2. amps-preamps
  3. 140541-4358

Carver Crimson 275 tube amp

I have searched for owners' impressions of this amp, but have found none.  I have never owned a Carver component, but have always admired his genius.  I would like to pair a tube amp with my Spatial Audio M3 Triode Masters and recently heard Don Sachs Kootenay KT88 amp, along his bespoke preamp, and was extremely impressed.  Compared to my Platinum-upgraded McCormack DNA .05 ss amp, the sound was even more fleshed out and 3-dimensional.  The SQ difference was far from subtle... and I loved it.   

I was clear with Jim Clark when I ordered the amp that the comparison of the Crimson 275 would be to the Kootenay so if I don't think it is the equal of it, I will return it.  Stay tuned for my listening impressions in a couple of weeks.  
whitestix
mrdecibel
3,162 posts
 
The biasing is explained in the owners manual ( can be found on d2girls thread ) A tube amp for my JBL 4367s.
whitestix OP
733 posts
 
Thanks for the reference, shown below.  I don't doubt that the Crimson would be a good mate for your JBL speakers!  For me, personally, a tube amp without auto-biasing is non-starter.  Tiny screwdrivers and a power-up amplifier are the not the way I roll anymore.  Cheers. 
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ADJUSTING THE OUTPUT TUBE BIAS ON THE CRIMSON 275

The front panel incorporates a bias meter. Turn the preamp volume control all the way down while performing bias adjustments. Use a small screwdriver and adjust the bias control (located on the rear of the amplifier) for 80 mA after the unit has warmed up for about 20 minutes. The normal range to use is from 60 mA to 120 mA, and changes here will vary the damping factor of the amplifier slightly. More current increases the damping factor, whereas less current provides a softer more tube-like sound. The design center is 100 mA, and that should be your starting point if you want to experiment. Personally, I found that I loved the sound best on my speakers when I had it set for their design center of 80 mA. It will vary from speaker to speaker, and most importantly with your taste.

The meter reads the combined current for all four output tubes, and it is normal for this current to vary slightly with changes in power line voltage.


jimclarkstereo
38 posts
 
A question to Jim Clark. It is not clear how the biasing function on the Crimson unit works.   I am guessing that one would not need a voltmeter for biasing, but it doesn't appear as though it has auto-biasing.  

Can you explain the biasing procedure?   Thanks.

The proceeder above is correct. Generally the bias is set close from when the amp was ran during burn in. After the amp warms up for a few minutes adjust as needed. Double check in 20 minutes. Personally I set them on 80 mA.. No meter is needed. The front panel meter read bias.

After this start up, you won't need to adjust bias again for years, unless you just want to experiment. The 350s use a similar circuit. I have ran those over 2 years, almost every day, without need to adjust bias. 

Really about as painless as solid state.
whitestix OP
733 posts
 
Great to learn that the bias setting in not much vary over time.   How do you actually do the biasing.... does it entail using a small screwdriver to adjust a potentiometer, confirming the correct mA setting on the meter on the front.  If so, where are the potentiometer located?  On the top of the amp or on the back.  Is it done sequentially for each power tube?  That is what I am getting at.  Thanks. 
jimclarkstereo
38 posts
 
Thanks for the question. There is a single potentiometer on the back panel. It has a slot for a small standard screwdriver. You adjust it and read the meter on the front panel.. After that, it will repeat the same bias setting each time you use it for years. It could vary with incoming line voltage, but that is normally very minimal. Basically, set it and forget it.  
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