Quote:
Originally Posted by david45
Analog Addict,
Thanks for posting pictures of these OB speakers. Considering the extra woofer and the 3db boost in terms of sensitivity, just how efficient are they and how low can they play?
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If I recall correctly, they are in the 92-94 db/w/m range and they go down to 40-45 Hz. I have never really found them lacking in the bass dept, although that may be a function of Dennis' listening room
Quote:
Originally Posted by david45
I am really surprised that a 300b amplifier with only 8 watts per channel can work so well in my system and it makes me wonder if a 45 PSE and its glorious 3.5 watts could be an even better fit especially if it is being hi-passed (?). Could it also benefit from the IIPS mod?
I realize that Denis still isn't offering his own version of your amplifier and that you recommend speakers that are 100db efficient or even higher, but I am intrigued nevertheless.
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Considering that you say that the meter isn't going much over 1 watt, even a 2 watt 45 SET amp may drive your speakers without strain, but I really am now a believer in the extra depth, richness and oomph the 45 PSE configuration adds. The IIPS is basically a voltage regulation scheme, and if I understand correctly, really shines in beam tetrode or pentode power tube applications where the rock steady voltage benefits the conversion to single ended output. (Dennis may correct me on this one) I do use voltage regulation on the driver tubes, but the Glo tubes don't have enough current capacity to handle regulating the power tubes.
Don't get me wrong, the PSE45 sounds amazing on the Inspire OB speakers, but I tend to run extremely high efficiency speakers because I love the sound of 50 year and older Altecs or Khorns, and the horn taming effects of highly engineered toob amps. I've tried to foist a pair of A7s off on Dennis for as long as he wants them, but they are too big (and possibly too ugly) for his shop.
Quote:
Originally Posted by david45
It's been a few months since your first listening session of the kt77 PSE prototype in triode and I also wonder how things are evolving as this is also right up my alley especially if it can be dialed-in to provide a maximum of mid-range magic similar to a 2a3-300b-45 amplifier but at affordable output tube prices.
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Heh, the problem with me commenting on the KT77 PSE prototype is that nothing ever seems to stay around the shop long enuff for me to really get familiar with the sound. Either it gets sold off, or it gets reworked to something else. I have heard a number of similar amps since then, and they are always very impressive, but to my ears they just don't have quite the same magic in the mid range, the honey that just drips out of the speakers when all is in alignment. In my mind, the magic really lives inside the tube, and the real art to amp designing and building is to figure out the best way to let the magic shine through. Dennis and I are in basic agreement in that the amplifier circuit/signal path should generally be made as simple as possible with a minimum number of high quality components. The complicated part of any design and build is getting the power supply as robust and clean as possible. Then with no limitations on them created by current or voltage fluctuations, or noise/distortion getting in the way, you just stand back and let the tubes do their thing.
Dennis is pragmatically handicapped by the fact that he builds in much greater volume than I do, so he has to use tubes that are one, consistent in their sound and build quality, and two, are available in enough quantity that he doesn't spend all his time trying to chase down enough tubes to properly outfit the number of amps that roll off the line. So that being said, I also have a love affair with old dusty triodes, so much so that I am going with this cockamamie 71-A build I've been planning.
Quote:
Originally Posted by david45
I am also considering a triode strapped amp built on the 45 chassis with 20 watts transformers and IIPS along with a pre just like Florida Boy and Musica Amantem.
Also in the cards would be to fly to North Carolina and stop by Cary for a listening session if that is a possibility that could help me make up my mind. 
Cheers,
David |
By all means, you should come to Cary NC and really see what all the fuss is about. A trip to the shop would be like a pilgrimage to Mecca for anyone who has ever heard an Inspire amp and loved the sound. If you manage to schedule a visit, I would be happy to take the PSE 45 over to the shop and let you have a listen to it as well. The Inspire speakers are also well worth hearing.
And for anyone who hasn't figgered it out, I was being sarcastic about the OB design not working with Inspire amps. Dennis would have never put the Inspire logo on the speakers if they didn't live up to his exacting quality and performance standards.
Oh yeah, before I forget, a certain radioman731 has put a brand new 2A3 amp up on E-bay for one lucky discerning consumer. Get it while it's hot!!!