UTC Linear Standard High Level matching transformers

[vaslejean]

Hi everyone,

I am seeking informations on the UTC LS-33/34 High Level matching transformers.
These transformers were part of the output tranformers line that utc was offering in their catalogs. I had the oportunity to hear an amplifier some 10 years ago that was using an UTC LS-33 as output. The amplifier made by the late Gilbert Preyale, was using a 5998 as output tube (single ended cathode loaded). Does anyone has experimented with these transformers? My understanding is that they are similar to a "universal" transformer by the multiple impedances configuration possible . But, the little info I could find over the internet seems to suggest that they can not handle any D/C. The UTC LS-33 rated for 20 watts weight over 6 pounds, the UTC LS-34 rated 40 watts, 18 pounds !

Mr. Preyale also made an srpp version of the amplifier afordmentionned that was running the 5998 at 500 D/C volts. The UTC LS-33 used in this fashion was providing more than 8 watts.

Would it be safe to use such a transfo for 2A3 se application ?

[Gluca]

The datasheet can help. Anyway I believe you cannot use it to load a 2A3.

[vaslejean]

Thank you for your reply...

The data sheet ,of both UTC LS-33 and 34 states nothing has to what current is admissible trough the transformers, but then UTC, on most available catalog data sheet, does not mention it neither for their Push-Pull transformer line , to the best of my knowledge.

Now again, the LS-33 is given for 20 watts and the LS-34 for 40 watts. Should the primary and secondary be configured for 2A3 ( as an example) is there any reason why they could not be put trough that task ? Is'nt the wattage given, indicative of the power dissipation admissble by the transformer ?

The transformer are respectively homologated for 500V (33) and 700 V(34) Hipot test.

[Gluca]

I read on the datasheet it is given as 600ohm primary so you must be sure there is enough inductance to load a 2A3. You might find a suitable arrangement of the primaries to secondaries to have a reflected load > 3K.

It looks like the LS-33 is a line-to-line transformer with additional voice coil windings, It should not accept any current ... I wonder how your friend could use it in a SE amp. Was it a parafeed amp?

Ciao
Gianluca

[korneluk]

Originally posted by vaslejean
Hi everyone,

I am seeking informations on the UTC LS-33/34 High Level matching transformers.
...
The UTC LS-33 rated for 20 watts weight over 6 pounds, the UTC LS-34 rated 40 watts, 18 pounds !
...
Would it be safe to use such a transfo for 2A3 se application ?

Yes, even though it is not apparent when first reading the specs. The trick is to take one of the secondary windings and use it in series with the primary to raise the inductance. You will have to do this by trail and error.

For example, with the LS-33 use both 600 ohm windings in series for 2400 ohms and 55H primary inductance. Certainly enough for a 2A3 or 300B parafeed circuit.

Take a peek at this thread:

Utc Ls-33

Enjoy,

-- josé k.

[vaslejean]

...

The amplifier was cathode loaded using a 5998. I am posting here the schematic that was published by La Nouvelle Revue du Son (september 1999 if I am right) The schematic has a reference for a transformer made by Magnetic S.A. french transformer maufacturer. Mr.Preyale had this company to wind an output transformer.
As he was planning to possibly manufacture the amplifier he could not possibly make it with a UTC for obvious reasons (avaibility for a start)

He did use a UTC LS-33 for the presentation I attended at Supravox in France.
The amplifier had a nominal power of 1.25 Watt clipping occuring at about 3 to 4 watts.

Gilbert Preyal was working on some very unusual tubes he apparently designed an amplifier that is using 8 EC-86 in se ended configuration that pulls-out about 6 to 8 watts. I beleive he was fond of the UTC transformers for prototyping. He passed away last march , or is it in march last year ?

He made a more conventional amplifier (plate loaded)se E55L .

[vaslejean]

My initial inquiery is getting some encouraging input. I am posting the schematic of the 5998 SRRP. I will have to experiment if I want to use the transformers otherwise than what is shown on this schematic.

Thanks to you all.

[korneluk]

what happened to the schematic?

[tubelab.com]

I have used the LS-33's for several experiments. You can run current through the primaries if the total DC flux through the transformer is zero. This means a P-P arangement. It will not work for a conventional SE where the plate current flows through the windings. It will work as a parafeed SE OPT since no DC flows through the transformer.

[vaslejean]

...It will not work for a conventional SE where the plate current flows through the windings. It will work as a parafeed SE OPT since no DC flows through the transformer.

It seems it did actualy worked for the prototyping of the E55L amplifier Mr.Preyale was working on at some point. He did used the 500(600) Ohms primary and then hooked the secondary on the 50 Ohms tap to get a reflected primary of about 3750 Ohms. Loading the transformer with the E55L at 180 Vdc with an Ia of 46ma... 1.3 Watts before any visible distortion on the scope.

Was the tranformer anywhere near self destruction ? Maybe ,but he did took time to make some measurement.

No mention made on that page to the UTC LS-33, though I am sure that is what he sued back then (march 2000) He did however specified a Lundhall output transformer for his final design.

The page is in french but then most will be able to get the idea. : http://preyale.melaudia.net/apE55L.php

Many thanks again.