New UL OPT Transformer from Magnetic Components

[tomlang]

Has both 6.6k and 4.2k input taps with UL taps. UL taps are 43% of 4.3KΩ TAPS
and 35% of 6.6KΩ.

Does the 35% at 6.6k have any practical use whatsoever?

Is having both 4.2 and 6.6k input taps a recipe for "disaster", wrt close-coupling and inter-capacitance of the windings, etc?

http://www.classictone.net/40-18080.html

[kheper]

Patrick Turner implies that using a 35% screen tap lowers the distortion - at least from pentode mode.

"The power output is for 12 x 6550 with 20% cathode feedback connected,
and the tube operation is very similar an ultralinear amplifier with about 35%
taps for the screens. Power is marginally less than pure beam tetrode, but
the distortion is far lower."

http://www.turneraudio.com.au/300w-outp ... raphs.html

He recommends using a 30% screen tap for the 6550:

"The Rout from the output tubes should be equal to the primary input load, so use
6550 wired as Ultralinear with approximately 30% screen taps."

http://www.turneraudio.com.au/output-trans-theory.htm

Some tubes may benefit from a 35% tap, but I know of none off the top of my head. Dennis Grimwood delves into the theory and detail of screen grid ratios, but does not mention a 35% tap. I think some James transformers have or had a 35% tap?

http://www.oestex.com/tubes/ulo.html

[Geek]

You thinking of grabbing a pair, Tom?

I'd love to hear what you think of them!

[tomlang]

I was thinking of getting a pair. I sent an email to them and received the response below. My main concerns are:

1. Usability for 6l6 tubes with 35% UL taps
2. Usability for EL34 tubes with those "extra" windings inside not used

#2 may not be a legitimate concern. Regardless, the only real way to see how these are is to hook 'em up!

Hello Tom,
As this part was recently released, we have not had any feedback yet.
The only thing our 40-18080 shares with the Dynaco A-470 is the primary and secondary impedances (except for the addition of the 6.6K Ohm taps), the core material and power level.

Our 40-18080 is based on the A-470 but is wound differently and is on a different lamination size. The performance is equivalent.

Thank you for your interest in our products. Please contact me if you have any more questions.

Mark Sacketti
V.P. of Engineering

[kheper]

KT88 amp with the James 6123 OPT @ 35%:
http://www.audiokarma.org/forums/archiv ... 62279.html

"I used the suggested James 6123 OPT and discovered when set to Z=5K the UL screen tap is actually at 35% not 43% (It would be 43% when using the 3.5K taps)"

The 35% tap will provide more output and more distortion than 43%, but with the 6.6k primary, you may not notice. As long as you do not exceed the max screen voltage with the 6L6, it may be worth trying. You could cut the unused winding wires short and tape them - if you never plan on using them.

[Gingertube]

The Radiotronics Ultralinear Articles by Fritz Langford-Smith from 1955 are an excellent place to look for basic Ultralinear theory.
The Radiotronics Magazine was the Sydney Australia AWV Tube Factory regular publication. Fritz was their chief engineer, this mag. and editing of the Radiotron Designers Handbook were some of his major works whilst employed there.
A lot of the Radiotronics Issues are here: electron Tube Data sheets - AWV, Amalgamated Wireless Valve Company
The Ultralinear Part 1 , Part 2 and Part 3 are in 05' 1955, 06' 1955 and 07' 1955 issues respectively. Want clean copies from scans of the original, this is the best place to get them - slow link, be patient.
Careful he quotes impedance percentage taps. You need to take the square root of these percentages to get turns tapping percentage.
Cheers,
Ian