A Wondrous Adventure: SLO Clone Build (Now with Clips)

FourT6and2

Supporting Member
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2,105
Clips toward the end.

Because my Metro Super Lead build-thread went so well (seen here: https://www.thegearpage.net/board/index.php?threads/799547 ), I've decided to do the same with a SLO100 clone. I'm still waiting for most of the actual parts to come in. But let's get thangs goin' with a rundown of all the tools I'll be using. First, I'd just like to give a shout out to some of the peeps that gave me helpful advice and info during the research phase of this build: Rob at C3 Amps, Olaf Krampe, The folks at SLOCloneForums (Wartime-Novelty, Joey, and mjtripper), and Joachim at Tube-Town.de.

The build will basically be a stock SLO but with two possible mods: 1) Elevated AC Heaters and 2) A switchable, loop bypass.

First up is a gun to bring da heat:





Some wire stripping tools. I'm using teflon hook-up wire. So I had to get a new hand-stripper because teflon wire has much thinner insulation than normal PVC. So I needed s stripper that could go smaller than the one I had, even for the same AWG. The tool on the left is a special RG-188 coax stripper for the Belden shielded cable I'll be using. It strips in three levels (outer jacket, braided shield, inner insulator) in one fell swoop. Handy.





Basic hand tools. Pliers, flat cutter, round-nose jeweler pliers for bending wire and component leads smoothly, and a wide, flat, non-serrated pliers to perfectly straighten leads/wire.





Other misc. stuffs. Component lead bender for resistors and caps and such on the PCB, supercool sharpie, orange wood sticks for (anal) probing, and an x-acto for zee slicin' unt dicin'.





The super pretty mil-spec, silver-plated, teflon hook-up wire. I chose the color palette for number one tone!





For years I've just been using cheap, ******, pain-in-my-ass soldering irons from Radio Shack. They get the job done. But the tips always corrode and melt away after like a week. And the temperature isn't regulated so the iron's tip fluctuates all over the place with regard to temperature. I decided to do it right this time and get a decent iron. I narrowed my choices down to Weller and Hakko. Weller has a good name. But the only two readily available irons were the WES51 and the digital version. Both pretty good. But this Hakko FX-888D has a ceramic heating element, has more features, is of much higher quality, and I got a bangin' deal on it that included a bunch of replacement tips of various shapes/sizes and a spool of Kester 44 Eutectic (63/37) solder—the good ****—all for less than the cost of the Weller unit alone. This iron makes soldering much easier, faster, and way more funtastic.

Oh and it LITERALLY (no joke) heats up from totally cold to 750 degrees F in about 20 seconds. It's magic, y'all.





Stay tuned for more updates. Parts should start rollin' in soon.
 
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big mike

Gold Supporting Member
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12,309
Been pondering a build myself, thanks for sharing and letting us follow along!

Subscribed!

50 or 100 watt version?
 
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453
I use a butane soldering iron and a Teledyne hot blade stripper for Teflon wire...
Good luck! It will be a great amp!
 

FourT6and2

Supporting Member
Messages
2,105
I use a butane soldering iron and a Teledyne hot blade stripper for Teflon wire...
Good luck! It will be a great amp!
The only difference is a butane iron can't regulate the tip temperature. And you don't have precise control over the exact temp. Hot blades are cool though. Hakko makes one too but it's overkill. I'm fine with good ol' hand tool.
 

eddy999

Member
Messages
220
Good luck with the build! My 50w SLO clone from 2010 is still going strong (thread) - a great project. I was happy with the stock AC heaters in mine, didn't bother experimenting with elevation as the hum was negligable.
 

cardinal

Member
Messages
5,045
Are elevated AC heaters suppose to be a way to reduce hum? If so, I'd give them a shot with a SLO clone. My only real complaint about the SLO was that its noise floor wasn't as low as most of the other amps I've used.

Very interested in this build! One day, I'd love to build an amp.
 

FourT6and2

Supporting Member
Messages
2,105
Good luck with the build! My 50w SLO clone from 2010 is still going strong (thread) - a great project. I was happy with the stock AC heaters in mine, didn't bother experimenting with elevation as the hum was negligable.
Nice work! Yeah you've got the power board with the mod section on it so should be easy to to DC or elevated heaters. If I have any questions I'll be sure to ask you ;)

Your PCB didn't come pre-populated did it?

And why did you run the preamp heaters (purple wires) from the pilot light instead of from the power tubes and under the preamp board?

Are elevated AC heaters suppose to be a way to reduce hum? If so, I'd give them a shot with a SLO clone. My only real complaint about the SLO was that its noise floor wasn't as low as most of the other amps I've used.

Very interested in this build! One day, I'd love to build an amp.
Yeah, elevated heaters should help to reduce AC hum a bit. But it also serves to reduce the cathode-to-heater breakdown voltage so your preamp tubes last longer (most of the Russian-made tubes fail in CF positions). The SLO uses CF positions so elevated heaters can help in that regard. You are basically raising the heater's ground reference from chassis-ground to something around 40-50 volts.
 
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eddy999

Member
Messages
220
Your PCB didn't come pre-populated did it?
No it wasn't pre-populated.

why did you run the preamp heaters (purple wires) from the pilot light instead of from the power tubes and under the preamp board?
A couple of reasons:

1. It was my first build so I basically copied the layout from Rob's (C3 Amps) build.
2. Running the wiring around the edge of the chassis keeps the heater AC away from the sensitive preamp section (a good idea in a high gain amp like this). I could have probably run the wiring between the choke and the preamp board and wouldn't have noticed a difference in noise, however see point 1 :)
 

FourT6and2

Supporting Member
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2,105
No it wasn't pre-populated.


A couple of reasons:

1. It was my first build so I basically copied the layout from Rob's (C3 Amps) build.
2. Running the wiring around the edge of the chassis keeps the heater AC away from the sensitive preamp section (a good idea in a high gain amp like this). I could have probably run the wiring between the choke and the preamp board and wouldn't have noticed a difference in noise, however see point 1 :)
Hmm, the photos and layout I have from C3 show the heaters being run under the board, just like in the real SLO. :dunno
 

eddy999

Member
Messages
220
Do you mean the preamp or power supply boards? I've just had a look at the pictures on his site again. He ran his heater wiring to a terminal strip under the power board, where he splits to go to the lamp and the preamp sockets. I didn't have room for a terminal strip so just ran around the outside to the lamp, and on from there to the heaters.

You can see in this shot the white wires run down from the strip to the lamp, and separate wires running to the edge of the chassis for the preamp sockets


and the other angle


My wiring was just pushed out closer to the edge of the chassis

 

FourT6and2

Supporting Member
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2,105
Nah, not those photos. I have other ones from other builds, along with photos of a bunch of real SLOs and the layout diagram from C3 which shows them run under the preamp board from the PI to between V7/V8, like in real SLOs. I wonder if that method actually induces hum or not?
 

eddy999

Member
Messages
220
Ah that explains it. It'd still rather branch off at the artificial ct and run either around the chassis or between the choke and preamp board
 

FourT6and2

Supporting Member
Messages
2,105
Transformers arrived today. The mailman complained about the weight of the box. So I guess that means they're beefy enough. :)

I think I might degrease the outside and paint the covers with some high-temp automotive paint (flat black), just to clean 'em up a bit.

 

big mike

Gold Supporting Member
Messages
12,309
I'd be tempted to paint the bells some wacky color.
Bright chevy orange or something.
 




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