diytube.com

Just trying to figure out if the existing bias circuit can be adapted for PPP Ike. Any recommendations? I want to avoid buying a separate transformer for the bias circuit if I can help it.

Thanks,

Min

Min, I meant to mention my thoughts on this earlier via email but forgot to. With the stock circuit, you can really kick out some watts - 60 to 70 - and the bias will remain super steady over time. I guarantee these will handle any speakers you throw at them. Meanwhile, adding the extra pair will screw up the stability and the entire Ike circuit would need to be changed and tested for stability. Even then, I doubt you would ever be half as stable as the PP circuit and the marginal power increase would still be fraught with less linearity and twice the power consumption, not to mention a tricky biasing scheme. You would need a huge PT, too.

Obviously, this is all about DIY, and I hate to discourage it but that's my two cents. If you had some speakers from hell and needed every last watt, I would suggest another 50 or 100V on your B+ and using KT120s biased aggressively.

Shannon

Thanks so much for your thoughts, Shannon. It sounds like the Ike circuit is better be left alone as is, especially since I have speakers that are efficient enough for a Darling. I think I can now modify my shopping cart at AES for the 5th time. =)

Min

Min,

I agree with Shannon's advice. The stock Eiclone circuit should have sufficient power. I went the PPP route initially and built a prototype. Then the project sat for a few years. The reason is that PPP increases the size and complexity of everything, PT, OT, bias network, etc. It also makes stability harder, although doable if you want to go that route. I still plan to build a pair of PPP Ikes someday.

I built a pair of octal Eiclones about this time last year, and could not be happier with the result. These are awesome amps and I have all the power I need. I'm driving a full range speaker (B&W 802's) and the low end is amazing. These are the best sounding amps I have ever used in my system.

I started off using JJ KT-88s biased at 64ma. Then, over the past winter I used some Tungsol KT-120s biased at 75 ma and then 90 ma. I really like this tube, but at 90 ma my PTs were getting pretty hot. So for the summer, I have a quad of Winged C 6550s biased at 60 ma. Everything I use sounds great.

If you have efficient speakers, the stock circuit will be everything you need and then some. If you still want to do PPP, you can rig a separate bias circuit. See my Ikezilla posts for the bias schematic that I did on my prototype. I used a Maryland Toroid PT that had a bias tap.
http://www.diytube.com/phpBB2/viewtopic.php?t=846

JT

I fully agree with you, JT. Your PPP project was actually what perked my interest. Please keep us posted.
Min