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In the Forum: Melquiades Amplifier
In the Thread: Single-stage Melquiades vs. DHT amps
Post Subject: Optimizing the 2A3Posted by drdna on: 2/14/2009
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 floobydust wrote:
As Romy pointed out, having high gain is not the same as power. If you're only barely cracking the volume control on your amplifier or preamplifier then it should be obvious that you have more gain than you need. If you're picking piece parts (either built, kit or implementing somebody else's design) then you need to manage the various gain of each component and determine how to best integrate them into a system. As far as the gain in the amplifier goes, it's a moot point IF you manage the overall system gain properly. I've done two SET designs over the past few years... and they are quite different on gain, yet have very similar specifications. There are both technical and financial reasons for each design but both have been optimized for performance, not gain. A brief word on power.... the 45 triode in a proper design will deliver a solid 2- to 2.5-watts and can be flat from 20Hz to 50KHz (or more) depending on the design, components and how it's actually built. A 2A3 triode will deliver up to 4.5 watts in the same application... please note that this is ONLY a 3dB change (double the power). As such, it's not really surprising that you (Adrian) realized little benefit from the 2A3 over the 45... you didn't gain very much (power). Having speakers which have higher sensitivity is a real requirement for using low power amplifiers. And even then, the last 1 to 2 octaves will require some additional help for anything beyond moderate listening levels. If you plan on using 2- to 5-watt SET amplifiers, you need to mate them with speakers of adequate sensitivity AND which will mate well with a low powered SET, of which most (if not all) have no negative feedback and have low damping factor. As for modifying your Moondog amplifiers, I would recommend against it. While you can effectively reduce the overall distortion and gain a bit of additional power, it's not worth gutting the amplifier and start swapping out expensive parts. If you're not happy with the amount of power now. You would likely be better off with a different (SET) amplifier which has enough power to meet your needs.

I think you may have misunderstood my post. I am not looking for more power or gain at all.

Really the idea of modifying the circuit came about as a thought to try and get the most out of the Sylvania tube and see if I am missing something in my assessment.

There is absolutely no need for more gain or power, as far as I know. The speakers are the EdgarHorn Titan horn loudspeakers, which I think have about 107 db sensitivity. As I said I keep the preamplifier on around 1-2 and it is passive! It would be very easy to sacrifice gain for an improvement in the sound quality, which is after all, as Paul said, the goal of it all.

My goal in audio is to achieve a connection to the Sound, or the living presence of the musicians and composers, the insight into the piece/performance that makes you reflect and ponder, the emotional connection that makes you want to listen, that makes you connect in such a way that you feel you are hearing the real live breathing musicians, not only that they are in the room but beyond that to the soul of the music of what they thought and felt, etc.

So it is a bit idiosyncratic for me, as minimizing distortion and getting a good frequency response are good, but not really my goal. An example: both the Sylvania and the Sophia mesh plate tubes have some limitation in the very low end and do not do the high frequencies exactly correctly; both also have tiny but noticeable amounts of distortion. However, I really love the Sophia tube quite a bit. It has a wonderfully rich, open, concupiscent midrange that I found especially involving on many classical pieces like Bruch's Scottish Fantasy. By comparison, the Sylvania has a midrange presentation that is audiophile neutral. It has an additional level of tangibility and dynamic ease that I have not found with the NOS tubes.

So my thought was: maybe I am missing out. Maybe I should try to optimize my circuit.

Anyway, I would love to hear about your sonic impressions also of the 2A3 tubes, as you have extensive experience with over 50 types. That is a treasure trove of information, and I would love to learn about your impressions.

Adrian

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