Happy new year all!
How about some output rolling QnA ...
- When choosing outputs, my amp (which is similar/ same-enough as several others out there) can handle 4 or 6 of 6B(LX)7s. Is it purely preference (in the sound) based? Is there any reason to prefer more or less for any other technical reason?
- Same story for 6080s. I know @mordy you like 4x 6080s (part of your "platform"), and recently @JazzVinyl also had 4x 6080s, but were heating externally. Given the amp can handle the sum of the amperes per tube (I believe my amp is ~13A max), why heat externally?
- There was also some dialogue back a while about running 4x Bendix 6080s (they will be hot) and a suggestion of at least using socket savers to "protect the amp". There was perhaps a suggestion that the whole enterprise was best avoided (even though they fit into the same sum-of-amps acceptability). Was this just a temperature issue? If so - is the goal to protect the amp itself from the raw heat? There were comments like "blow up the amp" that seemed worth understanding better!
- Depending on the amplification factor, the volume will be in various ranges on the dial (i.e.; low like 7-9:00, or near 12:00, or > 12:00). Is there any reason to care about this aside from volume dial precision? I mostly care for output rolling presently, but I don't think the answer to this is limited to caring about output tubes.
OK, that is enough amp-query for now!
Hi cd,
Interesting that you are concentrating on output rolling. There is a huge debate about how much impact the output tubes have on sound - 20%?, 50%? etc. I would avoid answering that question by saying that it is a question of synergy; for sure the output tubes play a very significant role re the sound. On the other hand, once I have found a combination I like, I mainly concentrate on driver tube rolling, but at times different drivers may need a change in output tubes to sound their best.
Re 4 or 6 6BL/X7: There are two factors involved: sound, and noise. The 6BLX7 tubes have a high amplification factor and in certain combinations the background noise and compatibility can be affected by using 4 or 6 tubes.
Re using 4x6080: To some it may sound like overkill since one pair supplies enough power. However, personally I have found that 4x6080 suits me better because it sounds better to me with a more filled out sound. I use a Bendix type graphite tube for slam and impact, and a RCA for warmth and mid bass. I think JV uses Sylvania/Mullard. These tubes definitely run hot. I also reduce the heat to the chassis by using socket savers which act as insulators. Than I use two small fans (3-4") to further lower the temperature. The amp should not go above 80C; with one fan it reaches around 45C and with two around 33C (some variations depending on ambient room temperature and tubes used).
Heat is the main enemy of electronics.
Re JV's use of external power I think it is an issue of having a quieter background - JV has to weigh in on this.
Re the volume, different tubes and tube combinations affect the volume. Recently i added a set of TFK EL11 to the pair of 6J5 drivers, and the volume went down a little. As far as I know, as long as the amp produces enough volume for what you need and there is no distortion, I don't think that it matters.
There is another debate whether a tube amp sounds better at high volume than at low volume, and some people try to adjust their sources so that the tube amp runs at high volume. Don't know the answer to this question. Personally, I use my GOTL mainly as a preamp, and by fiddling with the volume controls on my preamp and the GOTL I try to achieve a setting that produces the least background noise. Usually what works best for me is a volume setting around 9-10 0'clock on both the preamp and the GOTL.
I think that in the past Glenn was worried about running so many tubes at near the 13A capacity in the GOTL. However, he had told me that by adding external cooling you could go up to 14A. The most I have used is 12.4A and after extended use this seems perfectly safe using socket savers and fan cooling.
Disclaimer: All the above are my personal opinions; I don't have the electronic knowledge to verify this scientifically - all is based on use and personal observations.
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