Transfomer Change

[kid]

I noticed as I was just about to order my Jensen Transformers for my J99 project that the BOM has changed to a Cinemag transformer. What is the reasoning here? I hope not much else has changed since I ordered everything from Digikey months ago.

[tpryan]

You can use a Jensen transformer if you like, and they're easier to buy in small quantities. The new rev of the board is laid out for the flying lead version of the transformer instead of the PC mount version. Ask for a JT-11-DM with no channel frame. There have been some other minor changes to the BOM as well, so you may need to get a few more parts.

[kid]

Tim could you elaborate a little more on sonically what the difference between the two transformers is? Basically what is the motivation behind using the Cinemag?

[tele_player]

My guess is that it's related to Tim's offering a J99 full kit...

Tim - does the J99 full kit include op amps? Which ones?

[tpryan]

The CineMag parts measure and sound just as good as the Jensen parts, but cost a lot less, especially in quantity. The Jensen's are easier to buy in ones and twos, if you'd rather use them.

No op-amps are included in the full J99 kit, just like the A12.

[tele_player]

Exactly what I thought about the transformers ('especially in quantity')

I really like my J99's.

[tpryan]

Just to elaborate a bit, the two transformers have the same overall dimensions, use the same amount of nickel in the core, the same number of laminations, the same bobbin size, same turns ratio, same DC resistance, same winding technique, same type of insulation, etc., etc. They are interchangeable parts.

[tele_player]

Tim I hope you didn't misunderstand me - I didn't intend to criticize your choice. If you say they're interchangeable, your word is 100% good enough for me.

[kid]

Just to continue the love fest here. Only kidding Tim. Seriously I agree with tele-player that your word is 100% good enough for me. I just felt it was necessary to ask considering you obviously made some changes for a reason and just wanted to clarify them before ordering expensive parts. One other part change question is regarding U3. The BOM originally had this part as an AD706 which I ordered a while ago. The new one states an LT1013CP. Are these parts interchangeable?

[tpryan]

Actually, the AD706 has marginally better input offset specs than the LT1013, with a typical offset of 30uV for the 706 vs 60uV for the 1013. Either one is up to the job, but the LT1013 costs about $1.25 compared to $4 for the AD706. They're pin compatible, so either one will work on the board.