Sig, it certainly looks to be in the 'ballpark'. I should get the original unit out of storage and measure it sometime. In 1974, when we first made this design, it was specifically used with an Electrovoice T350 tweeter that had a sensitivity of 108dB/W or so. So, even at 1W, it was really, really, loud. It was designed for 8 ohms originally and modified (like you have) to also be OK at 4 ohms. That is about as low in impedance as we ever thought it would be used.
I am glad that you added the series resistors in the bases of the devices. Originally, we only used 4 MHz devices or less, and the series resistor did not seem necessary. Later, when we switched to ring emitter transistors, we added base resistors out of necessity, given the advice to me by the 'late' Jon Iverson.
I am glad that you added the series resistors in the bases of the devices. Originally, we only used 4 MHz devices or less, and the series resistor did not seem necessary. Later, when we switched to ring emitter transistors, we added base resistors out of necessity, given the advice to me by the 'late' Jon Iverson.
Mike,
Sorry I haven't been much help to you on the PCB thing, but I'm hip-deep in doing my own artwork here and there's only so much of that I can do in a day before my eyes go buggy. I've got a front end board, output boards, rectifier & first cap bank boards, regulator boards for both front end and outputs (are you regulating your rails?) which will be combined if I can manage it, and as if that wasn't enough, I'm on my third or fourth iteration for the front end board as I keep trying different variations on the basic topology.
Best of luck.
Grey
Sorry I haven't been much help to you on the PCB thing, but I'm hip-deep in doing my own artwork here and there's only so much of that I can do in a day before my eyes go buggy. I've got a front end board, output boards, rectifier & first cap bank boards, regulator boards for both front end and outputs (are you regulating your rails?) which will be combined if I can manage it, and as if that wasn't enough, I'm on my third or fourth iteration for the front end board as I keep trying different variations on the basic topology.
Best of luck.
Grey
A-40
I am going to have to take apart my A-40 mosfet amp. The housing will be used for the JC amp. If any of you guys want a couple of working A-40 boards let me know. I also have a couple of SYM amp boards.
If you have a couple of IRFP 9140 or 9240's I could use them. I still have a F4 board to build. Thanks, Mike.
I am going to have to take apart my A-40 mosfet amp. The housing will be used for the JC amp. If any of you guys want a couple of working A-40 boards let me know. I also have a couple of SYM amp boards.
If you have a couple of IRFP 9140 or 9240's I could use them. I still have a F4 board to build. Thanks, Mike.
Mike,
I would talk to the people at www.4pcb.com .
If you are a first time user, you will get a discount.
If I remember correctly, Ayre uses them.
Sigurd
I would talk to the people at www.4pcb.com .
If you are a first time user, you will get a discount.
If I remember correctly, Ayre uses them.
Sigurd