[mobayrasta]

I am curious as to what op-amps will work in the EE DAC. In my headphone amp I am using a Class A biased LM4562 and love the result. Would the same thing work in the EE DAC? I also have some TO99 49720 which are the metal can version of the 4562. Just curious what other people are using to make the SS side of the EE DAC better. Any advice or recommendations would be greatly appreciated.


Thanks.

Chris

[Occam]

There are 2 pairs of opamps that can be easily changed on the EE dac.The first pair consists of dual opamps 5532. The dip version of the LME49720/LM4562 is a straight swap, and will serve as the I/V converter, feeding both the solid state output, as well as the tube's.
The second pair of opamps are 5534, which provide the solid state outputs. These are singles, and as the compensation pins are not used, the LME49710 dip format is a straight swap.

Both the 553x and LME497x0 chips are low noise bipolar input chips shouldn't present problems.

I've used and like the LME497x0 series but can't comment on the efficacy of using metal can/browndogged single to dual boards, etc...

[mobayrasta]

There are 2 pairs of opamps that can be easily changed on the EE dac.The first pair consists of dual opamps 5532. The dip version of the LME49720/LM4562 is a straight swap, and will serve as the I/V converter, feeding both the solid state output, as well as the tube's.
The second pair of opamps are 5534, which provide the solid state outputs. These are singles, and as the compensation pins are not used, the LME49710 dip format is a straight swap.

Both the 553x and LME497x0 chips are low noise bipolar input chips shouldn't present problems.

I've used and like the LME497x0 series but can't comment on the efficacy of using metal can/browndogged single to dual boards, etc...

I am going to swap in a pair of LM4562's and a pair of LME49710's and see how it sounds. I have the 4562's on my sound card, and my headphone amp so I am pretty used to their sounds so I would probably like it in the DAC. A lot of people don't like them and think they are overly analytical, that is probably the reason I like them so much.....

What do you think about biasing them all into class A like I have them in my headphone amp. Really improved the sound in the amp, not sure if is ok to do in the DAC.

Thanks for the help.

Chris

[Occam]

Chris,

I'd think it would be straightforward to use a pull up resistor or ccs to bias the output singles further into class A. I'm not familiar with the specific topology of the I/V circuitry, so personally, I'd start with the LM4910 for biasing.

If you are actually going to use the output volume control (as opposed to keeping it full on, I'd replace it with a 20 or 25k potentiometer or stepped attenuator, to make it a bit more flexible as to what it can drive.

Regards,
Paul

[mfsoa]

Could someone please translate the descriptions of the above op amps into actual part numbers?

Thanks very much for your help.

-Mike

[mfsoa]

OK, curiosity got the best of me and I swapped both op-amps per the Dagogo update - A pr of LME49710 a pr of LME49720.
Installation was pretty straightforeward, even for me who has very little modding experience. (Put a clock and the LCAudio AD825 op-amps in a Rotel CDP once).
I did find that the pins were splayed a bit too wide to drop into the sockets, so wifey helped to persuade them into the holes. I guess the best thing would have been to bend them all slightly before attempting to insert.

Anyway, on power-up I got nothing.

After turning my amp back on  ... still nothing.

After waiting the full 30 seconds for the EE DAC to come alive (double  ) sure enough, curiosity did not kill the DAC!

But I'm not sure I'm liking the change. It is certainly faster, more extended, cleaner etc. but the nice broken-in-leather-chair feeling of the original op-amps may have been reduced too far. It's not digital nasty sounding, but kinds plastic-y. My Beethoven's 6th (LSO from the B&W Society of Sound) did not trip my aural orgasmatron meter like it used to, yet techno (Yello, The Eye) sounds great.

The difference in SQ was greater than that experienced when swapping tubes, IMO.

One thing though, (as Levi and others have said) is that the SS output is now much closer to the tube (RFT) output and sounds very good, w/ excellent dynamics and extension.

I feel myself getting pulled into the op-amp whirlpool - so many choices.

I wish Occam or Wayne would spill the beans on what they are using but of course understand if they want to keep mum.

So what are some more top candidates to try?  I really liked the AD825 I put into that Rotel- very full and powerful bass.

Time to do some learnin....

-Mike

[MarkM]

One thing though, (as Levi and others have said) is that the SS output is now much closer to the tube (RFT) output and sounds very good, w/ excellent dynamics and extension.
-Mike

I currently have the national semiconductor op-amps in as well and really like the solid state sound of this dac.
Before the change, I really like the Mullard tube. Popped in the Siemens Silverplate and the sound was much better, depends on the material between solid state and tube. 

Overall I am leaning towards the solid state in preference and must say the sound is very good. The tube coupling caps might need an overhaul with sonic caps.

I have a dozen of the Cree schottky diodes on the bench and might have to give them a whirl in the dac.  Made a nice improvement when I put them in the lite dac 60 and Van Alstine Ultra preamp.

Texas Instruments has some op-amps that look good spec wise, but the national semi are pretty good on paper as well.  Might be a matter of mixing and matching to season the sound of the I/V and solid state op-amps to your taste.

[mfsoa]

Maybe I'll try to balance the clean but slightly un-emotional sound I'm now getting w/ a different tube.

Choices, choices...

-Mike

[Levi]

Hi Mike, if you are lucky enough to get invited into Paul Occam's house, then and only then you can seek wisdom from the "king of OPamps".   

[horchai]

anybody gave bursons hd opamps a try? 

[mfsoa]

I had to take the LME49720 out - the sound was too whitewashed and uninvolving on the tube output.
Put the original back in and I definitely prefer it to the upgraded op-amp, in my system.

I left the 49710 in for the SS output and am very happy with the results - this is the best SS sound I've heard from the EE DAC, with some flesh on the bones coming from the original 5532 feeding the 49710. Very very good sound.

Now, I know we have been discouraged from doing this by Bill, but maybe any risk would be lowered if there was a list of drop-in op-amps that are safe to use in this circuit?  Please?

[Levi]

+1

Hi Mike, did you change tubes after swapping OPAmps on the tube output?  It is highly recommended that you change the tubes to see which one works with the new OPAmps. 

[MarkM]

I'm leaning towards the fet chips in the i/v stage of this dac, very nice sound.  I have a couple of different types on hand (opa2604, opa2134).   Cheaper than tube rolling for sure. 

[mfsoa]

Levi -Yes I did put my "softer" tube in along w/ the upgraded op-amps but it couldn't add what the op-amps seemed to be leaching out of the sound. Still prefer the stock op-amp for the tube but the 49710 in for the SS.

MarkM - Can you please define "..the fet chips..."?

Heck when good op-amps are $0.30, SOTA ones are $3 and the absolute nut-case jobbies are < $15, why are we bothering with which almost-unobtainable NOS $100 tube to use? Yeah, that warrantee thing again...

I encourage others to please chime in with what op-amps they have used, that didn't blow the DAC up 

I did a quick comparison vs. my Rotel RCD1072 CDP and the EE Dac (stock op-amp in I/V, 49710 in SS, RFT 12AU7 tube) is still softer, with less high-frequency emphasis and more body to the sound, on either output, fwiw.
-Mike

[MarkM]

National Semi's LME49720 are a bipolar design.  JFet types are mostly the Texas Inst. (Burr-Brown) ie. opa2604 or 2134.  I had those two on hand and tried them in my dac for the I/V stage. 

I preferred the 2134 over the 2604.  Even though these op amps are plug and play,(drop ins for NE5532) the caps and some resistors should be optimized to maximize the fidelity.   

I find the TI chips to add a bit of warmth to the mids and not quite as extended as the LME4970. (in the minimax straight up swap)

My choice is the SS output of the dac with the LME49710 for the ss output.  My system is comprised of a tube power amp, tube preamp and I like the flexibility of the Minimax's switchable tube/ss output.

There are better op amps out there, TI and Analog Devices have some very pricey ones(5-30 ea), but the NE5532 is a tried and true op amp to a price point.

Mike-not sure if this helps or confuses you.

[mfsoa]

That's big help, Mark - Thanks

I find the TI chips to add a bit of warmth to the mids

That's what I'm looking for as my class D amp doesn't add warmth on its own.

Expensive, but it seems like these would be nice, no? (Brown-dogged OPA827s):
http://cimarrontechnology.com/single-to-dualop-ampadapterpn020302.aspx

$70!! You could buy a TUBE for that 

-Mike

[wushuliu]

Another option. Discrete opamps designed by Audio-gd in multiple flavors:

http://www.audio-gd.com/Pro/diy/OPA/OPAEN.htm

[mfsoa]

Minor change in plans - I wanted to scavenge the AD825 adapter boards (from LCAudio) from my old Rotel CDP and use in place of the 5532 to see if 100x the parts cost would really make a difference  . Well, I open the CDP and the boards (2 AD825 per board) look too big for the EE DAC (if I could even get them out - man they are completely stuck in the socket!)

Oh well, thought I'd be able to put them to use as-is, as the AD825 is a highly regarded op-amp and sounded great in my CDP. (Now, if I desolder and get a brown dog...I'm not much of a solderer and the SMDs look kinda imposing to a newb, but I do have an ampdesigning friend who says no problem...).

C'mon peeps, spill your op-amp secrets! What else is a good swap for the I/V stage? (OPA2134 is on the way). The SS output? (OPA627 is on the way too)

OPA827?

Liked the Psvane tube in the dac and ordered one for it.

-Mike

[walkern]

I substituted the Audio GD Moon OPAs for the opamps that were stock in my Promitheus DAC and thought the upgrade was VERY worthwhile.  They are not cheap, but nicely built and easy to sub in.

Neil

[Oscillate]

"I substituted the Audio GD Moon OPAs for the opamps that were stock in my
Promitheus DAC ... the upgrade was VERY worthwhile"

I did the exact same thing ...the Promi DAC uses two single opamps. Needed to use
the optional extension leads so that the discreet Audio g-d opamps would physically fit
onto the DAC's circut board. I still have two Burson single opamps that I want to try in
that DAC also. The only stumbling block is that the Promi DAC normally supplies about
+/- 12v. And these discreet opamp modules apparently like +/-15v. So either I "change
the 180 ohm resistor to a lower value like 50 to 100ohms" to get +/- 15v or fiddle with
the two potentiameters to get a max of about 13.5v. Might have to look into a seperate
power supply for the opamps instead.

But anyway, the discreet opamp swap made a BIG improvement in the sound quality.
As I have stated ...before I could clearly hear the notes ...now I can hear the 'pluck'
of the strings! It is the best inexpensive tweak I've done yet.


Insert shameless advertising: If anyone is looking for new & unused  Burson
generation I dual opamp modules.