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Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum |
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#51 |
diyAudio Member
Join Date: Nov 2018
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The use of load lines is invaluble when aiming for max power transfer.However as I posted before in your case you need to make sure the o/p transformer has ample iron so as not to saturate when passing anode standing current +max signal.A good transformer manufacture will work this out for you as it depends strongly on core material.BTW a class A push pull output stage is far more forgiving in this regard as standing current is cancelled in the transformer.
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#52 |
diyAudio Moderator
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powering headphones, you will actually see much much less power than the graphs showed...
btw, speakers that are nominally rated at 8 ohms is only 8 ohms at one frequency and goes all over the place with different frequencies, i suspect that headphones are not much different...
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hard work erases ignorance..... |
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#53 |
diyAudio Member
Join Date: Nov 2018
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More on output transfomers.Care also needs to be taken when including a CUSTOM o/p transformer in the negative feedback loop.Thats a whole new world of pain!!!!
Re your point about headphone amps. I am an old timer and over the years can recall seeing many designs for valve headphone amps in the UK hobby press.Since almost everything ends up on the net these days they should be out there.I am no expert on google you may need something more specific. As I recall most seemed to use small signal triodes with No o/p transformer they were cap coupled. Really sorry I cant provide links. |
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#54 |
diyAudio Member
Join Date: Jun 2003
Location: Maine USA
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> intended loads of about 64-300 ohms, .... .... I can't decide between 5K:16 (17.7:1) and 5K:32 (12.5:1).
Use 5K:32. |
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#55 |
diyAudio Member
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Thank you
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#56 | |
diyAudio Member
Join Date: Jul 2005
Location: West Virginia panhandle
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Quote:
I would get the amp working with the 32 ohm transformer using a cheap speaker as a (mismatched) load, then try the headphones. Once working you can play with resistors in PARALLEL with the headphones to adjust the load seen by the tube for the best balance of power and distortion. Something between 33 and 1000 ohms will be the best. As I stated before, I believe that a 5K to 8 ohm OPT will be marginal at putting enough power into 300 ohm phones without getting the 45 too close to clipping. The 32 ohm OPT will have enough voltage on its output to feed the cans, and enough reserve power to feed a resistor, while keeping the 45 in its happy zone around half a watt or less on peaks.
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Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before...... |
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#57 |
diyAudio Member
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Thanks for the input George, much appreciated.
I will proceed with this and report my findings, but that will take a while. |
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#58 | |
diyAudio Member
Join Date: Apr 2011
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Quote:
http://www.tubebooks.org/Books/intro_Preisman_graph.pdf http://www.tubebooks.org/Books/Intro...onductance.pdf |
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#59 |
diyAudio Member
Join Date: Nov 2018
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You are really lucky to have so many good people reply to your post.All of them have given sound advice. I do understand your desire to learn and can only say ¬ learning drives us all forward.
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#60 |
diyAudio Moderator
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learn by doing, less talking.....
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hard work erases ignorance..... |
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Thread | Thread Starter | Forum | Replies | Last Post |
Understanding load lines | merlin el mago | Tubes / Valves | 86 | 6th December 2018 08:08 PM |
EL34,KT66,6L6GC,KT77:who works better with high impedance OT load in SE Triode Mode? | ygg-it | Tubes / Valves | 3 | 22nd May 2015 07:20 PM |
Understanding load lines | tvrgeek | Tubes / Valves | 20 | 18th January 2010 07:16 PM |
Need help understanding transformer impedance ratios and impedance matching | percy | Tubes / Valves | 5 | 28th February 2005 09:35 PM |
Understanding OPT primary Z and load matching. | percy | Tubes / Valves | 4 | 21st August 2004 01:30 AM |
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