2. amps-preamps
  3. 147225-115924

Tube Rolling for Pre-amps?

I have an Audio Research LS-16 that feeds a Madrigal Proceed HPA2 solid state amp. 

I did not choose this equipment; it was given to me. From what I can tell the original owner spent a good bit of time matching up these two components with the speakers, Aerial Acoustics 7Bs.

The tubes in the AR are original. Probably 10-15 years old? But with an extended period of not being used.

The system sounds good to me. I don't need to change anything.

However, I've been told that the tubes are old and may need to be replaced soon. I've also read a little bit about tube rolling but most of the articles I've seen talk mostly about tube rolling with amps and not pre-amps.

So I have some questions:

1) If the original owner wanted a system that sounded like a 'tube' system, why not have a tube amp and pre-amp? Does it make sense to have a tube pre but SS amp?

2) Other than outright failure, how will I know if my tubes _need_ to be replaced?

3) With a SS amp, will changing tubes in the pre-amp have a noticeable impact on SQ? In other words, is tube rolling for a pre-amp played through a SS amp a thing?

4) For someone like myself who is happy with the system and who is also easily frustrated by A/B testing is tube rolling the pre-amp even worthwhile? I can almost always hear a change when comparing various components but only rarely am able to say A is better or worse than B.

( I probably can't even articulate effectively what I look for in terms of SQ except that I like the bass to be tight, precise, well defined and not boomy. I do not like the music to be overly bright or tinny. I like depth and lushness but not overly warm. Not sure if these are things you alter with tubes.)

Thanks for any advice.


n80
djohnson54
396 posts
 
@n80 As a person with a tube preamp and a SS amp, I'll share my 2 cents.
  1. Many prefer to have both a tube preamp and a tube amp.  You get the full effect of the tube sound that way (depending on the equipment as some are more "tubey" than others).  However, tubes in a power amp wear much more quickly than preamp tubes and tend to fail more catastrophically than preamp tubes - possibly taking out resistors in the process.  You should be able to get between 5,000 and 10,000 hours from preamp tubes (again, depending on the equipment).
  2. Preamp tubes tend to get noisy before outright failure.  Right now I have a tube in the left channel of my preamp (BAT VK-3i) that sputters a little as it's warming up.  I've got a new set but haven't pulled the preamp out of the rack to replace them yet.  I looked when I ordered the replacements and the last set I bought was in 2012 but I'm not sure of the hours.  Of course if you know someone with a tube tester you could get them to check your tubes. :)
  3. In general, different preamp tubes DO change the sound but not as much as tubes in power amps.  Preamp tube rolling (SS amp or not) is definitely a thing with some people (who have more money than me!).
  4. I would say that, given your description of yourself, it's not worthwhile to just swap tubes.  However, when it's time to replace those tubes, check with folks here to identify the current helpful/honest tube sellers out there and consult with one or more of them.  If you explain what you're after soundwise, my experience is that they will be more than happy to make recommendations within your budget.
Dick
bsimpson
167 posts
 
I'd love Roger Modjeski or Kevin Hayes to chat here.

Kevin Deal @ Upscale Audio too.

Best audiophile reality TV show you could get.   
lowrider57's avatar
lowrider57
5,411 posts
 
I'll add to @djohnson54 comments. I'm an avid tube roller. At one time I was addicted to rolling NOS preamp tubes when I had a SS amp. 
Depending on the design of the preamp, rolling in a different brand or style of tube can make a significant difference to the overall sonics of a system. Characteristics such as dynamics, transparency, soundstage can all be affected. Many audioholics change tubes to take the edge off the highs, or conversely to add extension and "air."  The caveat is that the amp will play a role in how much of a change in sonics you hear. Your SS amp must be revealing enough to hear the changes from the preamp. But you will hear a difference in preamp SQ or sound signature.

Preamp tubes do last a long time; thousands of hours if purchased from a reputable dealer. A dying tube can become noisy or microphonic. But IME, you can tell when a tube has reached its life expectancy when your music begins to sound dull. There may be less extension, a flat image, or less colour or drive to the music.

I'm a firm believer in having a set of spare tubes on hand. For this reason maybe you should start shopping for a replacement set.


whart's avatar
whart
3,022 posts
 
Small tubes often don't fail dramatically in the same way that amp power tubes can- but they will lose their high frequency extension and punch over time. It's almost like a new pair of sneakers- more bounce. 
I'm not sure it is worth getting carried away with expensive NOS tubes in your preamp- look at the complement- are they 6Dj8? (that was pretty common then), and there are many types and manufacturers. Obviously, you won't know what the tubes sound like til you hear them in your unit and system. I'd refresh them for sure, but am not up on current production tubes. 
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