The board is very inexpensive, and I bought another set of boards from Aliexpress. In my next attempt, I want to modify the components to create a hybrid of Mimesis and Telos. The VBE will be removed. All of these modifications would be 100% consistent with the original Goldmund. I find it very easy to do with this board.
One more note about the 2n3958. There are very few originals left. I bought clones, not counterfeits, from Aliexpress and compared them with my original 2n3958 transistors. As expected, I didn't hear any significant differences in the sound. From what I understand from the Wiki, the 2n3958 sounds even better than the 2n5565. I haven't tested it, though. There are also very inexpensive 2n5565 clones.
By the way, I connected a 95db 4 ohm speaker to the power amp. If a source is connected to the input, there's no noise at idle. Not even when I put my ear to the speaker. Just silence.
By the way, I connected a 95db 4 ohm speaker to the power amp. If a source is connected to the input, there's no noise at idle. Not even when I put my ear to the speaker. Just silence.
I forgot to mention that I also selected four identical 2sc3421 and 2sa1358 transistors.
This wasn't easy because the P and N channels always have different hfe values. I had to contact different manufacturers to get the same hfe values. I bought transistors from ISC and CDiL. The Toshiba clones had hfe values that were too high. This doesn't match the datasheet. A poor copy of the transistor. But it might work well elsewhere. I didn't use them.
A single pair of 2sc3421 and 2sa1358 transistors would have worked too. However, I found the heatsink to be too hot at 50 C. With a double pair, the heatsink reached about 40 C.
The VAS transistors mpsa42 and MPSA92 had a temperature of around 40 C.
All at idle.
This wasn't easy because the P and N channels always have different hfe values. I had to contact different manufacturers to get the same hfe values. I bought transistors from ISC and CDiL. The Toshiba clones had hfe values that were too high. This doesn't match the datasheet. A poor copy of the transistor. But it might work well elsewhere. I didn't use them.
A single pair of 2sc3421 and 2sa1358 transistors would have worked too. However, I found the heatsink to be too hot at 50 C. With a double pair, the heatsink reached about 40 C.
The VAS transistors mpsa42 and MPSA92 had a temperature of around 40 C.
All at idle.
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Here are the measurements I promised: sine and square at 10 kHz. Clean! I think I'm a good craftsman, but I don't know much about electronics. Measuring and simulating isn't my thing. I prefer to rely on my ears when it comes to amplifiers.
Attachments
I ordered different transistors for VAS. As I understand it from the Goldmund Wiki, VAS has a lower current with FZT857 and FZT957. This is the configuration of the Goldmund Telos. As a result, this change produces more detail in the music. They are SMD transistors that I solder onto an adapter board, which I then solder onto the Hm3s board. Results to follow. I'll report back.