A new model:
The Fire Bottle PSE (parallel single ended)
17 watts
Dennis says possible the best amp he has ever heard.

http://s1255.photobucket.com/user/scottybmx1/library/

The last three images.

I still think, other things being equal (i.e., quality of design, implementation and components), single-ended tops any PP configuration, either normal or in parallel. The tradeoffs involve more ease and practicality of use vs absolute sound quality. Of course, the system has to be revealing enough to let you hear the sound quality differences.

I think the clue to best sound at affordable prices still revolves around SET-Triode strapped playing with a good set of sources, speakers and the rest. In fact, Dennis has been promoting the dynamics of Pentodes/Tetrodes strapped as Triodes over traditional "true" SE Triodes, stating the sound quality difference is almost negligible but the result is a higher dynamic ceiling (youtube interview). Just my $0.02.

I have tried just about everything I can think of and my Inspire SE EL84 amp continues to produce a bass-lacking sound. Not totally absent of bass, but sounding like it is down 3 to 4 dB from 150 Hz and on down.

I have used three different 6DJ8-type tubes, including NOS Amperex JAN 6922 and 7308. Five different EL84 tube sets. And three different recitifiers, including the stock 274B and two different 5U4GBs.

I've used three different preamps into it, including a very warm sounding Conrad Johnson PV10A.

I've used it to drive 4 different sets of speakers, from relatively inefficient Spica TC60 & Von Schweikert VM2 small monitors, to 90dB Focal bookshelves to 91dB Von Schweikert tower speakers.

I've listened at several volume levels, but mostly with the average volume level at 75 to 80dB, as measured by an SPL meter at the listening position. which is just 7' from the speakers.

I've evaluated it vs a Korato KVA-20 amp, which is an 18-20 wpc, 6CA7-based, triode-configured design. And an older Cary SLA-30 EL84 amp. The Inspire produces a lot less power, but should have easily handled the volume levels I was using, which required well under 1 watt.

Both of the other amps reproduced lower piano notes with rich harmonics and authority. Through the Inspire they were weak and lacking.

The midrange and highs were quite nice. Good transparency, engaging vocals.

Just today I thought of testing to see if the speaker terminals were wired out of phase. Will test that soon. It kinda sounds like the bass cancellation that one gets with out of phase speakers.

Any other ideas?

Bombadil... Welcome to AA! :wave:

Have you contacted Dennis?

I cannot really enjoy the experience without a SUB in my system. I use floor-standing speakers and that is not enough for effective bass reproduction. IME the weakest the amplifier, the less it is capable of reproducing lower frequencies as these demand lots of power, relatively speaking. The crossover setting advantage of using an active SUB improves the overall performance of the Inspire amp driving higher than 100 Hz frequencies. It is a matter defined by physics. YMMV

Totally agree with this approach.

Bombadil: Welcome to AA. (I’m relatively new here myself.)

Let me begin by saying that I’m not an expert – however I own a number of amps installed in multiple systems, so I have some experience tinkering around.

As you probably know, speaker sensitivity is specified based on a logarithmic scale. There’s a significant different between speakers rated at 91dB vs. 101dB (like my Klipsch RF-7 II). (My understanding is that 91dB speakers would require 10 times the power compared with speakers rated at 101dB in order to produce the same sound pressure level.) And, a few published specs like sensitivity and impedance don’t fully predict how speakers will interact with a particular amp. As I said earlier, IME the Inspire single-ended-pentode amp can be finicky about speaker synergy. My Inspire amp does not work well with my Klipsch Palladium rated at 96dB, 4 ohm. (Or my Snell Type CV that are rated at 90dB.)

My Inspire “Fire Bottle” SE Stereo Tube Amplifier HO when equipped with 6L6GC, 5AR4, and 6DJ8 reportedly puts out approximately 10wpc. Am I correct that’s probably twice what your Inspire EL84 amp produces?

This afternoon I listened to Bach Suite for Cello No. 6 BWV 1012 via my Inspire amp and Klipsch RF-7 II (101dB, 8 ohm, 2 way). And then I listened to Liszt’s piano transcription of Isolde’s Liebestod from Wagner’s Tristan und Isolde, which involves powerful lower piano notes. The audio quality was excellent – with no lack of richness or bass. (However, to be honest, I sometimes think that piano music is better served by a powerful solid state amp, due to the sometimes sharp “attack” of piano notes.) Subsequently, when listening to these same recordings but employing my Oppo player’s crossover and redirecting the low freqs to a 15” powered subwoofer, there was as much powerful bass as anyone could reasonably want from this music. (OTOH, for large scale symphonic music my Inspire / RF-7 /15” subwoofer delivers good sound quality – but not the dynamics of a push-pull KT88 amp that delivers six times the power.)

Bottom line, my Inspire hi-fi configuration will differ significantly in perceived “power” from a system that involves a 5wpc amp, lacks a crossover to off-load low frequencies to a subwoofer, and drives speakers that are rated at 91dB. FWIW, my understanding is that most audiophiles who use “flea power” (< 5wpc) amps use something like Klipschorn or La Scala (105dB sensitivity) – or other “tube friendly” speakers - and often employ a crossover to off-load deep bass to a subwoofer. And/or they’re listening to simple music that has little dynamic range and little bass (such as a folk singer / acoustic guitar), and/or their listening position is a few feet from the speakers, and/or they listen at low volume levels.

nhparrot probably had the best advice (and was a lot more succinct than my ramble): Ask Dennis. :)

I hope you get your system sorted out the way you want. Please keep us posted.

Based on recommendations from Simon, Peter and others, I picked up a pair of EL84 tubes and socket adapters. Will be swapping them in today to give them a test drive in my system.