Just A Thought About Mains Transformers.

Posted by Tubelcain (A) on February 10, 2013 at 06:53:44

A Few thoughts on Mains Transformers.

Big thanks to Kevin for your compliments regarding the Tale of two Amplifiers projects in an earlier post.

I noted that you have been having some further success with mods to your commercial PPP KT 120 amp by separating the filament & Ht transformers. This is in its self well established good practice to isolate noisy switching rectifiers from creating unpleasant common mode noise on the heater lines contaminating the heater/cathodes interface. I as well as others have spend much time money & effort trying to snub out this irritating & harsh sounding hash in my projects.

You mention your use of the LL2738 filament transformer to good effect. With the above still in mind I wonder how you sorted the HT & bias sides of the transformer as there would appear to be a gap in the present Lundahl range for such a Transformer?
The current1648-51 series being all-rounders which include filament windings.
Just A thought for further projects wish list, if Lundahal could be persuaded to produce a Ht/Bias trany only with say two equal 0-50-300-325 @475ma and a100v @40ma windings that this would flexible enough to please a lot of amp builders out there whilst keeping the transformer nicely balanced as per Lundahls design philosophy.
Whilst not perfect for everybody this would provide a good range of possible HT voltages (assuming the use of a hybrid damper/silicone bridge rectifier which seems to have found universal approval) such a transformer with some careful thought would keep the KT120/320B-XLS boys @DC525v & the WE300B/KT88 at DC420v very happy. Further lower voltage combinations would also be possible with a centre tap and full wave rectifiers for the 2A3/45/6B4G brigade, plus with solid state & capacitor input, 900 +v Dc for the 211/845/Gm70 Boys. Finding an off the shelf and flexible mains transformer has always been almost impossible and has usually meant having none Lundahl custom made transformer with say 6x secondary winding and the resulting intertwining hash. Just A thought Lundahl.

Thought Two. Adore the Lundahl Transformer Covers for the Bigger Transformer units & now for the 1663/82 size also. A very clever design which looks very Chic indeed.
How about the same design philosophy in a cover which would take two of the bigger Mains/output Transformers one each end. Also with a gap in between large enough to cut a hole one side to fit a mains in let/filter and a mains switch the other side. That would be one very pretty & cool way to deal with the dirty AC side of A Valve/Tube amplifier. Could also mount two Output Trannies in one cover with the output terminals on the back!! I think that Lundahl would be onto A commercial winner there, just thinking out loud.

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Topic - Just A Thought About Mains Transformers. - Tubelcain 06:53:44 02/10/13 (1)

RE: Just A Thought About Mains Transformers. - KevinC 05:53:48 02/12/13 (0)

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