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#1
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Unsual PP Output Topology?
Has anyone ever seen this topology covered in any text?
I would like to learn more about how to use it. What are the benefits, and what's required of the transformer?? I like the idea having the transformer in a feedback loop with the 6550. Any comments? anyone used it before? view schematic he http://www.nashaudio.com/Public/6550_OUT.pdf Thanks RonL I |
#2
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Has anyone ever seen this topology covered in any text? ** What: Ultralinear with 100% Cathode Feedback ? I would like to learn more about how to use it. What are the benefits, and what's required of the transformer?? I like the idea having the transformer in a feedback loop with the 6550. Any comments? anyone used it before? view schematic he http://www.nashaudio.com/Public/6550_OUT.pdf ** See: http://www.kbapps.com/audio/schemati...7poweramp.html Leslie amps used the same basic idea decades ago. ............ Phil |
#3
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Well.. I've worked on 1492 different 147 and 122's in my life, but I never
noticed It!! 100% cathode feedback. It that the offical name for it? Thanks! "Phil Allison" wrote in message ... Has anyone ever seen this topology covered in any text? ** What: Ultralinear with 100% Cathode Feedback ? I would like to learn more about how to use it. What are the benefits, and what's required of the transformer?? I like the idea having the transformer in a feedback loop with the 6550. Any comments? anyone used it before? view schematic he http://www.nashaudio.com/Public/6550_OUT.pdf ** See: http://www.kbapps.com/audio/schemati...7poweramp.html Leslie amps used the same basic idea decades ago. ........... Phil |
#4
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wrote
Has anyone ever seen this topology covered in any text? I would like to learn more about how to use it. What are the benefits, and what's required of the transformer?? I like the idea having the transformer in a feedback loop with the 6550. Any comments? anyone used it before? view schematic he http://www.nashaudio.com/Public/6550_OUT.pdf Yes. It is a form of distributed load that is widely used but more often the speaker winding is separate from the cathode winding. This makes a big difference to how it looks in the drawing which is perhaps why you don't recognise it. The ins and outs of distributed loading are many...used in different proportions by Quad, Mackintosh, van der Veen, and various current manufacturers. There may be a paper on Plitron's site. It is quite well covered in Menno van der Veen's "Modern High-End Valve Amplifiers". Using the speaker winding as shown means that the ratio of anode to cathode winding, and hence the amount of feedback, depends on the winding ratio between primary+secondary and secondary. It is unlikely that both can be optimised at once. Handy if you only have simple transformers to hand though. This limitation can be overcome by using the optimum ratio for the cathode, and then tapping that winding at the best point for the speaker. The common alternative is to use separate cathode windings altogether. I think this makes it easier to minimise leakage inductance between anode and cathode, and also avoids attaching the cathodes to the speaker terminals, which could pose problems for the average user and makes global feedback a little more awkward to implement. For an illustration of how cathode feedback alters the characteristics of the output valves: http://www.ivesonaudio.pwp.blueyonder.co.uk/modal.htm For the circuit of my amp, wired for the "UL30CF-10" option: http://www.ivesonaudio.pwp.blueyonde...6ch6schema.gif cheers, Ian |
#5
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wrote
100% cathode feedback. It that the offical name for it? Not really. "Distributed load" is a better term than cathode feedback, and it is not 100% because it is normally given as a percentage of the anode voltage. 100% wouldn't work... cheers, Ian |
#6
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Well.. I've worked on 1492 different 147 and 122's in my life, but I never noticed It!! ** How idiotic. Must be the result of top posting all your experiences. 100% cathode feedback. It that the offical name for it? ** Dunno - but 100% of the speaker voltage is being used as negative feed back to the cathodes in both in these examples. ........... Phil "Phil Allison" wrote in message ... Has anyone ever seen this topology covered in any text? ** What: Ultralinear with 100% Cathode Feedback ? I would like to learn more about how to use it. What are the benefits, and what's required of the transformer?? I like the idea having the transformer in a feedback loop with the 6550. Any comments? anyone used it before? view schematic he http://www.nashaudio.com/Public/6550_OUT.pdf ** See: http://www.kbapps.com/audio/schemati...7poweramp.html Leslie amps used the same basic idea decades ago. ........... Phil |
#7
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wrote in message
... Has anyone ever seen this topology covered in any text? I would like to learn more about how to use it. What are the benefits, and what's required of the transformer?? I like the idea having the transformer in a feedback loop with the 6550. Any comments? anyone used it before? view schematic he http://www.nashaudio.com/Public/6550_OUT.pdf Thanks RonL I Menno van der Veen published an article about several topologies and their properties some time ago amoung which is "your" circuit. See: http://www.plitron.com/PDF/PB/Article/Atcl_4.pdf Refer to circuit #7, "Super-Triode". I'd prefer to name it "UL with CFB", but who am I? Maybe I'd have to read the entire article to understand the authors remark "..newly invented..". For the moment though I'm missing the point of it. I guess answers on your questions are covered in the article, so I won't repeat them here. Rgds, Jan. |
#8
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IIRC, impedance is turns ratio squared. That would mean that he should
tie the "4 ohm" tap to ground instead of the 8 ohm tap. I would presume that he wanted the same voltage levels (but 180 degree out of phase) on both cathodes). |
#9
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"Bob" IIRC, impedance is turns ratio squared. That would mean that he should tie the "4 ohm" tap to ground instead of the 8 ohm tap. I would presume that he wanted the same voltage levels (but 180 degree out of phase) on both cathodes). ** Correct - the posted ( hypothetical) diagram is wrong on that. http://www.nashaudio.com/Public/6550_OUT.pdf .......... Phil |
#10
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Thanks All for putting me on track
RonL "Phil Allison" wrote in message ... "Bob" IIRC, impedance is turns ratio squared. That would mean that he should tie the "4 ohm" tap to ground instead of the 8 ohm tap. I would presume that he wanted the same voltage levels (but 180 degree out of phase) on both cathodes). ** Correct - the posted ( hypothetical) diagram is wrong on that. http://www.nashaudio.com/Public/6550_OUT.pdf ......... Phil |
#11
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Thanks All for putting me on track RonL ** Yeah - just slightly removed form being " rail roaded" !!! ............ Phil |
#13
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Phil Allison wrote: "Bob" IIRC, impedance is turns ratio squared. That would mean that he should tie the "4 ohm" tap to ground instead of the 8 ohm tap. I would presume that he wanted the same voltage levels (but 180 degree out of phase) on both cathodes). ** Correct - the posted ( hypothetical) diagram is wrong on that. Indeed, the grounded CT of the 16 ohm whole speaker winding should be for 4ohms from either end, and the 8 ohm connection should be between the shown 4&16 points. Don't expect diagrams posted on the web to contain correct information which has all the operating voltages and information relevant. Patrick Turner. http://www.nashaudio.com/Public/6550_OUT.pdf ......... Phil |
#14
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On Wed, 28 Sep 2005 00:04:43 -0500, wrote:
Well.. I've worked on 1492 different 147 and 122's in my life, but I never noticed It!! 100% cathode feedback. It that the offical name for it? Thanks! Probably not - since there is no guarantee that the feedback is 100%... because of the transfer of the transformer, I have no idea what the feedback percentage would be...it would depend on the ratio... but I would guess it's a lot lower... you would have to develop a voltage in the secondary to negate the cathode voltage developed , or something... which I doubt is happening! And who wants a zero gain output stage?? The only 100% here is the amount of current, not it's effect. |
#15
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On Wed, 28 Sep 2005 14:47:22 GMT, Patrick Turner
wrote: But the 4.84% of applied CFB is not a very significant amount of FB. Bingo. This connection was a regular feature of the earlier Audio Research amplifiers for years. No good reason at all to bother. Thanks, as always, Chris Hornbeck "I had a perspective on the booing, too. You can kill somebody with kindness." -Bob Dylan |
#16
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wrote:
Has anyone ever seen this topology covered in any text? I would like to learn more about how to use it. What are the benefits, and what's required of the transformer?? I like the idea having the transformer in a feedback loop with the 6550. Any comments? anyone used it before? view schematic he http://www.nashaudio.com/Public/6550_OUT.pdf Thanks RonL I The connexion shown needs to have the common (gnd) connected to the 4R tap which is the mid-point on the 16R secondary. By coincidence, I tried this on a simple PP 6V6 amp (pentode connected) with a Hammond 125E OPT on Sep 9/05. Here are some results measured with & without this very limited form of local voltage NFB. On the 8R connexion the amp internal Z without NFB measured 42.98R, rather high as one might expect for a straight pentode amp with no FB. With the simple NFB connected the internal impedance at the same point dropped to 16.62R, otherwise a Damping Factor (DF) of about 1/2. Would be a useful effect for a guitar amp, IMO. Cheers, John Stewart |
#17
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"John Stewart" The connexion shown needs to have the common (gnd) connected to the 4R tap which is the mid-point on the 16R secondary. By coincidence, I tried this on a simple PP 6V6 amp (pentode connected) with a Hammond 125E OPT on Sep 9/05. Here are some results measured with & without this very limited form of local voltage NFB. On the 8R connexion the amp internal Z without NFB measured 42.98R, rather high as one might expect for a straight pentode amp with no FB. ** But a 6V6 is a " Beam Power Amplifier " ( GE Essential Characteristics) - not a pentode. .......... Phil |
#18
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On Thu, 29 Sep 2005 12:27:04 +1000, "Phil Allison"
wrote: ** But a 6V6 is a " Beam Power Amplifier " ( GE Essential Characteristics) - not a pentode. Relevant in what way? Chris Hornbeck "I had a perspective on the booing, too. You can kill somebody with kindness." -Bob Dylan |
#19
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"Chris Hornbeck" ** A snipping psychopath. ........... Phil |
#20
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On Thu, 29 Sep 2005 12:44:59 +1000, "Phil Allison"
wrote: ** A snipping psychopath. Who always feels dirty after interacting with you. My fault entirely for attempting, yet again. Good fortune, Chris Hornbeck "I did it because he lied, 'cause he took you for a ride, because time was on his side, and because... I want you" -Dylan |
#21
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"Chris Hornbeck" ** A snipping psychopath AND serial topic rapist. ......... Phil |
#22
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Thanks for the info..I just had the idea for trying this
to keep from ordering an output trannie with dedicated cathode windings. It is a rather complicated thing to try to figure out with the ultralinear connections as Patrick pointed out. I was un-aware that Leslie had already done it! Again, thanks for kicking this around. RonL "Phil Allison" wrote in message ... "Chris Hornbeck" ** A snipping psychopath AND serial topic rapist. ........ Phil |
#23
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On Thu, 29 Sep 2005 13:03:12 +1000, "Phil Allison"
wrote: ** A snipping psychopath AND serial topic rapist. Your complete post: "** But a 6V6 is a " Beam Power Amplifier " ( GE Essential Characteristics) - not a pentode. .......... Phil" Close quote. Did I miss any asterisks? Or did I spell your name incorrectly? Jeez, guy, get a ****ing grip. There's still a real world out here beyond the keyboard. You're not alone. "Get stoical." (Movie reference _Smoke Signals_) Knowing one's enemies from one's friends is critical, and heartbreaking when impossible. All the best fortune to you and yours, Chris Hornbeck "I did it because he lied, 'cause he took you for a ride, because time was on his side, and because... I want you" -Dylan |
#24
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Some NG psycho called Hornbeck "Phil Allison" ** A snipping psychopath AND serial topic rapist. Your complete post: "** But a 6V6 is a " Beam Power Amplifier " ( GE Essential Characteristics) - not a pentode. ** But **NOT** the WHOLE post including context and the words mine addressed !!!!!! Chris Hornbeck is a GROSSLY autistic, PITA ****wit. There is simply no way to reason with the demented cretin and no point whatever in even trying. SO ** **** OFF** HORNBECK !!! ........... Phil |
#25
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Phil Allison wrote: Some NG psycho called Hornbeck "Phil Allison" ** A snipping psychopath AND serial topic rapist. Hey Allison, Have you ever had a washing machine agitator stuck up your ass? If you keep it up someone will. I just hope they use an old Frigidaire one so you go up and down instead of back and forth. |
#26
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"Bret Ludwig" Phil Allison wrote: Some NG psycho called Hornbeck "Phil Allison" ** A snipping psychopath AND serial topic rapist. Hey Allison, ** Hey Asshole, outing the likes of CH is what I do. Its my job. ........... Phil |
#27
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Phil Allison wrote: "Bret Ludwig" snip outing the likes of CH is what I do. Its my job. I hope it pays good. I mean, I'd hate to have people asking why my ass said "MAYTAG" in reverse script, you know? |
#28
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Phil Allison wrote:
"John Stewart" The connexion shown needs to have the common (gnd) connected to the 4R tap which is the mid-point on the 16R secondary. By coincidence, I tried this on a simple PP 6V6 amp (pentode connected) with a Hammond 125E OPT on Sep 9/05. Here are some results measured with & without this very limited form of local voltage NFB. On the 8R connexion the amp internal Z without NFB measured 42.98R, rather high as one might expect for a straight pentode amp with no FB. ** But a 6V6 is a " Beam Power Amplifier " ( GE Essential Characteristics) - not a pentode. ......... Phil So? JLS |
#29
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Chris Hornbeck wrote: On Wed, 28 Sep 2005 14:47:22 GMT, Patrick Turner wrote: But the 4.84% of applied CFB is not a very significant amount of FB. Bingo. This connection was a regular feature of the earlier Audio Research amplifiers for years. No good reason at all to bother. Thanks, as always, Chris Hornbeck Where you have a 500 watt amp, and the outout voltage into an 8 ohm centre tapped speaker secondary is about 63.24Vrms, then you have 31.6V available for series CFB for the two halves of the PP circuit using say 20 x 6550. If you have 250Vrms at the anode, and the grid to cathode voltage is say 25Vrms, then you only need 55.6Vrms of grid drive to each output tube grid, and very easy to do without the extra stage and bootstrapping that is employed by EAR and McIntosh. This amount of voltage FB is far more than in the case of the parsimonius amount you'd have with a 50 watt amp using just 2 x 6550, some 20Vrms with a CT for 10V CFB to each cathode. You still have bothers trying to arrange the speaker sec to suit a range of loads; I never bother to try to match to 8 ohms because nearly all speakers have slipped down to 6 ohms nominal with dips to 4 ohms or less. Patrick Turner. |
#30
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"John Stewart" Phil Allison wrote: "John Stewart" The connexion shown needs to have the common (gnd) connected to the 4R tap which is the mid-point on the 16R secondary. By coincidence, I tried this on a simple PP 6V6 amp (pentode connected) with a Hammond 125E OPT on Sep 9/05. Here are some results measured with & without this very limited form of local voltage NFB. On the 8R connexion the amp internal Z without NFB measured 42.98R, rather high as one might expect for a straight pentode amp with no FB. ** But a 6V6 is a " Beam Power Amplifier " ( GE Essential Characteristics) - not a pentode. ......... Phil So? ** What is your question ? ............. Phil |
#31
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Phil Allison wrote: "John Stewart" Phil Allison wrote: "John Stewart" The connexion shown needs to have the common (gnd) connected to the 4R tap which is the mid-point on the 16R secondary. By coincidence, I tried this on a simple PP 6V6 amp (pentode connected) with a Hammond 125E OPT on Sep 9/05. Here are some results measured with & without this very limited form of local voltage NFB. On the 8R connexion the amp internal Z without NFB measured 42.98R, rather high as one might expect for a straight pentode amp with no FB. ** But a 6V6 is a " Beam Power Amplifier " ( GE Essential Characteristics) - not a pentode. ......... Phil So? ** What is your question ? ............ Phil What is your answer? |
#32
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In article , wrote:
Phil Allison wrote: "John Stewart" Phil Allison wrote: "John Stewart" The connexion shown needs to have the common (gnd) connected to the 4R tap which is the mid-point on the 16R secondary. By coincidence, I tried this on a simple PP 6V6 amp (pentode connected) with a Hammond 125E OPT on Sep 9/05. Here are some results measured with & without this very limited form of local voltage NFB. On the 8R connexion the amp internal Z without NFB measured 42.98R, rather high as one might expect for a straight pentode amp with no FB. ** But a 6V6 is a " Beam Power Amplifier " ( GE Essential Characteristics) - not a pentode. ......... Phil So? ** What is your question ? ............ Phil What is your answer? He has no answers, nor an original thought in his head. Regards, John Byrns Surf my web pages at, http://users.rcn.com/jbyrns/ |
#33
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"John Byrns" = psychotic, autistic pig ** He has no answers, nor ever an original thought in his head. ............ Phil |
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