I would start here:http://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html#12AX7
This will give you a good idea of what to try. This is considered the de facto piece for tube rolling.
Also, some NOS tubes are very expensive. You may end up paying a lot for this fun.
Get the lowest noise tubes you can afford, especially for the phono stage. Your priority should be to locate reputable dealers, then look at their stock. Don't necessarily focus on the name brand. A properly tested tube with excellent test specs will make a big difference. People like Andy at Vintage Tube Services and Roger Modjeski at RAM Labs are great places to start. They are the only two people I'll deal with.
I'll add be sure to buy from a reputable person or dealer. If you plan to do lot of tube rolling you might consider a tube tester. The most important thing is to make sure your tube doesn't have a short. Most testers should be able to test for shorts, even an inexpensive one.
- Should I A-B test different tubes, swapping in/out quickly?
1 - I would not swap tubes quickly especially NEW/NOS because I have found they need a couple of hundred hrs to break in.
Can I mix & match brands, or NOS vs. New etc...?
2 - If you can manually adjust the bias you should be OK BUT I would not mix brands (although it may produce some interesting results). I have found different brands of the same tube types have their own distinct sound.
Should I start from source and move downstream (ph-stage, Line stage,... power amp) or vice versa?
3 - I have an integrated amp so I have no experience here
Get VERY familiar with the sound of your pre-amp with stock tubes. Make notes of the areas that you would like improve i.e. more impactful bass, extended highs etc. Once you have a list of attributes that you wish to improve, research for a tube that exhibit said traits or post on this forum for tubes suggestion i.e. looking for a 12AX7 with extended highs etc. When searching for NOS tubes you must have a game plan and an objective, otherwise it becomes an expensive guessing game.
Thank you mofimadness for that link. That is a great article. My experince with NOS Amperex 6dj8's in my phono section mirror the comments in his article. A lot of good info in the world of NOS preamp tubes.
Thanks for the tips.
BRF, I know what I want, extended bass and more dynamics. I have already been lining up some reference recordings that I have been listening to for a while.
I have already purchased a pair of telefunken 12AX7's so that will be the starting point. I realized after purchasing them that the SP-16 has 3 tubes in the phono section. And I spoke with ARC and they suggested to leave in the stock tube at the input as it must be low noise. I also wasn't aware that there was a low-noise so I have no way of knowing if the telefunken are or not (other than trying them out).
Knowing the above, next time I will buy my tubes from someone sepcialized in tubes, as recommended.
As for the Mofi's Audioasylum link, it was very informative, but I am not sure I ready to switch to 5751's.
Other respectable tube suppierls are : tubemonegr; Tube depot & brent jesse - you can get good NOS tubes w/o spending a fortune
Be careful pulling out and inserting tubes so you don't mash the tiny plug in the ceramic tube holder
If I want to improve the dynamics of the system is the pre-amp the best place to start?
A while back I upgraded the output tubes of my Mid-monos to KT88s. This did wonders for dynamics, no doubt as a result of the increase in power.
Would upgrading the input tubes (12ax7) of the power amps provide a bigger improvement (in terms of dynamics) than upgrading the phono stage of the pre?
My first experience with NOS tubes has not been great.
For simplicity reasons, I started out by swapping my input tubes on my power-amps (Quicksilver Mid-Monos) with the pair of Telefunken 12ax7s. It sounded great, it tighten the bass and added definition to the imaging of the individdual instruments within the sound stage.
During my second listening session, less than 4hours total I lost the left channel. I let things cool down for a few hours swapped back the old tubes and voila! We were back up and running. Clearly a faulty not so New NOS tube.
Luckily the audio shop agreed to exchange it.
"Would upgrading the input tubes (12ax7) of the power amps provide a bigger improvement (in terms of dynamics) than upgrading the phono stage of the pre?
Nick sr, I think thats almost impossible to determine in advance. I can tell you that the potential for improvement by changing the 12ax7s can be huge. Call a reputable pro who guarantees satisfaction with a credit/swap policy. Ive been most satisfied with Andy at "Vintage Tube Services" and Brent Jessee. Both stand behind their tubes and offer excellent advise. I cant imagine your regretting the calls.
FWIW, I bought my 12ax7s from Brent Jessee.http://vintagetubeservices.com/http://www.audiotubes.com/12ax7.htm
I brought the Tele's back to the store and they tested them, and they tested fine(?) 1100 microhms.
Regardless they exchanged them without question, so I took a pair of PSVANE 12AX7-Ts, plus some cash back.
Is this normal that a tube could test well and then be none functional when installed in the amp?
Phaelon, I checked the VTS site, it is fully very interesting information. It seems that the Tele's I had may have come from VTS as they were marked with a little red spot of paint on the top of the tube.
I am rollin' on. I will be listening to the PSvanes this weekend in the power amps.