to get as close as possible to replicating the old AP2622's. I think he has done a great job. I don't think you will get any closer unless you find some old AP2622's.

Other opinions would be nice too.

Cheers, Jeff

I used the Cinemags with my first API build and have brought Ed's for my next. I'll be excited to here the difference.

i have not used the CMMI-8 , but i've used both the the cinemag 75101 and ed's first version of the EA2622 (before he made them readily available, so they maybe prototypes) for inputs on a 312 circuit.  i've never used a real 312 unit with original 2622s (only Jensen) so i cannot comment on the originals.

though the cinemag is certainly nice sounding, i would say that ed's version of the 2622 has the best and warmest mid-freq. response when compared to the 75101 (though the 75101 is a higher turns ratio) or the jensen JT-110K that i've also used.  both the jensen and the cinemag have less mid punch/presence (subjective).

i have cinemags, jensens and ed's 2622 in 312 circuits and i like the EA2622 and the jensen input the best.  IMHO, ed's EA2622 is priced very reasonably, has THE vintage sound (with exceptional clarity and freq. response) and is built with quality.

if building anything with a 1:8 mic input, i would without hesitation buy an EA2622 (from jeff at classic audio of illinois - wait jeff is the only person selling them!  perfectly fine with me because he's great person too) instead of other options regardless of price.  

regards,
grant

(p.s. i'm not affiliated with anyone, but i have purchased directly from ed and jeff and used their products with great satisfaction - i guess i am biased.) ;D

Very convincing.  Thanks!

since that is a low ratio output, 1: or 1:2, there is not a lot of coloration from the output transformer.

i even tried to get some funk by using a nickel core and taking out the output cap, but it still sounds the same, actually, the steel core sounded a tad better.

uncle CJ is back!!  nice to hear from you CJ!!
you make a good point about the output transformer.  not much color to them, but still a very slight sound difference from each manufacturer (which would include uncle CJ).  more difference comes from the input transformer and the DOA in the 312 circuit.
regards,
grant

oh, i'm a danglin

always a danglin, post or no.

and i believe the CMMI-8 is a more cleaner or better performance
in relationship to the cinemag 75101
that's probably splitting subjective hairs but
i think they recommended it

where the hell have you been?

fishing in lake kanook?

did you see what happened to our sharks last year?

disgustin.


neve out, mannn.

So,  I think I'll give the EA2622 a try.  If I'm using Peter Purpose's mod what do I use for termination?  Does this transfo want a zobel network?  In other words,  how do I hook it up to my moded 325?

hi waterloo,
the original 2622 input transformer had a zobel of RC=5K1 and CC=220pF.  the 100K (R1) is the load resistor which i've included in my unit with the zobel as Peter P. has included (though the 312 schematic does not show this RL).  the 100K resistor should be between pins 5 & 8 of the 2622 with the 5K1 in series with the 220pF zobel (in parallel with the 100K resistor).

come to think of it, i haven't run a frequency sweep of my 2622 input build yet.  it sounds great, but i should measure it at some point to see if any adjustments are necessary.

i don't know about the 325 board layout, but you should be able to figure things out.  just reference the 312 schematic.

Hi waterloo,

As Grant said, you will want A Zobel with one of Ed's 2622's (like the originals). The 312 and my channel input schemo show a 5.1R in the Zobel. In reality, 10K was used with a 220pf on all of my input channels. I believe Ed said he found the same thing on the original 312 cards he has seen. On my pre's I use a 150K load R with a 10K, 220pf for the Zobel. I suppose season to taste.  8)

Cheers, Jeff

Thanks guys.  I'll be ordering soon Jeff!

Jeff, what would R3 be with your 25K pot?

waterloo said:

Jeff, what would R3 be with your 25K pot?

Click to expand...

With a 25K pot, change R2 to 200 ohm, R3 to 20K and C6 to 82pf.

Cheers, Jeff

Gracias!

There was another trafo discussion started on another thread which led to more questions for me... this thread is perhaps more suited so I'll ask here, but here is the other thread for those who wish to read it:
http://www.groupdiy.com/index.php?topic=33970.20

Basically, what got me all confused is this post by MikeFatom:

actually mean, that the only configuration that worked perfectly for me is,

Input TX : CM75101APC wired for 150 ohm input.
RL = 17K.

Click to expand...

This trafo, wired 150 Ohm (1:10)  should have 150K as RL to "work properly," right?  What am I missing here?


So, I started wondering about trafo loading and zobels... The EA2622 is a 1:7 trafo, yet the recommended RL (150K) is the same as for the Cinemag 75101, which is 1:10...  This would give you an input impedance of 3K vs 1K5 with the Cinemag. Does this not make a difference in the sound? I'm assuming Ed (who knows much more than I do about trafos) was the one to suggest this value and I'm curious to know why/how.

Of course, I did not consider the zobel.  I know you select zobels by passing a square wave through the trafo while the trafo is in the circuit, right?  But how does the zobel resistor affect the overall load on the trafo?  Meaning if you use the values Jeff suggests, (RL=150K, zobel = 10K + 220pF) what is the effective load on the EA2622 and what is the input impedance? 

Thanks!

you can try different values to get the best sound.

your wiring will add to the cap you use in the zobel, so everybody will have slightly different chassis capacitance.

so put in the right value resistor, then try caps.

the scope is nice, but the ear is better, because as soon as you hook up the scope, the leads will disrupt the true value you need for the zobel.

kind of like the brownian uncertainty jive.

some transformers have enough internal c to where you need no zobel.

also, hook a mic cable to the chassis, feed the signal into the mic end of the cable.

is pri c reflected to the sec?

that is a hard circuit to screw up, it should sound like sweet creamery butter, no matter how much you mess with it.

i think it's that discrete op amp thing.