I have never done a distortion versus frequency measurement so I can't provide one right now. I use a stand alone 1kHz oscillator so I probably need to calibrate my Focusrite and figure out how to do the measurement.
But your measurement does not show high distortion throughout the audible frequency range so distortion may not be the cause of the edgy sound.
You can temporarily resistor load the VFET in place of the CCS to hear if there is a difference in sound.
Your distortion plots show quite a large amount of noise. If you have high sensitivity speakers, that amount of noise is probably quite audible. With a regulated power supply or CRCLC supply, the ripple is probably quite low so that noise could be due to tranformer placement, component/wiring layout, grounding issues.
But your measurement does not show high distortion throughout the audible frequency range so distortion may not be the cause of the edgy sound.
You can temporarily resistor load the VFET in place of the CCS to hear if there is a difference in sound.
Your distortion plots show quite a large amount of noise. If you have high sensitivity speakers, that amount of noise is probably quite audible. With a regulated power supply or CRCLC supply, the ripple is probably quite low so that noise could be due to tranformer placement, component/wiring layout, grounding issues.
As it turns out, I do have high efficiency speakers and the preamp is dead quiet, no hum or hiss at all. I have seen those harmonics on other measurements too. To be honest, I have not spent time hunting down the source of those harmonics, and maybe I should.
Good idea about the resistor load. I will try that.
Good idea about the resistor load. I will try that.
Gate Stoppers!
Mike, I took your suggestion of the 10k resistor on the output. Previously, there was nothing on the output--my hope was that the amp would provide the loading. With a 10k resistor added, the response got a little worse with 3 db down at 20 Hz, whereas previously it was only one db down. Most importantly, it did not change the edginess.
But the output resistor recommendation got me thinking about other resistors. I added a 1Meg resistor from the gate to ground, and this seemed to help with the edginess. Then I noticed that I completely forgot to add the gate stoppers. Adding those in made a huge difference. Edginess completely gone. Does that mean some level of oscillation was happening without them? Remember that there is no source degeneration to hold things back. I am guessing it was some sort of instability.
Anyway, now this is much better. The edginess is gone. 'Ssss' sounds are much more natural and without coloration. Soundstage is amazing and so is the bass definition. It has a great ability to distinguish between instruments that are operating in the same frequency range and hold them there even when things get loud. This is definitely in the conversation with a BA-3 and the 10Y. Thanks for your help, Mike and Ben! On to more listening!
P.S.: I think I will build out that buffer to see what it does.
Mike, I took your suggestion of the 10k resistor on the output. Previously, there was nothing on the output--my hope was that the amp would provide the loading. With a 10k resistor added, the response got a little worse with 3 db down at 20 Hz, whereas previously it was only one db down. Most importantly, it did not change the edginess.
But the output resistor recommendation got me thinking about other resistors. I added a 1Meg resistor from the gate to ground, and this seemed to help with the edginess. Then I noticed that I completely forgot to add the gate stoppers. Adding those in made a huge difference. Edginess completely gone. Does that mean some level of oscillation was happening without them? Remember that there is no source degeneration to hold things back. I am guessing it was some sort of instability.
Anyway, now this is much better. The edginess is gone. 'Ssss' sounds are much more natural and without coloration. Soundstage is amazing and so is the bass definition. It has a great ability to distinguish between instruments that are operating in the same frequency range and hold them there even when things get loud. This is definitely in the conversation with a BA-3 and the 10Y. Thanks for your help, Mike and Ben! On to more listening!
P.S.: I think I will build out that buffer to see what it does.
I can't find any information for K78B/K278B. Are you sure you have that right?
I do have some KP926B that I intend to choke load and use as a voltage gain stage for my follower amps as my resistor loaded 2SK82 Luminaria can't quite put out enough voltage for my THF-51S Mu Follower amp to clip.
I do have some KP926B that I intend to choke load and use as a voltage gain stage for my follower amps as my resistor loaded 2SK82 Luminaria can't quite put out enough voltage for my THF-51S Mu Follower amp to clip.
I got few SRCC SSA3301C from yahoo, but its package is very big similar to 2sk180.The seller provided the same data sheet you attached #310. I think both SSA3301C and 2sk78B uses same chip with different package. 2sk78b is in plastic DIP package so dissipation capacity may be very less compared to SSA3301C, rated 30watts.
I also collected few SSA251C and SSAP400M vfets from SRCC .Both SSA251 and 2sk77b share same chip but have different packing. SSAP4004M is P channel SIT. yes, P channel.
Packing is very similar to 2sk77b. but not complement to 2sk77B.Still not found SSAP4004M Data sheet.
I also collected few SSA251C and SSAP400M vfets from SRCC .Both SSA251 and 2sk77b share same chip but have different packing. SSAP4004M is P channel SIT. yes, P channel.
Packing is very similar to 2sk77b. but not complement to 2sk77B.Still not found SSAP4004M Data sheet. Somewhat off topic, but has anyone had their hands on the K78B/K278B? I bet those would be fun to play with
How's the kitchen Michael?
I hope that doesn't come across as hassling you as that's not my intention, just curious about the prospect of a SIT-based preamp while I work on my SissySIT and 2SK180 follower projects (for which I'll have a 2P29L tube preamp).
Thanks
Thanks Michael and good luck with your recipes - does the dude have a toque blanche?