Dacmagic1 after upgrade. Some advice please.

[SoNic_real_one]

Originally Posted by gk7

Are you speaking from experience or is this the usual China bashing ?

Experience. 6 cips that are obsolete and I did try different China-based suppliers (one said "Japan" but packager arrived from HK), all had cleand the paint labeling (polished off) and laser engraved with the "better" part name. Some had laquer applied after that, very proffesional looking if you never saw the original part. Measurements showed that was a "normal" part, still "working", but not what I paid for.

Good luck buying parts from China. US government had "surprises" in their military gear.

[Reference1042]

After a bit more research it appeats Fake components are a pretty big issue in the industry, and not limited to EBay, or buying from China.

IHS: Counterfeit parts represent $169B annual risk-

Another interesting article on the Subject

Electronic Components Distributor - Worldwide Supplier of Electronic Parts Including Obsolete Electronic Components

An extract from the above:

"The counterfeiting problem is most prevalent in mainland China. Although we do not purchase directly from that region we continue to receive counterfeit parts on a weekly basis. Often the counterfeits supplied to us are from long time good standing suppliers who are just not trained or prepared to detect counterfeits.

So it appears that even if you buy from a reputable supplier there is still a risk that you may be unlucky enough to recieve counterfiet components.

I agree that EBay is certainly the most risky, but if you do your research properly, and read the feedback before buying it can be a very handy buying resource, and sometimes allows you to buy items that are not available elsewhere.

Im always apprehensive buying on Ebay, infact buying from a non UK supplier is always a last option, It is a nightmare when something goes wrong with the order.

Was looking to try a selection of different opamps in the dacmagic, which is why that ebay selection looked like a good option.. definately want to put the 2604's back in to see if the slight issues i am getting have been caused by the opamp change, or by using oscons instead of the electrolytics. Maybe ill just buy some from farnell, or RS if there are fakes flying about.

[kevinkr]

I haven't found Oscons to be particularly suitable as audio coupling caps although they seem to be quite effective on supply rails with a lot of HF noise.

If you got counterfeit op-amps on eBay you could have ended up with something as mundane as the 4558 dual (or worse) in place of the LM4562 you thought you were getting. I don't buy semi-conductors or electrolytic capacitors on eBay any more unless very rarely buying from a U.S. or U.K. seller, and usually go to Mouser, Digi-Key or Allied instead.

[Reference1042]

I selected the oscons after seeing them recommended on various articles on the web, and spoke to an engineer who mods hifi, he said i should measure the voltage over all the existing caps. And any that were running under 6v will be on the digital rails, and should use oscons for these. Whether i have misunderstood what he said is a possibility, as i am very new to modding audio.

Was then told by another diyaudio member after ordering the stuff from mouser that infact the oscons may cause issues due to lower resistance than electros.

Is there any chance that using oscons where i have may have made the bottom end sound slightly wooly and not as tight as before. And a slightly harsher sound? Or is it more likely to be the opamp change?

[SoNic_real_one]

Just add those 0.1uF and you will get rid of any oscillations induced by the low-ESR oscons.

[Reference1042]

Originally Posted by SoNic_real_one

Just add those 0.1uF and you will get rid of any oscillations induced by the low-ESR oscons.

Thanks for clearing that up sonic. That makes sense when i think about it.

Maplin sell a few different types of film caps, would you mind having a quick look to see if any are well suited. There are mylar, polyester and polypropylene caps. They all look the same to me

[SoNic_real_one]

Go with ceramics.
Polypropylene is the best of film caps, but might have higher inductance, are better in series with signal.

[Reference1042]

Bloody maplin, I need to go to 2 stores to buy 4 ceramic caps. They only keep 2 in stock at each store.

As i say, maplins is no longer an electronics store. It should rebrand as toys r us.

Surely they don't take up that much space?

USELESS!

[SoNic_real_one]

RadioShack here suffers of the same transformation. From a DIY store, now the sell mostly cell-phones, batteries and TV's.

[Reference1042]

What a joke. Don't think ill ever go back to Maplin again.

Have just had to go to 3 stores for 4 tiny ceramic capacitors. They say the reason that they don't keep them is because they don't sell. But how can they sell items when they don't keep any in stock??? Has always been like that in maplin......crazy min stock is 1, maximum is 2.

Shortsighted accounting and streamlining by bean-counters, and managers.

Are companies at all surprised that people would rather buy off the net.

The crazy thing is that in most cases they have caused this themselves....they are actually putting themselves out of business by refusing to hold basic items in stock that take up no space. They have 2 large empt racks of drawers that should be full to the gunnels with components.

So frustrating!!!!!!!!!!!!