Wolcott Audio tube amp:
http://www.wolcottaudio.com/WA_Pres_why.htm
http://www.wolcottaudio.com/WA_Pres_specs.htm
Best tube amp?
http://www.wolcottaudio.com/WA_Pres_why.htm
http://www.wolcottaudio.com/WA_Pres_specs.htm
Best tube amp?
Which watts are the right watts in SS amps?
Wolcott Audio tube amp: http://www.wolcottaudio.com/WA_Pres_why.htm http://www.wolcottaudio.com/WA_Pres_specs.htm Best tube amp? |
I'm not sure I've ever seen any transformer coupled amp show damping over 100 into 8 ohm. I'm also not convinced that the drawbacks of feedback are so bad it should be completely avoided. I feel like thats a knee jerk reaction like many people have about guns. It's just a tool to be used.The thing about feedback is there are more variables than the formula taught in school! You have to deal with RFI being injected into the amp via the speaker cables (and most designs don't...) and the amp has to have sufficient phase margins prior to application of the feedback... here is a great article about how to apply feedback properly: http://www.normankoren.com/Audio/FeedbackFidelity.html Since feedback is rarely applied with this sort of care, its incorrect to say that eschewing it is a 'knee jerk' reaction. Its misapplication is audible! With regards to speakers, there is never a need for 100:1 (or more) damping; almost any speaker made is overdamped with a damping factor that high. Here is another great article that despite its age has stood the test of time, written by the head engineer of Electro Voice: http://www.dissident-audio.com/Loudspeakers/CriticalLSDamping.pdf Note that at the time of this article, there were speakers that needed far less damping than even 5:1, and there are still speakers around today that barely need that or even less (as an example, Nelson Pass demonstrated a small yet very impressive open baffle speaker at RMAF about 10 years ago that was driven by a current source amplifier, so the damping factor in that system was less than 1:10 and you did read 1:10 correctly, yet it played bass quite well). It was Electro Voice and MacIntosh that led the way in championing the idea that the amplifier should be a voltage source and the speaker voltage-driven, back in the late 1950s and into the 1960s. But the simple fact is that this model simply did not and does not encompass all speakers and speaker technologies (any speaker that does not employ a cabinet would be an example, as well as many speakers that do have cabinets..). In addition, all amplifiers that are capable of acting as a voltage source are push-pull, and such amps (with rare exception) have distortion characteristics wherein the distortion actually **increases** below a certain minimum power level, typically about 5-7% of full power. So if you use a speaker that is too efficient for the amp, you will not be getting the best sound out of it. The voltage model is intended to eliminate equipment matching issues, and if you are only interested in box store mid fi, none of this is a problem. But in high end audio there is quite a bit of diversity such as planar speakers, horns, full range devices as well as more conventional designs, SETs, OTLs, class A, class D, etc. because everyone is approaching the goal of electronics sounding like real music in a different way. So if you apply a generalization such as 'all amps should be voltage sources' right away it is belied by very notable exceptions! The bottom line is that equipment matching is still very much with us and won't be going away anytime soon. |
I’m also not convinced that the drawbacks of feedback are so bad it should be completely avoided. A little story about feedback. An output transformer "GOD" wound up some very nice massive cores for a friend of mine who was his buddy cost no object, interleaved to the hilt. I ended up with these cores when he passed away. The transformer "GOD" I got in touch with and he got me to get some special C-Cores from Egypt where apparently is the best silicon. These transformers could be changed via the separate interleaved winding tabs for 16,8,4,2,and even 1ohm. They sounded magnificent on a big pair of 150w tube monos I had, and I decided that maybe because the transformer were that good that there was maybe no need for feed back to help them have a lower output impedance. So I put on a variable feedback pot that could be changed from 30db down to zero. Adjusting the volume for the change in gain, it was clear as a bell that zero feed back was by far the best and because the transformers were that good the bass remained tight and dry. So that proved to me, feedback is good in tubes to get better bass with lower output impedance, but it does have a negative effect on the rest of the music. Cheers George |
Go ahead and spend gobs of money on those pure class A amps that burnout after 7-10 yearsAny truth to this? (i.e. is a class A amps life span known to be less than other designs) If so, is there anything that can/should be done from a practical perspective to prolong the longevity of a class A amp? Thanks. |
If so, is there anything that can/should be done from a practical perspective to prolong the longevity of a class A amp? Keep them biased right, Pass recommends palm hand test on the hottest part of the heatsinks being able to keep them pressed for at least 6 seconds (no brickies hands) any shorter and it’s running too much Class-A, and also keep them in a well ventilated spot. Cheers George |