no signal, bridge.
5hz.
100hz.
2khz.
10khz.
20klhz.
50khz.
100khz.
300khz.
senoidal 20khz.
the preamplifier.
1.177 / 5.000
Hello, first of all I want to make it clear that, as almost everyone knows, Chinese advertisements and clones often do not even look like what they advertise. In this case, I want to make known what I consider a bargain. Leaving aside the title we have a preamplifier that I consider excellent, at a ridiculous price of 10$ with shipping (at least to Spain), small size (easy to connect if you want an integrated amplifier), you only need a 15-0-15 v. transformer, or a switched source for example of equal value for another 7$, it has its regulators, with its capacitors that really work very well, at the input it has an OP JRC-5532D, then BC550 and BC560, everything quite normal, I ordered 2 units, assembled it and passed it through the oscilloscope, the result is excellent (in my opinion and the price) I put captures of up to 400khz in square wave, the sine wave logically better, it responds from 5hz without problems, I have tried other clones and other originals that I have, and this one on paper gives better measurements, something that measures well can't sound bad. The sound, the little I have tried so far, is quite good, better than the Denon 1500pra that I have.
and other clones except the PASS 1.7, for me it is better for more detail, dynamics and width, but for the price it is gold, now here come the more technical forum members (I am not) who could suggest improvements, for the already excellent preamp, I attach captures from the oscilloscope, greetings.
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as I said at the beginning, for me it is excellent, I will try the modifications of the video, although I have already tested with other operational, I will also try to pair the transistors (I have many of different types), but the audio is special, and the measures often are not what we like to hear, the Pass 1.7 has much worse measures (the one I have) and is 30 times more expensive, but I like it better.
I will do tests with different operational and the changes that Benny says and I will comment it, greetings.
I will do tests with different operational and the changes that Benny says and I will comment it, greetings.
Thanks hifiamps for sharing links to
Michael Beeny's Youtube channel << Click Here!!!!
In my humble opinion that is by large margin the best DIY Audio Youtube Channel.
His videos are very well structured, he goes systematically through the subject and explains everything in just sufficient depth.
What I like in his video is his honest approach, his language is rich and he deals with everything in the finest (old-fashioned) British manner. I appreciate that very much. Very nice but also critical when necessary, but without unnecessary fuss.
I recomend everyone here to visit that site. It pays off.
Regarding the subject of this thread:
Michael went in great detail in his video and presents his and Ron's measurement results along with proposals for improovements. That is a team work of Michael Beeny (NZ) and Ron Schauer (USA).
I already have three preamps but I will build this one too, for fun and for possible use in my future projects. The kit form China arrived today in the morning and I'm looking forward to repeat Michael's and Ron's work.
Michael Beeny's Youtube channel << Click Here!!!!
In my humble opinion that is by large margin the best DIY Audio Youtube Channel.
His videos are very well structured, he goes systematically through the subject and explains everything in just sufficient depth.
What I like in his video is his honest approach, his language is rich and he deals with everything in the finest (old-fashioned) British manner. I appreciate that very much. Very nice but also critical when necessary, but without unnecessary fuss.
I recomend everyone here to visit that site. It pays off.
Regarding the subject of this thread:
Michael went in great detail in his video and presents his and Ron's measurement results along with proposals for improovements. That is a team work of Michael Beeny (NZ) and Ron Schauer (USA).
I already have three preamps but I will build this one too, for fun and for possible use in my future projects. The kit form China arrived today in the morning and I'm looking forward to repeat Michael's and Ron's work.
hello again, as I have here some discrete and monolithic OPA, which at the time I provided in this previous a year and a half ago (I have already bought 6 with the last 2, for friends and for cacharrear), I put screenshots of 3 types AD828 and 2 discrete 8802 and Fever OP1, have some better measure but little, and I did not notice improvement in sound, when I have time I will change the capacitors to see, the other 4 I paid them to 26eu. still very cheap.
AD828 at 20khz there are already variations, I did not follow.
8802 20khz. 8802 100 khz.
8802 300khz. 8802 500khz.
Fever OP1 Fever OP1 10hz.
Fever OP1 20Khz. Fever OP1 100Khz.
Fever OP1 300Khz , as you can see there is not too much variation, in sine wave square sling is perfect, I have not noticed improvement in the sound with any of these or with the OPA 1612 that I also have out there, greetings.
AD828 at 20khz there are already variations, I did not follow.
8802 20khz. 8802 100 khz.
8802 300khz. 8802 500khz.
Fever OP1 Fever OP1 10hz.
Fever OP1 20Khz. Fever OP1 100Khz.
Fever OP1 300Khz , as you can see there is not too much variation, in sine wave square sling is perfect, I have not noticed improvement in the sound with any of these or with the OPA 1612 that I also have out there, greetings.
Attachments
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I installed the 1k resistors, I have done tests with different capacitors, my conlusion is worse than the original, maybe a R500 resistor, would be better, and would remove the overshoot of the ups and downs, but for now I will not do more tests, I have no time, I hope it serves as a guide, and I do not know if it will serve to improve the sound, the measures in certain measures are somewhat relative, can measure well and not sound too, greetings.
R1K C100pf. 100khz R1K C100pf 300khz
R1K C47pf. 100khz R1K C30pf. 100khz
R1K C30pf. 100khz
R1K C100pf. 100khz R1K C100pf 300khz
R1K C47pf. 100khz R1K C30pf. 100khz
@alpefe Thank you for posting this valuable information. I'm always looking for budget audiophile equipment. Results with the 1K1 feedback resistor (from the second Michael Beeny video) are very similar to yours with overshoot at 100kHz with both the 5532 and 4562 (less overshoot). The 5532 has some overshoot at 20kHz with the 1K1 feedback resistor, the 4562 is better.
In the comments, MB says regarding the 4562: "It does suggest in the application notes to fix a single cap across the plus and minus supply rather than 2 caps to ground. Connect right at the pins of the IC sockets power in with ceramic cap of 1uf. Fits very well on the back of the PCB." This to prevent HF oscillation of the 4562.
In the comments, MB says regarding the 4562: "It does suggest in the application notes to fix a single cap across the plus and minus supply rather than 2 caps to ground. Connect right at the pins of the IC sockets power in with ceramic cap of 1uf. Fits very well on the back of the PCB." This to prevent HF oscillation of the 4562.
if in the first I bought I put a 100nf capacitor in the power supply of the OPA, but in the end what I need is the final result in sound, and it was the same so I have not put them back, when I have time I want to make a plate to use other BC that I have old and for me better sound, because I have compared those that come in the package, and there is a notable difference in the gain, with the same reference that I have here old, more than 20%d loss, and some I have thousands so I can pair them perfectly, and although in the measures is not noticeable, the final sound if, greetings.
Hi @alpefe and thanks for sharing!
Meanwhile I have built my clone and have performed some measurements. Indeed, this preamp has remarkable bandwidth and top square wave response.
I went a bit further to measure distortion. I have used Arta software, Xonar U7 MKII sound card and Akitika 2ppm 1K sinewave generator.
Here are the results on the screenshots shown below. As expected, distortion is low, 0.0019% at 100mVRMS output and increases with the output voltage to 0.32% at 500 mVRMS. It appears that this preamp is useable up to 300mV output, RMS. Replacement ofthe 100R resistor with 1K has made just slight improvement.
Ciao!
Meanwhile I have built my clone and have performed some measurements. Indeed, this preamp has remarkable bandwidth and top square wave response.
I went a bit further to measure distortion. I have used Arta software, Xonar U7 MKII sound card and Akitika 2ppm 1K sinewave generator.
Here are the results on the screenshots shown below. As expected, distortion is low, 0.0019% at 100mVRMS output and increases with the output voltage to 0.32% at 500 mVRMS. It appears that this preamp is useable up to 300mV output, RMS. Replacement ofthe 100R resistor with 1K has made just slight improvement.
Ciao!
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I looked in the store and they had 1uf ceramic capacitors (smaller), I put them on the power supply legs and it improved, but from 2-2.5v we start to have a small overshoot (I have not changed the OPA, because I do not know if I have the referenced one, the others have a lot of oscillation), but it is very adequate, given that the RCA standard is up to 2.4v., greetings.
1k. 2.5v. 100khz. 1k.3v. 100khz.
470r. 2.5v. 100khz. 470r.3v 100khz.
1k. 2.5v. 100khz. 1k.3v. 100khz.
470r. 2.5v. 100khz. 470r.3v 100khz.
Hi to all
i have seen this pre amp too! 😉
C- 3850 clone pcb
i just ordered the pcb only because i do not trust the components and for me its more work to check and re solder everything.
at the mofi pages it is written that the output voltage is about 22mV on the R22 emitter resistors at the output. i do not believe that this information is correct. it is just 1 mA at the output....this is nonsense.
Please can you measure this ? i guess about 22mA
chris
i have seen this pre amp too! 😉
C- 3850 clone pcb
i just ordered the pcb only because i do not trust the components and for me its more work to check and re solder everything.
at the mofi pages it is written that the output voltage is about 22mV on the R22 emitter resistors at the output. i do not believe that this information is correct. it is just 1 mA at the output....this is nonsense.
Please can you measure this ? i guess about 22mA
chris
Attachments
For changing opamp without checking the behavior is not a good idea.
i would check with maybe 1k load and some capacitive loads (47nF.....330nF)... at square wave response.
expert know more then ma:
12 point checklist by hifisonix
chris
i would check with maybe 1k load and some capacitive loads (47nF.....330nF)... at square wave response.
expert know more then ma:
12 point checklist by hifisonix
chris
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All components in kit are fine. I have measured them all and all were OK. BC550 had hf 470 ... 491, and BC560 hfs were 503 ... 511. "Originals" from ONsemi are made in China. I know that from Mouser invoice and from oficial ONsemi documentation. Even MAGA hats are "made in China". There is nothing wrong with Chinese products just our "reputable" importers are making huge profits.
Don't be so pessimistic @chermann! 😎
With inputs shorted, there is about 4mV drift, almost the same at the both channels.
Have a pleasant weekend.
I ordered multiple audio kits now, the 4th preamp (a bit excessive....), 3 of them with parts. All branded electronic parts were original (to my knowledge), actually not even one part looked even slightly dodgy. But then 75-100EUR for a kit is not "cheap", but reasonably priced, so there is enough wiggling room to use original parts. And: The manufacturers know the DIY scene, sending out fake parts will terminate their business within weeks; judging by the number of sales, that seems like a bad idea. However domestic chinese mechanical parts are not that great, they mostly work, but more expensive branded parts certainly are way better.
What I really do like about the kits is the "no problems in sourcing oddball parts" - while the parts are mostly not expensive, the shipping costs are usually much higher than the parts costs. And I see no reason to order 100 of part X that I'm never going to use again either...
Hi Berlusconi
If you look at the voltage diagram at the pcb layout and on the schematics you will find the red marked values and you also can see the resistors value.
so my guess is that on a 22R resistor should have bee a voltage drop about 22mV--> this is just 1mA at the output stage of this pre amp this is nonsense.
kr
chris
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I orderd a complete board too. I have good and bad experiences with some preamps or amps offered at Ali or Ebay. Many thanks to "alpefe2 to share this offer at Aliexpress . Perhaps this board is a exeption. The chinese often make mistakes if speaking of voltage or current...
I will give the preamp a try...
Greets
Peter
I will give the preamp a try...
Greets
Peter