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

Showing 3 responses by newbee

newbee
4,751 posts
 
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.
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.
newbee
4,751 posts
 
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.
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