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Never Owned a Tube Amp and Want Advice

Hi All, 

I have never owned a tube amplifier before and am planning to purchase one with a minimum of 50 watts per channel to mate with 8 ohm 88 dbl speakers.

My hope is experienced audiogoners will share their expertise regarding how to approach this. While I realize listening is the best way to learn about sound and compatibility; I want to learn a better understanding about brands with less maintenance and longer tube life, how to decide between mono or stereo,can a newbie play with bias or is auto biasing a better first choice, etc.

I would also appreciate what to look for in selecting a used tube amp to identify one that might be in need of repair. For example, with solid state depending on the brand, capacitor replacement can be more of a concern. Any advice on what to look out for or ask about with used tube amps would be appreciated.

A big question I have is how to understand the relationship between power tubes like E34's, 120.s, etc. and, I guess the driver? tubes like 12au7's and 12at7's. That  is to ask which is more critical to the overall sound of the amp? FWIW, I routinely tube roll with my preamps.  

I 've read through a number of threads but maybe someone can point me to good ones I may have missed. 

Thanks for listening,

Dsper
dsper
hilde45's avatar
hilde45
5,383 posts
 
FWIW, here's the description of the 60 wpc amps from Quicksilver. Notice the comment about both being able to handle difficult speakers AND also having the finesse of a low powered amplifier. I've put some lovely KT77s in mine, and it's really does a delicate job with much of the acoustic I listen to, but has filled the room easily with orchestral stuff. Speakers are 87db, 8 ohm.

Via Quicksilver:
The new sixty watt amp retains the high damping factor and low distortion of the Horn Mono but with enough power to handle inefficient and difficult to drive speakers. The new power transformer has the same high grade core material as the output transformer. Also a new circuit increases the power tube bias at higher powers allowing the amp to have low distortion all the way up to clipping. At reduced powers this circuit gives the efficiency, finesse and delicacy of a low powered amplifier.

Power Output 60 watts into 4 or 8 ohms
Power Bandwidth 14 Hz to 70 KHz
Damping Factor 20
Input Sensitivity 1.2 volts
Input Impedance 100 Kohm
I.M. Distortion: less than 0.5% at 60 watts
Tube Complement two KT88, 1-12AX7, 1-12BH7
Power Consumption 100 watts at idle 200 watts at full power


larryi
4,285 posts
 
As I've stated above, I am a fan of low-powered tube amps.  I own a pushpull 45 amp, a pushpull 349 amp and a parallel single-ended 2a3 amp.  I like the sound of all of them.  If forced to pick a favorite, it would be the pushpull 349 amp (5.5 watt), followed by the parallel single-ended 2a3 (6.5 watts).  The very best amps I've heard were both very exotic--one is a custom-made output transformerless amp and the other is a pushpull 252 amp (a tube similar to a 300b, but much rarer).  In other words, I would not say that any particular topology is superior to another--there are good examples of each tube amp type.
atmasphere's avatar
atmasphere
12,116 posts
 
Don't run your new tube amp without a load attached as it can destroy the unit.
If the amp is of competent design, *as long as there is no signal at the input* this should be no worries. Our amps do not care about the input and output condition- they are unconditionally stable- you can even pull power tubes out while its playing and the amp acts as if nothing happened.

jjss49's avatar
jjss49
6,612 posts
 
you can even pull power tubes out while its playing and the amp acts as if nothing happened

NOT RECOMMENDED... seriously

might be true for ralph's amps but this is something that is best NEVER to do
gkr7007's avatar
gkr7007
159 posts
 
As long as this is going to be your first I have a couple of recommendations.  The Carver Crimson 275 is rated at 75 watts per.  It will run on 6550's, kt66, kt88, (supplied), and kt120's.  And the amp runs on a circuit that just allows the tubes to cruise along and allows the tubes to have a very long life.  You can put your hands directly on the power tubes on not get burned.  The drivers are 12 xx7 series, (I think 1 12ax7, and 2 12au7.  If you swap out these stock tubes to NOS you will have a giant killer that will drive just about any speaker you throw at it.  Auto bias and you can manually adjust bias to go more or less "tubey" sound.  And heres the kicker....
$2700 or less for new.
Another consideration is Don Sachs Kootenay 120 amp.  Another kt88 based amp.  Great piece.
  
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