kozard

That looks nice. Sounds like I should look into FlatCAM. How many different bit sizes did you need to use to make the board? If you don't mind me asking what are the sizes and types of bits that you used?

How is the project going? Have you listened to it yet?

Does anyone have a KSA-5 schematic in KiCad that they are willing to share?

Would 5551/5401 work?

Perhaps the range of the Vbe multiplier (resistors and/or pot) needs to be adjusted if you want to use the larger heatsink and lower temperature? Not sure what is best in this case but sometimes a certain temperature is targeted (such as 50C in another design).

By faster do you mean lower capacitance? Or higher fT/Current Gain - Bandwidth Product? I ask since at 10V I think the Cob for 2SC5171 is about 16pF versus 4pF for each MPSA06. So 4x MPSA06 would be about 16pF. And 2SC5171 has higher fT. So does it mean in this case that one 2SC5171 would not be slower than four parallel MPSA06? I could certainly put four parallel TO-92 but I would like to understand it better before I do the layout. I have a bunch of genuine 2SC5171/2SA1930 from dead receivers that I used the chassis/heatsink and transformer to make KSA-50 monoblocks. So I am looking for the best place to use them. Otherwise I can just get some MPSA06/MPSA56. I found a couple Spice models for 2SC5171/2SA1930 but I don't know if I can trust them. One had quite a few default looking values. I also have some leftover TTC004B (12pF Cob) and TTA004B. I have not found the BD139/BD140 Cob yet.

I was wondering about the four paralleled MPSA06 and four paralleled MPSA56. Why would that be done instead of using something like one BD139 and one BD140? (Or perhaps 2SC5171 & 2SA1930?) I ask since I am thinking of trying my hand at making a KiCad layout and so I would like to understand the reason for this design choice.

Perhaps try the KiCad TO-92 "Hand Soldering" footprint? Are you using MPSA06/MPSA56?

I was wondering if anyone could comment on the best transistor types for each section of the KSA5? I have available from various projects over the years: BC327-25/337-25 BC546B/BC556B BC550/BC560 BD139/BD140 2N4401/2N4403 2SC945/2SA733 2SC1815/2SA1015 More recently I pickup up some other interesting types: 2SC2655/2SA1020 2SC2382/2SA1013 D669A/B649A & D667/B647 From recycling a couple junked receivers I also have some genuine Toshiba 2SC5171/2SA1930. I was wondering if they would make some very nice outputs for a HPA? (Or perhaps I should stick with lower Vce transistors for best performance?) There are also 2SC2240/2SA970 in there but I guess those are too high Vce and will suffer from hFE non-linearity at low voltages. I ask since I have seen MPSA06/MPSA56 used almost everywhere in KSA5 and another clone (red board) I think uses BC almost everywhere (BC546B/BC556B?) So I am wondering if more careful choice between a larger variety of types might be advantages? I should add that all of my headphones are 40 or 42 Ohms. If MPSA06/MPSA56 is truly best for KSA5 then I need to order them.