SuperliteII or SuperliteIIb

Superlite_II_w_SS-rectifier_MOSFET-source-follower_layout-b.jpg

OK, I'm going to differentiate between the two, Terry Stinger designed the Superlite II pcb and distributed it through his company http://guitaramplifierpcbs.com/SuperLite_PCB.aspx. Unfortunately Terry was killed in a motorcycle accident before the build documentation was completed, and before questions could be dealt with. Terry's widow Roxane was contacted by the wattkins.com site operator and with his help she started selling Terry's pcb's again.

The Superlite II was Terry's take on the Superlite, he had previously done a pcb for the Superlite circuit designed from the Radstringz SS-diode Superlite schematic. It was designed so that could be used in a VJr chassis for an amp conversion. The original pcb had some noise issues, so he scrapped that and started over with input from people at http://www.AX84.com. What came out of that was part of the circuit was more Marshall-like than the original with a new twist, the Superlite II used a 230V power transformer. The low voltage circuit required a few circuit modifications, like the split-load plate resistor on the second stage and different resistors in the power supply rail.

So from the Superlite II with input from Zaphod_Phil (the designer of the original Superlite circuit) came the SuperliteIIb, sacbluesman and I were the guinea pigs. The first change was the choice of using a higher voltage transformer, that made it necessary to make some circuit changes. The SuperliteIIb retains the cold biased partially bypassed first stage but Phil wanted to change the plate resistor to a standard 100k plate resistor (more Marshall like). Phil commented that C7, the 500pf cap placed parallel to R11 was optional, initially I left it off of my amp as I only had a Strat and Tele so I didn't think I'd need any more highs. Later I added an on-off-on SPDT switch for a 3-way voicing, up switches in the cap for the bright mode, in the middle position it's just the 470k resistor for the 'normal' mode, and down it switches in an 82k resistor parallel to the 470k for the 'thick' mode. With the higher voltages the split-load plate had to go, the higher voltages make the amp have more cleans. R12 on the schematic is an 820 ohm, because the amp doesn't have the "standard" Marshall cathode follower, which adds it's own smooth compressed overdrive, putting a 680 ohm cathode resistor in R12 gives that stage some of the character of the Marshall stage with cathode follower. In the original schematic C8 was labeled as not used, at the higher voltages the SuperliteIIb needs C8 for gain and harmonics, C8 in the range of 0.68uf to 2.2uf works well. The next change to the Superlite II is to use a 10n (0.01uf) mid cap in the tone control, that and the 500k bass pot make the tone stack have better control of the low frequencies. Change out R20 to a 100k like R21 and the circuit changes are done. Then with a higher voltage power transformer use the original dropping resistor values; R4 2.2k, R5 8.2k, and R6 27k (maybe a 22k to raise the preamp voltages some).

Here's the latest schematic: http://www.rh-tech.org/public/Superlite_IIb_2-7_Schematic_V4.pdf

Comments

rock_mumbles
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Joined: 11/05/2011
Mark's SuperliteIIb with ClassicTone Power and EZ81

here are the voltages on Mark's amp with ClassicTone power transformer and EZ81:

B+ 345V

EL84
plate 333V
screen 319V
cathode 12V
with 148 ohm cathode resistor