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First Watt J2

I'm looking for an amplifier to drive my 8 ohm 94 dB DIY back-loaded horn single 6.5" driver speakers. Looking at the specs for the J2, it looks like it would be a good option as it appears to behave much like an OTL or a current source device. The F2 is another option but its voltage source behavior may be less suitable for these speakers. Am I looking the right way at the differences between these two amplifier designs and their suitability for this type of speaker design? I'm thinking of pairing my Aric Audio Unlimited tube preamp - 600 ohm output impedance, with the J2.
Thanks.
128x128kalali
analogluvr
800 posts
 
Why not buy an actual tube OTL like an atmosphere???
kalali's avatar
kalali OP
1,645 posts
 
Al, thanks for the input, as always. My remark regarding the J2 as being a current source amplifier was solely based on the power output specs of 25w@8 ohm and 13w@4ohm vs. the F2 specs of 5w@8ohms and 10w@4ohms which seemed to imply a voltage source amplifier, e.g., doubling the power as the impedance is halved. I completely missed the (significant) difference in the amplifiers’ output impedance which seems to be more in line with what Nelson seems to recommend for the type of speakers in question, higher the better all other things being equal. Interestingly, I experimented with what he had suggested in that paper by adding different value resistors in line with the speakers and running them using my Adcom 545 amplifier. The results were not satisfying. The added resistors seemed to veil the sound and made the speakers quite dull sounding. 

ghosthouse's avatar
ghosthouse
3,718 posts
 
In addition to the helpful input from Almarg, you might also benefit from emailing Nelson Pass.  He does reply.
d2girls's avatar
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d2girls
641 posts
 
How much did the f2 cost retail when it was available?
wolf_garcia
4,650 posts
 
Get an SIT3...4 grand and it's yours! Note those supposedly work best with 4 to 8 ohm speakers.
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