Adcom DAC owners.Help w/ tool I need

fbm211

Ok.Ill shoot reference another email and see if I can send it back if it doesnt fit.Now its time to break in the new residents in my apt building.Its move in weekend here at state college.All those new penn state students are all over the place and classes start a week early this year.Cant have any more home football games before the students arrive.

Systems

fbm211 wrote: »

Ok.Ill shoot reference another email and see if I can send it back if it doesnt fit.

You do realize that 2 of those modules are needed right?

fbm211

yes. And I told them to send me two and charge me for two since they havent done so for the first one yet

Systems

After looking at the schem again I see they have put a small ferrite inductor in series with the output.It is unusual to see these used on analog signal lines and actually "might" have a more adverse affect on SQ than a coupling cap .(They are usually used to filter high frequencies on digital lines and power supply lines). If it were me I would replace them with a wire jumper,they are labeled L500 and L501.Also I would remove caps C550 and C551 but don't add a jumper in thir place.These caps in conjunction with the inductors form a filter, so they will not be needed if you remove the coils.

fbm211

OK and thanks for being so helpfull.I was also going to replace those analog out RCAs with something better like WBT nextgen silver connectors somewhere down the road too.Would replacing the standard wire and ground jumpers with VH audio OCC silver wire be a good idea.What guage and cotton or teflon(FEP)insulation? http://www.vhaudio.com/wire.html (Actually I plan to rewire the whole thing with silver wire) Ive seen some of musical design/john hilligs work and he does this on his more expensive mods.

ben62670

The short runs with silver may, or may not make an audible difference. I wouldn't go **** on rewiring the whole thing. The jacks are right there at the board. One thing with aftermarket jacks is that they may require drilling a larger hole, and they are more likely to twist inside the case do to the single jack, and Teflon sleeves.
Ben

Systems

fbm211 wrote: »

OK and thanks for being so helpfull.

Your welcome.

I was also going to replace those analog out RCAs with something better like WBT nextgen silver connectors somewhere down the road too.

If you have the budget by all means use the WBT's they are premium connectors.I usually use the Typhany style CONNEX 53451's as they are hard to beat for the price.see link http://www.partsconnexion.com/catalog/connectors.html

While your at it you might also change the digital input RCA to a true 75 ohm BNC connector.Ideally both ends of the digital cable(which should be 75 ohm) and the transports digital out connector should be BNC as well.See Vampire 56013 http://www.partsconnexion.com/catalog/connectors.html

As Ben said use some short pieces of good wire for the analog outs,but IMO I think it would be a waste of time and money to rewire any power harness's with exotic wire.

fbm211

GV#27 wrote: »

DIP,other possibilies are the OPA2604,2132 and LM4562.

What about the OPA2227PA....OPA227

Systems

fbm211 wrote: »

What about the OPA2227PA....OPA227

I have no experience with this one,although the 2227 would work in your DAC .While it can't tell you how it sounds the data sheet does'nt show it to be anything out of the ordinary.
You could install a hi quality Dip socket with machine pins,this would allow you to easily swap in and out different opamps to see which one sounds best.

fbm211

Yo GV, thats exactly what I was looking for, I just couldnt remember what it was called.I had been reading about what different mod places could do to upgrade DACs and I came across one that installed something like that so you could upgrade opamps as better ones became available. Where can I get some of those to fit my board?..And thank you...Digi key has em but Im unsure of what to get.Pin spaceing,,, 6pin to pkg,,, etc...

Systems

8 pin like this. http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=AE7301-ND

fbm211

Cool.Thanks,I just ordered 2of them.And 2 OPA227s and 2 OPA2134s.Im going to order 2 627s too when I have some extra cash.I still havent heard from reference so I might get one of thos sioc to dip boards if I dont.And get the 825s from digi-key

Systems

fbm211 wrote: »

Cool.Thanks,I just ordered 2of them.And 2 OPA227s and 2 OPA2134s.Im going to order 2 627s too when I have some extra cash.I still havent heard from reference so I might get one of thos sioc to dip boards if I dont.And get the 825s from digi-key

627's and 227's won't work as they are single op amps.The 2227 is the dual op amp version.The 2134 will be fine.

Systems

Just to clarify things,the 7AA op amps in your unit are duals so there are 2 complete op amps within the single 8 pin chip so you must replace them with duals.The OPA 227 contains just a single op amp in the 8 pin chip.So the OPA 2227 is 2x the OPA227 and the OPA2134 is 2x the OPA134.The AD825 modules you were considering would work because 2 op amps where contained on each adaptor board.

fbm211

I just checked my digi key order and here is what I ordered.Please let me know if I got the right parts...https://sales.digikey.com/scripts/sales.dll?action=resumeorder;soglue=24339372;access_id=17070 I used this sote as a reference for part #s.And reviews. http://www.tangentsoft.net/audio/opamps.html

mmadden28

fmb211-I just sent you a PM

Systems

Yes your parts # appear correct.The link to the op amp comparison looks interesting I will give it a read.

Systems

This looks interesting,2 x the mighty OPA627 already mounted on an adapter board. http://cgi.ebay.ca/1-MODULE-OF-2-Pre-Mounted-OPA627AU-Op-amps-on-Adapter_W0QQitemZ230284589005QQihZ013QQcategoryZ36332QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

fbm211

Yeah that does look like a good idea.I was going to order two of those browndog adapters if I have to get the AD825s from digi key.Ive pretty much given up on reference audio mods.

fbm211

After further reserch i have come across a very interesting mod idea.(Thanks GV)So in a couple weeks Im going to get a IC socket that you can put TWO single opamps into.Im going to go with 4 OPA627s (2 in each IC).These will go into U502 and U503.I will compare these to the 2227s and 2134s that I should recieve this week.I scored a nice sony DSC-P51 digital camera for 10.50 on the bay last night so hopefully Ill be able to post some nice CLEAR pics.Hows the 700 mod ben??And if you forgot I still have that 6503 driver in a box with your name on it

ben62670

fbm211 wrote: »

Hows the 700 mod ben??

I am not ready to do the mod yet. I asked Adcom for a service manual, and I have not yet received it.

Ben

Systems

fbm211 wrote: »

Im going to get a IC socket that you can put TWO single opamps into.Im going to go with 4 OPA627s (2 in each IC).These will go into U502 and U503.I will compare these to the 2227s and 2134s that I should recieve this week.

Sounds like a great plan,I ll be interested in hearing your impressions of the differences between these 3 .I would again suggest (as I did in post#39) removing L500,L501 and installing a wire jumper in their place as they "may" (notice I said may) mask some of the differences between the op amps.


Good luck.

Systems

Oh,Just in case you were not aware, the IC socket and the op amps have a notch in the center on one end which determines the direction in which they should be installed.

Systems

..dooh double post.

fbm211

I recieved my opamps today from digi-key, and that MASSIVE catalog.I hope the digital camera arrives friday so I can post some before/after pics..As for the catalog Im looking for those 2 IC adapters that you can mount two single opamps onto.(4x OPA627BP).Oh, I was aware of the notch but not where it is located.Is it on the bottom of the chip?

Systems

fbm211 wrote: »

Im looking for those 2 IC adapters that you can mount two single opamps onto.

I haven't seen them in the catalog but you might look in the Aries section.

Oh, I was aware of the notch but not where it is located.Is it on the bottom of the chip?

http://focus.ti.com/lit/ds/symlink/opa2134.pdf its on the top side,centered at one end.If you look closely you will see it in the pic to the left of the O in OPA.

fbm211

I have to admit after removing the board and seeing the underside Im just a little freaked out at the solder joints.So tiny and close together...I do not know if I have the skill to do such fine soldering.Did they have machines do the soldering to these things??I have three kinds of solder.Cardas tri,cardas quad,and WBT silver.The tri has a higher melting point(no lead) than the other two and is harder.Which would be the best choice and any tips on diong such fine work??I know I must be careful not to have any solder joints touch each other.

ben62670

Go to Radio shack and getthe silver solder on a spool not in a tube. It is very fine gave, and very nice for the type of work you are doing. There will be nay sayers, but I have used this stuff exclusily for electronics. Very easy to work with, and clean;)
PN 64-13 E .022 dia. 1.5 oz.

Systems

If you don't have a lot of soldering expierience I would use the solder that has the lowest melting point.Trying to learn on a densely populated PC board with silver solder might prove frustrating.As well it is best that parts and PC traces do not recieve too much heat.

fbm211

Ok guys.Its a good thing I upgrade my PC every year or so.Ive got a-lot of old boards and cards laying around so Im gonna practice on one of those a few times till I get the knack.I have watched vids on soldering so I know the basics,its just a matter of getting a feeling for it.Thanks for the advice.Ill take a trip to the shack sat.