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.
Last edited:
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.
Great work with this circuit, thank you. I experienced the oscilation problems when I used the 2sk135/J50 mosfets. I tried many different compensation techniques, but only the oscilation frequency changed. The sound and oscilliscope measurements are otherwise very good. I am now trying your suggested driver changes. I also found a fault on the PCB with the offset trimpot pin arrangement, which is different to the circuit diagram layout and did not adjust properly. I changed the trimpot pins to connect like in the circuit diagram.
Unfortunately, I can't see that the trimpot pin are incorrect on the layout and don't match the schematic. Everything seems to be fine, and the bias setting works very well for me.
Did you solder the gate resistors directly to the MOSFETs? Gate resistors should be placed as close to the gate as possible. Perhaps that's why it oscillates if the resistors are placed on the board and too far from the MOSFET gate pins.
What do you mean, it sounds good and the oscilloscope measurements are good too? If the amplifier oscillates, the oscilloscope should show it.
I would like to help.
Attachments
Last edited:
Thank you very much for the published information.
I have ordered both bare PCBs and completed amplifier board. I plan to use the completed board as a template to facilitate the build from the stratch. I have also ordered components from Mouser, except the missing 2SK50. I plan to use INTERFET alternatives, but I'm not sure which replacements are adequate.
Which components did you use for your build and where they are available?
I have ordered both bare PCBs and completed amplifier board. I plan to use the completed board as a template to facilitate the build from the stratch. I have also ordered components from Mouser, except the missing 2SK50. I plan to use INTERFET alternatives, but I'm not sure which replacements are adequate.
Which components did you use for your build and where they are available?
What are INTERFET alternatives? I'm not familiar with the term.
I get Hitachi TO-3 from old PA power amplifiers, which I buy on eBay. That way, I know they're carefully selected and genuine.
I buy all my other transistors here in Germany from Kessler and Reichelt Elektronik. I can't buy from Mouser. Shipping costs are too high and minimum orders are too large.
I also buy transistors like MPSA from Aliexpress. I compared these with the clones from ISC and CDiL from India. The results showed that the Ali transistors are also good. The Hfe values are what matter. They have to be the same.
I get Hitachi TO-3 from old PA power amplifiers, which I buy on eBay. That way, I know they're carefully selected and genuine.
I buy all my other transistors here in Germany from Kessler and Reichelt Elektronik. I can't buy from Mouser. Shipping costs are too high and minimum orders are too large.
I also buy transistors like MPSA from Aliexpress. I compared these with the clones from ISC and CDiL from India. The results showed that the Ali transistors are also good. The Hfe values are what matter. They have to be the same.
Last edited:
I'm not sure and haven't checked, but I think the pre-assembled Hm3s boards from Aliexpress have larger component tolerances.
They work, but one forum member wrote that they're very sensitive and fail after just a year. One possible reason for this is that the driver transistor gets very hot. Furthermore, the Chinese manufacturers use very high (33p) capacitors. These act as brakes to prevent possible oscillation. If the components were selected more precisely, one could use 4.7p capacitors like the original, and the amp would naturally be more sensitive but stable with better harmonic distortion.
They work, but one forum member wrote that they're very sensitive and fail after just a year. One possible reason for this is that the driver transistor gets very hot. Furthermore, the Chinese manufacturers use very high (33p) capacitors. These act as brakes to prevent possible oscillation. If the components were selected more precisely, one could use 4.7p capacitors like the original, and the amp would naturally be more sensitive but stable with better harmonic distortion.
I don't have any long-term experience yet and am very curious to see how long my power amplifiers will last.
First, thanks for your quick reply.
I have purchased 9 pairs of EXICON ECX10N20 (2SK1058) and EXICON ECX10P20 MOSFET (2SJ162) in August of 2022. So I have a direct replacement for the output stage. So I'm missing now just 2SK30. My first guess is to use 2SK209 (TO-236 with T92 adapter) but that's not my final decision.
But thanks for the info about the quality of semiconductors from aliexpress. I used to purchase just power transistors and mechanical stuff. I'll give them a chance now with an order for 2SK30A
I wish you a pleasant end of this Sunday.
I'm not sure and haven't checked, but I think the pre-assembled Hm3s boards from Aliexpress have larger component tolerances.
I have purchased 9 pairs of EXICON ECX10N20 (2SK1058) and EXICON ECX10P20 MOSFET (2SJ162) in August of 2022. So I have a direct replacement for the output stage. So I'm missing now just 2SK30. My first guess is to use 2SK209 (TO-236 with T92 adapter) but that's not my final decision.
I also used to purchase from Reichelt but was disappointed with their slo...........ow response and the lack of quality semiconductors. Now I prefer Mouser. They ship fast to the EU, and I get it TAX free and without import duties (they have opened department in the EU) and their shipment travel just like a rocket (they aren't far from the Cape Canaveral 😉 . Fast. And they have almost everything. Transportation isn't prohibitive, it's free for shipments above €50. I like them very much.I buy all my other transistors here in Germany from Kessler and Reichelt Elektronik. I can't buy from Mooser. Shipping costs are too high and minimum orders are too large.
But thanks for the info about the quality of semiconductors from aliexpress. I used to purchase just power transistors and mechanical stuff. I'll give them a chance now with an order for 2SK30A
Don't worry, I'll use that just as a template and dich it into the bin.I'm not sure and haven't checked, but I think the pre-assembled Hm3s boards from Aliexpress have larger component tolerances.
I wish you a pleasant end of this Sunday.
Last edited:
I also bought the 2sk30a from Aliexpress. 10 pairs were enough to get 5 identical pairs. The mono listening test in my workshop showed that the 2sk30a from an unknown manufacturer worked well. Easily adjustable offset, no noise. I've decided to use 2n3958. I hope they create a broad soundstage. A forum member wrote in the Goldmund Wiki that the 2n3958 sound like more of everything: more bass, more treble, more detailed mids. How something sounds is a matter of taste. I've been inspired by the positive reviews and trust the 2n3958.
I also wish you a nice Sunday and much success in making Goldmund G29 hm3s👍
I also wish you a nice Sunday and much success in making Goldmund G29 hm3s👍
I'm sure that's the best option, but 2N3958 is obsolete for years. Though, there are plenty of offers at Aliexpress, but I wonder if...I've been inspired by the positive reviews and trust the 2n3958.
I have ordered 2SJ50 from Aliexpress and also 2SK209 (TO-236 with T92 adapter) from Mouser. I will decide after measuring alternatives. I simply don't trust my gut feeling this time. (Otherwise, my best decisions ever were made purely on my gut feeling.)
I'm curious to see if they can find a usable 2sj50 from Aliexpress. The 2sk209 is a good and interesting replacement. If I remember correctly, it was compared here in the forum to the legendary 2sk117. A very similar transistor. Please write and share your experience assembling these transistors.
But of course I will. This project is a fine challenge and an opportunity to learn. Thanks for sharing. By theway, I have found some info on available adequate dual jfets comparable to 2N3598.Please write and share your experience assembling these transistors.
Does anyone have information about Dönberg Electronics (https://www.donberg.ie/descript/2/2n_3958.htm) from Ireland? Alegedly they sell new 2N3598. Slightly expensive, but why not. We live just once.
Last edited:
There's a replacement for the 2n3958. It's called the LS3958, but it comes in an SOIC8 package. You can get it from DigiKey for €7.53. Free shipping on orders over €50. Otherwise, shipping is €18. 🙃
A Goldmund-experienced forum member compared the LSK389 and others. Here's the link to his sound description.
I have compare LSK389 and LSK489 on my clone. Conclusion: I like 389 a little bit than 489.
The LSK489 makes the sound a bit more airy (very subtle) and less "luxurious", and bass is "weak foot".
I have further experience with genuine NS 2N3958, I think it the best among the dual JFET I've ever tested. The sound of 2N3958 is luscious, like a sexy woman; its punchy...
Has anyone tried the SST404 or LSK489 on this clone?
I have been using the 2N5565 on another simulation I have been doing, and above duals give much better gain and phase margins in LTSPice's Tian probe simulations.
I have compare LSK389 and LSK489 on my clone. Conclusion: I like 389 a little bit than 489.
The LSK489 makes the sound a bit more airy (very subtle) and less "luxurious", and bass is "weak foot".
I have further experience with genuine NS 2N3958, I think it the best among the dual JFET I've ever tested. The sound of 2N3958 is luscious, like a sexy woman; its punchy...
- Home
- Amplifiers
- Solid State
- Is HM3S a Goldmund clone?