Thank you for your explanations. If you can, write your comparisons of the original and the clone. I didn’t have the opportunity to have the original, but the clone impressed me, the Chinese surprised me.👍🙂
Ok I’ll try to explain.
I have tested some high quality amps and they normally have some + and - on their list.
Right now I’m listening to an GamuT D200i updated by Michael Edinger. Another favourite is a Krell KSA80B.
Both equally good as they have pros and cons depending on your preferences.
In this company the A-46 has nothing to to offer. Sorry to say it not better on any of those amps on anything.
The A60 clone however can ”compete”. It has a speed and “openness” which bests the best amp.
It doesn have the ”to die for soundstage” of the D200i or the “super organic dont make me angry temper” of the Krell. But it makes you believe there is a musical happening, and that’s very good!
So top 3 in my book😁🎶
I have tested some high quality amps and they normally have some + and - on their list.
Right now I’m listening to an GamuT D200i updated by Michael Edinger. Another favourite is a Krell KSA80B.
Both equally good as they have pros and cons depending on your preferences.
In this company the A-46 has nothing to to offer. Sorry to say it not better on any of those amps on anything.
The A60 clone however can ”compete”. It has a speed and “openness” which bests the best amp.
It doesn have the ”to die for soundstage” of the D200i or the “super organic dont make me angry temper” of the Krell. But it makes you believe there is a musical happening, and that’s very good!
So top 3 in my book😁🎶
I appreciate your messages. Thank you very much for your amp comparison. Post here on the forum, I think our friend will not mind. 
Hi @deerhunt,
It appears that we went almost the same way to get to the truth:
1. Dartzeel was a great dissapointment but a good lesson: people pay way too much for below the average products just for sake of of their notorious name.
2. I have compared A60 schematics to the original. There was some similarity, but obviously the designer used the original just as a template and did really good job. There are several similar amplifiers at Aliexpress. E550 seems to be a great candidate to test.
3. After meassuring A60+ I have realized that exactly the right blend of the 2nd harmonic did the magic.
4. Finally, for some reason many people underrate chipamps that may produce amazing results and still leave enough room for creativity.
It is pleassure sharing experiences with you and many other great guys on this great site for the enthusiasts.
Thank you all
It appears that we went almost the same way to get to the truth:
1. Dartzeel was a great dissapointment but a good lesson: people pay way too much for below the average products just for sake of of their notorious name.
2. I have compared A60 schematics to the original. There was some similarity, but obviously the designer used the original just as a template and did really good job. There are several similar amplifiers at Aliexpress. E550 seems to be a great candidate to test.
3. After meassuring A60+ I have realized that exactly the right blend of the 2nd harmonic did the magic.
4. Finally, for some reason many people underrate chipamps that may produce amazing results and still leave enough room for creativity.
It is pleassure sharing experiences with you and many other great guys on this great site for the enthusiasts.
Thank you all
Thanks for your exploration, knowing that I have just accomplished a nice poweramp 😄.
For those interested in building A60 I publish almost 100% accurate schematics in the attached file.
I’m sure that everyone realizes, sooner or later, that there is a great deal of bias in audio market as well as in audio DIY community. By “bias” I mean cognitive bias, not transistor bias. There are so many »well known« but never verified "facts". Too many "serious" members re-iterate the same adage without any practical experience except simulations, pure hearsay. One of them is that just some brands of active components guarantee proper operation, excluively. What to do then when known brand abandons their own products?
While building and testing this amplifier I have realized how false are claims about generic components produced in "developing countries". I have measured components using curve tracer and by measuring amplifiers in frequency region. In particular CDIL 2SA970/2SC2240 performed flawlessly.
What I’ve found is that performance of generic components is adequate. I wouldn’t generalize this conclusion because many diyers have reported difficulties with fakes, but purchasing generic components from reputable suppliers is safe way to obtain generic transistor otherwise abandoned by the original producer.
While building and testing this amplifier I have realized how false are claims about generic components produced in "developing countries". I have measured components using curve tracer and by measuring amplifiers in frequency region. In particular CDIL 2SA970/2SC2240 performed flawlessly.
What I’ve found is that performance of generic components is adequate. I wouldn’t generalize this conclusion because many diyers have reported difficulties with fakes, but purchasing generic components from reputable suppliers is safe way to obtain generic transistor otherwise abandoned by the original producer.
I am embarking on this project (basic A60) along with an MBL6010 preamp. I just ordered bare PCBs on aliexpress. I read through this entire thread before deciding. Going with CDIL for 970/2240. Pays to research before ordering components. A lot of valuable information here. May take awhile to acquire all parts as well. This transformer looks like a winner for this project and doesn't cost all that much either. I've build a lot of low voltage guitar pedals and a 5E3 clone guitar amp but have been out of the hifi hobby for years. Hope I do well with this one. Looks rewarding.🙂
You need 2 such transformers, and this is already $ 136 + delivery. If you need one, then a good option is there on Aliexpress 4x36v and 2x12v. The price is about $ 80 with delivery.
I also came to that conclusion after examining the wiring. I could go down in VA rating and do two transformers . Antek claim to be good to go 20% above rated specs so I wonder if two 200VA would suffice. Otherwise it's 300VA per board if going Antek. Their lower rated units have better shielding anyway. That aliexpress transformer is almost $160 total cost to ship here otherwise I would have already stopped looking and just got it.
Hi Berlusconi,
Thank you for details explaination of how to do grounding with this.
A few question:
1. The steps here are for when you externalize the power supply unit from the PCB (hence step 5,6,7), and have a dedicated power supply ground to connect to the star point (step 8). If there is no external power supply, and the transformer is connected directly to the PCB as of this board version (https://vi.aliexpress.com/item/1005001670632239.html?gatewayAdapt=glo2vnm), where do i find the power ground to connect to star point? Can i directly connect transformer ground (second terminal from the right in the input section of pcb) to star point?
2. Why mustn't we connect GND of signal input to anything? according to hifisonix article (https://hifisonix.com/wp-content/uploads/2021/04/Dual-Mono-Wiring.pdf), he still use two wire cable for input signal throughout to the PCB. What he did different is connect the input ground to chassis via a capacitor (i actually don't understand that part of him as well. if you can explain).
3. At step 15, you said install a 1K resistor between GND and IN+. Do you mean shorting GND and IN+ with a resistor? why would that improve the sound? why don't we connect signal ground directly from RCA to GND on PCB?
Hope you can understand my English. Looking forward to your reply. I have this board prebuilt given for me as present from my colleague but suffer from noise/hum so i'm trying to learn to improve it.
Thank you.
Hi anhhct,
1.
First, please go to thread "understanding star grounding"and read just posts #1, #2, #4 and #7 by member digi01. He brilliantly addressed the problem of grounding in a concise and clear manner. You don't have to read anything else there. Another useful source can be found elsewhere in an article "A Complete Guide to Design and Build a HIFI LM3886 amplifier" by by Scott Campbell, section "Designing the Ground Layout".
Now, look at the diagram (author: digi01) below from the thread "understanding star grounding".
It is possible to mathematically prove that in a multi-channel audio amplifiers all "return paths" must be connected at just a single point to avoid interference among individual channels.
Note that RCA connectors are connected together and then connect to the star point. This provides return paths for all inputs without violating the rule of a single connection.
2.
I've heard somewhere that a 1K resistor between GND and IN+ improves the sound by eliminating noise from the input and it worked for me.
3.
I have used a dedicated power supply because I could afford it and it reduces 50Hz ripple and associated frequencies. That reduces noise, even though without dedicated power supply is quite silent, almost inaudible.
I do not connect amplifier to the speakers before I make sure everything is good. Instead, I observe noise in frequency region by using measurement rig connected to an USB sound card. This approach is much more convenient than "listening" to the noise. You can easily see (instead of hear) what frequencies cause troubles and helps identify the cause of noise.
1.
First, please go to thread "understanding star grounding"and read just posts #1, #2, #4 and #7 by member digi01. He brilliantly addressed the problem of grounding in a concise and clear manner. You don't have to read anything else there. Another useful source can be found elsewhere in an article "A Complete Guide to Design and Build a HIFI LM3886 amplifier" by by Scott Campbell, section "Designing the Ground Layout".
Now, look at the diagram (author: digi01) below from the thread "understanding star grounding".
It is possible to mathematically prove that in a multi-channel audio amplifiers all "return paths" must be connected at just a single point to avoid interference among individual channels.
Note that RCA connectors are connected together and then connect to the star point. This provides return paths for all inputs without violating the rule of a single connection.
2.
I've heard somewhere that a 1K resistor between GND and IN+ improves the sound by eliminating noise from the input and it worked for me.
3.
I have used a dedicated power supply because I could afford it and it reduces 50Hz ripple and associated frequencies. That reduces noise, even though without dedicated power supply is quite silent, almost inaudible.
I do not connect amplifier to the speakers before I make sure everything is good. Instead, I observe noise in frequency region by using measurement rig connected to an USB sound card. This approach is much more convenient than "listening" to the noise. You can easily see (instead of hear) what frequencies cause troubles and helps identify the cause of noise.
Attachments
Hi Berlusconi,
Thank you for the explaination and recommendation of the two resources.
I've gone through them and get a bit of hang about grounding. Even though it's still unclear to me how star grounding can be mathematically proven to reduce noise, proving it is not really neccessary, as it's a standard used by many.
What i'm still struggling to figure out, is where would be the main power GND, to wire to the star point? Since i don't have an external PSU, the PSU is onboard with the amp module. And i will have two of them. Should i connect the two GND post on the main input station (circled in picture bellow) to the star? That position is for connecting the transformer GND wire into the module, and it is before any capacitor or rectifier. If i use it as the point from which I wire to the star, is it the correct way to have power GND and signal GND together?