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DEF Amp
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Old 4th November 2017, 10:08 AM   #241
Nag is offline Nag  India
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8 days more BAF . exciting
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Old 4th November 2017, 05:19 PM   #242
Nelson Pass is offline Nelson Pass  United States
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DEF Amp
I will be talking briefly about both the DEF and the DEFiSIT, and bringing
working copies of each.
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Old 4th November 2017, 05:56 PM   #243
Michael Rothacher is offline Michael Rothacher  United States
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DEF Amp
Yeah, Boyeeeeee

Someone at the show keep us up to date, we need actionable intelligence.
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Old 4th November 2017, 06:19 PM   #244
massimo is offline massimo  Italy
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Quote:
Originally Posted by Nelson Pass View Post
I will be talking briefly about both the DEF and the DEFiSIT, and bringing
working copies of each.
I do hope you won't ignore the XquiSIT (or whatever will be named the VFet SE design).
Can't wait for the schem!
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Old 6th November 2017, 07:28 PM   #245
Antoinel is offline Antoinel  United States
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DEF Amp
Default Experimenting with DEF wired in a Common Gate Configuration

The attached schematic describes the application under study. Note the following construct:

1 DEF is idealized for simplicity. It is comprised of SJDP120R085 N-JFET and its match IRFP9140 P-MOSFET. Their gates are joined and biased by a common negative Vgs which is AC grounded [meaning common gate].
2. My DEF on the bench idles at +/-1.5A from a +/-17 V PSU which is a simplified classical rectifier circuit.
3. The joined sources of the FETS is the input to DEF; meaning it accepts current and lots of it [limited by bias].
3. An integrated power amp [IPA] is the source of power current that is pushed through the joined sources of DEF.
4. The integrated power amp driving the DEF can be/is your choice as shown. Mine is a utility compact SONY which delivers ~10 W/8 Ohms I used to demonstrate the concept. It has controls for volume and independent tone, plus miscellaneous input sources, AM, FM, CD tape Video [aka Aux in this case].
5. The current which enters the joined sources of the FETs in DEF exits in its entirety at their joined drains. The exit port of DEF's AC current is the center tap of the dual polarity PSU's power transformer as indicated.

Here's how it works. It does so cleanly without any oscillation or problems.

1. A loudspeaker is connected in series [inserted] between the power output port of the integrated amp [IA] and the joined sources of DEF.
2. The ouput current of IA enegizes the loudspeaker, it enters the joined sources of the FETs and exits in phase and in its entirety [magnitude] at their drains as described above.
3. I gave the output current two choices via the shown toggle switch. Dump it to ground[1] or send it back [2] to the power output port of [IA] as Positive Current Feedback [PCF].
4. It is important to note that the exit current of DEF be it PCF or grounded must return to the PSU of the integrated amp where it originated in the first place. This PCF current will not make a second pass through the loudspeaker and continue to recycle indefinitely.
5. With PCF engaged, the power output of the integrated amp is "bootstrapped". This has the benefit of increasing the actual impedance of the loudspeaker[possibly doubled], plus causing other potential and beneficial sonics.

Enjoy the crisp and clean sound of this arrangement.
Attached Images
File Type: png ComBaseDEF.png (44.9 KB, 807 views)
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Old 8th November 2017, 03:56 PM   #246
flocchini is offline flocchini  United States
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Default DEF "Integrated" Amp

Could a DEF output be mated with a B1 to become an "integrated" amp?

Best and thanks

Bob
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Old 8th November 2017, 04:33 PM   #247
Nelson Pass is offline Nelson Pass  United States
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DEF Amp
Of course, although the gain is a little low. To go to full output on the amp
would require a source at 3.5 volts.

Given that the input to the DEF amp is the same pair of Jfet followers, you
could simply add an input pot and selector.
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Old 8th November 2017, 04:36 PM   #248
flocchini is offline flocchini  United States
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Thanks Nelson

Just thinking of what to do with the B1 I have sitting in the garage

Best

Bob
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Old 10th November 2017, 01:07 PM   #249
Soundhappy is offline Soundhappy  France
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Quote:
Originally Posted by Nelson Pass View Post
I will be talking briefly about both the DEF and the DEFiSIT, and bringing working copies of each.
Lucky Diyers who can be at BAF17 an hear this hot new amplifiers.
The full silicon carbide DeFiSIT are extraodinary i guess.
Interested by schematic with obtainable parts.
Festival it's start happen after tomorrow
Attached Images
File Type: jpg F1BE97E9-A972-4137-8203-A99815478BA0.JPG (54.6 KB, 660 views)
File Type: jpg E9EDF4A9-A042-4FB4-9142-A28C132E9AE3.JPG (78.3 KB, 599 views)
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Old 16th November 2017, 07:57 AM   #250
indra1 is online now indra1  Indonesia
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Default ValDEF - Valve DEF buffered amplifier

For me, the DEFiSIT output stage is simply the most beautiful topology. Thank you Mr Pass for sharing with us.
Since tubes are more accessible for many of us compared to the SIT transistors, I adapt the DEF biasing scheme and sim a tube as input to an enhancement N MOSFET and P Lateral MOSFET pair and get very good results beyond expectation.
Triode transfer function, 0.081% THD at 1W into 8 ohm, negative phase H2 dominant, monotonic distribution. 100k input impedance, 9.94 DF. -1.47dB (0.84) gain, clipping at 19V input, 16V output, ~15W output with 180V and bipolar 23v PSU.
Attached Images
File Type: gif 6V6 ValDEF TriC.gif (103.5 KB, 512 views)
File Type: gif 6V6 ValDEF TriC FR.gif (26.4 KB, 503 views)
File Type: gif 6V6 ValDEF TriC FFT.gif (18.9 KB, 129 views)
File Type: gif 6V6 ValDEF TriC log.gif (23.2 KB, 133 views)
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