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Old 8th February 2008, 11:35 PM   #11
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Quote:
Originally posted by Shoog
Also why go to the trouble of using some of the most linear valves available and then kill their signature by wrapping large amounts of negative feedback round them.
Who said anything about using "large amounts" of gNFB? You never saw anything like that from me, I guarantee you. My designs use very little, as compared to SS designs. (But that's a whole 'nother story, and BJT amps need lots of gNFB.) The latest project has variable gNFB that maxes at 12db(v). For the most part, I don't use more than 6.0db of gNFB. The other design I did doesn't use much more.

As for using linear valves, optimizing the open loop performance before adding the gNFB is the major part of my design philosophy. gNFB is an enhancement, not something you use to sweep your design errors under the carpet. As for "signature", I have no idea as to what this is supposed to mean. Everything I ever heard that relates to this concept has been in a negative light, such as the "MOSFET sound" from some really ill-concieved designs. Or as related to gee-tah amps (as in the "Marshall sound", or the "Fender sound") where fidelity isn't a consideration, or necessarily desireable. I leave such arguements to the axemen, since I don't play.
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Old 9th February 2008, 02:45 AM   #12
SY is offline SY  United States
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Would you not admit that an over zealous use of feedback kills the very quality which good triodes bring to the mix
That depends on your definition of "over-zealous use." If the amp is designed to be unconditionally stable with feedback and care is taken to avoid blocking, then the use of feedback is, in my experience, a positive. This assumes speakers that want a low driving imnpedance (i.e., 99% of them)

But I will point out that I'm not aiming for effects boxes, I want my amps and preamps to not audibly alter the signal, just make it bigger. Others may have different goals and my comments are not relevant to that approach.
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Old 9th February 2008, 08:14 AM   #13
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I would have to say that my experience of using gNFB hasn't been great and I have achieved better results with different approaches. That doesn't make me an out and out enemy of it though and I'm certain I would use it in the right place.

We will have to agree to differ on this one.

Shoog
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Old 9th February 2008, 12:48 PM   #14
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Yeah !

Just a pinch of salt, no more

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