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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Re: Because in my own extensive tests, it lost information... posted by Eli Duttman on March 18, 2007 at 05:36:29:
Hi."TANSTAAFL" is short of There Aain't No Such Thing As A Free Lunch".
Mind you, take care to use it as it is the official name of wire supplies company in USA, specialized in HV (25KV) & HT (538C) wires.
Agreed to your comment on UL needs high qualtiy O/P iron which are "expensive" to buy.
Here is what Norman H. Crowhurst said his his publshed paper in Nov 1959:
"In the case of Ultra-Linear the choice of the tube operation is vertually one btween pentode & triode. The tappings on the transformer primary "split the difference" between connecting the screen to B+ or directly to plates. The first is pentode, the second is triode. Connecting them to a tapping results in Ultra-Linear. The achieves practically the efficiency of a pentrode while maintain the linearity or lower-order distortion of a triode.
This would seem to be ideal. The difficulty is that, to work perfectly, the transformer must maintain the correct tapping, both in voltage & phase, of ALL audio frequencies. This is not too difficult for the low frequency end but, at the high frequency end, stray leakage inductances between different parts of the winding, along with the winding intercapacitances, can really play HAVOC
with an U-L circuit resulting in some quite weird waveforms at some specific frequencies."The solution as Norman suggested is to get a "correctly designed" U-L transformer to "avoid any spurious deviation from correct tapping up to a frequency beyond the audio range and ALSO beyond the cutoff of the transformer".
This not impossible, but only relatively few irons so built under the name of U-L achieve this objective.
Frankly, I modified my ST-70 with switchable UL/triode strapped, I always listen with the power tubes triode strapped since day one as I am not that impressed by its original U-L mode.
c-J
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Follow Ups
- That sounds similar ! - cheap-Jack 09:41:35 03/19/07 (6)
- A good example of what I meant - Ray Moth 10:14:13 03/19/07 (5)
- No, U-L was invented by Alan Blumlein in 1937, - cheap-Jack 10:45:07 03/19/07 (4)
- Re: No, U-L was invented by Alan Blumlein in 1937, - Ray Moth 19:04:44 03/19/07 (2)
- Good question on "Ultra-Linear". - cheap-Jack 13:39:39 03/20/07 (1)
- Misinformation - fatbottle 03:46:15 03/22/07 (0)
- Now that's a ref. I'd really like to read! - Try-ode 11:07:10 03/19/07 (0)
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