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Old 02-20-2015, 10:09 AM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by TUD1 View Post
The rectifier tube in that was in my Zenith when I got it was a GE Electronic 6X5GT. I'll be doing away with it altogether. I'll also be sure to replace the electrolytics with a higher working voltage.
My Zenith chairside has the same chassis. That chassis uses the direct coupled triode driver and 6AC5 triode output. Why????? most of the other Zeniths used penthodes.
Mine came with, probably the last 6X5GT's made. It has the small internal structure like the 6X4. I'll leave it!
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Old 02-21-2015, 09:01 PM
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DavGoodlin DavGoodlin is offline
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Quote:
Originally Posted by dieseljeep View Post
My Zenith chairside has the same chassis. That chassis uses the direct coupled triode driver and 6AC5 triode output. Why????? most of the other Zeniths used penthodes.
Mine came with, probably the last 6X5GT's made. It has the small internal structure like the 6X4. I'll leave it!
I wondered this as well and looked at a book I just got "understanding hi-fi circuits" by Norman Crowhurst. What I took away was this:
The triode output versus the pentode has lower harmonic distortion but the plate efficiency is also much lower, reducing output power. Additionally, the handling of varying plate load, due to output transformer and speaker reactance across the frequency spectrum is improved with the triode. It is likely a tradeoff that Zenith accepted in exchange for better fidelity.

This odd feature of the Zeniths is motivation enough to recap (and replace the tranny) and give it a serious listen.
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Old 02-21-2015, 09:33 PM
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rca2000 rca2000 is offline
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Tube data sheets show the 6AC5 capable of 3-4 watts, with around 250 or so plate volts...-in SE..which your chassis is.
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