Thanks ZM.
I'm tempted to use a pair of the TH-51S devices as they can be bolted directly to the heatsink without a bracket so superior heat transfer/dissipation.
I'm tempted to use a pair of the TH-51S devices as they can be bolted directly to the heatsink without a bracket so superior heat transfer/dissipation.
I have just simmed it. Same. Bias -3.5 for 182, -6,2V for 180. No difference in harmonics, slight in 'amplification'.
Note, I have a transformer coupling with Jensen JT-123 FLPCH from Gate->Source though. So sort of bootstrapped. That way I do not need a high amplification driver stage. Now the whole single stage amplification is just short of 10x.
I've been collecting bits and pieces ready to start building, hopefully next week.
My initial objective is to build the follower and bias circuits but power them from a basic 36V SMPS - I want to check the frequency response of the circuit and heat management aspects of my heatsink/chassis and if that checks out I'll move on to adding a better power supply and improving the aesthetics.
Just to remind, my build will be bandwidth limited, rolling off below around 150-180Hz as it will be driving the 'full-range' section of a Pass Open Baffle (I have a chip amp to provide the bass). Below is the circuit I'm working on (note the film cap on the output, made possible by the bottom end rolloff, which, with the speaker load, creates a LP filter with a -3dB point at about 114Hz). This is the cap I'm looking to use on the output:
https://www.mouser.co.uk/ProductDetail/KEMET/C4AQLEW6180M3AK?qs=81r%2BiQLm7BQN1XzD5EnFuw==
My initial objective is to build the follower and bias circuits but power them from a basic 36V SMPS - I want to check the frequency response of the circuit and heat management aspects of my heatsink/chassis and if that checks out I'll move on to adding a better power supply and improving the aesthetics.
Just to remind, my build will be bandwidth limited, rolling off below around 150-180Hz as it will be driving the 'full-range' section of a Pass Open Baffle (I have a chip amp to provide the bass). Below is the circuit I'm working on (note the film cap on the output, made possible by the bottom end rolloff, which, with the speaker load, creates a LP filter with a -3dB point at about 114Hz). This is the cap I'm looking to use on the output:
https://www.mouser.co.uk/ProductDetail/KEMET/C4AQLEW6180M3AK?qs=81r%2BiQLm7BQN1XzD5EnFuw==
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Thanks Ben, it's looking promising.
Some lengths of heavy aluminium 'U' section arrived yesterday so today I'll be drilling and tapping...
Some lengths of heavy aluminium 'U' section arrived yesterday so today I'll be drilling and tapping...
The Tokin doesn't care about frequency. The choke, otoh might if you are running it close to saturation.
The only way to lower the distortion is to raise the current and use a monstrous choke. At least 5A 🙂
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And by largely increasing the voltage.
At 24V = -38dB @2.2A; and at 40V = -46dB @ 2.4amp. (my reliable source, LT Spice.., 2SK182)
At 24V = -38dB @2.2A; and at 40V = -46dB @ 2.4amp. (my reliable source, LT Spice.., 2SK182)
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Yes, yes. My current iteration dissipates about 96W on the SIT but very tempted to raise this to 125W by raising both current and voltage.
I wish something like this was easy to prototype. Or even more extreme like 200:8ohm @200v.
Fwiw, the measured distortion on my THF51 amps is much lower than what the SK180 model i use predicts.
And apart from reducing distortion raising current leads to a lower output impedance, a decisive parameter for my speakers.
I'm not trusting much in sim with THF51 model, for THF51 amp, let alone 2SK180 model - for THF51 amp ....... speaking of THD levels
. . not very trustworthy maybe, but it does allow a design decision here and there.
I saw analog_sa's comment on dissipation, yes on paper mine got pretty hot too, even with the .35 K/W I will use, still upwards from 50 degrees.
So I'll have to see what the minimum is.
The 25V Mah-version is easy. Two amps is not too much.
At 70V Vds & >1,1 Amp I will have a problem.
And then, in practice, my devices are not flat at all. So they will get hotter and hotter.
I saw analog_sa's comment on dissipation, yes on paper mine got pretty hot too, even with the .35 K/W I will use, still upwards from 50 degrees.
So I'll have to see what the minimum is.
The 25V Mah-version is easy. Two amps is not too much.
At 70V Vds & >1,1 Amp I will have a problem.
And then, in practice, my devices are not flat at all. So they will get hotter and hotter.
In parafeed or PP, toroid power transformer works well enough for prototyping. We just need to remember that max applicable voltage at 50 Hz is 2.5x that for 20Hz. However max current is dependent on wire diameter alone. In short a >62.5W power transformer should be good for 25W audio. Since impedance ratio is square of turns ratio, 110V pri with 22V sec power transformer should work well enough as 200:8 ohm (5:1 ratio) impedance transformer within it's 2.5x derated power limit.
Regular toroid cores will go into saturation with a few ma of DC current, so forget SE application with DC current such as the Mofo.
. . not very trustworthy maybe, but it does allow a design decision here and there.
I saw analog_sa's comment on dissipation, yes on paper mine got pretty hot too, even with the .35 K/W I will use, still upwards from 50 degrees.
So I'll have to see what the minimum is.
The 25V Mah-version is easy. Two amps is not too much.
At 70V Vds & >1,1 Amp I will have a problem.
And then, in practice, my devices are not flat at all. So they will get hotter and hotter.
I underlined "levels"
I'm also using LTS extensively, as much I know and developed own level of skill, enough to know in what I can trust and what is better to ignore and make final decisions in physical world
so, not disputing you, at all
What is very interesting on paper, is that the 2SK180 and 2SK182 models are so different that in a choked lamp, the K180 has many more harmonics , say 2-7, nicely degraded; while the K182 shows only 2-3 or maybe a tad of 4th.
The degradation is interesting, the level not, indeed, like you say. The level changes at a whim on paper. Just change the parameters a bit.
The K182 is more lineair. Maybe, compare like the 211 being more lineair than the 300B.
In practice. This is very interesting, as Jean Hiraga has shown that amplifiers that have the slow degradation of the K180 sometimes have sounded better . .
For me, the most important issue is to get the second the way you like. With a slight projection forward (like I have right now, great on some music, the players are in the room, (specifically the Klara radio is great in this) or backward (which I had for many years). There are so many puzzling elements here.
The degradation is interesting, the level not, indeed, like you say. The level changes at a whim on paper. Just change the parameters a bit.
The K182 is more lineair. Maybe, compare like the 211 being more lineair than the 300B.
In practice. This is very interesting, as Jean Hiraga has shown that amplifiers that have the slow degradation of the K180 sometimes have sounded better . .
For me, the most important issue is to get the second the way you like. With a slight projection forward (like I have right now, great on some music, the players are in the room, (specifically the Klara radio is great in this) or backward (which I had for many years). There are so many puzzling elements here.