Paul McGowan: …is that it leads to success.
Perhaps the hard way, but sometimes it’s the only path there. Thanks for all the kind words of encouragement about the amp not living up to what I wanted but, here’s the thing about failing, it pushes you harder to succeed and in the process of figuring the problem out great things usually emerge.
If everything just went according to plan life’d be pretty boring – and for those of us afraid of failure (and who isn’t?) – once we get over the initial disappointment most of us roll up our sleeves and really get moving. So, on that note, what will be my first steps?
As I’ve been traveling as of late and enjoying time off in the northern parts of our country I’ve been contemplating what to do – why would the amp sound somewhat closed in, less open and have a stiff top end that sounds recessed? What are the probable causes? It occurs to me that when we designed the new all FET front end stage that we had to resort to a constant current source on the FET gain transistor. The reason for this was greater linearity and because we’re using MOSFETS for the outputs of the analog gain stage, keeping a constant current helps bias these devices. But there’s a problem with a constant current source connected to a gain transistor – far more gain than is perhaps manageable – because the current source looks like an infinite resistor.
One of the hallmarks of a “closed in” sound that we learn, as designers, can sometimes be attributed to the problem of too much open loop gain – in other words, too much gain before feedback results in too much feedback – and this, in my experience can be the cause of such a sound. So as soon as I am back from my trip I’ll figure out a way to keep the constant current source working, yet limit the open loop gain so the amount of feedback is low. We’ll see what that does.
Some of the most open sounding preamps and amps have little to no feedback and that’s for a reason – this very problem I am describing. No feedback at all has its problems, and too much has them as well.
I’ll let you know what we find as we dig a bit deeper.