Is this a good LM3886 Kit?

[tomchr]

Depends on the impedances in the circuit. I suggest reading Franco Ch. 5 or the similar chapter in Jung's book. You can find the full reference for both on my website: Reference Texts and Links

Jung's book is a free download from ADI. Franco is the best opamp book I've found to date. It's absurdly expensive (just as most other texts, sadly).

You can also simulate the DC servo with either part and see which gives the lowest DC offset. Doing the math by hand is pretty easy, though.

Tom

 

[Mayday]

Having recieved this (original post link), I can now say there are four opamps on the board;
2x OP07 (top two)
2x NE5534 (bottom two)

There's no schematic for the kit, only a stuffing guide.

 

[AndrewT]

Check the power pins of the 4 opamps.
A single opamp has power to pins 7 & 4
A dual opamp has power to pins 8 & 4

The two that you mention are both single, so power should go to 7 & 4.

 

[Mayday]

Hi, yes the PS pins conforms with the single opamp standard.

 

[AndrewT]

What do the four opamps do?
Two single channels for the DC servo on the power amplifiers?
Two single opamps for what?

 

[Mayday]

Tbh,
I don't know, input buffer?
I'll take of the only documentation that came with the amp and post it in a few minutes.

 

[Mayday]

Documentation, and jumpers I have yet to figure out the purpose of.

 

[AndrewT]

They don't give you much.
I'll guess:
the two op07 have 0.68uF and 681k twice for each opamp. That indicates you may have a non-inverting DC servo for each channel.
Trace out the PCB traces and try to reverse engineer that part of the circuit.

The two jrc5534 have 680pF and 523r. These could be input filters to attenuate RF interference. The 4u7F polarised caps could be DC blockers between the stages. reverse engineer this section.

The components along the right hand edge are associated with detecting faults and protecting the chipamps.

The 317 & 337 have 178r + 1k96. These look like voltage settings for the regulators giving ~ +-14Vdc.
find out where the 24Vdc from the mc7824 is going. reverse engineer this part.

The four 0.1uF look like caps across the rectifier. If so then you do not fit them. Reverse engineer this part.

 

[Mayday]

I'll do that, I'll have to do it on a day that is "good" day, ie less pain.

 

[Mayday]

I found some additional info in an ebay listing, see attached pics.

 

[dotneck335]

Huh?

 

[Mayday]

In regards to my post?
I simply took screenshots of an ebay listing and attached them.

 

[tomchr]

Gotta love the Chinglish instructions.

Tom

 

[tom2016]

I understand why many people go to eBay and buy Chinese boards and other stuff. It really is very inexpensive in most cases. My problem is with the vendors who steal other people's intellectual property and sell it as their own. The hidden cost there is that people who spend years researching and testing have they work stolen and sold for pennies on the dollar. In my opinion, that's squashes the little guy who has put their heart and soul into designing a good product.

 

[scottjoplin]

It's a cultural thing in the case of China http://digitalcommons.law.yale.edu/cgi/viewcontent.cgi?article=1168&context=yjlh

 

[tom2016]

Yes Scott, I know all about it. We ran into this many times as a Microsoft authorized reseller. Pirating copies of Windows and other software like Microsoft Office was very commonplace and the offenders could not be prosecuted.

 

[Mayday]

Gotta love the Chinglish instructions.

Tom

LOL!
Yes, I'm trying to make heads or tails of those...

I understand why many people go to eBay and buy Chinese boards and other stuff. It really is very inexpensive in most cases. My problem is with the vendors who steal other people's intellectual property and sell it as their own. The hidden cost there is that people who spend years researching and testing have they work stolen and sold for pennies on the dollar. In my opinion, that's squashes the little guy who has put their heart and soul into designing a good product.

I agree on stealing other peoples work, but to my knowledge this is not a clone of anything.
That being said, I do own a BCL clone.

 

[flyingfishtw]

I understand why many people go to eBay and buy Chinese boards and other stuff. It really is very inexpensive in most cases. My problem is with the vendors who steal other people's intellectual property and sell it as their own. The hidden cost there is that people who spend years researching and testing have they work stolen and sold for pennies on the dollar. In my opinion, that's squashes the little guy who has put their heart and soul into designing a good product.

That's a part of chinese online audiophile culture I guess, last time I saw a guy steal tomchr's Composite LM3886 PCB and brand his own name on the PCB on hifidiy one of the biggest in china, but he only receive critiques, bcs most members on the web don't believe how can LM3886 out perform it's datasheet specs, and call him a scam. Good that discussion is removed.

On the forum, even management of website do only pirated boards, the motto is, copy and change parts tune it even better. Then what you will see is people put expensive parts on it, some modification doesn't even make sense, like 50k pot followed by ad797.

So for years, they're doing MBL6010, A1 preamp, quad606, NAIM NAC152XS an so on, any self designed circuit (without copying a fancy brand name), won't catch attention at all.Since real good parts cost a lot, not everyone is willing to spend that money, so you got that whole fake parts demand, hopping a 10 dollar OPA627SM will sound fantastic.

and lots of merchants they sell only copied board, since that's the only thing sells. And because they're spending so much energy on copying other people's old designs, so you don't see much new op amps using in circuits. It's a whole different eco-system out there

 

[dotneck335]

Having received this (original post link), I can now say there are four opamps on the board; 2x OP07 (top two) 2x NE5534 (bottom two) There's no schematic for the kit, only a stuffing guide.

Have you completed it yet? How does it sound? Do you have any equipment to measure its performance? And, have you been able to reverse-engineer a schematic out of it?

 

[Mayday]

Have you completed it yet? How does it sound? Do you have any equipment to measure its performance? And, have you been able to reverse-engineer a schematic out of it?

Hi,
No I am waiting for a few parts (I will use different parts from those supplied in a few spots), amongst them is the heatsink.
I don't have a scope good enough to measure the perfomance, I'll simply have to use my ears.
No, not been able to create any schematics from the PCB yet. I have to do these things on days where my levels of pain are more reasonable.
I have 4 herniated discs in my spine along with spondylosis and some other stuff. Lifting heavy weights for many years was apparently not the best idea I've ever had.