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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: Re: Any amps with tubes will have more distortion and will distort the frequency response posted by Soundmind on June 9, 2006 at 20:20:46:
I agree with the majority of this. I should mention that 'graininess' is a subjective term and not meant to imply that all SS amps will overtly display such a quality, or that tube amps cannot do so. IMO, this subjective characteristic when present results primarily from interelectrode junction capacitance nonlinearities such as exhibited with high K dielectric materials such as barium titanate capacitors and intrinsic silicon.The triode OTL I designed achieves its low output impedance through a combination of negative voltage feedback and positive current feedback (along with good open loop bandwidth flatness). Wrt Miller effect, I partly overcame that in this design with a differential cascode input stage, the cascode topology being used with TV tuner triodes in the '50's and '60's and commonly applied today in solid state linear input stage architectures to maximize bandwidth. As a result the DC coupled OTL has a closed loop bandwidth in excess of 100khz into an 8 ohm load.
Wrt distortion, the DC coupled triode OTL has characteristics more typical of a typical tube amp (in its midrange) than a SS amp, but I could change that rather easily by converting the cascode input topology to cascade, gaining another 15 db of open loop gain and reducing distortion at clipping to around 0.05% until the first order open loop pole kicks in, at least. But, having strong subjectivist tendencies, I elected to go the route of less overall loop feedback (although this amp has several local feedback loops) and accept higher measured distortion:)
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Follow Ups
- Re: Any amps with tubes will have more distortion and will distort the frequency response - Tom Dawson 20:42:25 06/09/06 (2)
- Re: Any amps with tubes will have more distortion and will distort the frequency response - Soundmind 04:05:19 06/10/06 (1)
- Re: Any amps with tubes will have more distortion and will distort the frequency response - Tom Dawson 19:45:51 06/11/06 (0)
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