Hello all,
I am fiddeling around with my own otl (circlotron) design, which was inspired by the thorens tem 3200, but only with tubes. The concept uses an input transformer. I will use a input transformer the first time and after having read several product datasheets I could not pick the best input-transformer by myself for my board build up.
I have looked at Jensen JT-11SSP, CineMag CMOL-4x600T2 and Lundahl LL1527XL. Could someone please give me a recommendation, what product would be the best for this application?
Here are some Data:
- Ratio 1:1
- Input = about 2.7V peak to peak
- Input = RCA and XLR true balanced input
- mue-metal shielding
electrostatic shield between primary and secondary side
- the input-transformer is also used as phase splitter for the first stage (see the picture below)
In the picture below I have modelled a input-transformer (including stray capacities) with data I have collected (I don´t know if I have made it right)
I am fiddeling around with my own otl (circlotron) design, which was inspired by the thorens tem 3200, but only with tubes. The concept uses an input transformer. I will use a input transformer the first time and after having read several product datasheets I could not pick the best input-transformer by myself for my board build up.
I have looked at Jensen JT-11SSP, CineMag CMOL-4x600T2 and Lundahl LL1527XL. Could someone please give me a recommendation, what product would be the best for this application?
Here are some Data:
- Ratio 1:1
- Input = about 2.7V peak to peak
- Input = RCA and XLR true balanced input
- mue-metal shielding
electrostatic shield between primary and secondary side
- the input-transformer is also used as phase splitter for the first stage (see the picture below)
In the picture below I have modelled a input-transformer (including stray capacities) with data I have collected (I don´t know if I have made it right)
Attachments
As a first experiment, you can try a small transformer like those spika inter stage unit. They usually uses low voltage and are cheap. Perhaps not applicable to the final artwork.
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They are pretty much similar and all are low input impedance. The Jensen and Cinemag are surely better specified/characterized....
So, unless your preamp or source is happy with 600R load none of them is suitable.
In such case you need to look for a high impedance bridging transformer which is also suitable for phase splitting. It's basically the same kind of transformer but high input impedance. Jensen and Cinemag surely make such kind of transformer, typically 10K input impedance.
So, unless your preamp or source is happy with 600R load none of them is suitable.
In such case you need to look for a high impedance bridging transformer which is also suitable for phase splitting. It's basically the same kind of transformer but high input impedance. Jensen and Cinemag surely make such kind of transformer, typically 10K input impedance.
Thank you for the input impedance information. I took another look at the data sheets. It seems that Jensen does not supply a high resistance split transformer. But I found the Lundhal 1690 and the Cinemag CM-13102.
Are those more suitable?
Are those more suitable?
Yes they seem to be fine. You will likely need a RC series network in parallel to each secondary winding to get a smooth high frequency response or use a source impedance higher than specified (600R-1K).
The Jensen isn't particularly expensive (something like $50), and I consider them to be very transparent. At least in my neck of the woods, Lundahl is considerably more expensive.
I didn't find a Jensen with split configuration and high impedance input. Could you give me the type designation?
Go for the Cinemag.
I would have added Sowter who used to make nice bridging transformers but they have sold their company and the current production is not as wide as before. But you can ask....the model 1475 is a nice one and doesn't need compensation networks in most cases. I can see that this type is one that has priority so it should be available...in theory.
I would have added Sowter who used to make nice bridging transformers but they have sold their company and the current production is not as wide as before. But you can ask....the model 1475 is a nice one and doesn't need compensation networks in most cases. I can see that this type is one that has priority so it should be available...in theory.
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If you have to have an input TX, then you have many choices, and likely a few pairs to buy before you decide you have gotten one good enough. If you can tolerate a tube phase splitter, almost the same process comes to play; which one? A LTP? A self biased split-load? and so on..LOL
I'd try a pair of 12A4 first... 🙂 LTP with a current reg in the tail.
cheers,
Douglas
I'd try a pair of 12A4 first... 🙂 LTP with a current reg in the tail.
cheers,
Douglas