Good or Bad idea?

[megasat16]

....to mod the Opamps and DAC in my Proceed PDSD? I am currently upgrading all electrolytic in my PDSD. The PCBs are doubled sided through hole type boards so I have to be more careful with them. But I guess I can upgrade op-amps if there will be a major improvement for sound. Currently, here is what in the PDSD. I don't know if it's even possible for DAC upgrade.

AD823AN X 2 (Opamp)
PCM1702 X 2 (DAC)
SN74HCT00N X 1
BB OPA2134PA X 2 (Opamp)
MAL LF351N
74HCT4051N
2N3904
MC7805CT (NLBR929) X 2
LM2940CT
L7905ACV
LM2990T

[GV#27]

I assume the AD823's are used for the I/V conversion and 2134's for the low pass filter/ output buffer?As long as they are not SMD types you might try Nationals LM4562's(my current fave) in place of the 2134's.
Are there any ouput coupling caps?if so they might be worth changing to a premium film type.
I'd Leave the the 1702's alone.


Proceed made some very good products.

[megasat16]

Thanks Fred! I think you nailed in about the OP-AMPs. The plugin card has a small switch (subwoofer on / off) to use it as a subwoofer channel or just regular channel.

I neither have Schema for it nor do I know anyone who has the Schema for it so I don't know. Proceed does make an excellent gears back then and even with 20Bits DAC, it has one awesome DAC. I put some Peectures for you!

[GV#27]

Nice.It appears they use universal 2 ch DAC modules x 3 to get their 5.1 output.And each ch has it's own duigital volume control(The CS3310's).I don't see any coupling caps so it likely has a servo.Swapping Op-amps should be unproblematic since they are 8 DIP's.Are those BB opamps closest to the output 134's or 2134's?

[GV#27]

After taking a closer look it appears that the AD823'S do the I/V and LPF functions,the first Burr Brown (middle near big brown film caps) is likely a servo and the Burr Brown's closest to the output are the line driver/output buffers,1/2 of each chip for the single ended(noninverted) output and the other half for the inverted part of the balanced output.Replacing these two with LM4562's might be worthwhile.

[megasat16]

Thanks Fred! The two OPA2134PA near the outputs are probably the final stage of the preamp. I guess these two can be swapped out with LM4562 as you suggested. Any place I could buy the LM4562 cheap?

Any likelihood of running into oscillation? Guess I should try first. :)

[megasat16]

Nice.It appears they use universal 2 ch DAC modules x 3 to get their 5.1 output.And each ch has it's own duigital volume control(The CS3310's).I don't see any coupling caps so it likely has a servo.Swapping Op-amps should be unproblematic since they are 8 DIP's.Are those BB opamps closest to the output 134's or 2134's?

I think there is an EPROM (EEPROM) loaded with proprietary software to be front or rear or center and sub channels use. I looked at all 3 cards and they looks identical in all other aspects.

[GV#27]

Digi key carries the LM4562 approx $6 ea.


You should have no oscillation issues as it appears there is plenty of local decoupling/bypassing supplied by the red film caps and brown electrolytics next to the chips.If the 2134's are stable so should the 4562's be as they are not super hi speed devices.

[megasat16]

I just looked at DigiKey but the 8DIP packages are not in stock. I checked with Mouser and the same thing. May be eBay stuff? :D

[megasat16]

While I was searching for the LM4562 and found this. I looked for LME49720 from DigiKey but they don't have 8DIP too. TO99 Metal cans are expensive.

http://www.diyaudio.com/forums/showthread.php?t=107344

[megasat16]

Finally found 8DIP for LME49720 at Newark.

What cha think, Fred?

http://www.newark.com/national-semiconductor/lme49720na-nopb/operational-amplifier-op-amp-ic/dp/46M5435

Newark also has LM4562NA for $4.10. So, I am going to get quite a few of them since they are harder to find these days. Let me know if you need some, Fred! I'll mail them to you. :)

[ben62670]

OpAmps don't roll as easy as tubes, but I have had some fun:)

Edit: here are the LM4562's
http://www.newark.com/national-semiconductor/lm4562na-nopb/operational-amplifier-op-amp-ic/dp/32M1177

[GV#27]

I hope it's not a sign that the 8 pin DIP version will soon become extinct:(


found 8DIP for LME49720 at Newark.

What cha think, Fred?I have'nt tried it but it is a very close relative of the 4562 so should be good.




Newark also has LM4562NA for $4.10. Let me know if you need some, Fred! I'll mail them to you. :)Thanks muchly James,I actually do need a pair for a project.I can refund you the costs via paypal.

[megasat16]

OpAmps don't roll as easy as tubes, but I have had some fun:)

Edit: here are the LM4562's
http://www.newark.com/national-semiconductor/lm4562na-nopb/operational-amplifier-op-amp-ic/dp/32M1177

Ben, you and I found LM4562 on Newark about the same time too. :D You just found it a minute earlier than me. Thanks!

[megasat16]

I hpoe it's not a sign that the 8 pin DIP version will soon become extinct:(i F

I have'nt tried it but it is a very close relative of the 4562 so should be good.

Thanks muchly James,I actually do need a pair for a project.I can refund you the costs via paypal.

I think 8 Pins DIP are going to become obsolete soon. I can't find them in MCM, Mouser, DigiKey. They are dropping the cheaper line and only carrying TO-99 versions.

Are you sure you only need a couple? I guess it's time to stock up on them if you need them. I am thinking to order like 12 or more.

As for the cost, don't worry about it. We are good. ;) You just need to send me a couple of cold ones from Canada. :D

[lightman1]

What the f*ck are talkin' about, Dan?

[megasat16]

hehe...Lightman lost the bush he regularly uses. Wassup Russ? ;)

[GV#27]

I think 8 Pins DIP are going to become obsolete soon.No doudt,many of the newer chips are only available in SMD packages.:(


Are you sure you only need a couple? Yeah thats all for now their for a preamp for my new puter


As for the cost, don't worry about it. We are good. ;) You just need to send me a couple of cold ones from Canada. :DWow thanks James,do you prefer Molson's or Labatts?

[GV#27]

What the f*ck are talkin' about, Dan?Hey who let you in here?:eek::D

[ben62670]

Fred what do you think about the LM's over the OPA's?
I hope they don't us DIYers with smd's.

EDit: What do you think about OpAmps in pre's compared to transitors? I see you are a fan of the BOZ and other pass designs.

[lightman1]

hehe...Lightman lost the bush he regularly uses. Wassup Russ? ;) No shrub is safe!!!

[lightman1]

Hey who let you in here?:eek::D
The door was unlocked. I let myself in.

[GV#27]

Fred what do you think about the LM's over the OPA's?When comparing the 2134 vs 4562 in active crossovers my impression was that the LM part was more "transparent" and less "electronic" sounding for lack of a better description.


EDit: What do you think about OpAmps in pre's compared to transitors? I see you are a fan of the BOZ and other pass designs.
IC's will generally have lower noise and distortion but we know that doesn't mean much as far as SQ goes. The BOZ is somewhat noisy (think tubes) but definately more musical than the best IC opamp pre I have(a Jung designed AD744/811 combo) though the opamp design beats it in the bass having a tighter more detailed bottom end.

However the Jfet/Mosfet discrete opamp I have been using for the last five years or so is still my fave by a comfortable margin vs everything I have built before or since.It wins in the information retrieval dept,being detailed without getting clinical or harsh sounding.Aswell it throws a huge soundstage and has excellent bass extension and drive.Powering it with dual stage discrete regulators and a 100VA toroid likely doesn't hurt either.:D

[megasat16]

No doudt,many of the newer chips are only available in SMD packages.:(

Yeah thats all for now their for a preamp for my new puter

Wow thanks James,do you prefer Molson's or Labatts?

Save the Molsons for personal visit. :D Just kidding. I am looking forward to the mod. :)

[lightman1]

Who the f*ck is Fred? And the only Molsons I know are the ones that make beer in Canada....Eh?

[megasat16]

Who the f*ck is Fred?

Now I am sure you lost your shrub or herb or whatever that is. :D :p


And the only Molsons I know are the ones that make beer in Canada....Eh?
Yep, that's the Molsons I want. You got problems with that? :) :D

[lightman1]

OH SH*T! You are one of those Cornadians!

[megasat16]

No! I Do Not Think So! I am 100% not canukians.

[GV#27]

OH SH*T! You are one of those Cornadians!Just sit there ,be quiet and drink your Pabst Blue ribbon won't ya.


No! I Do Not Think So! I am 100% not canukians.Well I'm a purebread Canuckistani thank you.;)

[lightman1]

Just sit there ,be quiet and drink your Pabst Blue ribbon won't ya. PBR Sucks.

Well I'm a purebread Canuckistani thank you.;)
Well at least you're Canadian with some Greek heritage.

[lightman1]

Stupid fukin Merican. Can't multi kwote.

[megasat16]

Ok. A Rainy Day, A Windy Day, A Boring Day. But I decided to swap out the BB2134s from the front channels DAC board in the PDSD finally. The new LM4562s were put in place of BB2134 as GV suggested.

Wow...I am liking the new result. If there was ever so slightly harshness and a bit too warm (even could be pronounced as darker tone) mids with the older BB2134s were totally disappeared and instead I am getting smoother, very liquid mids with better tonal balance. I only listened to the new LM4562s for half an hour and I am noticing slight improvements with time. I think it's still burning in so I am hoping it'll improve a bit more when it's totally burned in.

Thanks GV! I know you aren't here but finally one of my little project got wrapped up with very good results. If I have time, I'll swap out all the lytics with the newer Nichicon caps and some Poly Caps.