Note that all schematics on these pages are (c) Copyright,
1996-1998, Steve Bench. All rights reserved. You may use or
build these FOR YOUR OWN use freely. You may NOT build and/or sell
for commercial profit, any of these without a royalty agreement
in place with the author.

You may place these schematics on your web page if you credit the

Note that high voltages are present in these circuits. The author
IS NOT RESPONSIBLE for ANY injuries, damages, etc. associated
with construction, or use of these circuits.

The Tube (valve) crossover shown here is a 3 pole lowpass and
highpass used for a 2 way crossover design. The circuit needs
+150VDC and 6.3V filament power for its operation. A suitable
power supply is shown on these pages as SUPPLY1.GIF.

The circuit is a modification of a unity gain non-inverting
Sallen-Key circuit that provides 18 dB per octave rolloff
characteristics. The center frequency shown on the schematic,
but may be modified to any frequency with suitable scaling.
Some representative value changes are shown in this document.

A 3 way crossover may be implemented by cascading two similar
circuits as:

in---------- xover hp----------------------------high freq amp
                   lp----xover hp----------------mid freq amp
                               lp----------------low freq amp

Value changes for other crossover frequencies:

        LF Side        LF Side        HF Side        HF Side        HF Side        LF Side        LF Side        LF Side        HF Side
Freq        R4        R5,6        R9        R10        R11,12        C2        C3        C4        C6,7,8

800        90.9k        100k        88.7k        18.2k        1.3M        2200pF        0.01u        270pF        2200pf

80        90.9k        100k        88.7k        18.2k        1.3M        0.022u        0.1u        2700pF        0.022u
85        84.5k        93.1k        82.5k        16.9k        1.2M        0.022u        0.1u        2700pF        0.022u
100        732k        806k        154k        32.4k        2.2M        2200pF        0.01u        270pF        0.01u
125        576k        634k        124k        25.5k        1.8M        2200pF        0.01u        270pF        0.01u
170        422k        464k        154k        33.2k        2.2M        2200pF        0.01u        270pF        5600pF
200        365k        403k        158k        33.2k        2.2M        2200pF        0.01u        270pF        4700pF
400        182k        200k        174k        36.5k        2.7M        2200pF        0.01u        270pF        2200pF
850        84.5k        93.1k        82.5k        16.9k        1.2M        2200pF        0.01u        270pF        2200pF
1000        73.2k        80.6k        154k        32.4k        2.2M        2200pF        0.01u        270pF        220pF
2200        73.2k        80.6k        154k        32.4k        2.2M        1000pF        4700pF        120pF        100pF
3300    73.2k   80.6k   82.5k   16.9k   1.2M    660pf   3000pf  82pF    270pF
4800        73.2k        80.6k        75.0k        16.2k        1.1M        470pF        2200pF        62pF        91pF