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#1
Posted to rec.audio.tubes
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Pulteq mic amp
What's the odd grid stopper and anode resistor for in this
dual CF output stage, please? http://www.ivesonaudio.pwp.blueyonde...0Mic%20Pre.jpg Ian |
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#2
Posted to rec.audio.tubes
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Pulteq mic amp
In article ,
"Ian Iveson" wrote: What's the odd grid stopper and anode resistor for in this dual CF output stage, please? http://www.ivesonaudio.pwp.blueyonde...0Mic%20Pre.jpg Is that a Pulteq mic amp, or a Pultec mic amp? Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
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#3
Posted to rec.audio.tubes
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Pulteq mic amp
John Byrns wrote
What's the odd grid stopper and anode resistor for in this dual CF output stage, please? http://www.ivesonaudio.pwp.blueyonde...0Mic%20Pre.jpg Is that a Pulteq mic amp, or a Pultec mic amp? Dunno, can't remember. Whatever Pulse Technologies made. I didn't make up the file name, and neither of your suggestions appears on the sheet. If it were up to me, I'd go for tec. Maybe it was posted by a foreigner. But what about that output stage? Ian |
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#4
Posted to rec.audio.tubes
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Pulteq mic amp
Ian Iveson wrote: What's the odd grid stopper and anode resistor for in this dual CF output stage, please? http://www.ivesonaudio.pwp.blueyonde...0Mic%20Pre.jpg Puzzled me too. Graham |
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#5
Posted to rec.audio.tubes
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Pulteq mic amp
In article ,
"Ian Iveson" wrote: John Byrns wrote What's the odd grid stopper and anode resistor for in this dual CF output stage, please? http://www.ivesonaudio.pwp.blueyonde...0Mic%20Pre.jpg Is that a Pulteq mic amp, or a Pultec mic amp? Dunno, can't remember. Whatever Pulse Technologies made. I didn't make up the file name, and neither of your suggestions appears on the sheet. If it were up to me, I'd go for tec. Maybe it was posted by a foreigner. But what about that output stage? What about it? It looks like a fairly ordinary cathode follower using two paralleled triodes. If you mean the two resistors used to parallel the grids and plates of the two triodes, they were probably put in to insure against spurious RF oscillations. Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
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#6
Posted to rec.audio.tubes
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Pulteq mic amp
Ian Iveson wrote:
What's the odd grid stopper and anode resistor for in this dual CF output stage, please? http://www.ivesonaudio.pwp.blueyonde...0Mic%20Pre.jpg Ian Possibly something to to with accounting for small differences in bias points between the two halves of the valve? Cheers Ian |
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#7
Posted to rec.audio.tubes
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Pulteq mic amp
Ian Thompson-Bell wrote: Ian Iveson wrote: What's the odd grid stopper and anode resistor for in this dual CF output stage, please? http://www.ivesonaudio.pwp.blueyonde...0Mic%20Pre.jpg Possibly something to to with accounting for small differences in bias points between the two halves of the valve? It wouldn't affect that to any significant degree anyway. Graham |
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#8
Posted to rec.audio.tubes
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Pulteq mic amp
Ian Iveson wrote:
What's the odd grid stopper and anode resistor for in this dual CF output stage, please? http://www.ivesonaudio.pwp.blueyonde...0Mic%20Pre.jpg Ian This is an interesting circuit. It is quite close in topology to the classic dc coupled triple used in the early Neve transistor mic pres. It has the advantage that there is only one zero in the open loop circuit which avoids the very low frequency hump you get with two or more zeros. The dc path from the CF to the input cathode means the closed the feedback factor is fixed at dc rather than rising towards open loop at low frequencies with capacitor coupled feedback. Cheers Ian |
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#9
Posted to rec.audio.tubes
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Pulteq mic amp
Ian wrote:
What's the odd grid stopper and anode resistor for in this dual CF output stage, please? http://www.ivesonaudio.pwp.blueyonde...0Mic%20Pre.jpg This is an interesting circuit. It is quite close in topology to the classic dc coupled triple used in the early Neve transistor mic pres. It has the advantage that there is only one zero in the open loop circuit which avoids the very low frequency hump you get with two or more zeros. The dc path from the CF to the input cathode means the closed the feedback factor is fixed at dc rather than rising towards open loop at low frequencies with capacitor coupled feedback. It struck me as thoughtfully designed for quality of sound. But it was the poles that caught my eye. The two halves of the output stage will move out of phase with each other. Is that the dominant pole, I wonder. Output tranny specs would be interesting. Ian |
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