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<p>I have often thought of my life as one lived by different people. *I feel distinctly different than when I was a boy, a teenager and a young man. Different enough that I seem almost like different people. *And one of those different people used to be far more impatient than the me of today. *So much more impatient that whenever I came into our engineering offices with a look of excitement, the engineers would flee for their sanity. *I would routinely yank hard at the rudder, stopping one project to start another. *While not entirely cured of this tendency, I would have to say I am much better than days gone by.</p>
<p>I have learned that I have to stand in line and wait my turn. *Such is the case with the new power amplifier we are designing. *I have been standing in line waiting to test out the latest front end. *I have now moved up to first in line and I thought I’d give you a sneak peek at what’s under the covers.</p>
<p>For those of you who have followed my Posts on a regular basis you may remember I delayed the launch of the PerfectWave Power Amplifier project, scheduled for release this month, because I was unhappy with the sound. *The high frequency part of the sound, to be specific. *The highs just weren’t there. *Sure it measured perfect, but sonically the amplifier sounded dull and lifeless on the top end.</p>
<p>My suspicion of why this happened centers around the input stage of this power amplifier, which is broken into two sections: the input stage and the output stage. *The original input stage was designed around a combination of bipolar and JFET devices in a classic discrete fully balanced amplifier topology. *There were lots of devices in the parallel amplification stages, minimal feedback, high output bipolar current buffers, high input impedance JFET buffers. *It’s a derivation of circuitry we’ve used for years and has served us well.</p>
<p>But the sophistication of the Hypex output stages are such that I am guessing they are revealing some of the closed in nature of this type of input stage more than I would like. *That closed in nature goes hand-in-hand with the amount of feedback in the stage and the way it’s implemented.</p>
<p>I know, I can see some of my readers eyebrows raising at about the same rate the hair on the back of their necks is shooting up reading that. *But I can tell you that as the level of feedback goes down, the degree of openness goes up. *In fact, there seems to be a direct 1:1 relationship when auditioned as a straight preamplifier.</p>
<p>So, you might ask, why not simply remove all the feedback and get on with it? *Well, in the end that’s what I’ve done but it was not without a great deal of agony as a designer because feedback provides a number of benefits that have to be made up some other way if you’re going to get the results you need.</p>
<p>I’ll explain what I did on the input stage tomorrow. *My fingers are crossed that perhaps by this weekend I’ll be auditioning the new amp.</p>
<p>It’s hard standing in line just to roll the dice.</p>
<br /><span class="c4"><img src="http://www.pstracks.com/wp-content/plugins/wp-spamfree/img/wpsf-img.php" width="0" height="0" alt="" class="c3" /></span>
[Source: http://www.pstracks.com/pauls-posts/rolling-dice/12755/]
<p>I have learned that I have to stand in line and wait my turn. *Such is the case with the new power amplifier we are designing. *I have been standing in line waiting to test out the latest front end. *I have now moved up to first in line and I thought I’d give you a sneak peek at what’s under the covers.</p>
<p>For those of you who have followed my Posts on a regular basis you may remember I delayed the launch of the PerfectWave Power Amplifier project, scheduled for release this month, because I was unhappy with the sound. *The high frequency part of the sound, to be specific. *The highs just weren’t there. *Sure it measured perfect, but sonically the amplifier sounded dull and lifeless on the top end.</p>
<p>My suspicion of why this happened centers around the input stage of this power amplifier, which is broken into two sections: the input stage and the output stage. *The original input stage was designed around a combination of bipolar and JFET devices in a classic discrete fully balanced amplifier topology. *There were lots of devices in the parallel amplification stages, minimal feedback, high output bipolar current buffers, high input impedance JFET buffers. *It’s a derivation of circuitry we’ve used for years and has served us well.</p>
<p>But the sophistication of the Hypex output stages are such that I am guessing they are revealing some of the closed in nature of this type of input stage more than I would like. *That closed in nature goes hand-in-hand with the amount of feedback in the stage and the way it’s implemented.</p>
<p>I know, I can see some of my readers eyebrows raising at about the same rate the hair on the back of their necks is shooting up reading that. *But I can tell you that as the level of feedback goes down, the degree of openness goes up. *In fact, there seems to be a direct 1:1 relationship when auditioned as a straight preamplifier.</p>
<p>So, you might ask, why not simply remove all the feedback and get on with it? *Well, in the end that’s what I’ve done but it was not without a great deal of agony as a designer because feedback provides a number of benefits that have to be made up some other way if you’re going to get the results you need.</p>
<p>I’ll explain what I did on the input stage tomorrow. *My fingers are crossed that perhaps by this weekend I’ll be auditioning the new amp.</p>
<p>It’s hard standing in line just to roll the dice.</p>
<br /><span class="c4"><img src="http://www.pstracks.com/wp-content/plugins/wp-spamfree/img/wpsf-img.php" width="0" height="0" alt="" class="c3" /></span>
[Source: http://www.pstracks.com/pauls-posts/rolling-dice/12755/]