Can you lower gain requirements on tube amp?

I have a Cary Rocket 88R tube amp (30w tri/60w UL) that requires more gain then I'm used to to get to 'realistic' (ie louder) listening levels (90db+). I have a Promitheus Ref4 TVC passive that I love, but volume knobs at full throttle sometimes still isn't loud enough. I literally need it go to 11.

Specs on the TVC state -48db to 0. I'm curious if I can do something to the amp, ie roll different driver tubes or??.... to decrease the gain requirements? I've also contacted Nicholas at Promitheus to see if he can modify the gain, haven't heard back yet.

I will also state that my speakers are Usher 6381 rated at 87db/8 ohm. The Cary drives them well, but wondering if the speakers sensitivity relates to loudness (ie more sensitive speakers would generate more loudness at the same volume settings?)

I don't want to introduce a tubed buffer into the mix -- tried it and didn't like the sound. Want to work with what I have if possible. Thanks

FYI tubes in the Cary are:
kt-88 output
12BZ7 / 12AX7 / 12AY7 drivers (currently using 12BZ7)
EL-84 / 6BQ5 current source
2 other things -- I like to run in triode over UL, though UL gives me a 2db boost. Also, does voltage into the TVC affect volume? ie if I had a source with higher output would it increase volume? My current cd player is rated at 2V, +/-3dB output.
You can buy a different amp with lower input sensitivity. You can't change the Cary to get higher output other than the triode/UL option afforded. KT88's are high output tubes so rolling them won't make much or any difference.

You can buy an active pre-amp and get units with up to about 26db of gain which would be plenty.

You can get a CDP/DAC with high gain output (my Wadia had 2, 4 & 6db options).

Other than that about the only thing I can think of would be a possible problem with the passive set up, ie. using inappropriate IC's (too long or electrical values) but I doubt that this is your problem as that would be more frequency dependent than broadband unless they were really long!

But, FWIW, something just doesn't seem right to me about this 'problem'. It is almost as if something is damping your system down. With 87db speakers and 60wts you should be getting some very loud sounds even without pre-amp gain added. Are you using more than one pair of outputs from the 'preamp'? Some pre-s have two outputs which do no act independently of each other and create an additional load on the line out and can greatly reduce the pre-amp out put.

Anyway, that's all I know. Hope it helps a but.
Your only option, if you want to continue using the equipment mentioned, is to up the output voltage of your source(which you didn't mention). Do you find that some of your recorded material provides adequate SPLs? There's a wide disparity in recording levels between various labels/engineers, and that will affect what reaches the Cary's inputs. The output of the Rocket 88 isn't really enough to drive an 87db system to what I'd consider high SPLs anyway. I owned one(tried it with a Placette Passive Linestage) and, if they could be easily converted to higher powered monoblocks: I'd have a pair.
Agree with Rodman, You're obviously underdriving your speakers. Neither UL or triode will do the right trick in your situation.
Thanks so far.

Newbee/Rodman -- are you suggesting that a source with higher voltage will produce more gain at the amp end? My cdp is rated at 2V, +/-3dB output. To answer your question: yes, much of my recorded material does provide adequate SPL's, albeit at close to or at the volume knobs wide open.

The Cary's input sensitivity is 1.2V for full output.

Sounds like some of you are suggesting that the speaker load is also contributing to the lack of loudness, I would concur with that. However, the sound is very full, not missing anything and this coming from after using 160w class D amps. I prefer the Cary. My listening space is roughly 10' x 15' x 12' -- an area within a larger open space but still I would consider small/med size, which helps. And with other preamps with either more gain or active, I am able to achieve all the volume I need. I just prefer the TVC, hence the thread.
Hi Tholt- Your CDP's voltage output depends on the recording level of the disc being played. Some aren't putting out enough to adequately drive your system. I REALLY enjoyed my Placette Passive with certain discs. Others just didn't get it. That's why most listeners employ preamps rather than passive linestages or attenuators. Many sources need the gain that a preamplifier provides to satisfy the listener's SPL appetite. YES- More sensitive speakers would compensate for the lowered system output levels of those recordings(they'd play louder with same wattage).
Tholt, re DAC/CDP output voltage - I am presently running 4 digital sources. One with 2v, one with 2.2v, one with 3.5v and the latter varible at 2,4 & 6v. I have never measured the difference in db's at the speaker between each output level so this is a WAG, but I think the increase from 2 to 3.5v (or 4v) would be at least 9 or more db's. On the Wadia I would use either the 4 or 6v setting to drive the amp direct. This has nothing to do with recording level on the CD although that can vary at times. But, FWIW, personally I prefer to run my Wadia thru an active lines stage as well and I use the 2v setting.

BTW, also IMHO, I think amps with a .5v imput sensitivity are far more compatable with passive line stages, and interestingly less so when used with high gain active line pre-amps. Thats how its has worked out for me anyway.
I have SS Sunfire Symphonic reference amp with 1.2V input sensitivity. Virtually there's no way that it will sound right with passive preamplification.
When I used to have VTL MB100, they will sound at their best either with unity gain active preamp or passive(.7V input sensitivity).
Did you talk with Dennis at Cary;maybe he can mod your amp to handle the input voltage swing that your preamp is outputing to the Cary's.
Dump the TVC for a true active preamp with good impedance specs. That will solve it the fastest, and probably cheapest at this point, plus add some missing dynamics and body which is why your looking to do this all in the first place!

Good luck
I have never measured the difference in db's at the speaker between each output level so this is a WAG, but I think the increase from 2 to 3.5v (or 4v) would be at least 9 or more db's.
Doubling the voltage is an increase of 6dB.
It is often said that a good rule of thumb for putting db volume changes in perspective is that a 10db increase subjectively sounds "twice as loud."

It is also important to keep in mind that the subjective perception of loudness is highly dependent on the dynamic range of the particular piece of music. A classical symphony, for instance, typically covers an enormous decibel range, from the soft passages (which typically comprise most of the music) to orchestral peaks. That will result in a given volume control setting producing a much lower subjective perception of loudness than the same setting would produce on highly compressed material (that maintains a fairly constant volume), such as many popular releases.

Re voltage increase vs. db increase, Kirkus is of course correct, but I'll add that the formula to convert the ratio of two voltages to db is 20*log(v1/v2), where v1 is one of the voltages, v2 is the other, the asterisk denotes multiplication, and "log" is logarithm (base-10). If you put the smaller number on top you will get a negative result; if you put the larger number on top you will get the same answer but with a positive sign.

To convert two power levels to db, the formula would be 10*log(P1/P2).

A given db change anywhere in the path through the system will produce the same resultant volume change, whether it is output voltage, input sensitivity, or speaker efficiency. Assuming, of course, that nothing is clipped or overdriven as a result.

-- Al
Well it sounded like 9db's! :-)

Thanks Almarg for the info. I just never thought that db's and v's might share the same relationships. Makes sense though...........when I THINK about it.