[chadh]

I enjoy listening to music a great deal, but I don't really have a lot of interest in lengthy dispassioned critical listening to evaluate gear.  If I can quickly discern differences between things, then I'm happy to opt for the better sounding gear.  And over the longer term I can often gauge my overall level of satisfaction with the sound, and that can influence my choices. 

Right now I'm interested in deciding whether there is any value in changing the tubes in my pre-amp.  Potentially, the tubes will have a very decided impact on the tonal presentation of the music.  This is important to me.  Usually, it's easy to make quick switches between gear in order to reveal the obvious tonal differences that the gear generates.  But this seems hard with tubes.  You have to wait for tubes to cool in order to pull them out of the pre-amp, and then there's a period during which the new tubes need to warm up.  Given that auditory memory is fairly unreliable, it's not clear that there's much point in doing this.

So, what are the best approaches to assessing the impact of tube rolling experiments?  Is it better just to live with some new tubes for a few weeks and then see how I feel about them?  Is it worth trying direct comparisons between the tubes with the necessary long intermission between tests?  Or do I really need to take a more structured approach to testing?

Chad

[rydenfan]

While auditory memory is short I believe that I have a good general sense of how my system sounds. I can usually tell pretty quickly how a tube change has effected my system. The other option is to take some notes from your favorite test tracks and then compare it to listening to the new tubes. Keep in mind most tubes need 100 hours on them to sound their best.

[BillB]

I tend to swap out tubes pretty quickly, got nice rubby knobby gloves for that purpose but really by the time you shut down everything else they are usually cool enough to handle.

I would take the time to get to know a song really well, one where you know every nuance because you have listened to it so much. For me it is Lou Reed's "Walk on the wild side". I can gauge a tubes performance based on the instrument seperation (nice and simple in this one), the sound of the bass, and the back-up singers...in the second "do doo do" segment if they sound like they are walking toward me and end up practically in my face I know things are good.

Swapping tubes is a good experience, I support buying used lots on Ebay for super cheap until you find what you like. I got lucky with my VTL as it uses a single 12at7 on the output so picking up 15 or so mixed ones for $5 was cake and I ended up with 30+ tubes for about $25-30 invested.

Don't be opposed to trying modern makes and Russian NOS equivilents too...I have really been impressed with the NOS Russian stuff...the price is certainly right and the sound is great.

Oh, another thing I have noted and this is a longterm effect:

If I make a change that I think I like and find weeks later that I have not listened to music and find excuses not to listen then I know the change was not good and I subconsiously know that. It took me a while to realize that was the cause and not just "a phase".

[turkey]

I just hold them up and shake them to see what they sound like.

[CSI]

Good advice about buying tubes in lots if you plan to do a lot of experimenting. Preamps will vary in how they respond to tube swapping but all of them will show an audible change. It won't be very subtle. If you were designing your preamp and wanted to make a change what direction would you go in? Do you want a sound that is brighter? Softer? More laid back? More forward? Clearer on vocals? If you are using your mfg. original tubes they are probably pretty neutral so think in terms of moving away from that. Then talk to a good tube seller for advice. If they know your preamp they can probably help you zero in on a new sound. Even good NOS tubes aren't terribly expensive. If you are running 12AU7's early Mullards can be had for $40 or so (premium grade). Upscale audio is a great source of info - particularly if you have a brand of preamp they carry. Are there published reviews on your preamp? Some professional reviewer may have done some tube rolling during the evaluation of your preamp and will offer his opinions on how alternate tubes changed the sound (see reviews of the Cary SLP-03 and EE Minimax for examples).

[richidoo]

I listen to a tube for a while, then switch to another, then back, each a week or so at a time. I try to notice things I like and things I don't like about each. I don't listen for anything in particular, but just let the ideas come to me. Sometimes a tube sounds good off the bat, but I discover annoying attributes after a while. Also, changing to a lower distortion tube will uncover faults in other parts of the system. A clearer sounding tube is not always the best answer, although it is an opportunity to fix the other parts to achieve higher overall performance. Some people use tubes to add more distortion and cover up problems, while others use them for the potential for low tonal and spatial errors.

Don't put too much faith in other peoples' opinions about a particular tube that you read online. You have to buy the tube, break it in and listen to it in your own system to know anything about it. The same tube will sound different in a different amp circuit. You have to give a tube 50-100 hours before you can judge it. It will sound completely different up and down several times before it finally settles. Some tubes need even longer. My GT E34Ls tubes need 400 hours before they are finally stable.
It's all fun until you realize you're insane, then back to solid state for a while. 

[BillB]

Yeah what he said!

I have definitely found those annoying tributes in the past. When I put Sylvania blackplate 12at7s in the VTL I was stunned by their soundstage and clarity, then later on I realized that they broke up quite easily on anything but acoustic music and they became annoying.

Which goes to show, listen to a variety of music while comparing!!

[rajacat]

Even solid state won't protect you from audio nervosa because you can roll caps and change the sound quality and this too mandates many hours of break-in. At least tubes don't require you to break out the soldering iron.

-Roy

[chadh]

Thanks a bunch for everyone's input on this.

My pre-amp was designed for a pair of 6sl7 tubes.  But when I purchased it, I was anxious to try something that used 6sn7s.  The amp maker insisted that the amp would work with a wide range of octal tubes, including the 6sn7s, and these would give lower gain (which was desirable in my system at the time). 

Well, my super-sensitive chip amp is out of the system now, and I'm using a little 5w SET amp.  Now the extra gain I might get from the 6sl7s in the pre-amp is probably useful for me.  I have the ones that were shipped with the pre-amp (some sort of Russian tubes: labeled 6h9c), but am considering looking for others.  The Russian tubes have been in for a few days.  It's clear that the presentation is different from that with the 6sn7s, but without having a direct comparison it's hard to identify exactly what is different.

Luckily, I don't need to be in a hurry with any of this.

Chad

[twitch54]

Keep in mind most tubes need 100 hours on them to sound their best.

Myself, while I believe in break-in, I don't see that long a time, more like 25-50 hrs...tops, considering most tube gear one buys is run in for a period of time anyways.  But I'm open to better explanation, so please enlighten me what it is inside a tube that takes 100 hrs to sound 'best' ???

[Philistine]

I listen to a tube for a while, then switch to another, then back, each a week or so at a time. I try to notice things I like and things I don't like about each. I don't listen for anything in particular, but just let the ideas come to me. Sometimes a tube sounds good off the bat, but I discover annoying attributes after a while. Also, changing to a lower distortion tube will uncover faults in other parts of the system. A clearer sounding tube is not always the best answer, although it is an opportunity to fix the other parts to achieve higher overall performance. Some people use tubes to add more distortion and cover up problems, while others use them for the potential for low tonal and spatial errors.

Don't put too much faith in other peoples' opinions about a particular tube that you read online. You have to buy the tube, break it in and listen to it in your own system to know anything about it. The same tube will sound different in a different amp circuit. You have to give a tube 50-100 hours before you can judge it. It will sound completely different up and down several times before it finally settles. Some tubes need even longer. My GT E34Ls tubes need 400 hours before they are finally stable.
It's all fun until you realize you're insane, then back to solid state for a while. 

I agree with this, get an instant reaction and then live with them to see if they have any downside.  Think of it as being like a new girlfriend, the first date is new and exciting, but living with them reveals all the personality defects.  The question then is can you live with her long term or not.  Also the newer ones come in nice shiny boxes and can be bright and brash, whereas the older vintages can often perform better.

[Bigfish]

I roll in tubes and typically leave the room for 30 mins. while they warm-up.  I then go back to the room and select one of my favorite tunes and listen.  With listening to that one song I will decide to keep the tubes playing or switch back to the tubes I had just rolled-out.  If I like them enough to keep them in I will keep them in several days and then switch back to my favorite tubes.  I believe it is important to go back to my previous favorite tubes to reestablish that sound comparison and then roll the new tubes back in again.  The thing that is amazing to me is the impact that rolling tubes have on the sound from my system.  It is fun but it can also be frustrating!

Ken

[mjosef]

With tubes, long term (a week or two) listening does it for me. I roll the tubes(s) in listen for a week...after a week or two roll my old tubes back in...I can usually tell by then the differences (if any) I hear.
Lately I have been evaluating a few 12AT7s...I had EH12AT7 in originally, rolling in a NOS tele's I immediately noticed that a slight hum level I had lived with was lower overall. Some things you can tell right away, others may take more time.
YMWV.

[SET Man]

Hey!

   I don't do tube rollin' much. But in my system I usually notice the different right away with both my amp and pre tubes. Well, or at least with those tubes that I've a tried.

   Still... noticing the differences right away is one thing. But is the change better or worse and can I live with that is another story. And this is when a long term or should I say a short term come in of which I will listen to those tube for a few days and than go back to the old one and really see which one I like and could live with.

   Well, in the perfect world tubes of the same type should all sound the same but sadly this is not ture.... so keep on rollin' with those tubes. 

Take care,
Buddy

[Anji12305]

As a recent returnee to the thermionic glow, I have two basic observations about tube rolling and one suggestion.

The heater current varies slightly among tube types, make certain the transformer supply can handle the load.
I have taken under advisement that hot things stabilize in no less than 30 minutes... no hot swapping.

Last; if you have signal tubes operating in tandem (or worse yet as a trio) it is worthwhile to pay a premium for matching services.

I think the best evaluation tools are at your feet...
if your toes are tapping, you're on the right track.

Of course, if you're listening to the Sheffield Drum track or Amanda McBoom - feel free to disregard my simplistic approach.