A60(+) Amplifier. Build this?

vmk2002

Member
2021-04-14 4:29 pm
Earth
Hello Berlusconi. I want to ask which motherboards sound better in your opinion, A60 (6 transistors) or A60 + (16 output transistors)? It would also be great if you could tell me about the size and number of woofers in your acoustics. Did you experience a lack of bass or not? Thank you in advance!
 
  • Like
Reactions: 1 user
Hello VMK2002,
First, I'm glad to see you again after a long time. I was worried about you. How did you solve the problem of hum?
If you still have that problem, look a this superb thread:

understanding star grounding

For multichannel designs this diagram from that thread post #7 is especially important. Studdy it carefully. The trick is so simple that you don't see quickly. Study it carefully indeed and you will see the trick.

Back to your questions:

A60 and A60+ are essentially the same amplifier with different number of transistors in the output stage. It is impossible to distinguish one from another. A60+ has more power and may drive lower impedance speakers, hence provide more power.
A long time ago I made decision to use 8 Ohm but high sensitivity speakers . My woofers have sensitivity of 97 dB and I really don't need much power . I use just two Vifa NE225W-04/08 8''. That's more than enough for me.

I don't plan to use my equipment outdoors so the both 60 and 60+ are powerful enough.

Kind regards my dear VMK2002 and don't leave us for so long time again. :)

Edit: No lack of bass. The best side of this amplifier is exactly the way it reproduces bass and it has lots of punch, when needed. Investigate the input stage and you will see why. It can amplify any low frequency without roll-off. It has bandwidth practically from zero Hz.
 
Last edited:
  • Like
Reactions: 1 user

vmk2002

Member
2021-04-14 4:29 pm
Earth
Hello Berlusconi. I have been listening to this power amplifier for 2 months now. I have already reported that my preamplifier-power amp combination was not optimally matched to each other (excessively loud sound at the very beginning of the volume control range). Although they were recommended and bought in one Chinese store. But like any non-brand item from China, this technique needs to be improved. I just, as I reported earlier, changed the mode of operation of three pairs of transistors (A970, C2240) and perhaps the influence of the "servo drive" on OP07. To do this, I increased the value of the 22 ohm resistor to 470 ohms. I'm talking about boards on transistors 5200/1943. Now a couple of boards for MJL4281/4302 are ready.
On one of them, I could not eliminate the noise at all until I got rid of OP07 (removed from the connector).
Without OP07, the pauses in the music are absolutely quiet. If I have free time, I will check and listen to new boards and share the results.
At the same time, I changed the DAC (to ESS9018) Muses 8920 to Muses 02. I listen from Raspberry + Volumio. It might be easier to hear the difference now. Another option for the sound source is CD on the CS4398 (XRCD, K2HD, HDCD and SACD).
 
I finished painting, the first photos. The platform for the transformer is shiny. There was a small joint, I ordered a diagram sticker and covered it up.There is a removable platform from below, as well as a cover from above.:)
 

Attachments

  • IMG_0309.JPG
    IMG_0309.JPG
    590.8 KB · Views: 73
  • IMG_0310.JPG
    IMG_0310.JPG
    416.2 KB · Views: 63
  • IMG_0312.JPG
    IMG_0312.JPG
    586.1 KB · Views: 72
  • IMG_0313.JPG
    IMG_0313.JPG
    557.1 KB · Views: 78
I just got my boards for A60. They seem to be version 1.1.
The boards will replace the NHB-108 which has it's shortcomings. I'm hoping for some more bass control and stabile soundstage. Still with a warm and organic sound - let's find out:)

I have a couple of questions for the nice community. Please share yor knowledge.

1. Does these boards I have any known issues like errors in print or lay-out/traces?
2. Is aux voltage of 17,2VAC too high? What are to max voltage for the aux circuit components?
3. From heat dissipation - is it best to mount the boards with power transistors facing down? Or perhaps it doesn't matter?
4. Is there a circuit diagram with readable component values or I have to trust the screen print?

Thanks in advance!


IMG_7538.jpg
 
Last edited:
I just got my boards for A60. They seem to be version 1.1.
The boards will replace the NHB-108 which has it's shortcomings. I'm hoping for some more bass control and stabile soundstage. Still with a warm and organic sound - let's find out:)

I have a couple of questions for the nice community. Please share yor knowledge.

1. Does these boards I have any known issues like errors in print or lay-out/traces?
2. Is aux voltage of 17,2VAC too high? What are to max voltage for the aux circuit components?
3. From heat dissipation - is it best to mount the boards with power transistors facing down? Or perhaps it doesn't matter?
4. Is there a circuit diagram with readable component values or I have to trust the screen print?

Thanks in advance!


View attachment 1053210
Hi!
I have bought these, but did not built them yet. I made a schematic though. Good luck!
I follow this thread and I hope to build one some time!
:) morten
 

Attachments

  • A60_skjema.JPG
    A60_skjema.JPG
    158.7 KB · Views: 102

Berlusconi

Member
2019-09-21 7:39 pm
I'm glad to see increased interest in this amplifier.
Meanwhile, I've made some improvements and have performed new set of measurements on both boards. New measurements indicate very low THD and noise values, about 0.003%!
I will join this thread again and share my experience in building this fine amplifier. A60 indeed sounds better than several 'famous' DIY amplifiers I've built.
 

Berlusconi

Member
2019-09-21 7:39 pm
It's very different from the real A60
Indeed Mark, it is just 'inspired-by', but I don't care for usual marketing spin, what I really appreciate is the real world performance and measurements. I've tried quite a few DIY kits and this amplifier has the best performance/sound. I have kept JLH 2003 version, Krell KSA50, STK4042Xi chipamp and 3 pairs of A60(+) which are my favorite. All other projects, including DartZeel NHB-108 clone, ended-up in the bin.
 
I just got my boards for A60. They seem to be version 1.1.
The boards will replace the NHB-108 which has it's shortcomings. I'm hoping for some more bass control and stabile soundstage. Still with a warm and organic sound - let's find out:)

I have a couple of questions for the nice community. Please share yor knowledge.

1. Does these boards I have any known issues like errors in print or lay-out/traces?
2. Is aux voltage of 17,2VAC too high? What are to max voltage for the aux circuit components?
3. From heat dissipation - is it best to mount the boards with power transistors facing down? Or perhaps it doesn't matter?
4. Is there a circuit diagram with readable component values or I have to trust the screen print?

Thanks in advance!
1. None that I'm aware of
2. You rather use a small transformer with two 12VAC secondaries. These are too cheap to save the money on them. Separate secondaries are essential to avoid ground loops.
3. Don't worry, just have large heat sink for output devices. Othertwise, heat dissipation will limit your choice of the quiescent curent. With adequate heat sink you may extract the first 20-24 Watts of pure class A performance.
4. The values on the silk screen are all correct. You only have to take care to install IC1237 in correct direction. Also, smaller boards are mirrored, so take care that components are soldered in correct direction.
Take care and welcome aboard
 
There are many good photos of the A60 and A60+ on the forum here. You just need to carefully look at them and install them according to the pictures. It is natural to look back at the diagram. If necessary, I will post high-quality A60s. Aliexpress also has the right boards and there are large photos on which you can easily prepare this amplifier. As the respected Berlusconi wrote, he has no flaws. Good luck.;)
 

Attachments

  • IMG_0130.JPG
    IMG_0130.JPG
    209.7 KB · Views: 38
  • IMG_0136.JPG
    IMG_0136.JPG
    467.7 KB · Views: 37
  • IMG_0135.JPG
    IMG_0135.JPG
    601.2 KB · Views: 33
  • IMG_0138.JPG
    IMG_0138.JPG
    413.1 KB · Views: 34
  • IMG_0131.JPG
    IMG_0131.JPG
    554.4 KB · Views: 37
  • Like
Reactions: 1 user
Those of you who have the actual PCB's could check if what I'm saying is correct:

It could be possible to maybe double-up the relay contacts (and half the contact resistance, i.e. improve damping factor / improve the sound). Of course, this would need to be checked with a multimeter on an actual PCB...


1652356681234.png