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Buffer for Pass' LXmini OX/EQ
Buffer for Pass' LXmini OX/EQ
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Old 1st November 2017, 03:25 PM   #11
Davey is offline Davey  United States
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NP,

Very nice.

Dave.
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Old 1st November 2017, 05:17 PM   #12
Nelson Pass is offline Nelson Pass  United States
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Buffer for Pass' LXmini OX/EQ
Quote:
Originally Posted by Klarskov View Post
Those boards look appetizingly neat - to say the least! Any chance of a schematic?
Of course, but I am putting it off until after BAF. Also, SL has not yet
personally approved the performance of the 3 way, and that might make it
subject to change.
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Old 19th December 2017, 05:45 PM   #13
WalterW is offline WalterW  Netherlands
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Buffer for Pass' LXmini OX/EQ
Nice, all J113 JFET's ?
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Old 20th December 2017, 07:02 PM   #14
Nelson Pass is offline Nelson Pass  United States
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Buffer for Pass' LXmini OX/EQ
2SK170, 2SK370 and LSK170 at about 10 mA are my favorites, but you can
use J113's if you are prepared to AC couple the follower output and degenerate
the current source for lower current.

A J113 with maybe 100 ohm source resistor will give you about 20 mA, which
is about the most I would run, dissipation becoming an issue at higher current.
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Old 20th December 2017, 07:08 PM   #15
Nelson Pass is offline Nelson Pass  United States
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Buffer for Pass' LXmini OX/EQ
BTW, probably final artwork is done, and I think SL will be happy with the
latest iteration of the 3 way version after I relented and put gain in the
circuit for the woofer.

We should have both crossovers as partial kits in the store real soon now,
which would include boards and the parts that go on the boards. They are
being set up to fit in Galaxy 2u 230x230 chassis and use a 24V external
supply.

As soon as SL signs off on the latest, we will be set to go.

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Old 20th December 2017, 07:11 PM   #16
Dennis Hui is offline Dennis Hui  Canada
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Buffer for Pass' LXmini OX/EQ
Most excellent. A perfect reason to build speakers and more amps.
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- NP 2002
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Old 29th December 2017, 02:02 PM   #17
mkc is offline mkc  Denmark
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Buffer for Pass' LXmini OX/EQ
Quote:
Originally Posted by Nelson Pass View Post
I relented and put gain in the circuit for the woofer.
Hi Nelson,

May I ask how simple a gain-stage you ended up choosing?

The reason why I ask is that a couple of years ago I made an active cross-over, for a friend of mine, using OPA2134. It works great.

But, no fun in that, so we have been toying with the idea of trying to redo the high-pass section, which comes in from 110 Hz and up. The ideas has been from doing some of it using valves to my thought of trying to do it with jfets using B1 style buffers. But, I might have the need for some gain. Hence my question.

Being on the subject of B1 style buffers compared to the "new" B1 push-pull buffers. The original B1 buffer has very good performance for such a simple buffer. Any subjective reasons for choosing the PP version over the SE version in a high pass filter where capacitors in the signal path is unavoidable?

Btw. I do have some SJ74 and he is a very good friend , but I would like to save them if the benefit is only a little better measured performance.

Mogens
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Old 4th January 2018, 05:50 PM   #18
Nelson Pass is offline Nelson Pass  United States
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Buffer for Pass' LXmini OX/EQ
Actually I am still playing with it. The one that has artwork at the moment
is just a Fet 2 stage, with a current sourced N ch Jfet pair driving a P ch
Mosfet which is also current sourced. You can see similar circuits in the
"DIY Op Amps" article at FIRST WATT
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Old 4th June 2018, 01:57 PM   #19
davidismynaim is offline davidismynaim
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I am really interesting in making a 3 way LXmini with subs, did this active corssover ever get to the store as a kit, I could not find it? thanks for any help
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Old 4th June 2018, 05:27 PM   #20
Nelson Pass is offline Nelson Pass  United States
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Buffer for Pass' LXmini OX/EQ
The current status of the LXmini crossover is that I am waiting for some
potentiometers to arrive while packing up the kits to go to the DIYaudio
store. 100 should ship by end of next week.

Kit consists of pcb, packet of 16 selected/matched Jfets + resistors specific
to them, and the rest of the resistors, capacitors and pots needed.

This is powered by a 24V wall wart and fits in the store's Galaxy 2u
230 x 230 chassis. Management is planning a rear panel with holes for
8 rca and power connector.

Documentation will be posted shortly.

I just finished the Jfet gain stage required by the LXmini+2 and Studio,
so this will also be appearing before very long.
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