[emac]

Hi guys!

emac,
Inside of my Constantine+, the two rectifier caps (below the transformer) were Nichicon Fine Gold (not Muse) and they were 35v, 2200uF. So, I replaced them with BG (FK), 35v, 2200uF. The other cap to the left of the transformer was also a Nichicon Fine Gold, and it was 16v, 2200uF. I replaced that with a BG (FK) 50v, 2200uF. That BG is the one that is just a hair too tall. I measured the space that I have, and I read the physical measurements of the BGs, but somebody goofed. Probably me. No biggie, I can still get the lid on.

Les,
The caps are soldered so you need some soldering skills and a little bravery to do the mod.

It's interesting and somewhat scary that whoever does the MHDT Labs DACs doesn't even follow his own spec sheet.  I'm not sure how much of a difference it makes though.

Les: The soldering isn't as difficult as it sounds.  The boards are somewhat forgiving.  A little practice helps though. 

[Quiet Earth]

It's interesting and somewhat scary that whoever does the MHDT Labs DACs doesn't even follow his own spec sheet.  I'm not sure how much of a difference it makes though.

I understand what you mean. At first glance, it's a scary thought. But if you think about it a little longer, it's amazing that the guy (MHDT) even has a spec sheet. I mean, he has a viewable Bill Of Materials on his website, and he is only one guy! There are whole companies that aren't that organized.

I think his dacs have also gone through some updates and parts changes. Maybe his BOM hasn't been updated yet. My Constantine+ is said to have the Analog Devices 826 op amp. Instead it has an LM4526. And, the op amp is not mounted in one of those little op amp sockets. Instead it's soldered directly to the board. It also looks like he moved it to the bottom side of the circuit board to avoid a noise issue.
Some of the caps on the original Constantine were not Nichicon Fine gold. I think they were Muse. Maybe he can't get the Muse on a consistant basis and he had to change to the Fine Golds. There are tons of issues like this when you are a manufacturer. Making small improvements and dealing with parts availability issues. I applaud the guy for what he has done so far. I'm impressed.

As far as what value those rectifier caps should be? Well, I think 2200uF is probably more than enough for the two bridge rectifier caps. 3300uF may have been overkill. Maybe 3300uF was the best choice for what was available at the time. Who knows.

[Quiet Earth]

.

Les: The soldering isn't as difficult as it sounds.  The boards are somewhat forgiving.  A little practice helps though. 

This is absolutely true. Just don't practice on your audio gear if you have never soldered before. 

[Les Lammers]

I have soldered but am not sure I would be comfortable with the other caps. Do you have to remove the circuit board from the DAC to take them out?

[Quiet Earth]

Just remove the top and bottom covers and you're good to go. But here's the thing. If you're not feeling too confident about it, then don't. Nothing worse than messing up a piece of gear that you like just to tweak it a little. Or practice removing and soldering in caps on a piece of junk until you feel confident.

Also, if you're not sure about what you're doing (electrically), then don't do it based on what you read here.

Friends don't let friends beat up their gear. 

[Les Lammers]

I'm not a tech and am confused about the polarity of the caps. I may take the bottom cover off and have a look. Logically, it would make sense to have better caps in the power supply.

A friend just told me about Isoclean Fuses. They have been favorably reviewed. I am going to get a few and the DAC will get one.

http://www.positive-feedback.com/Issue22/isoclean.htm

vendor link: http://www.aaudioimports.com/

[Quiet Earth]

I'm not a tech and am confused about the polarity of the caps. I may take the bottom cover off and have a look. Logically, it would make sense to have better caps in the power supply.

The "power supply" caps, (i.e. the polarized electrolytics) have a series of "-" (minus signs) running down the length of one side. That indicates that the lead on that side of that capacitor is negative. The lead on the other side (which does not have a "+" marking) is positive.

It is important to remember which of the two holes is positive and which is negative after you remove the cap. I always draw a little picture and write down the polarity before I remove any capacitor. Often, there is a little "+" sign marked on the top of the circuit board. This indicates where the positive lead goes. I think the MHDT board was labeled this way too. You won't see the "+" sign until you remove the cap though, because it is underneath the capacitor. Also, you won't see anything if you remove the bottom of the case except for solder joints and a couple of parts.

For what it's worth, the stock capacitors in there are not bad quality. I don't even know what the improvement is yet (if any) because the Black Gates are still burning in. If your DAC is new or if you turn it off when you're not using it,  I would suggest leaving it on. A charged capacitor is a happy capacitor. The DAC consumes so little energy and it runs so cool that you should just leave it powered on 24/7. It will sound much better (even stock) if you do.

Also, I was surprised at how much improvement there was with the stock DAC after 1 week of signal running through it. Again, if you have a new one of these, you really owe it to yourself to get to know the thing and let it run in before you start changing parts. (I'm not saying this to the recent posters here, but to anyone else reading this and considering buying a new one.) Often, we start modifying things before we give what we have a chance. Or we think that it is only a good value if it is modified.

I hope I haven't encouraged everyone to start ripping their DAC apart. I'll post more about the BGs later.
QE

[emac]

Also, I was surprised at how much improvement there was with the stock DAC after 1 week of signal running through it. Again, if you have a new one of these, you really owe it to yourself to get to know the thing and let it run in before you start changing parts. (I'm not saying this to the recent posters here, but to anyone else reading this and considering buying a new one.) Often, we start modifying things before we give what we have a chance. Or we think that it is only a good value if it is modified.

I hope I haven't encouraged everyone to start ripping their DAC apart. I'll post more about the BGs later.
QE

Rip 'em apart!!! 

Seriously though, Quiet Earth is right.  The stock DAC is very good, and you should know how it sounds before you start messing with it.  You'll learn a lot about the sound of the different caps and parts by doing so.

I'm also considering getting one of those Isoclean fuses for the DAC.  I'm going to be using my modded Constantine as part of a DAC shootout, and I want it to sound as good as it can. 

BTW, anyone know what type of resistors are being used in here?  I refuse to spend a lot of money on resistors, since there are about 30 of them in there, but there might be something better out there.

[Les Lammers]

I agree. I put the OIMP caps in after the DAC was burned in. I will put the Isoclean in after the caps settle in.

[Quiet Earth]

 BTW, anyone know what type of resistors are being used in here?

On the Ebay page for the Paradisea, it says :

"MHDT labs specially ordered flameproof military low noise resistors. These professional and military spec resistors are manufactured by vacuum sputtering deposit metal film on high thermal conductivity ceramic rods."

So there you go, they are low noise metal film resistors. What would you upgrade them to, tantalums?
That is a lot of rework. 

[emac]

On the Ebay page for the Paradisea, it says :

"MHDT labs specially ordered flameproof military low noise resistors. These professional and military spec resistors are manufactured by vacuum sputtering deposit metal film on high thermal conductivity ceramic rods."

So there you go, they are low noise metal film resistors. What would you upgrade them to, tantalums?
That is a lot of rework. 

Thanks.  Just wanted to get a sense of whether they were decent.  And if they are military grade, then that's fine.  I'm not interested in spending $5+ per resistor for 30 resistors in a $300 DAC.  And anything I get in my price range isn't likely to be much of an improvement. 

[Quiet Earth]

Well, it's been a solid week now. The Black Gates in my Constantine+ have more than 168 hours of burn in. I moved the Constantine back over to the big rig for another listen. Geez Louise ............ can you say m i d r a n g e ? There's midrange aplenty now. Did I goof? Where's the bass?

It occurred to me that I could have screwed up and made a bad solder joint,  thus leaving a capacitor out of circuit. In a quick panic, I played the stereophile test CD, the one with the bass warble tones, just to make sure the DAC is still passing the low end. Yup, it's still there. Solid to 31 Hz. (I don't worry too much about anything below 31Hz since I don't have a sub.) OK, relax then, settle down and just listen to some music.

Wow,,,,,,, that midrange. It's very prominent. There's a lot of detail there that wasn't there before. It's not offensive, I just don't remember it before the BG mod. Normally when you think of detail, you think of high frequency extension. I'm hearing all kinds of midrange detail now, but no treble brightness. It's a very clean midrange, but it makes the DAC sound a little leaner and less balanced. What to do? Play more music.   Hmmm,,,,,bass heavy CDs still have the bass prominence, but that midrange. Whoa. Keep spinning those CDs. OK, good. Different recordings sound different, as they should. I'm calming down now.

I started to think about things that I could do next, like removing any unnecessary MHDT bypass caps and getting the output coupling caps back to 2.0uF (for greater weight in the bass). But then I remembered something very important :

Black Gates are going to take more than a week to settle in. Sometimes 3-4 hundred hours is needed.

Give that man a gold star. Let's wait and see what happens before we draw any conclusions. I've been through this before. Why should it be any different now? How 'bout another week of burn in? Sounds good to me since I'm in no hurry anyway. Besides, this little DAC is certainly going in the right direction and I can enjoy it right now while it's burning in. Think I'll drag it back over to the studio and start working on some tunes this week. Should be fun.

So,,,,,,,,,,,,, in the words of California's Governator : "I'll be back."

[Les Lammers]

QE,

I would give the BG 500 hours B4 you panic or listen critically. Some days when you listen it is like waking up with a really ugly woman and seeing a marriage license.

Les

[Quiet Earth]

I hate when that happens. 

[shooter]

Quiet Earth
What output caps are you using? The Russian K40Y paper in oil cap has the most bass output with all the caps I tried so far, it may help the tonal balance on your Constantine, the largest value I've seen is 1uf, so you will need to parallel a couple.

[Les Lammers]

I think I am going to eat some Wheaties and install BG's when I am sure the OIMP's are fully settled.

[Quiet Earth]

Quiet Earth
What output caps are you using? The Russian K40Y paper in oil cap has the most bass output with all the caps I tried so far, it may help the tonal balance on your Constantine, the largest value I've seen is 1uf, so you will need to parallel a couple.

I'm using 0.47uF Audio Note copper paper in oil caps. I put these in because I already had them in my parts box, and I just wanted to hear if they were an improvement over the stock MHDT caps. Boy, were they ever! The bass quantity seemed just fine with them too, and the DAC was quite balanced overall. But then ---------  the Black Gate mod. 

I know the BGs need a couple more weeks to run in. I just wanted to post my initial impressions after a week of burn in. I went through this with the BG FKs in my Audio Note DAC. It took a good three weeks to settle and I only upgraded three capacitors on the digital power supply board. So, I'm not sweating it.

I do believe that my Constantine is headed in the right direction though. I might check into those Obligato copper PIO caps in two more weeks. I can get 2.2uF in just about the same size as the 0.47uF AN caps. There's a couple of other things that I may explore too. But for now, I will just let it cook for another week before another listening session. I have some other things to keep me busy anyway.

[Quiet Earth]

I think I am going to eat some Wheaties and install BG's when I am sure the OIMP's are fully settled.

 
 

[shooter]

I like the Obilgatos, the Russian caps definitely have more bass, I have no experience with the Audionote caps, don't know if the .47uf cap is large enough to get full bass response, keep us posted about the BGs.

[emac]

Looks like I'm going to be putting up my modded USB+ Constantine in a DAC shootout in a couple of weeks.  I wanted to see if anyone had further suggestions for mods while I still have a chance.  Trying to keep it reasonably priced.  The following is what I've done so far:

1. Changed opamp to OPA2107.
2. Biased and decoupled the opamp. 
3. Changed output caps to Radio Shack metal film caps.  Surprisingly good change. 
4. Changed out all of the MHDT Labs film and foil caps w/ Radio Shacks.  Again, nice improvement.
5. Changed out all electrolytics to Rubycon ZLs except for the power supply caps, where Rubycon's don't come as 3300uF 35V.  Tried contacting Percy Audio for Nichicons, but no reply. 
6. Stillpoints ERS over the chips and transformer.  Helpful as well.

I'm likely going to get an Isoclean fuse, but I wanted to see if anyone else has other ideas for me. 

Thanks.