Abrise
Member
Comments and tests on a LM audio MIN400A China made Purify inspired amplifier.
This post is not an incentive to follow in my footsteps but is for informational purposes. I’ll try to point out facts only.
Where I live, I am a French expat in Thailand, there is not many high-level products tested on ASR locally available besides Topping or SMSL products. I already have the excellent Topping PA7, but for my last amplifier I wanted something excellent but different. Buying and having it shipped from the west from Audiophonics, VTV, Buckeye or the likes is long and complicated. Moreover, guarantee is almost impossible to claim cross continent anyway because of shipment time, cost and custom issues. So, I have just purchased for 620€ including transportation on AliExpress, a Purifi like based amplifier. The device is also for sale elsewhere on Aliexpress for twice this price!
The original offer is on Taobao https://item.taobao.com/item.htm?sp...XzChad&id=662513179130&ns=1&abbucket=4#detail , it’s at a similar price but if you are not Chinese you cannot buy easily on Taobao .
There is already a thread on this product, but it has turned into politics and philosophy, a bit limit on ASR. No facts of manufacturer misbehavior have been proven although this thread is up for more than a year now. https://www.audiosciencereview.com/forum/index.php?threads/chinese-purifi-1et400a-clone-amp.36470/
This amplifier is extremely well placed into @Matias list https://docs.google.com/spreadsheets/d/1ZlTOYxmPs938gqHjtDABkWS-MApu7uJjzIGnJ2Elm6Y/edit#gid=0
There has been an extensive testing with superb results https://www.l7audiolab.com/f/min400a/ However these results, certainly honestly obtained, are -at least as it is presented by the vendor -misleading to the normal reader as you’ll understand later.
I will make a few tests to check if my unit is at par with the one tested by l7audiolab. I think that the manufacturer has low volume and although he says that he controls all units shipped, I better check myself. Also, there is a small difference as I choose the unit with a small form factor and with a passive volume knob.
Purchase and transportation
This experience has been quite stressful. At payment I wasn’t given the choice of shipment. Parcel was supposed to arrive 13 days after payment. But the shipment took place 13 days after the payment. Contact with seller was inexistent. I thus started to be scared a little bit. In 20 years of practice, I have never been scammed with AliExpress but usually I choose well known shops. At last, it is shipped. But it’s going first to Japan. What?... To summarize the parcel travelled from Hong Kong to Japan to China to Indonesia to Singapore to Thailand to…Home. Strange Fedex logistics. All together 23 days from purchase to final delivery. Usually, it takes a week or two. By the way 23 days is no longer than having things shipped from Europe.
Manufacturer specs
Power at 1% distortion: 200W*2 8 ohms, 350W*2 4 ohms
Distortion: less than 0.00025% at 1kHz 100W i.e. -112dB
SN: above 125dB, measured 127dB.
Frequency response: 20-20hKz - 0.02dB.
Manufacturer writes that the connection board and power supply unit are his design. The buffer which can be disabled is 14dB gain.
Iddle power is 16W
Unpacking
I weighed the parcel when it arrived and took a video of the opening. The shipment box is the only box. There is no manual neither plug cable inside.
Here is a photo.
First tests
My test equipment is: SMSL-D6S xlr output as the DAC, 4x2 Ohms 200W resistors as the dummy load and voltage divider when necessary, E1DA cosmos class B, Topping HS02 isolator, Surface Pro PC with REW. This setup is good enough to make valid measurements for the expected results. (at least 10dB better.)
And the first result is …
At 5W 4Ohm THD+N of 97dB. A SINAD of 97dB puts the amp into the excellent category inside @amirm scale. However, I was disappointed as I was waiting for SOTA values as per L7Audiolab measurements 10dB better.
To better understand the amp I have made a lot of other tests but to make a long story short here are just 2 other graphs
THD+N vs level BW 20kHz showing a max power of 170W at 8 Ohms. Read 500Hz not 500kHz
And this more than acceptable multitone test at 5W 8Ohms around 18bits
But why am I so far from the manufacturer specs and L7Audiolab tests ?
After a sleepless night, I decided to disable the buffer. Getting 14dB less gain and a DAC with an output of 5V only, the amp will not be very powerful. To do this I have to take out the 2 amplifiers mini boards and change the position of 4 jumpers.
Immediately I could see the difference in test results: 10dB improvement! I went back to l7Audiolab test and realize that to get 5W on 4Ohms he puts 1.05V at the amp input and to get 150W on 8 Ohms he puts 7.94V. Thus, there is no input buffer in his device under test. And the natural gain of the amp is 4.3 or 12.6dB. I believe that the absence of input buffer should have been written clearly in the report text.
Here are the culprits perverting the signal, they are supposed to be OPA1612 but the marking is erased.
With a max of 5V at my DAC level I will get a max of 115W on 4Ohms or 55w on 8 Ohms. It might be enough, I don't know.
Tests without the input buffer
5W 4Ohms 1kHz spectrum analysis shows now excellent results SINAD of 106 dB within 2dB from l7Audiolab testing
Multitone test at 5W 4Ohms almost 19 bits very nice.
Frequency response 5W 4Ohms Is excellent
Another test at 90W close to the max I can go with no buffer. THD+N 97dB excellent but was expecting even better
So now I have to choose among
1/Keeping the amplifier without the buffer and get a more than excellent device but limited at 115W 4 Ohm
2/Put back the existing buffer amplifier and getting an excellent amplifier with quite a lot of power.
3/Replace the buffer amplifier by a better one.
For this last alternative I need support.
-does it make sense that the input buffer causes a damage of 10dB to the specs ?
-would it make sense to replace the small modules by another amp and which one?
This post is not an incentive to follow in my footsteps but is for informational purposes. I’ll try to point out facts only.
Where I live, I am a French expat in Thailand, there is not many high-level products tested on ASR locally available besides Topping or SMSL products. I already have the excellent Topping PA7, but for my last amplifier I wanted something excellent but different. Buying and having it shipped from the west from Audiophonics, VTV, Buckeye or the likes is long and complicated. Moreover, guarantee is almost impossible to claim cross continent anyway because of shipment time, cost and custom issues. So, I have just purchased for 620€ including transportation on AliExpress, a Purifi like based amplifier. The device is also for sale elsewhere on Aliexpress for twice this price!
The original offer is on Taobao https://item.taobao.com/item.htm?sp...XzChad&id=662513179130&ns=1&abbucket=4#detail , it’s at a similar price but if you are not Chinese you cannot buy easily on Taobao .
There is already a thread on this product, but it has turned into politics and philosophy, a bit limit on ASR. No facts of manufacturer misbehavior have been proven although this thread is up for more than a year now. https://www.audiosciencereview.com/forum/index.php?threads/chinese-purifi-1et400a-clone-amp.36470/
This amplifier is extremely well placed into @Matias list https://docs.google.com/spreadsheets/d/1ZlTOYxmPs938gqHjtDABkWS-MApu7uJjzIGnJ2Elm6Y/edit#gid=0
There has been an extensive testing with superb results https://www.l7audiolab.com/f/min400a/ However these results, certainly honestly obtained, are -at least as it is presented by the vendor -misleading to the normal reader as you’ll understand later.
I will make a few tests to check if my unit is at par with the one tested by l7audiolab. I think that the manufacturer has low volume and although he says that he controls all units shipped, I better check myself. Also, there is a small difference as I choose the unit with a small form factor and with a passive volume knob.
Purchase and transportation
This experience has been quite stressful. At payment I wasn’t given the choice of shipment. Parcel was supposed to arrive 13 days after payment. But the shipment took place 13 days after the payment. Contact with seller was inexistent. I thus started to be scared a little bit. In 20 years of practice, I have never been scammed with AliExpress but usually I choose well known shops. At last, it is shipped. But it’s going first to Japan. What?... To summarize the parcel travelled from Hong Kong to Japan to China to Indonesia to Singapore to Thailand to…Home. Strange Fedex logistics. All together 23 days from purchase to final delivery. Usually, it takes a week or two. By the way 23 days is no longer than having things shipped from Europe.
Manufacturer specs
Power at 1% distortion: 200W*2 8 ohms, 350W*2 4 ohms
Distortion: less than 0.00025% at 1kHz 100W i.e. -112dB
SN: above 125dB, measured 127dB.
Frequency response: 20-20hKz - 0.02dB.
Manufacturer writes that the connection board and power supply unit are his design. The buffer which can be disabled is 14dB gain.
Iddle power is 16W
Unpacking
I weighed the parcel when it arrived and took a video of the opening. The shipment box is the only box. There is no manual neither plug cable inside.
Here is a photo.
First tests
My test equipment is: SMSL-D6S xlr output as the DAC, 4x2 Ohms 200W resistors as the dummy load and voltage divider when necessary, E1DA cosmos class B, Topping HS02 isolator, Surface Pro PC with REW. This setup is good enough to make valid measurements for the expected results. (at least 10dB better.)
And the first result is …
At 5W 4Ohm THD+N of 97dB. A SINAD of 97dB puts the amp into the excellent category inside @amirm scale. However, I was disappointed as I was waiting for SOTA values as per L7Audiolab measurements 10dB better.
To better understand the amp I have made a lot of other tests but to make a long story short here are just 2 other graphs
THD+N vs level BW 20kHz showing a max power of 170W at 8 Ohms. Read 500Hz not 500kHz
And this more than acceptable multitone test at 5W 8Ohms around 18bits
But why am I so far from the manufacturer specs and L7Audiolab tests ?
After a sleepless night, I decided to disable the buffer. Getting 14dB less gain and a DAC with an output of 5V only, the amp will not be very powerful. To do this I have to take out the 2 amplifiers mini boards and change the position of 4 jumpers.
Immediately I could see the difference in test results: 10dB improvement! I went back to l7Audiolab test and realize that to get 5W on 4Ohms he puts 1.05V at the amp input and to get 150W on 8 Ohms he puts 7.94V. Thus, there is no input buffer in his device under test. And the natural gain of the amp is 4.3 or 12.6dB. I believe that the absence of input buffer should have been written clearly in the report text.
Here are the culprits perverting the signal, they are supposed to be OPA1612 but the marking is erased.
With a max of 5V at my DAC level I will get a max of 115W on 4Ohms or 55w on 8 Ohms. It might be enough, I don't know.
Tests without the input buffer
5W 4Ohms 1kHz spectrum analysis shows now excellent results SINAD of 106 dB within 2dB from l7Audiolab testing
Multitone test at 5W 4Ohms almost 19 bits very nice.
Frequency response 5W 4Ohms Is excellent
Another test at 90W close to the max I can go with no buffer. THD+N 97dB excellent but was expecting even better
So now I have to choose among
1/Keeping the amplifier without the buffer and get a more than excellent device but limited at 115W 4 Ohm
2/Put back the existing buffer amplifier and getting an excellent amplifier with quite a lot of power.
3/Replace the buffer amplifier by a better one.
For this last alternative I need support.
-does it make sense that the input buffer causes a damage of 10dB to the specs ?
-would it make sense to replace the small modules by another amp and which one?
