Difference between CM-75101APC and CMMI-8PCA

[Category 5]

What exactly is the difference between these 2 transformers? Most of the people building 312 clones are using the CM-75101APC.

Shane

[tpryan]

This is a question for CineMag.

[Category 5]

Just a follow up, the 75101APC is a 150/600:15k transformer and the 8PCA is a 150:10k transformer.

The lower step up of the 8PCA will allow driving of the op-amp a little hotter, and thus derive slightly more character from that stage at equal gains.

Also, the 75101 appears to have a dual impedance primary while the 8PCA is 150ohms only.

The original 312 circuit used the 2622 (a 1:3.5 or 1:7 tranny) and later moved to several other more modern designs, including a Reichenbach version of the 75101APC. The founder of Cinemag is the son of Ed Reichenbach and has taken over the craft. Newer versions of the 312 use the 1:15k Jensen JT-115K-APC or the "Reichenbach" RE-115K-EPC (made by Cinemag now?).

At any rate, the 312 seems to have used many input trannys during it's lineage, but the earlier models apparently used the 1:7 or 1:8 ratio transformers so the 8PCA is probably better than the 75101 for emulating the early "vintage" API sound.

The other Jensen, Cinemag, and 1538XL Lundahl are said to have slightly more gain, and thus drive the op-amp less. This results in less distortion and a supposedly "cleaner" top end, but not quite as much of that API signature sound that made the early models and consoles famous.

This is all based on forum research, so feel free to correct me, but for others with the same questions about input transformers I thought this could be helpful.

Also, a kind soul at one of the forums was able to dissect a real 2622 input tranny, and soon discovered that Sowter is offering an exact (and expensive) replacement for this part. The jury is still out on the sound, but the current favorites for the 312 clones (with the goal of API sound) are the Cinemags. the CM75101 seems to be favored by most of the DIY'ers, but that puzzles me because concensus says the 8PCA might get you closer to the original API sound. The newer stuff is not nearly as highly regarded.

Care to comment on why you chose the 8PCA Tim? Or is it safe to say you came to the same conclusion as I did based on what I dug up in the other forums?

Shane