what power tubes are you using in the Shanglings? I don't own your amps, but have been using EH 6CA7 output tubes with great success. They still have the fantastic midrange of an EL34, but bring some of the KT dynamics and improved bass. On top of that, they are very inexpensive.
Regarding your question to replace preamp: I find an octal tube based preamp provides superior frequency response and dynamics that a miniature nine-pin cannot touch. So you might want to consider keeping your existing preamp.
You bought the wrong tube amps, if good bass reproduction was a goal. Get something with some bigger transformers...a KT-88 based design.
Or, if your in love with your amps...try subwoofers.
also see if you can back your speakers a bit more into the corners or against the wall - might get them to load up a bit that way
Thanks so far
jalapenos - yes i do think the EL34 advantage in mids is essential. I'll try and roll in some EH 6CA7's. Also will try to load my speakers with ledshot or dry sand to tighten the bass.
All I could find doing a quick search was that the Ushers are 4 ohm nominal. That could translate into well below 4 ohms and could explain the weak bass and perhaps truncated highs as well. Most likely, you have a poor amp and speaker match and might have to decide which you like more and get rid of the other.
I would attach the speakers to the 8 ohm tap and then the 4 ohm taps. If the 4 ohm taps improved the sound, but still sorely lacking in bass, I would ditch the amps or the speakers, or at least consider that they aren't going to play well together.
If you cannot move your speakers nearer your front wall and/or add a subwoofer, you may want to try a more powerful tube amp whose output impedance is lower, or better yet, for good bass, a solid-state amp may be the best bet. You may not like the rest of the presentation of the SS amp, but for bass, it probably will outmuscle most tube amps.
These speakers were voiced with class A solid state amplification and are capable of amazing bass slam and authority. Suggest ditching your amps and getting an Usher 1.5 amp if you like the speakers. Keep the tube preamp. I heard them at RMAF 2006 and was extremely impressed. BTW, I am basically a tube guy.
I had the same issue with my Manley Stingray and a power cord from DCCA placed on my Cary cdp solved the problem.
Started with Don's Source pc which did a good job and now I'm using his Ref 1 on the Cary and honestly, the bass couldn't be better.
Just my 2 cents.
Presumably the woofers on the Ushers are wired in parallel, so the impedance is lower at low frequencies than in the treble region. Maybe only one woofer goes up to meet the tweeter.
At any rate, a solid state voltage-source-approximating amplifier will deliver double the wattage into a 4 ohm load as into an 8 ohm load. The speakers were designed with this expectation in mind. On the other hand, a tube amp is less likely to approximate a voltage source, and therefore less likely to deliver the increased power output into low impedances that the speaker was designed to take advantage of. So in the region where the two woofers are operating in parallel, the net output with that amplifier is less than the speaker's designer intended. The result is weak bass.
That's my guess, anyway.
YOur tube pre (or CD player) may have inverted polarity/phase. Meaning you need to switch the +/- speaker leads at the speakers
Icorem: Just for the hell of it, I replaced (only for a short period) my PrimaLuna 6 monobocks (70wpc) with my old acurus a150 solid state amp (150 wpc) just to see what the difference would be. Besides the obvious immediate differences, I noticed the biggest change in the sound was the lack of bass the a150 had compared to the tube monoblocs.
food for thought. good luck.
Thanks for all comments so far.
I definately want to keep my tube amps for their overall advantage (to my taste - is it). I will try some of your suggestions and see if there is any improvement.
I will try playing with speaker positioning although my listening room structure is problematic.
Icorem, I own Esound CD-E5 and Dussun V8i int amp and thinking about picking up a pair of Shanling SP-80. Speaker is IRS Sigma (200 lb 3 way with ribbon mid range and tweeters). I bought Usher Be-718 Tiny Dancer on impulse hooked to Usher R1.5 but just sold it. Isn't bass strength of Esound CD-E5? Would you say CD-E5 and SP-80 was good combo for classical music? Thanks in advance.
I owned a pair of Usher 6311 and tested them with various amps : for me they are not an easy load and do not match well with tube amps.
I achieved very good results with Nuforce amps / ModWright pre.