Dacmagic1 after upgrade. Some advice please.

[Reference1042]

I recently upgraded a dacmagic1, replacing the below items. I was wondering if someone would be able to take a look at what i have replaced so far.

Im new to modifying audio, and would really appreciate some feedback as to where i may have gone wrong, and, or, where i may improve on what i have done to date.

The 2 opa2604ap opamps were replaced with lm4562na into 8 pin gold plated sockets.

All caps were replaced with same values. As follows:

14x 100uf 10v Vishay OS-CON organic polymer capacitors for to replace the existing electrolytics

10x 3300 uf 25v Panasonic FC to replace the existing smoothing electrolytics.

4 x nichichon FG to replace the existing 47uf 16v on the opamps

6 x nichicon KW 2200uf 16v caps

10 x nichicon KT caps 10uf 35v

I have heard a difference after the mods, But before i go any further i would like to make sure there are no problems with what i have done to date. I do feel it sounds a bit harsh at times, and the bottom end sounds a bit wooly. I wonder if i have introduced an issue somewhere with the oscons, or opamp change, or elsewhere.

I was considering buying a scope, but don't have much experience using one, not sure if it would be a waste of time and money at this stage.

Could post some pics of the mods done if it would help

Thanks

[SoNic_real_one]

Try some extra 0.1uF decoupling on each OpAmps power rails. Pin 4 to GND and pin 8 to GND.

[Reference1042]

Originally Posted by SoNic_real_one

Try some extra 0.1uF decoupling on each OpAmps power rails. Pin 4 to GND and pin 8 to GND.

Thanks sonic, very helpful.

What type of decoupling caps would you recommend?

Was also thinking of trying some other opamps, first to see if maybe it is just the lm4562's i don't like. possibly even retrying the original opa2604's as they actually sounded sweeter. With a much larger stereo image, much tighter bottom end as well. Maybe try a few others as well while I'm at it.

If i did the decoupling mod to the opamp dip sockets, is this intended for the lm4562 only ?

Or will it be suitable for any opamp i happen to try that is a suitable replacement?

Also, are there any other areas where it may be prudent to add decoupling caps?

Thanks again.

[SoNic_real_one]

The 0.1uF is a good addition for any OpAmps, but the faster they are, the more they need those capacitors:
http://www.analog.com/static/importe...als/MT-101.pdf
See page 5,6 of above. Film is best for audio. Ceramics are good too (at least some of them).

[Reference1042]

Originally Posted by SoNic_real_one

The 0.1uF is a good addition for any OpAmps, but the faster they are, the more they need those capacitors:
http://www.analog.com/static/importe...als/MT-101.pdf
See page 5,6 of above. Film is best for audio. Ceramics are good too (at least some of them).

Found this selection of opamps on ebay for £20, there are some monos, which will not really be much good to me. But looks quite a wide range.

http://www.ebay.co.uk/itm/Audio-OPAM...ht_11646wt_982


Do you think this is a pretty good selection of alternative opamps for the dacmagic, or would i be better buying in pairs?

Could someone suggest a list of decent alternatives to the lm4562 and opa2604?

Thanks

[SoNic_real_one]

Don't buy from eBay, especially from China - you will get fakes and then complain that the "recomended OpAmps suck". The fakes have laser engraving now, look "authentic", but I think you don't want a "jelly-bean" OpAmp labeled as LM4562.
Buy from a distribuitor. I think Farnell is in your area?
I did try OPA2604 and wasn't impressed. Only sligtly better than 5532, good if you really need j-fets. LM4562 is equal to LME49720 (renamed to match the naming scheme). National now is owned by TI.
If you are in SMD work, you can try also AD8599. I did like it.

[Gopher]

I don't understand why these people in China go to so much trouble making fake op-amps. Most large quantity orders will always be placed through authorised distributors. E-Bay sales can't be that big.

Also, why do people take the risk of buying off E-Bay when going to the distributors will often only cost a few dollars more for the genuine article. Are they stupid or just hooked on E-Bay???

[gk7]

I haven´t seen the schematic of the Dacmagic, but if it had FET opamps (OPA2604) originally, it´s probably not a good idea to replace them with bipolars (no matter how "good" they are).

[gk7]

Originally Posted by SoNic_real_one

Don't buy from eBay, especially from China - you will get fakes and then complain that the "recomended OpAmps suck". The fakes have laser engraving now, look "authentic", but I think you don't want a "jelly-bean" OpAmp labeled as LM4562.
...

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

[SoNic_real_one]

Well, usually the DAC's don't require j-fet's, they are sometimes used in older devices for other reasons - speed.
Sure, only schematic can elucidate that for sure.