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So what is it that is the most important element in giving a particular amplifier it's sound? Is it the type of amp (PP vs SE, etc), is it the type of output tube (2A3 vs 300B, etc), and how much does the driver tube or tubes effect all of this?
I just got through trying 1/2 of a 6em7 as the driver in my low voltage 845 in place of the 1/2 of a 6sn7 I had been using. I was expecting more of a difference than I heard I guess. Of course they both are triodes, and that may have something to do with it too.
I am curious what you folks finds makes the biggest difference to the sound of the amps you build or breadboard.
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IMHO, I have found that everything one does makes some difference but I believe that the two most important stages are the input stage and the output stage. The slew rate is set at the input stage voltage amplifier all other stages must follow it's rise and fall times. Most second and third stages are current mirror/impedance conversion stages. It's this ability to keep up with the input stage that separates the men from the boys. And if you introduce feedback then it's possible to make an amp that is an impossible steep mountain to climb in it's ability to keep up with the input stage voltage amp. I'm no school trained EE just a audiophile who builds his own gear and these forums are replete with OPINION but I agree with Paul Klipsch in that "...what this country needs is a good 2 watt amplifier." The first two watts are the most important watts. The second most important thing is the output stage perveance/transconductance and it's ability to damp a load current wise that is almost a dead short. And I believe that the best way to couple a amp to a reactive load speaker is through a very good transformer. There are a few good ones and a few bad ones and many many mediocre ones; you know the BELL CURVE. Moe Bias
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare
The B+ must be very clean, well regulated, with a smooth not peaky noise floor and tube damper rectification performs this best. Solid state rectification is inherently dirty and it's a pain to clean up a dirty noise floor. The noise floor will be amplified along with the music! M.B.
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare
I have heard a lot people would should know (JC Morrison for example)say that the quality of the power supply is the foundation of any amp; get that wrong and it's like building a house on sand. I think most of us don't spend enough time on them.
Edits: 10/19/14
I've had good results with a 6em7 voltage amp/cathode follower with SE power triodes. Only two sockets and a beefy driver for your triode output tubes to overcome the Miller capacitance.
The other octal arrangement I've liked is a 6sn7, paralleled for the extra current with a current source (CCS) on the plate. It gives you PS isolation, a horizontal load line and max gain from the tube along with a healthy output impedance and current available.
Long time ago, I built a 6sl7 srpp 2a3, it sounded OK but nothing exciting. A year ago I built another amp, everything is identical, same output transformer, identical driver and output tube, but it is a 6sl7 // dc 2a3, the sound is amazing. Same ingredient but totally different result. So my answer to your question is topology.
How clean is the B+ is also my priority when building an amp. Of course, there are many way to skin a cat, depends on individual experience and belief, so I am sure there will be many different answers to your question.
I am not a DIYer. I listened to a lot of 2A3s DC and cap coupled. My impression is that, for both typologies, the quality of the OPTs can be responsible for large sonic improvements. Quite a few years separate my hearing of a Baby Ongaku SRPP-Cap coupled with Magnequest Silver OPTs and a pair of Fi 2A3 dc amps and i was enthralled by both. I have changed the OPTs on the Fis to a Magnequest OPT with interleved windings in the secondary and got a nice improvement. My last wish in life is to save 6K and get the silvers!
This doesn't vitiate your statement about the importance of typology, but I have heard a lot of cap coupled 2A3s with SRPP front ends and better OPTs make a big difference.
Observe, before you think. Think before you open your yap. Act on the basis of experience.
You should be finding this out yourself .
Al
I am in the process of doing just that, but I am also interested in what other people have learned. Apparently you aren't.
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