OK, I admit it. You can calculate circuit values until the cows come home but sometimes it's so much easier and faster to just dial it in. I've been a ham and involved in engineering for over 35 years, and I gotta tell ya, these are undoubtedly some of the most indispensable tools I have ever had.

With the low and high value Resistor Sub Boxes, rather than providing resistance decades like most resistor sub boxes do, I decided to provide 45 of the most common values on two rotary switches. It seemed more practical to use the standard values we would most likely incorporate in the amps. The resistors are metal film and are rated at 1/2 watt.

For the Capacitor Sub Boxes, I decided to provide the most common values that we typically see in guitar amps. Just like the resistor sub boxes, it seemed pointless to include some oddball values that we wouldn't use anyway. The poly caps are rated at 630VDC, the ceramics are 1KV. The electrolytic caps in the ECC-HV type Sub Box are rated at 500 volts DC, and are 105 degree C parts, while the electrolytics in ECC-L type Sub boxes are rated at 50 volts and are meant to be used for experimenting with the capacitor value in cathode bypass caps in preamp and power amp circuits.

The LSUB Inductor Sub Boxes are rated at 200ma and 400ma, although I wouldn't run them all day at that current. The units are meant to be used for temporary insertion in a circuit while developing your high voltage supply. The inductance ranges are 0 (straight wire) to around 16H and zero to 10H.

The RSUB Power Rk-Ck Sub Box is used for dialing in cathode bias by substituting it for the cathode bias resistor in a cathode biased output circuit. The box includes two terminals to connect an electrolytic capacitor in parallel with the cathode resistance. The rheostat is rated at 500 ohms and 25 watts.

The Rk-Ck Preamp Sub Box has both a pot and a selection of 12 different electrolytic capacitors in parallel with the pot for dialing in the cathode bias components of a preamp stage. The electrolytic capacitors are rated at 50 volts, and the pot is 2 watt, 5K linear.

The High Power Resistor Sub Box has a 47K 5 watt pot. With it, you can quickly dial in the dropping resistors in your high voltage (B+) power supply chain for the screens and on down the line.

The Low Power Resistor Sub Box is a 50K, 2 watt wirewound pot you use for final tweaking in the power supply chain feeding the preamp stages. Believe me, tweaking this way and dialing in a sweet spot will just make your jaw drop, it is so easy and fast. I realize these are unregulated power supplies, but getting it close and 'nominal' by this method saves a ton of time.

And finally, the C-Cap Sub Boxes are full wave or full wave bridge rectifiers with adjustable sag so you can emulate a tube rectifier of a certain type in the development of your high voltage circuit. The C-Cap Sub Box is adjustable from a 5Y3GT to a straight SS (no sag) rectifier and everything in between. For instance, if you determine by the setting on the C-Cap Sub Box that your amp sounds best between the setting of a 5V4 and a 5AR4/GZ34, you can use a 5AR4/GZ34 with a power resistor in series to split the difference between the two. The label on the C-Cap Sub Box indicates the approximate resistance between straight SS through and including a 5Y3GT, so you can do the math easily to determine that series resistor value.
This box is about 1/4" taller than our copper cap module since it contains a rheostat. It also has two mounting feet on both ends, the same as the copper cap module. It may be installed in an amp permanently and used as an adjustable-sag rectifier.
The only issue is that the rheostat has a wiper and might move some due to the vibration in a combo amp or in a head sitting on a speaker cabinet. You could experience some slight noise or scratching sound if that occurs.

Qty Price Part Number Description Use
$35.00 CSUB_SMC    Capacitor Substitution Box, Silver Mica capacitors, 15 values, 47pF - 1000pF @ 500VDC.    Tone stack, frequency shaping, etc.
$45.00 CSUB_MAL    Capacitor Substitution Box, Mallory 150 capacitors, 12 values, .001uF - .22uF @ 630VDC.    Tone stack, interstage coupling, bypass.
$45.00 CSUB_SPR    Capacitor Substitution Box, Sprague Orange Drop capacitors, 12 values, .001uF - .22uF @ 400VDC.    Tone stack, interstage coupling, bypass.
$35.00 CSUB_PEC    Capacitor Substitution Box, Weber polyester capacitors, 12 values, .001uF - .22uF @ 630VDC.    Tone stack, interstage coupling, bypass.
$35.00 CSUB_PPC    Capacitor Substitution Box, Weber polypropylene capacitors, 12 values, .001uF - .22uF @ 630VDC.    Tone stack, interstage coupling, bypass.
$35.00 CSUB_CCC    Capacitor Substitution Box, ceramic capacitors, 12 values, .001uF - .22uF at 1KVDC.    Tone stack, interstage coupling, bypass.
$45.00 CSUB_ECC-LL    Capacitor Substitution Box, electrolytic capacitors, 12 values.  .1, .22, .33, .47, .68, 1, 2.2, 3.3, 4.7, 6.8, 10, 16@ 50VDC.    Preamp and power amp cathode bypass, low values.
$45.00 CSUB_ECC-LH    Capacitor Substitution Box, electrolytic capacitors, 12 values.  6.8, 10, 16, 22, 33, 47, 75, 100, 150, 220, 330, 470 @ 50VDC.    Preamp and power amp cathode bypass, high values.
$45.00 CSUB_ECC-HV    Capacitor Substitution Box, electrolytic capacitors, 8 values.  10, 20, 30, 40, 50, 60, 80, 100 @ 500VDC.    Power supply filter.
$45.00 LSUB0-16H    Inductor Substitution Box, Zero to 16H @ 200ma.  0, 1, 2, 4, 8, 16 Henries.    Power supply choke.
$45.00 LSUB0-10H    Inductor Substitution Box, Zero to 10H @ 400ma.  0, .3, .6, 1.5, 3, 6, 8, 10 Henries    Power supply choke.
$35.00 RSUB Preamp Rk-Ck    Resistor and Capacitor Substitution Box, 5K linear pot and selection of 12 electrolytic caps. .68, 1, 2.2, 4.7, 10, 20, 33, 47, 68, 100, 220, 330uF @ 50VDC    Preamp cathode resistor and capacitor.
$25.00 RSUB Power Rk-Ck    Resistor Substitution Box, Power Rheostat, 500 ohms, 25 watts, with connection terminals for parallel electrolytic capacitor.    Power amp cathode resistor and capacitor.
$25.00 RSUB_PWR-LO    Low Power Resistor Substitution Box, 0-5K, 2 watts.    B+ power supply resistor string filter node adjustment.
$35.00 RSUB_PWR-HI    High Power Resistor Substitution Box, 0-50K, 5 watts.    B+ power supply resistor string filter node adjustment.
$35.00 RSUB_MFR-L    Resistor Substitution Box, metal film resistors, 1/2 watt, 45 values, 100 ohms - 100K.    Low level signal circuit resistors.
$35.00 RSUB_MFR-H    Resistor Substitution Box, metal film resistors, 1/2 watt, 45 values, 51K - 10 Meg.    Low level signal circuit resistors.
$35.00 CCAP_SUB-FW    Fullwave Rectifier Substitution Box, Variable from 5Y3GT to SS Recto (no sag).    Fullwave (SS or Tube) rectifier substitution.
Temporarily Out Of Stock $35.00 CCAP_SUB-BR    Bridge Rectifier Substitution Box, Variable Sag to emulate a tube rectifier.    Bridge rectifier substitution.