api312 input transformer question

[Jonkan]

Has anyone tried the sowter input transformer clone?

Im still trying desperately to decide if im going with the oep or the sowter. The oep is cheaper for shure, but im worried that it might be too coloured for me to use since the api clone will be my main preamp for a long time to come.
(atleast until I can afford to build some other preamps).

Any opinions on the matter?

/Jonas

 

[jrmintz]

I have the Sowters hooked up to my 312 boards, I jusn't haven't had time to finish them up and try them out. I will as soon as I can, though.

:thumb:

 

[robomatique]

I would also be very interested in some results of the OEP vs Sowter :grin:

Robert

 

[Category 5]

[quote author="jrmintz"]I have the Sowters hooked up to my 312 boards, I jusn't haven't had time to finish them up and try them out. I will as soon as I can, though.

:thumb:[/quote]

Please Please...tell us as soon as you can. I am very interested to know if the Sowters are a direct replacement.

Also, to answer someones question I saw earlier (maybe even another thread) the Cinemag that I have in my clone is the CMMI-8PCA. This is a 1:8 transformer, unlike the 1:10 ratio parts that the others have been mentioning (including the Cinemag). I haven't tried the 1:10, but since the 1:8 give 18dB of voltage gain and the output is wired for 1:2 there is a decent amount of gain to be had from the op-amp. This is as it should be I think, especially when using a real 2520 (after all, you want to hear the 2520 a little bit right?).

I think the 2622 is a 1:7 ratio (right?) which is obviously closer to the 1:8 than the 1:10 part, so I am curious as to why nobody has mentioned the CMMI-8PCA.

It sounds excellent! Plenty of punch, and A-P-I signature mid growl.

Shane

 

[dukasound]

Hi
I received today from Prifile P4804 outpur transformer. I will try with different input transformers.
Now I have Lundahl 1538 and OEP and I will order JT-110K-HPC.
What about R4 and C5. On original schematic with 2622 it is 5,1K and 220p. Fabio suggested one 100K parallel to secondary then 31K and 22p too parallel to secondary. What value are OK with Lundahl and OEP?
Also, what with C6 and C7 (1000p) with this transformers?
Thanks
Duka

 

[Bauman]

You guys may find it very interesting, regarding the subject.

http://www.groupdiy.com/index.php?topic=45807#45807

One customer of Tim from Seventh Circle Audio has reported that CMMI8-PCA from Cinemag gives very close to original results...

I'm still wondering how the CM75101 sounds compared to the original...

:roll:

cheers!
Fabio

 

[wilebee]

well put Kev

Wil

Wilebee

 

[andre tchmil]

speaking of transformers: is a 20 VA (2x10VA ) with 7818/7819 regulators enough to power 2X API 312 ?

 

[Bauman]

Andre,

I'm using 24+24VAC, 20VA toroid to power a pair of 312 right now...

cheer
Fabio

 

[Category 5]

[quote author="Bauman"]You guys may find it very interesting, regarding the subject.

http://www.groupdiy.com/index.php?topic=45807#45807

One customer of Tim from Seventh Circle Audio has reported that CMMI8-PCA from Cinemag gives very close to original results...

I'm still wondering how the CM75101 sounds compared to the original...

:roll:

cheers!
Fabio[/quote]

I have built a couple of these kits a LOVE them. Yes, I am using the CMMI-8PCA. It is a 1:8 ratio version of the CMMI-10PCA (1:10) which is the current transformer AP-Eye is using in the 3124 now. The CM75101 WAS at one time the transformer they used, but since earlier models used a 1:7 ratio the 8PCA is closer to the vintage units.

Addition - the 75101 can be strapped for 600ohm input impedance while the other two are 150. I imagine 150 is the preferred slection, but you could probably righ it up to be switchable from the outside (instead of jumpers) to allow another color option.

The sound diffrence between the 8PCA and the 10PCA is likely very minimal, but the 8PCA with it's lower voltage gain will allow you to derive more gain from the op-amp, thus getting a tad more color in that stage of the pre.

Either way, the Cinemags are probably the way to go. The transformers are awesome and Tom and David are awesome guys who are very willing to help educate others (hence the above information). They are deserving of our business in my opinion. Plus, I don;t think any of the other alternatives will give such a "true-to-original" sound.

Apparently the head engineer from A-P-eye has just left to start his own company, and he is using the CMMI-10PCA exclusively in all of his designs.

Shane

 

[dukasound]

Thanks Shane for this info.
Can we direct order and what is a price?

Second parts of last post was:

What about R4 and C5. On original schematic with 2622 it is 5,1K and 220p. Fabio suggested one 100K parallel to secondary then 31K and 22p too parallel to secondary. What value are OK with Lundahl and OEP?
Also, what with C6 and C7 (1000p) with this transformers?
Thanks
Duka

 

[Bauman]

Good stuff Shane, thanks!

Hope you get the opamp boards soon.

:thumb:
Fabio

 

[andre tchmil]

fabio, Do you mean 20VA total , or 20VA each rail ?

 

[Bauman]

20VA total Andre. :thumb:

 

[andre tchmil]

thanks :sam:

 

[dukasound]

Does 2622 two primary windings is connected parallel or is used only one winding? I mean when we used 1:7 ratio. I think Chris was talking about this.
Thanks
Duka

 

[dukasound]

[quote author="dukasound"]Does 2622 two primary windings is connected parallel or is used only one winding? I mean when we used 1:7 ratio. I think Chris was talking about this.
Thanks
Duka[/quote]
Anyone knows :?: :?: :?: :?:

 

[CJ]

Paralell

 

[Zee1usa]

I am still undecided on which input transformer to use:

1) CMMI8-PCA

2) CM75101

:?

I will be using the "Melcor"


Anyone have a reason of which one I might prefer or would be best suited or is this somthing I will just have to decide on my own?

Do you think the sound will be much different using on vs. the other?

Thanks,

Z

 

[Category 5]

With the 8 you will get less gain from the input transformer, and thus more character from the 2520...albeit by a small amount.

The 75101 is wired for dual input impedance, but I suspect you'll keep it set for 150ohm input, same as the 8.

You'll get more gain from the 75101, but I think the 8 has plenty. A-P-eye has used both transformers in their preamps, so both are considered genuine parts. I assume the sound difference will be minimal though.

Shane