Which Firstwatt Clone For C&C Abbys

I just got a pair of Cain & Cain Abbys, and am in the process of swapping out their current drivers to get closer to original specifications. They have Audio Nirvana Super 6.5s in them. I've ordered Fostex FF165wks.

I'm a chassis and power supply away from either an Aleph-J or F6, who's stuffed PCB's are leftover from previous projects. I was hoping the Aleph-J would be a good match, but I'm also willing to build something new. I plan to put a Nutube B1 in front of whatever amp is selected, because I'm enamored with it driving my M2x in a different system.

Any shared experience is greatly appreciated.

Currently, I'm listening to them driven by a McIntosh MC275 which will most likely not remain in play for this. I find it a bit lifeless in the midrange, and am looking forward to replacing the drivers.
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I can only speak from personal experience.

I’ve gone through a lot of experiments with fullrange drivers in a variety of open baffles, front horns and now large back horns.

I’ve gone through Fostex, modified Fostex, Tang Band, Lowther, Lii Audio and Sonido field coils in a variety of sizes.

I have built ACA monoblocks, F2J clone monoblocks, a round one Sony VFET amp and a pair of Babelfish J2 amps.

I also have a pair of Quicksilver Horn Monoblocks designed for use with high efficiency horn speakers.

Out of all the amps the one I keep returning to for use with fullrange/widebands is the F2J. It is just remarkable with these drivers to my ears.

If you haven’t, you should take a look at NP’s articles on current source amps.

Edit: BTW, I use a DCB1 preamp I built and added some Jensen transformers to the output for an extra 6dB of gain. A few picks of the F2J in a few scenarios.


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Thanks Chromenuts. I just did some reading on the current source amps. Did I understand correctly that this can be simulated with a crossover wired in series at the expense of efficiency? If so, does the Aleph-J produce enough output to drive that?

I'd love to try an F2J, but I don't know if I'd find SemiSouth parts.
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Series passive crossovers are a requirement for filters being used with current source amps as I understood the article.

I’m not sure what you mean by “simulate”…the behavior of a current source amp?

I don’t remember reading that in particular…it has been a while.

I think there may have been mention of adding series resistance to fullrange drivers with voltage source amps…which is something I’ve read about several times but haven’t tried myself.

I believe using a current source amp negates the need for that added series resistance people use with voltage source amps.

I wouldn’t be the one to ask technical questions about the Aleph J or its response to added series resistance.

I’ve made it in this hobby by riding on the coat-tails of greater minds.

Maybe ZM or someone else will chime in.

Building an F2 is not too difficult…I’ve seen a blog where it was done on perf board…can’t find it now.

You could check in this thread and see if kinku or anyone else has any PCBs to sell…


If you really want to build an F2J it is possible…at a cost…


…or you could beg Papa for a pair or be around when he’s feeling generous and gives some away 😉
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Wow - thanks for all the responses. Chromenuts, I reached out to Kinku to see if he has any more boards and semiconductors to sell. If not, I'll dig into these links.

BTW: Simulate was a poor choice of a word for what I was thinking (Post #3). I was trying to ask if the series connected crossover would produce similar results as driving the speakers from a current source amp.
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@Dennis yes…its a great blog and I was on the verge of trying it myself for the F2 when I found it years ago as I just done some simpler circuits for voltage regulation on perf board and it was fun…then kinku popped up with his boards and that was just easier.

Twitchie’s experiments look very interesting…like I said “the coat-tails of greater minds”…the lives of the greedy and brave!

I’m more if a paint by numbers guy. My pop always said “A little knowledge is a dangerous thing.” 😉

@ppinto1 Sounds like a good plan.

I’d have to go back and read the article again to refresh my memory regarding adding series resistance with fullrange drivers. I do vaguely recall Papa talking about it in the article now.

I recently came across another thread where series resistance with fullrangers was being discussed.

Member GM was involved. He seems very knowledgeable and I’ve found his posts helpful several times in the past.
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There was not a thread devoted to the subject per se.

I have just come across the subject several times within other threads…especially since I recently acquired a pair of Kirishima back horns and have been poking around on the subject of tuning them a bit lately.

A google of “using series resistance with fullrange drivers” spit out several DIYAudio threads that discuss the topic.

Dennis linked Papa’s article above where I think he discussed subject.
Thank you very much, both of you

It's been quite a long time since using these. One of the guys here is playing with the Coral beta8 driver on an OB using the standard F5 amp and I've forgotten about the effects of a series resistor on the driver with a voltage gain amp, not something like in the discussion as above.

Curiously, are those super R100 jfets still available and genuine from the "capacitordistributor" as per that eBay link?
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That listing has been discussed more than once in various threads.

They do, in fact, appear to be genuine.

I see the description has been altered…they used to be described as “matched”…but that was simply based on the fact that they were from the same production batch number.

Edit: BTW…you don’t need matched Semisouth to build the F2J. I built mine with unmatched Semisouth thinking I would save my curve traced sets for other projects. They sound spectacular.
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I built this amp about 5 years ago, I don't use the F2J on a daily basis but this amplifier works very well.
Go ahead and built this amp, I am not aware of an amplifier working better with fullrange speakers, even my 2 different pairs of Elsinores are happy with the few watts.
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