Hi Gerd 🙂
In a basic CS amp, the effective input capacitance of the 182ES is very, very high, i.e. >14,000 pf. More gain, more Miller. Even with a 600 ohm source, you wouldn't make audio band. Have you measured the bandwidth?
In a basic CS amp, the effective input capacitance of the 182ES is very, very high, i.e. >14,000 pf. More gain, more Miller. Even with a 600 ohm source, you wouldn't make audio band. Have you measured the bandwidth?
That figure is fine, but it is the "intrinsic" input capacitance of the part standing alone. When you use it in a common source amplifier that figure is increased due to the amplification effect between input and output and proportional to the voltage gain of the amplifier. This is the effective input capacitance. So, 2500 gets multiplied 6 times.
See Lab Hangout #4
I imagine this causes some confusion because we often talk about the "input capacitance" of an amplifier, meaning the effective input capacitance in a circuit with gain rather than the intrinsic input capacitance (ciss) of the part itself. 🙂
See Lab Hangout #4
I imagine this causes some confusion because we often talk about the "input capacitance" of an amplifier, meaning the effective input capacitance in a circuit with gain rather than the intrinsic input capacitance (ciss) of the part itself. 🙂
Measure the effective input capacitance. That's the one that actually matters here.
See Lab Hangout #4 for instructions. If you know the output impedance of your source and the -3db point, you can simply calculate it.
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The 182ES really needs a 50 ohm source (or buffer) or better. I'm sure this accounts for some of the "softness" you're hearing.
The good news is that your hearing is good 🙂
I have also found (IMHO) that CCS's can take some of the liveliness out of SITs, leaving them sound a little more conventional, but that's purely my opinion based on limited experimentation.
The good news is that your hearing is good 🙂
I have also found (IMHO) that CCS's can take some of the liveliness out of SITs, leaving them sound a little more conventional, but that's purely my opinion based on limited experimentation.
Oops, I see you posted at the same time I was posting. I'm sure that will work if the output impedance is 50 ohms or less and it can swing enough voltage to make your circuit happy, i.e. drive it to full power with a little room to spare.
THX Mike,
SIT and CCS is only starting point…..all surrounding was already here from the first SIT with SK82… some time ago….. 🙂
pure SIT with bulb or thick film resistors will follow and I will compare too….
SIT and CCS is only starting point…..all surrounding was already here from the first SIT with SK82… some time ago….. 🙂
pure SIT with bulb or thick film resistors will follow and I will compare too….
I'm sure 😎 knows the secret to getting active loading to work well. In the meantime I wouldn't want to sound as though I'm discouraging experimentation in that area. On the contrary, we'll need to unlock the secret if we want to build a monster. 🙂
@Michael, would a LuminAria (with input buffer) have a low enough output impedance to drive the L'Amp. I haven't built one yet, but am considering this all SIT combination.
Also, my test with 2SK76 turned out to be not very successful, gain was only 7dB which was expectantly low, but lowest THD @1W I could reach was 0.4% and not any better than the 182ES, and my function generator's 5Vpp max output was not sufficient to drive it to give 10W so didn't measure THD @10W.
However, I finally settled with a 2SK180, at Vbias of -6.7V, Id of 2.4A and B+ of 45V, THD @1W was 0.4% and THD @10W was 1.1% 😀, with 15dB gain. Only issue was the heatsink used was not big enough to dissipate the heat, so I had to use a cooling fan, but I can get a bigger heatsink later.
Also, my test with 2SK76 turned out to be not very successful, gain was only 7dB which was expectantly low, but lowest THD @1W I could reach was 0.4% and not any better than the 182ES, and my function generator's 5Vpp max output was not sufficient to drive it to give 10W so didn't measure THD @10W.
However, I finally settled with a 2SK180, at Vbias of -6.7V, Id of 2.4A and B+ of 45V, THD @1W was 0.4% and THD @10W was 1.1% 😀, with 15dB gain. Only issue was the heatsink used was not big enough to dissipate the heat, so I had to use a cooling fan, but I can get a bigger heatsink later.
I suppose my buffer is nonsense
http://www.diyaudio.com/forums/pass-labs/269379-live-lab-hangout-1-1-posted-49.html#post4333346
no headroom…... Voltage at source of the J-Fet too low.
I will check with Spice and reissue….. :-(
http://www.diyaudio.com/forums/pass-labs/269379-live-lab-hangout-1-1-posted-49.html#post4333346
no headroom…... Voltage at source of the J-Fet too low.
I will check with Spice and reissue….. :-(
@cwtim01
LuminAria should drive a 2SK180 L'Amp just fine, as will any preamp with say <100 ohm output impedance and enough voltage swing to get you to full power with some room to spare.
I've been enjoying my 2SK180 L'Amps (84V B+ See video), they sound pretty good to me 🙂 They need big heat sinks tho.
LuminAria should drive a 2SK180 L'Amp just fine, as will any preamp with say <100 ohm output impedance and enough voltage swing to get you to full power with some room to spare.
I've been enjoying my 2SK180 L'Amps (84V B+ See video), they sound pretty good to me 🙂 They need big heat sinks tho.
adding the 10uF cap at the input where it should be….
makes Vsource around half of the Vdrain.
but distortion is a bit high, I will go on and report…
of course all is still Spice now…..
and I could also use Mikes buffer from Luminaria but the voltage is much higher so ……..I´ll have to look...
A good 'ol B1 will swing 4 or 5V, I believe, and has an output impedance something like 50 ohms. 🙂
G. , my golden Eared Personal German 😉
considering that I know 5% of secret vodoo on which you are working ...... I can urge you to check this one :
http://www.diyaudio.com/forums/pass-labs/66397-buffer-blues.html#post748555
or , ditto : http://www.diyaudio.com/forums/attachments/pass-labs/52083d1129848383-buffer-blues-forblues.pdf
edit : ha ! #500
editedit: you can always parallel few more little critters , for more juice
considering that I know 5% of secret vodoo on which you are working ...... I can urge you to check this one :
http://www.diyaudio.com/forums/pass-labs/66397-buffer-blues.html#post748555
or , ditto : http://www.diyaudio.com/forums/attachments/pass-labs/52083d1129848383-buffer-blues-forblues.pdf
edit : ha ! #500
editedit: you can always parallel few more little critters , for more juice
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