Or perhaps a FE "offset" could be used to bias the SIT. The SIT source voltage would be approximately Vsupply/2, so the FE output would need to be more negative (Vsupply/2 + Vbias). However that imbalance would decrease the output capacity of the FE. It's hard to say without seeing more of the PCB/schematic.
Another interesting specification is 35W at 8 Ohm and 60W at 4 Ohm. I think for that to happen the mosfet would have to contribute quite a bit to the power output. The speaker output would probably have to be connected directly to mosfet source. Or I could be totally out to lunch. It would be interesting to see the 4 Ohm distortion at 60W.
Another interesting specification is 35W at 8 Ohm and 60W at 4 Ohm. I think for that to happen the mosfet would have to contribute quite a bit to the power output. The speaker output would probably have to be connected directly to mosfet source. Or I could be totally out to lunch. It would be interesting to see the 4 Ohm distortion at 60W.
The FE seems complementary, 2013/313. That even possible without a dual rail supply for the front end?
The power supply is single ended, but that is not of interest here. Any conventional voltage gain stage for a front end will "work".
The interesting thing is the complementary circuit which biases the output SIT.
Maybe I will post that on Christmas...
The interesting thing is the complementary circuit which biases the output SIT.
Maybe I will post that on Christmas...
I do not think you are out to lunch. Looking forward to father Christmas posting some mo’ (hopefully!).
My assumption with a BA3 like FE is wrong. The truth is more on Ben Mah side.....I suppose!
I wish all a Merry Christmas!
I wish all a Merry Christmas!
A BA-3 like FE (or perhaps a F5/F5 like circuit used as a front end) could work as it could be powered by a unipolar power supply. And with a unipolar power supply, the output would have DC voltage in the general vicinity of the voltage needed to bias the SIT, with an adjustment of the "offset", as I had mentioned previously. And Nelson has confirmed that "the complementary circuit.....biases the output SIT".
Tokin SITs have a wide range of Vgs so I would think that for uniformity of performance for the production run of amplifiers, the SITs would need to graded and sorted for at least Vgs in order for uniformity of FE parts and performance. Nelson probably has hundreds if not thousands of Tokins so that would not be an issue,. 🙂
Tokin SITs have a wide range of Vgs so I would think that for uniformity of performance for the production run of amplifiers, the SITs would need to graded and sorted for at least Vgs in order for uniformity of FE parts and performance. Nelson probably has hundreds if not thousands of Tokins so that would not be an issue,. 🙂
Yikes! Tens of thousands?
I've been looking into building a little stash of these (I know, late to the party) and I'm seeing prices kissing $100 bill.
Wanna sell a few? 😎😎
I've been looking into building a little stash of these (I know, late to the party) and I'm seeing prices kissing $100 bill.
Wanna sell a few? 😎😎
I made with my simplified mind a simplified and quick and dirty LTspice and there is some success.....
But I am far from understanding what I do......
:--))
Around 2.3A, distortion is too high because H2 is too high, I did not yet, if ever, find the way how to change this.... the idea with a second cap and another resistor at the output did not change H2 in my Spice.
But I am far from understanding what I do......
:--))
Around 2.3A, distortion is too high because H2 is too high, I did not yet, if ever, find the way how to change this.... the idea with a second cap and another resistor at the output did not change H2 in my Spice.
Attachments
Hm, seems that I have difficulties to understand this sentence.....
" This arrangement is unique in that the SIT is given a single ended
Class A bias current by the P channel Mosfet which is allowed to make a smaller
contribution to the output, typically about 20%. This is seen on the right hand side of the
schematic where the output goes through two sets of power resistors and capacitors."
For me irritating as not native speaker.
And of course I am used that the CCS is always giving maximum 50% in Nelson designs.
Maybe I mix it up with the Aleph way of adding some more power.
" This arrangement is unique in that the SIT is given a single ended
Class A bias current by the P channel Mosfet which is allowed to make a smaller
contribution to the output, typically about 20%. This is seen on the right hand side of the
schematic where the output goes through two sets of power resistors and capacitors."
For me irritating as not native speaker.
And of course I am used that the CCS is always giving maximum 50% in Nelson designs.
Maybe I mix it up with the Aleph way of adding some more power.