LP275M teflon capacitors

[stereoquest]

Microstrip,

The LP275 schematic on Audio Aficionado must be an early testing unit schematic. Apart from the input stage and 6n30's with their regulation--- from what I have seen compared to my pair it is mostly the same otherwise.

[plurn]

Originally Posted by Coppy

I'm now remembering that the LP275 trannies have to be bigger as they have to service twice as many output tubes. Each output tube needs it's own winding for input, thus twice as many input windings for the LP275 as the LP140. I assume the output windings must be larger to accept the signal from more on the input side. These big transformers where there are eight output tubes are complex beasts.

The schematics do not show the LP275M output transformers having any more input windings than the LP140M output transformers. Each output tube does not need its own winding for input, as there is some paralleling of tubes involved. The schematics do show different model numbers for the transformers however. It does make sense that the LP275M output transformers would be larger than in the LP140M in order to handle the extra capacity.

[stereoquest]

Gents ,

For the benefit of all I have attached a link which explains Vacuum Tube Output Transformer Measurements-- how to Determine Turns & Impedance Ratio & Matching To Tubes.

[ame]https://www.youtube.com/watch?v=Yzo3A-NywSs[/ame]

[stereoquest]

Here is another informative clip-

[ame]https://www.youtube.com/watch?v=nNlPgirHP48[/ame]

[plurn]

Hi stereoquest - I think we may all be talking about different things. I was not talking about number of turns, or impedance ratio. I was referring to Coppy's comments "Each output tube needs it's own winding for input" and "These big transformers where there are eight output tubes are complex beasts", which I read to mean that Coppy thought that each tube had its own wire going into the transformer (eg 8 individual wires for 8 output tubes, or 4 individual wires for 4 output tubes) and that each of those wires were wound around the transformer core individually (as its own winding) for input making the transformer more complex.

My point was that the transformers are not like that and the tubes outputs are paralleled before being fed into the transformers. So the transformers themselves are not necessarily more complex just based on there being more tubes.

I may have misread what Coppy was writing about though - I am not sure.

In any case, it probably doesn't really matter - they are amplifiers and they do their job of amplifying. As users we don't really need to know the low level details. Though it is interesting.

[stereoquest]

Gents,

From the clips above it will be clear that there is no way you would use the same transformers for amplifiers with double the output. It will also be clear that the larger transformer has a reduced turns ratio and should incorporate thicker gauge winding's which will give :

1.)Wider bandwidth
2.)increased damping factor
3.) the increased damping will be over a wider bandwidth as well

By default the 275 will have the above over the LP140 and that is only in the output transformer.

Having owned both there is absolutely no contest - The LP275 wins hands down across all volumes . It has an ease of presentation that the smaller unit cannot not provide. I believe the LP275 to be a steal on the second hand market, there is nothing remotely close to it other than the ART mono's which are based on the LP275----(Input stage aside of course) .

In the case of the LP line of Amplifiers Bigger is without question better. In the case of the ART mono's output transformer compared to the LP275's -I believe them to be the same .

[stereoquest]

No worries plurn, fully understand .....just thought to throw in some interesting clips for those who wish to go a little deeper.