2. amps-preamps
  3. 1249244359

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
tholt
tholt OP
547 posts
 
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.
rodman99999
5,988 posts
 
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).
newbee
4,751 posts
 
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.
marakanetz's avatar
marakanetz
5,473 posts
 
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).
rleff
1,065 posts
 
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.
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