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Hybrid tube/MOSFET headphone amp
Hybrid tube/MOSFET headphone amp
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Old 19th March 2016, 01:15 AM   #1
davygrvy is offline davygrvy  United States
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Lightbulb Hybrid tube/MOSFET headphone amp

Hi,

I was messing around in SPICE and think I solved the PSRR problem with a white cathode follower using depletion-mode MOSFETs. I appear to have given it a 26dB improvement.

Is it elegant or another lame-o dud?

The top jfet gets the current sense relative to the supply and send it to the bottom one that inverts and adjusts for matching swings.


Hybrid tube/MOSFET headphone amp
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Old 19th March 2016, 07:08 PM   #2
davygrvy is offline davygrvy  United States
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Here's a slightly different one that can bring a 25 ohm Denon AH-D2000 to its full 1.8 watts.

I changed the VAS p-device to a Supertex VP0550 which allows the I-to-V resistor to be larger as the D-MOS turn-on is much higher. This gives much more open-loop gain. Each output device dissipates just 900mW at full load or 1.3W at idle.
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Last edited by davygrvy; 19th March 2016 at 07:21 PM. Reason: added LTSpice file
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Old 19th March 2016, 08:28 PM   #3
davygrvy is offline davygrvy  United States
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That CCS with the LND is superfluous
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Old 20th March 2016, 07:52 PM   #4
davygrvy is offline davygrvy  United States
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PSU will look something like this using a Hammond 12.6VAC or similar TXFMR
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Old 6th April 2016, 07:41 PM   #5
hpeter is offline hpeter  Slovakia
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i like how its done. +1
been thinking similar but with semelabs lateral
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..BLOG.. XMOS_U8/PCM5102A > LL1544A > 6H9C+gyrator > 2A3_SOV/JJ > LL1660 > STAX SR207 _ SR L300 _ SR007 # LL2748 > 394A > LC 12H/1000µ // 4-125a test
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Old 6th April 2016, 07:43 PM   #6
davygrvy is offline davygrvy  United States
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Those are enhancement mode. I guess you could do white cathode follower with them, but it won't self-bias
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Old 6th April 2016, 07:47 PM   #7
hpeter is offline hpeter  Slovakia
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triodes are like self fb, plate is signal out, but at same time could be used as fb input.
when triode is working into opt, that´s easy.
how to make it work in other schemas..quite hard
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..BLOG.. XMOS_U8/PCM5102A > LL1544A > 6H9C+gyrator > 2A3_SOV/JJ > LL1660 > STAX SR207 _ SR L300 _ SR007 # LL2748 > 394A > LC 12H/1000µ // 4-125a test
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Old 6th April 2016, 07:54 PM   #8
davygrvy is offline davygrvy  United States
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Interesting.. A small change to get the bottom biased, and this might just work.

Possibly not tempco stable, though.
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Old 6th April 2016, 08:02 PM   #9
davygrvy is offline davygrvy  United States
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Ooops, Semelabs... sorry.. The spice I did for the Semisouth power SiC JFETs. I was wondering why you asked about.. give me a few moments. a BUZ900, okay?
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Old 6th April 2016, 08:14 PM   #10
davygrvy is offline davygrvy  United States
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For a BUZ901P. I like it
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