Stanley,
Firstly, yes the 9610 will vastly improve things. But something still isn't right.
Your rise times aren't too bad, meaning the fet is turning on ok. It's the turning off which is the problem. Not sure whether this is an input stage issue or vas ccs issue, but I would try lowering the resistor that feeds the ccs to 2k to make sure you get enough base current to run the ccs. Really, the value you have should work, I'm just guessing 🙂
P.S thanks for taking the time to build this thing! We need more feedback.
Firstly, yes the 9610 will vastly improve things. But something still isn't right.
Your rise times aren't too bad, meaning the fet is turning on ok. It's the turning off which is the problem. Not sure whether this is an input stage issue or vas ccs issue, but I would try lowering the resistor that feeds the ccs to 2k to make sure you get enough base current to run the ccs. Really, the value you have should work, I'm just guessing 🙂
P.S thanks for taking the time to build this thing! We need more feedback.
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I think if you build this design with the 2SK170 input and BJT vas you will be disappointed, as I was. Building it with a MOSFET front and bjt vas is another story.
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I do of course encourage you to try. I only had the bd140 at hand, not exactly a highly regarded transistor, but my gut feeling is that the extra OLG provided by the MOSFET vas is needed when using a relatively low gain device at the input.
However, the bjt vas and MOSFET input were brilliant.
Hopefully soon we will have some impressions from other builders.
A regular BD140 as VAS will provide at least 10db lower THD
that any fet or hexfet..
No, I have just noted that quite a few people don't hold them in high regard.
Yes, but if it were all about simulated distortion figures we wouldn't be persisting with a jfet front end, which simulates worse than both the MOSFET and BJT versions...
That said, I thought both the BJT and MOSFET inputs sounded very good, if not better in some ways.
Miib, why not build it and try both?
That said, I thought both the BJT and MOSFET inputs sounded very good, if not better in some ways.
Miib, why not build it and try both?
Not mine but the said bjt one ,if a BD140 is entitled to have an opinion...😉
The input Jfet doesnt degrade significantly the perfs of the topology
since most of the gain is provided by the VAS , hence the BJT superiority
for this exact purpose.
Mr window watcher,
in my case, 25 cents for a Phily-16, but who's counting (tablespoons).
Hi,
with considerable effort, devices were developed for voltage amplification, it would have been much more convenient to utilize readily available MOSFETs (but maybe they forgot to check it out with LTSpice).
with considerable effort, devices were developed for voltage amplification, it would have been much more convenient to utilize readily available MOSFETs (but maybe they forgot to check it out with LTSpice).
I seriously doubt it would be appreciated at the Hot Shot part deuce thread, by either side.
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