0 Members and 1 Guest are viewing this topic. Read 11867 times.
here's a description, from a pro-audio site. (realize that musicians may actually want more compression/distortion.)http://www.vvtamps.com/support.htm :"...What is Cathode bias (aka) Auto Bias versus fixed bias?Cathode bias is an early method of biasing tubes where a resistor is placed in the cathode. Current draw through this resistor makes the grid potential negative with respect to the cathode. And, changes in tube conduction are automatically compensated by changes in bias so it’s also referred to Auto Bias. In Fixed Bias a negative voltage is applied directly to the grids of the output tubes. It should be noted that preamp tube are almost always cathode biased whereas output tubes may be either or both. Without getting into the technical issues of the difference between a fixed bias/cathode bias we will talk about the tonal qualities and how they differ in the real world.The Pros and Cons.Fixed Biased:Fixed biased amps are more efficient, it is a brighter, tighter, punchier tone and needs to be pushed louder to find a warm sweet spot. Fixed bias also increases the headroom of the output section keeping the amp cleaner as it gets louder, yet the transition into grind is bit edgier. This design also requires you to bias the amp when replacing output tubes.On the whole, most amps are fixed bias, your Blackface Fenders, Marshalls, and many of the newer amps such as Boogies etc.Cathode biased:Cathode biased amps have a slightly browner tone giving them a real warm appeal.They also seem to have a rounder more full tone at lower volumes, and transition into grind smoother than a fixed biased amp. They also begin to compress sooner and have a more round, less focused low end, as well as a sweeter compressed, less edgy top end. They also have slightly less headroom.Cathode biased amps don’t need to be re-biased when installing a fresh set of output tubes (but the set still needs to be matched). It is also a good idea to try and replace the output tubes with the same current draw as the originals. Most manufactures of tubes use a numbering system or color code to identify the tube’s draw. This keeps the tubes at the proper operating point....here's a plug from primaluna (which the o.p. is considering); note that primaluna basically states what i said originally: "...For Tube-output stages the "fixed bias" system is most commonly used, because of its superiority in efficiency and least intrusion in the signal path. The most well-known other option is called "self-bias" or "cathode-bias", and this requires a big capacitor to bypass a big resistor, with the potential of affecting audio quality a lot more, and definitely burning a lot of wasted power in the already quite inefficient tube output stage....", but then goes on to explain why its system is better:http://www.hifi-notes.com/primalunaprologueone24-en.htmif you do a web search, you will find a lot of info on the differences...doug s.
I think it has to do with the character differences between two different bias schemes. This certainly does apply to home audio as well as guitar amplifiers, because your amplifier is going to have a certain character, and a voice of its own.I thought it was a good article.
Thanks Quiet Earth,it's cool. I have made a note, however, to NEVER ask a question on a forum again.
If staying on-topic is that important to you then perhaps this isn't the forum for you. Nearly all hot topics here go on several tangents.http://www.audiogon.com/cgi-bin/cls.pl?intatube&1322224010&/Manley-stingray-with-box-and-pManley Stingray: $1,600 used.
I'm very close to purchasing a Primaluna Prologue 2 or Classic, but wondering if there are any alternatives.
Since knowledge is indeed, power, let me share this with you.http://www.grammarbook.com/punctuation/capital.asp
No need to respond, as I won't be back.
If I wanted to purchase blindly, I would have never asked the question. Also, the Yaqin was a great suggestion and I appreciated it. The only reason I am not going with it is because the eBay seller states all sales are final and I'd be stuck if I didn't like it.As far as knowledge being power, well you are right, but there is a time and a place for everything and this was neither. That Virtue amp is not even a tube amp. The Manley is like a $5,000 amp and all the stuff about fixed bias, well that wasn't the question, now was it.In closing, your not being sure what my problem is, is because I don't have one. I just choose to NOT ask further questions because most couldn't stay on topic if it was a circle on the ground with the word "topic" painted on it.
I know tubes have kinder distortion for your tweets but I personally would want more than 40 Watts for 85.5db speakers. This is totally and unequivocally my own sentiment that in noway is meant to be considered as an unsolicited advise of any kind what so ever. Whoever reads it should just ignore it.
Doug, sorry for adding to the derailing of your thread. Don't get discouraged, keep asking and learning. To qoute Sir Francis Bacon "Knowledge is power".
W.W.A.M. Why Waste A Manley?
I was wondering what that stood for in your earlier post!
