It's cool Wayne you wouldn't even notice once they are soldered. I got 2 boards just incase I mess up the first one. Never soldered surface mount components before. Going to build mine as a headphone amp.
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It's cool Wayne you wouldn't even notice once they are soldered. I got 2 boards just incase I mess up the first one. Never soldered surface mount components before. Going to build mine as a headphone amp.
I've soldered fets on three of these boards so far and didn't notice that! It you want help, PM me. It's a lot of fun. Thin gauge solder, and fine point tip are really helpful—I also put down some paste flux—holds the parts—guarantees flow. Bent needle nose tweezers are also very welcome to hold the part while touching down with a bit of solder preloaded on the iron tip...
I solder SMD components like this everyday at work. I wear an OptiVisor with the #3 lens (1.75x magnification), and have good lighting. Place some flux on the pads. I have an X-Acto knife in my left hand and tweezers in the right hand to place the part. With the knife tip holding the part exactly in place during the process, I set the tweezers down and grab the iron. With a tiny bit of solder on the tip of the iron, a quick touch is all you need. Spin board around and finish the last two connections. Again, only a tiny amount of solder and a quick touch. Just enough to do the job without overheating the part. I clean with Isopropyl Alcohol / acid brush / KimWipe to finish the job.
Ive just had a look at the BOM list avdesignguru posted for Digikey and noticed the resistors are all 0.4 watts. Would I get away with these for R11 and R12 if I build the higher power version for a headphone amp? I read that these resistors should be 0.5 watt but for the sake of 0.1 will it cause any issues?
About soldering SMDs...
I just took delivery of a set of Super Regulators and the Fire-Metal solder (partly to support diyaudio! Thanks 6L6 for the suggestion)
Boy, that's fine solder. Man, those are tiny pads!
Can this be done with my legacy 1/8" tip or do I really need to spring for a finer point?
I'm afeared.
I just took delivery of a set of Super Regulators and the Fire-Metal solder (partly to support diyaudio! Thanks 6L6 for the suggestion)
Boy, that's fine solder. Man, those are tiny pads!
Can this be done with my legacy 1/8" tip or do I really need to spring for a finer point?
I'm afeared.
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The higher powered ones: KSC2690AYS / KSA1220AYS and Toshiba equivalents: TTA004B,Q / TTC004B,Q. I read on one of the schematics that if you build the higher power version you can change R11 and R12 resistors for 15 ohm or 20 ohm to increase the bias. I was wondering which would be better suited or whether to just leave them as stock 27 ohm.
Has anyone else compared boards using the "small" transistors vs the "large" ones?
I recently rewired this preamp, reversing which side power input was with the side with input RCAs. This allowed use of one of Teabag's I-Select relay boards which have pads for Alps blue pot. One volume pot shaft extender and associated wiring later, ready to fire up.
My original build was with smaller outputs, with rewire I used another pair (older mono boards w/o mounting holes.)
This set of boards with larger outputs is more stable ( of my 2 builds ) with DC output than the smaller version. It is possible that something about the original build (bad solder on jfet?) or parts that caused this difference. One board was stable around 2-3 mv, while the other would adjust the same, it always seemed to drift up to 7-17 mv.
Sonically the large outputs seem fine. I'm letting it burn in a bit, but initially it seems a little less forgiving than the smaller outputs easier sound.
This is with it used as preamp, not as headphone amp.
Maybe just me? Both sound fine I might add.
Russellc
I recently rewired this preamp, reversing which side power input was with the side with input RCAs. This allowed use of one of Teabag's I-Select relay boards which have pads for Alps blue pot. One volume pot shaft extender and associated wiring later, ready to fire up.
My original build was with smaller outputs, with rewire I used another pair (older mono boards w/o mounting holes.)
This set of boards with larger outputs is more stable ( of my 2 builds ) with DC output than the smaller version. It is possible that something about the original build (bad solder on jfet?) or parts that caused this difference. One board was stable around 2-3 mv, while the other would adjust the same, it always seemed to drift up to 7-17 mv.
Sonically the large outputs seem fine. I'm letting it burn in a bit, but initially it seems a little less forgiving than the smaller outputs easier sound.
This is with it used as preamp, not as headphone amp.
Maybe just me? Both sound fine I might add.
Russellc
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That is certainly possible with two different power supplies, but here, same power supply, only boards changed. Original had small outputs, I added I-Select, but that doesn't affect sound. I think I just need to adjust ears maybe. Awful good sound. I need to build my new one piece board version and install it.
Russellc
Russellc