Building a 1996 Super Lead Overdrive SLO 100 style amp into a 15 watt chassis

[dinkyguitar]

Nice to see someone building SLO type amps...

I build a 50w clone using C3 amps kit which is "supposed" to be same parts. I also used the O'Netics transformers.

I have to say, I love the SLO sound, so much so that I built a combo last year using Rob's design.

On the combo I wired in an FX loop, and a step down voltage regulator powering my delay & reverb pedals which are mounted on the back panel of the SLO combo.

I have lots of SLO pics, build instructions, layouts, etc. that I collected during my 50w build.

IM me if you need anything.

dinky

 

[rschiller]

I'm cautiously optimistic this will work because it's what I i did to replace the channel switching relays in my Prosonic-inspired amp (panel only, not footswitchable). But I can see that it just might not go well in this amp, in which case I'll get to give those switching components a try, thanks!

Each spot in the circuit (VR1 - VR4) where there was originally an optoisolator, i replaced it with a 10MΩ resistor so that all the usual electrical connections of the original are preserved. That should work reasonably like to how each optoisolator in its high resistance state works. Across each 10M resistor are the terminals of a simple 3PDT switch (VR3 and VR4 which switch between the Normal and OD master volumes could be combined into two resistors but only one pole).

Then i just picked terminals for the two switch positions OD/Normal according to the schematic: OD mode VR 2 and 3 on, Normal mode VR 1 and 4 on. On in this case is a short across the 10M resistor rather than the optoisolators' low resistance state. So 10MΩ instead of 50MΩ, and 0Ω instead of 500Ω, but I expect that that won't really mean much w/ respect to the impedances for the signal. We'll see.

View attachment 1123581
I built the crunch/clean DPDT switch today too

I like the opto-isolators because it uses simplest possible switiching of a SPST foot switch and you don't have to reach for the front panel to switch. Of course I always added a switch on the panel in parallel with the FS.

 

[Snfoilhat]

 

[Snfoilhat]

First noise today!

Not a tone-shaping mod, but one of the Valvewizard techniques I used was the arc protection at startup on the two DC-coupled cathode-followers V3 and V4. In each little package are a 10k resistor and a diode. http://www.valvewizard.co.uk/dccf.html

Supervising the addition of the heater wires

Runnin!


I double checked the wiring against the schematic, I vacuumed out the chassis and took a break, I double-checked the schematic )), and I tested out the power supply with the amp on the light bulb limiter. Everything looked good.

@Ten Over 's bias supply scheme was perfect for this PT and the 10k-L Fender bias pot.

Installed tubes with the bias cool. Still good. I took the amp off the light bulb limiter and set the bias to 23 mA per tube, using the voltage drop across the OT primary method. With the plate voltages that resulted, this put plate dissipation right around 60% of 14 watts.

All the controls work like expected (minus the presence control, which I left unhooked). I only played for a few minutes but checked out clean and crunch and overdrive, and it all works, though I can hear some noises I'm guessing are lead dress issues.

Pretty pleased with all this so far! If anyone followed my first, abandoned (er, paused?) SLO type thing from last year, this amp already performs better than that one which is a relief.

Here is the updated schematic and the DC voltages. Changes from the last set: the inclusion of the arc protection at V3 and V4 and I gave the extra 20 µF section of the cap can to the B2 group (phase inverter, effects send and effects return)

thanks!

 

[Snfoilhat]

15 seconds of the overdrive channel for your amusement, DIYers

Settings:

***
I hooked up the presence control, heard the piercing positive feedback squeal, flipped the output transformer primary leads, and tested things out again. I realized the bass control was sweeping backward -- there's a fine example of how one's own judgement of their work in those early, glorious moments when an amp actually runs can benefit from the cold appraisal of a skeptical mind I didn't notice!


Today I did notice that I can't palm mute alternate picking without all the up-picks sounding like barf

Next steps include a building head shell, practicing Tornado of Souls a couple hundred more times, seeing what problems associated w/ lead dress o or other gremlins may pop up when the master volumes aren't < 2, and finally, eventually hearing what the power tubes' overdrive character might be. Some time when the cats aren't sleeping


thanks for all the help!!

 

[owlexifry]

such a good and clean looking build

i really wish i had the initiative / motivation to include the crunch channel when i did my homebrew SLO
(to be fair though, i didn't really have much understanding in what i was doing back then, i kinda just blindly followed robrob's layout and hoped for the best )

the overdrive channel is amazing, but i'd love to dabble with the crunch.
real keen to hear some A/B between the two.

 

[Snfoilhat]

I made a quick demo of the crunch vs overdrive sounds, looping a 16 second piece of guitar playing.


crunch

overdrive

The switching system I built tends to make a little noise the first time I switch the channels upon turning the amp on, then goes away. I left it in the recording for the curious. Not a pop but a sort of zip! (though what we hear here is mixed up with the sound of digital recording clipping, I think). There are a lot of controls to adjust and these are just two sounds I like, so I don't know that you can't get a good crunch sound in the OD channel and vice versa, but to me the crunch channel shines for power chords and this kind of alt country intro I borrowed for the demo. The OD sound seems to have a different treble sound to my ears. Even at this 'bedroom' volume there's all sorts of extra content, ringing, sometimes feedback, and it's thicker sounding. A lot of fun so far!

I also finally got around to testing the effects loop. I wanted to rearrange my board first, and in the chaos I got distracted and accidentally powered up my old digital delay with 18V instead of 9V and burnt a component in the pedal's power supply. Like the 11V zener or the first electrolytic or the voltage regulator for the 5V supply. (I hope it's one of those things! )That will be the stuff for a thread in the Stomp Box if I manage to repair it.

There's a Hammond box with three mono feed-throughs underneath the board, and now the modulation pedals meant for the amp's effects loop are dedicated to that, out of the regular signal chain. I didn't record any A/B of pedal sounds in front of the amp versus in the loop. Lots of people have done that and I just wanted to make sure the amp's loop was working correctly so I'm happy with it whether or not it sounds much different

thanks a lot!