[rajacat]

Anybody know if the op amps that are compatible with the Paradisea will work with the Constantine too?

Thanks,
            -Roy

BTW the  2.2uf  Copper film Obbligatos bypassed with .1uf Obbligatos that I installed in my Constantine replacing the stock output caps, are finally burned in and I'm very happy. There is a marked improvement in the extension and transparency.

[t-head]

Pele,

Those look nice. Would the opamps drop in to the existing DIP in the Paradisea+? Thanks.

t

[Quiet Earth]

I'm going to experiment with the two negative feedback resisters next week, just to see if I can get a little more dynamic range out of the op amp without driving it into compression.

Well, I did a little experimenting with the two feedback resistors, R18 and R19. First, I doubled their value from 3k to 6k, which increased the gain quite a bit. Although this did make the sound much more lively and dynamic, it seemed like it was just way too much gain. The output of the DAC was so high that I could barely use my passive TVC volume control. It was turned down almost all of the way and it was still very loud. Also, it seemed like the op amp was starting to drive itself into peak compression from having too much gain. So, I dropped the gain down a notch by using 4.7k ohm resistors, and that took care of that. The DAC still has quite a bit more gain and the dynamics are much better, but it isn't so much that it drives itself into distortion. I'm going to leave it here for now. (Oh yeah, I also changed the two feedback capacitors from 120pF to 470pF. This was a good compromise too.)

The only down side to doing this gain adjustment (dynamic range expansion) is that the output of the DAC is quite a bit higher than it used to be. If anyone is interested in trying this but they already have to much system gain, then they will probably not like the results. In other words, if your stereo is already kind of loud with the volume control on low, then you will be overloading your pre-amp (or amp) with the larger output from the DAC.

Oh, I almost forgot. I used carbon film 1/2W resistors that I bought from Handmade Electronics, and I think that they sound much better than the metal film, MHDT resitors. Even if you don't want to change the value of these two resistors, I think that you can get better sound by using the very best resistors in these locations. I might spring for the AN tantalums once I decide that the value I chose is permanent. I also upgraded the quality of R16 and R17 to 1/2W carbon films. These are the resistors that set the constant current source to the TDA-1543, and they also form a voltage divider for pins 3 and 5 of the op amp. Use the very best resistors here that you can. Keep the values the same too. (OK, I cheated. I kept the ratio the same but the values were slightly off. The voltage divider is still basically the same. So is the current to the TDA.) Pins 3 and 5 also benefit with a bigger bypass capacitor than the yellow MHDT cap. This is C23. I have a 16V,100uF Elna Sillmic ll in this location along with a 16V,10uF Elna soldered right next to pin 5 of the op amp. I think that a single Elna 16V,47uF at the original C23 location is really all that you need. You will hear much better bass and lower midrange definition when you do this. The Elna capacitor is cheap and it only needs 100 hours to run in. (Just turn it on for 4 days.)

Having done all of this I really have to question the validity of swapping op amps without investigating the bias voltages and feedback resistance for each kind of op amp. I'm not saying that improvements aren't happening when you randomly swap them, I'm just wondering if you could have achieved the same improvement by optimizing the op amp that's already in place. I don't really want to try all of the different op amps, so I will just stick with the one that came with my DAC.
I also wonder why a tube buffer is needed in the Paradisea when you gan get so much output from the op amp in the first place. You would think that a maxed out op amp with a step down transformer could outperform a gain suppressed op amp and tube buffer. Just speculating. Of course that's a whole 'nother product altogether.

Anyway, I'm done for now. I like what I've done so far, and now I'm just going to enjoy it. Hey, that's what I bought it for!  

I had a lot of fun with this thread too.

[Quiet Earth]

Here's a pic  : 

http://s7.photobucket.com/albums/y297/Quietearth/?action=view&current=March7thupdate.jpg

[emac]

Well, I did a little experimenting with the two feedback resistors, R18 and R19. First, I doubled their value from 3k to 6k, which increased the gain quite a bit. Although this did make the sound much more lively and dynamic, it seemed like it was just way too much gain. The output of the DAC was so high that I could barely use my passive TVC volume control. It was turned down almost all of the way and it was still very loud. Also, it seemed like the op amp was starting to drive itself into peak compression from having too much gain. So, I dropped the gain down a notch by using 4.7k ohm resistors, and that took care of that. The DAC still has quite a bit more gain and the dynamics are much better, but it isn't so much that it drives itself into distortion. I'm going to leave it here for now. (Oh yeah, I also changed the two feedback capacitors from 120pF to 470pF. This was a good compromise too.)

The only down side to doing this gain adjustment (dynamic range expansion) is that the output of the DAC is quite a bit higher than it used to be. If anyone is interested in trying this but they already have to much system gain, then they will probably not like the results. In other words, if your stereo is already kind of loud with the volume control on low, then you will be overloading your pre-amp (or amp) with the larger output from the DAC.

Oh, I almost forgot. I used carbon film 1/2W resistors that I bought from Handmade Electronics, and I think that they sound much better than the metal film, MHDT resitors. Even if you don't want to change the value of these two resistors, I think that you can get better sound by using the very best resistors in these locations. I might spring for the AN tantalums once I decide that the value I chose is permanent. I also upgraded the quality of R16 and R17 to 1/2W carbon films. These are the resistors that set the constant current source to the TDA-1543, and they also form a voltage divider for pins 3 and 5 of the op amp. Use the very best resistors here that you can. Keep the values the same too. (OK, I cheated. I kept the ratio the same but the values were slightly off. The voltage divider is still basically the same. So is the current to the TDA.) Pins 3 and 5 also benefit with a bigger bypass capacitor than the yellow MHDT cap. This is C23. I have a 16V,100uF Elna Sillmic ll in this location along with a 16V,10uF Elna soldered right next to pin 5 of the op amp. I think that a single Elna 16V,47uF at the original C23 location is really all that you need. You will hear much better bass and lower midrange definition when you do this. The Elna capacitor is cheap and it only needs 100 hours to run in. (Just turn it on for 4 days.)

Having done all of this I really have to question the validity of swapping op amps without investigating the bias voltages and feedback resistance for each kind of op amp. I'm not saying that improvements aren't happening when you randomly swap them, I'm just wondering if you could have achieved the same improvement by optimizing the op amp that's already in place. I don't really want to try all of the different op amps, so I will just stick with the one that came with my DAC.
I also wonder why a tube buffer is needed in the Paradisea when you gan get so much output from the op amp in the first place. You would think that a maxed out op amp with a step down transformer could outperform a gain suppressed op amp and tube buffer. Just speculating. Of course that's a whole 'nother product altogether.

Anyway, I'm done for now. I like what I've done so far, and now I'm just going to enjoy it. Hey, that's what I bought it for! 

I had a lot of fun with this thread too.

That's awesome Quiet Earth.  Thanks for the info.  Will certainly go ahead and give your changes a shot in my Constantine. 

Though I'm still not sure what you did with the placement of some of your small value caps (e.g. the black ones). 

[Quiet Earth]

I'm still not sure what you did with the placement of some of your small value caps (e.g. the black ones). 

Sorry for the bad photo.    The small rectangular "black" capacitors are actually brown. They are the silver mica caps. I did relocate C13 and UC7 as described earlier in this thread. Basically, I found a through hole that was closer to the IC that was getting bypassed and I moved the capacitor lead to that hole. I found the closest ground hole wherever I could. I also moved one leg of C14 closer to the TDA chip, using the .05uF Obbligato cap. All that really did was bypass a longer circuit board trace going into the TDA1545A. I don't know if that was necessary or not, it's just something that I tried.


C24 and C25 are 470pF silver micas (the old blue feedback capacitors to the op amp)
C5 is also a 470pF silver mica (+5V line, already with a Blackgate N)
C12 and C13 are 4700pF silver micas
UC7 is a 3300pF silver mica (+5V to usb chip)
C14 is a 0.05uF Obbligato (slightly relocated to cheat the long trace on the circuit board)
C10 is a 0.05uF Obbligato
C11 is a 0.1uF,50V Blackgate NX (This is only active when you flip the switch to optical.)
The only two caps that I took out of the circuit are C21 and C22.

It's getting kind of late. I'll check this list in the morning to make sure I didn't make a mistake.

[Pelé]

Pele,

Those look nice. Would the opamps drop in to the existing DIP in the Paradisea+? Thanks.

t

Just barely. The capacitor c28 next to the DIP dosen't allow the module more than 2/3 down the socket, but it still works  Any one out there done some upgrading regarding the powerregulater LM317T?

[Les Lammers]

Just wanted to add an upgradesuggestion that has not been mentioned in this thread. Referenceaudiomods.com has an OPA627 Module, Dual OPA627, 8 Pin/DIL http://www.referenceaudiomods.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=RAM&Category_Code=OPAMPS. For the time being they are out of 627's, but deliver the module with lm49710's instead. It is everything they brag about on their site, and IMO the best opampsolution.

What was the difference in sonics that you perceived from the change?

[Pelé]

The separation of the instruments. Not only is the singer in the room with you, but also the entire band and especially the drummer. More microdetails in the highs. It makes you want to relisten every drumsolo in your collection.

[Les Lammers]

The separation of the instruments. Not only is the singer in the room with you, but also the entire band and especially the drummer. More microdetails in the highs. It makes you want to relisten every drumsolo in your collection.

Thanks Pele,

Have you made any other changes? I have changed the output coupling caps OIMP V caps with a Vitamin Q by pass and C11 to a Vitamin Q .18uf. The coupling caps made a nice difference. So did changing C11 to a PIO made the sound smoother and less plastic but still very detailed. So I just bought 12 .1uf 1000V Russian K40 PIO caps for $35 delivered and will replace the 6 .1 uf MHdt caps with them. These caps have a good reputation and are a good value. I am not suggesting that you do the same with the caps. I will post after I change the .1uf's.

I looks like you could resolder the cap that impedes the opamp board and get it all the way into the socket.

Les

[Quiet Earth]

I just bought 12 .1uf 1000V Russian K40 PIO caps for $35 delivered ....

Les,
Where do you buy these capacitors? Do they have a brand name?
Thanks,
QE

[t-head]

Pele,

Thanks for the reply. Did you make any other changes to resistors or caps associated with the opamp circuit. Thanks again...

t

[Les Lammers]

I just bought 12 .1uf 1000V Russian K40 PIO caps for $35 delivered ....

Les,
Where do you buy these capacitors? Do they have a brand name?
Thanks,
QE

HI QE,

They are Russian K40-9's these are regarded as the *best* Russian PIO caps. I have used them before and they are very good. Nothing can touch them for the $$$. I got them from this e-bay seller:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300204383284

The DAC only uses 6, but the sale was for 12. So if you want to try them I'll split the order with you. He also has a lot of 500 for sale but that's a little over the top for me. 

C11 in the Paradisea is a .22 uf. I originally installed too small of a value and paralleled 2 .1uf 1000v K40's that I had.  Now we are talking. The glare and sibilance is gone, gone, gone. I don't know what the function of C11 is but this made a significant positive difference. Tone and timbre is excellent.  I may replace them with a .22 uf Jensen as it will be physically smaller and allow adding the K40's that are coming. But doing this precludes using the opamp upgrade from Reference Audio. There just is not enough room inside. I don't know if I need to change anything else, except maybe add a few more of the smaller value K40's.

Les

[Quiet Earth]

Thanks Les!

I appreciate the offer to split the order but I just wanted to know where to get those kind of caps for the next project - if there is a next project  . I think I'm done for now with my Constantine+. No more cap rolling for a while . . . . .


 

[Les Lammers]

Thanks Les!

I appreciate the offer to split the order but I just wanted to know where to get those kind of caps for the next project - if there is a next project  . I think I'm done for now with my Constantine+. No more cap rolling for a while . . . . .


 

Right. I believe you. Really I do. 

If anyone wants some of these caps let me know. They are so inexpensive that they are usually sold in large lots. The K40-9 in the aluminum cylinder are the
better caps. There are K42's too but they are not as good.

[Oscillate]

My Paradisea+ has the LM4562NA op-amp in an 8 pin socket.
Has anyone else who has this same DAC done the following:

1) Measured the voltage the LM4562NA op-amp is receiving?
2) Installed a Burson Dual Discrete Op-amp? What sound changes did you notice?

Thanks in advance

[Quiet Earth]

My Constantine+ also has the LM4562. The factory set voltages are as follows:

V+ at pin 8 measures +9Volts
V-  at pin 4 measures -9Volts
The left and right non inverting inputs (pin 3 and 5) are set to +3.3 Volts with no audio in. They are bypassed with a .1uF capacitor (C23) at the factory. A larger value of capacitance will eliminate motorboating (i.e. clear up the bass and lower midrange).
The left and right audio signal from the TDA1545 go into pins 2 and 6
The left and right audio signal that come out of the op amp are located at pins 1 and 7

http://www.national.com/images/pf/LM4562/20157255.pdf

[Pelé]

The separation of the instruments. Not only is the singer in the room with you, but also the entire band and especially the drummer. More microdetails in the highs. It makes you want to relisten every drumsolo in your collection.

Thanks Pele,

Have you made any other changes? I have changed the output coupling caps OIMP V caps with a Vitamin Q by pass and C11 to a Vitamin Q .18uf. The coupling caps made a nice difference. So did changing C11 to a PIO made the sound smoother and less plastic but still very detailed. So I just bought 12 .1uf 1000V Russian K40 PIO caps for $35 delivered and will replace the 6 .1 uf MHdt caps with them. These caps have a good reputation and are a good value. I am not suggesting that you do the same with the caps. I will post after I change the .1uf's.

I looks like you could resolder the cap that impedes the opamp board and get it all the way into the socket.

Les

Just OIMP V caps, a cryo 396A, a Feinsicherung type II fuse and a shielded cabel. I am saving the money for some black gates.

[drmike]

hey les,
i'll take the xtra caps.
thanks,
drmike

[Les Lammers]

They are coming from Russia and may take a couple of weeks. You can PM me and I will post here when they arrive.