New Cinemag mic transformer CMMI-3.5

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tk@halmi

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Joined
Jun 3, 2004
Messages
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Location
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Has anyone tried the new Cinemag transformer CMMI-3.5C? It is a 1:3.5 turns (9.7dB gain) part that came out this summer and I am really curious if someone has experience with it.

I am stoked about it because it seems to handle large signals with low distortion and it matches the 2N4393/PN4393 input noise profile rather well (my favorite substitute for 2SK170s for differential input pairs). Also, I like getting less gain at the transformer stage for improved headroom through the amp.

Thanks,
Tamas
 
[quote author="wilebee"]Hey tamas have you ever tried a 2n5566 for a front end fet pair?
Wilebee[/quote]

Yes, it is the best dual JFET available to me after the 2SK389. It sounds best when run at high currents, at least 5ma in each leg, more if your design can stay stable at insane slew rates. The best price is at Arrow for $4 of the 2N5565 part.

Tamas
 
Dan,

Thank You Sir for getting Cinemag to make it. (Wow, I don't think it could have come with a better recommendation then that.)
Oooh, I just realized that technically it could be a great upgrade to my JT-11K8-APC (tiny core) based amp as well.

Tamas
 
[quote author="tk@halmi"]Dan,

Thank You Sir for getting Cinemag to make it. (Wow, I don't think it could have come with a better recommendation then that.)
Oooh, I just realized that technically it could be a great upgrade to my JT-11K8-APC (tiny core) based amp as well.

Tamas[/quote]

Tamas,

I have a Presonus MP20 mic pre that I swapped generic transformer for JT-11K8-APC's in. Do you think the Cinemag would offer any appreciable increase in s sound quality or linearity over the Jensen. I have it couple to twin AD797 op-amps (great chips btw) but it still has a bit of forward midrange. If the Cinemag is more linear it may be a good substitue in this circuit. the Jensen is also a 1:3.5 transformer.

Shane
 
[quote author="Category 5"]
I have a Presonus MP20 mic pre that I swapped generic transformer for JT-11K8-APC's in. Do you think the Cinemag would offer any appreciable increase in s sound quality or linearity over the Jensen. I have it couple to twin AD797 op-amps (great chips btw) but it still has a bit of forward midrange. If the Cinemag is more linear it may be a good substitue in this circuit. the Jensen is also a 1:3.5 transformer.

Shane[/quote]

Well, Dan explained it pretty well. :grin:
IMHO, it would be a substantial improvement especially if you have the AD797s fitted already. The major issue is that the physical dimensions of the CMMI-3.5C are about x2.5 of the 11K8-APC. The Cinemag is a large core transformer akin to the CMMI-5C or the JT-16 devices with wire leads instead of PC mounting. If you can figure out how to fit it you got it. Dont' forget to replace the secondary termination resistor with an 18K instead of the existing 15k resistor.
Cinemag quoted me a tad over $56 for the CMMI-3.5C for qty 1 to 10. Compare that to the 11K8-APC that costs $47 and has all sorts of problems with bandwidth and distortion.
If the CMMI-3.5C fits you may consider the CMMI-5C and get and extra 4dB gain, perhaps lower noise a bit. The proper loading network would have to be added for that though.

Tamas
 
don't worry about offending Jensen. they have so many OEM's that we are nothing more than a speck of dandruff on their sports jacket, which they have to flick off from time to time. (quanity 1 orders, etc) same with LUndahl. Thats why I like Brian Sowter. He doesen't make a dime off the vintage stuff, he is doing it because he is a cool guy who probably digs vintage audio and wants to support us DIY'ers.. He has plenty of OEM bussiness also, so he is really doing us a great service that is probably more of a time consuming pain than anything else.
good luck getting jens4en or LL to do a fairchild output!

cj
 
Dan,

Would this transformer work well with an MPSA18 input?
I am thinking running about 1ma through each leg of the opamp's LTP.
Based on the noise curves published by OnSemi the 1.8k source impedance should give pretty low noise at that current still.

Thank You,
Tamas
 
It works just fine, with that little opamp layout over in the other thread, by the way.

Two of those in series with the old "Brittish standard pot in the middle of the feedback of both stages" style pre works rather well.
 
[quote author="Dan Kennedy"]Two of those in series with the old "Brittish standard pot in the middle of the feedback of both stages" style pre works rather well.[/quote]I'm trying to draw a picture of this in my mind, but it isn't working... (could be cause i've lost my mind :wink: )
 
I don't even know what anyone is talking about anymore. :shock:

So, the first, is that the white whale of Mellville that everyone's pursuing?

And I'm envious of some people's knowledge of British preamp design.

(Ciphers upon ciphers. Sorry for the headache.)

Bear
 
> Brittish standard pot in the middle of the feedback of both stages

BSPITMOTFOBS.gif
 
[quote author="Dan Kennedy"]It works just fine, with that little opamp layout over in the other thread, by the way.

Two of those in series with the old "Brittish standard pot in the middle of the feedback of both stages" style pre works rather well.[/quote]

THanks, JEff
 
FWIW for the guitar players that gain setup is used in the older marshall blues breaker effect. I like how it splits the gain in effects. I did not even think of its us in other audio stages.
 
[quote author="Gus"]FWIW for the guitar players that gain setup is used in the older marshall blues breaker effect...[/quote]Interesting... Isn't the "Hamptone" pre similar to this?
 

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