I have a SE triode headphone amp based 5687 actually with OPT air gaped so no output cap.
I want to use cascode CCS in place of OPT load, I have DN2540, IXTP 01N100D & LND150 so I'm looking for the best suited CCS for my needs: what upper or lower position device, etc.?
Also I need to use the OPT to reduce the output impedance but I have doubts if I need an output capacitor between the CCS & the output gaped transformer, if yes how can calculate the value?
TIA guys.
I want to use cascode CCS in place of OPT load, I have DN2540, IXTP 01N100D & LND150 so I'm looking for the best suited CCS for my needs: what upper or lower position device, etc.?
Also I need to use the OPT to reduce the output impedance but I have doubts if I need an output capacitor between the CCS & the output gaped transformer, if yes how can calculate the value?
TIA guys.
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I kind of had a similar setup with a pair of 6E5P tubes in triode mode instead of 5687s.
Sound wise the only real difference I heard was very high up in the frequency range where I started to have a rising response due to capacitance. But after fiddling with gate resistor values on each device I got them to all sound virtually identical.
Through a lot of experimentation, I ended up going a completely different route for the upper CCS device. I now use untied SIC jfets. They cost a few more bucks than a DN2540, however they are lower noise and they are MUUUCH better about thermals.
For the bottom device, I just find some cheap jfet that can handle the current and voltage.
I have found that jfets just give a little more clarity than the depletion mode mosfets. IDK if that is because of the differences between mosfets and jfets, or if it is simply because the jfets are not trying to go thermonuclear on me.
As far as capacitors go, there is no equation sadly. The equations I have found are for inductors. When you try to do the math and you assume your CCS has about 1M of impedance, you end up with a capacitor value in the several thousand uf range.
However what I do is just start off with a 5uf capacitor, and 99 times out of 100 I find that a capacitor between 5 and 8uf is more than enough.
Sound wise the only real difference I heard was very high up in the frequency range where I started to have a rising response due to capacitance. But after fiddling with gate resistor values on each device I got them to all sound virtually identical.
Through a lot of experimentation, I ended up going a completely different route for the upper CCS device. I now use untied SIC jfets. They cost a few more bucks than a DN2540, however they are lower noise and they are MUUUCH better about thermals.
For the bottom device, I just find some cheap jfet that can handle the current and voltage.
I have found that jfets just give a little more clarity than the depletion mode mosfets. IDK if that is because of the differences between mosfets and jfets, or if it is simply because the jfets are not trying to go thermonuclear on me.
As far as capacitors go, there is no equation sadly. The equations I have found are for inductors. When you try to do the math and you assume your CCS has about 1M of impedance, you end up with a capacitor value in the several thousand uf range.
However what I do is just start off with a 5uf capacitor, and 99 times out of 100 I find that a capacitor between 5 and 8uf is more than enough.
Thanks for the info. Could you be more precise about what SIC jfet are you using and for the bottom device what jfet. A schematic will be perfect.
Mine experience with DN2540 for upper device is the same like yours.
Mine experience with DN2540 for upper device is the same like yours.
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Sure
UJ3N065080K3S UnitedSiC | Mouser
That is the jfet I most often use. They do have higher power ones that go as high as 1200v at 63A 😱. They will obviously handle just about anything we could dream of throwing at them in the tube world.
For the second device, something like this should work.
Blocked
As far as a schematic goes, jfets are depletion mode devices. They follow the same schematic a DN2540 would use. I also use 1K gate resistors as well.
Could you post your schematic, so we don’t have to guess how you made the actual CSS?
I’m sure others could be interested as well.
Thanks, Gerrit
I’m sure others could be interested as well.
Thanks, Gerrit
Why? Mine load are 300 ohms headphones.
So CCS in place of OPT followed with parafeed capacitor followed with OPT
So CCS in place of OPT followed with parafeed capacitor followed with OPT
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https://3.bp.blogspot.com/-uTdrpOuO...PBQ/Gbu4GCdado8/s1600/DN2540+CCS+Cascaded.jpg
Im not at my desk so its hard to get you a proper schematic. But its literally the same thing as the schematic right there. All you do is you replace the mosfet symbol with a jfet symbol.
No idea. Other than exceedingly rudimentary knowledge, I know nothing about SS parts and their output impedance.
Thanks for the schematic. This is more or less similar to one of my 10M45S CCS devices.
Regards, Gerrit
Regards, Gerrit
That`s technically correct, however, I personally dislike that constant current source. I like resistors.
Hi Merlin,
Ale is tell abouth that long time ago:
Hybrid Mu-follower Output Impedance – Bartola(R) Valves
or, if you wish:
RE: impedence of CCS mu output - Michael Koster - Tube DIY Asylum
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