Hello All,
I am interested in gathering information about building an amplifier that uses a sit like THF51S as its final device with an output transformer like Hiraga's Nemesis or Susan Parker's Zeus. The output transformer would also make it easier to adopt a working point other than the usual low voltage / high current. Probably the THF51S at 250volt and 300 / 400ma is more linear than the usual working points and could be an alternative to an SE of 845 or 211 with the advantage of only needing 10 / 15volt of signal (against the 160volt of the 845 or the 60volt of the 211) In my case this amplifier would work in a multi-way system where it would drive the mid-bass horn from 100 to 700Hz, so it would be easier to build the output transformer by limiting the response at the bottom.
Any suggestions?
I am interested in gathering information about building an amplifier that uses a sit like THF51S as its final device with an output transformer like Hiraga's Nemesis or Susan Parker's Zeus. The output transformer would also make it easier to adopt a working point other than the usual low voltage / high current. Probably the THF51S at 250volt and 300 / 400ma is more linear than the usual working points and could be an alternative to an SE of 845 or 211 with the advantage of only needing 10 / 15volt of signal (against the 160volt of the 845 or the 60volt of the 211) In my case this amplifier would work in a multi-way system where it would drive the mid-bass horn from 100 to 700Hz, so it would be easier to build the output transformer by limiting the response at the bottom.
Any suggestions?
if you want some preliminary work, instead of actually building mock-up circ and playing with settings, you need proper U-I graph, covering entire area of interest
so, ideally (at least) 300ma and (at least) 300V
rest is easy...... except finding adequate proper OPT
some interesting reading, besides those you did mention, though it will not give you any specifics for THF51:
https://www.firstwatt.com/pdf/art_arch_nemesis.pdf
https://www.firstwatt.com/pdf/art_sit_nemesis.pdf
so, ideally (at least) 300ma and (at least) 300V
rest is easy...... except finding adequate proper OPT
some interesting reading, besides those you did mention, though it will not give you any specifics for THF51:
https://www.firstwatt.com/pdf/art_arch_nemesis.pdf
https://www.firstwatt.com/pdf/art_sit_nemesis.pdf
Another pertinent writeup by a Swedish gentleman, wonder if he is on this forum?
https://www.lennartlabs.se/#!/projects/articles/blnemesis
https://www.lennartlabs.se/#!/projects/articles/blnemesis
Awesome article and work. Most of the listening impressions resonated strongly with my own impressions of the Tokin SIT in a choke-loaded follower.
I tried this very briefly using Tokins and home-made OPTs. There was a thread on it, see post #40 for the SIT stuff. I may revisit this.
I rolled my own OPT. Then I made an Arch Nemesis with it.
I rolled my own OPT. Then I made an Arch Nemesis with it.
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Joined 2006
A friend of mine bought a nice diy set of 2sk180 SE amps a few years ago from Japan using Tango FG-50s output transformers (no circuit provided). He said they sounded like his 2A3/300Bs, and better than his Yamaha B-1 in the highs. 😀😁
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If you just want to give this a try without having to buy a big badass SE output transformer with a suitable gap to swallow the large DC current, you could do some first experiments with a push-pull transformer (or just a any transformer with two symmetric primaries). Use one primary for the Tokin, and balance the DC bias by running the same DC current through the second primary in opposite polarity. This will cancel the DC magnetic field in the core, avoiding saturation.
Thank you all for the contributions. In the meantime I managed to find a pair of Tango Hirata FG20 64 and then I solved the problem of the OPTs. At this point the idea is to create a two-stage with input transformer (balanced input, single ended output)
to drive the high CIN of the THF51S I could choose another Vfet like the 2SK60 or 2SJ18 (gain 4, output 12 ohms) a kind of Sakuma solid state style; with a 1: 2 input transformer and setting a working point at about -13 volts the sensitivity of the power amp would be around 2 volts and maybe there could also be some harmonic cancellation between the driver and the power amp.
The alternative to the 2SK60 would be a triode, maybe DHT, maybe Thoriated Tungsten with a downward transformer (4: 1) to drive the THF51S (also very Sakuma style ...)
Since I have no experience with SS amplifiers it is almost certain that I have not considered some aspect that should have been considered.
Tips?
to drive the high CIN of the THF51S I could choose another Vfet like the 2SK60 or 2SJ18 (gain 4, output 12 ohms) a kind of Sakuma solid state style; with a 1: 2 input transformer and setting a working point at about -13 volts the sensitivity of the power amp would be around 2 volts and maybe there could also be some harmonic cancellation between the driver and the power amp.
The alternative to the 2SK60 would be a triode, maybe DHT, maybe Thoriated Tungsten with a downward transformer (4: 1) to drive the THF51S (also very Sakuma style ...)
Since I have no experience with SS amplifiers it is almost certain that I have not considered some aspect that should have been considered.
Tips?