Does anyone know,
What’s the problem, if SE output transformer use in PP method.
Sine I have a pair of LL1623 SE 80mA . Is it suitable for PP method ?
Thank you.
What’s the problem, if SE output transformer use in PP method.
Sine I have a pair of LL1623 SE 80mA . Is it suitable for PP method ?
Thank you.
SE doesn't have the center tap to hook +B for tubes. If you use two trafos, the resulting will not act as a true pushpull trafo because of lack of magnetic coupling between primary half winding.
It is possible with lundhal transformers..
http://www.lundahl.se/wp-content/uploads/datasheets/1620_3_7_9202.pdf
Not a problem with low impedance tubes? I don't know..
I raised a similar question recently ...
OPT for SE and PP
The amp they were designed for can be configured as PP or PSE. Presumably there must be some trade-off for the flexibility, but a transformer with multiple taps and an air gap seems to be like the equivalent of a socket set!
OPT for SE and PP
The amp they were designed for can be configured as PP or PSE. Presumably there must be some trade-off for the flexibility, but a transformer with multiple taps and an air gap seems to be like the equivalent of a socket set!
They are selling smoke. SE transformers need a single primary winding (With eventual taps for impedance matching or ultralineal ) and air gap in the core to prevent saturation because of DC imbalance.
PP transformers need a center tapped winding (With eventual taps for UL too) but don't need (and in fact it is avoiding to) use any kind of gap.
So surely they are selling a gaped core with a center tapped primary, say, a poor mix between them.
PP transformers need a center tapped winding (With eventual taps for UL too) but don't need (and in fact it is avoiding to) use any kind of gap.
So surely they are selling a gaped core with a center tapped primary, say, a poor mix between them.
I doubt that anyone using Lundahl OPT's would use those words to describe them. The pair I have do sound quite nice, and they are actually well made double C core transformers. Umlike these assumptions, they are NOT one size fits all.
I have not seen the exact units discussed here. I do have a pair of LL-1663/P-P units. https://www.lundahltransformers.com/wp-content/uploads/datasheets/1663.pdf
In that case there are THREE DIFFERENT models of the same transformer. All have the same ELECTRICAL winding specs. The multiple primary and secondary taps allow for configuring the interleaving for the intended application. Each has a DIFFERENT CORE GAP, depending on the intended application. The /PP unit has a near zero gap for push pull applications. It is specified for 40 watts @ 30 Hz, with an unspecified (but sufficient) primary inductance.
There are TWO models for SE applications, one specified for 50 mA resulting in a 35H primary inductance, and one specified for 100mA resulting in a 17H primary inductance. Both of these are specified for 8 watts @ 30 Hz.
Yes, you could use one of the SE units for a P-P amp, but you would give up a LOT of power handling capability and primary inductance.
Attempting to use one of the P-P units for SE applications would result in severely distorted bass at power levels over a watt or so, if that due to core saturation from the DC current.
Respectfully, knowing what the mean audiophile call for "sound good", it doesn't imply nothing. I know people that feels extremely happy with only a medium quality amp, or still worse, the sound of their cell phones :-(.
Then it is not the same model. There must be a difference in the part number, and a difference in the manufacturing process.
True. Although if the traffo has natural gap from non interleaving steel thinkers, then it may or not work properly given DC and power from it. A low turns primary with low Amper*Turns not reaching saturation of the core in audio peaks, perhaps will work and moreover, "sounding good" for some people.
Mine are LL1663/PP zero, or small gap for P-P use.
There are also LL1663/50mA and LL1663/100mA versions.
This is stated in the spec sheet I linked to.
The core gap is the difference in the three different models. The manner in which the different windings are interconnected is also different for P-P or SE applications, also shown in the spec sheet.
OK, from an engineering perspective, The P-P OPT's that I have are specced for 40 watts at 30 Hz, quite a lot for an OPT that weighs 1.35 kg. I'm sure that you know that what's being used to drive the transformer under test has a lot to do with how it performs.
I bought these transformers for their small size, since I was building a push pull tube amp in a 2 RU chassis (3.5 inches tall). I was not expecting a lot. I am driving these with a pair of tiny 6GF5 TV sweep tubes which do have local feedback applied to them to lower their output impedance. The amp will make 40 watts at 30 Hz into an 8 ohm resistor with just a hint of saturation showing on the scope. If I remember right the THD was 3 or 4%. The amp makes over 50 watts @ 1 KHz, and over 40 watts @ 20 KHz, both at 3% THD.