[srobertson]

After years of waiting (yes, years), I've finally decided to grab some parts and put together a PIMETA, and I'm relatively settled on using the Monica2 for a DAC. Although I do most of my listening at a computer, I'd still rather avoid a USB sound card; since most of my music collection is in MP3 format (thanks, emusic) I sincerely doubt the jitter that remains after the reclocking on the Monica2 will be noticeable. In any case, I have a couple of questions about the specifics of the design that I want to run by you friendly folks.

* Is there another DAC that you would recommend over the Monica2? If so, why?

* I want to put both components in the same case, so that this thing has some semblance of portability (and because cost was spiraling upwards at an alarming pace). Aside from grounding issues, is there any reason this is dumb (e.g. noise)?

* For power, I'm going to be using 9v rechargeable batteries in a separate enclosure in three sets of two (one powers DAC, one powers PIMETA, one recharges). Monica's power will be at +9V (two in parallel); but even with 600 mA stored I fear that the quiescent draw of the LM317 alone (it's used as a current source, biasing some 1N4148s into a relatively linear range for use as a shunt rectifier, so a minimum of 50mA) would drain the batteries unacceptably fast. I plan to wire up an LM317 in a more traditional configuration. Do you think this will provide comparable voltage regulation, and is it generally a reasonable idea?

I'm sure I'll have more questions later; for now, thanks for your help!

Steven

 

[fran]

I have a monica 2 DAC - its very nice, is a good bit quieter output than most CDPs but, what you get is good. Heres the thing though - I always thought that you needed 12V to make it sing. I know that you can use upto 13.8V. Would you not think of trying out a 12V SLA and then downregulating to the 9V for the pimeta - although that would seriously affect your portability! If you do got that route, I think I remember reading somwhere that its a good idea to put in a few big caps post SLA because the battery can't cope too well with sudden transient demands and the caps would take care of this.

I'm interested to see how you get on..

Fran

 

[threEchelon]

The Monica is great but has a small soundstage, sort of a portable-fi sound. You may like the small soundstage or you may be wanting more.

 

[srobertson]

Quote:

Originally Posted by fran /img/forum/go_quote.gif Would you not think of trying out a 12V SLA and then downregulating to the 9V for the pimeta - although that would seriously affect your portability!

Actually, the PIMETA was supposed to be driven at 18V; I was looking for an excuse to use nice Amphenol connectors for geek coolness factor, and exposing all four terminals in a single cable so that the board could run them in series or parallel seemed like a sensible idea at the time.

However, after a little bit of reason crept in, I realized that I was looking at over $150 for a suitable charger, six good 9V NiMH, case, connectors, ... at that point the idea "let's save money by just using battery power" kind of died.

One of the SLAs in a UPS died very recently, and I'm feeling bold, so I think I'm going to go for a TEPS (or something like it; I'm having fun salvaging crap from my overlarge hardware graveyard). (I know, what does the UPS have to do with anything? Well, instead of just replacing it with an expensive SLA, I'm stripping the more expensive parts from the UPS (it was cheap anyway) and building a DC-DC converter for the gear it was powering. If I don't blow this up, then I'll feel comfortable that the TEPS will be up to snuff.)

I might choose to add an SLA battery later, though, to make it "portable".

 

[Filburt]

I saw this thread over on DIYHifi and thought it might be useful: http://www.diyhifi.org/forums/viewtopic.php?f=2&t=1216

 

[srobertson]

Quote:

Originally Posted by Filburt /img/forum/go_quote.gif I saw this thread over on DIYHifi and thought it might be useful: http://www.diyhifi.org/forums/viewtopic.php?f=2&t=1216

Up until now I'd heard nothing but glowing reviews for the Monica2. I honestly was concerned about a couple of the points peufeu mentioned in that thread, but I chalked it up to my relative inexperience in electronics. Thanks for the link.

*sigh*... seems like I'm looking for a new DAC.

 

[MisterX]

How about one of those pictures is worth a thousand words type post's?

Quote:

*sigh*... seems like I'm looking for a new DAC.

Sounds like a good idea to me.

 

[cotdt]

that was brutal, MisterX

although -4dB at 20kHz is acceptable to most people.

 

[fran]

Have to say that yes, I did notice the narrowing of the soundstage - thru speakers anyway, but I didn't notice treble roll-off. But then I can only hear to about 16kHz any way. Which maybe equates to 2dB down or so. It would be interesting to see the same graph for other NOS DACs.

I'm not an expert on DACs at all, but I like the monica, I have it here beside the PC and I use it quite a bit (thru headphones).

Anyway you could get one to try out or something before you buy? Those posts on the forum link posted are pretty vehement, aren't they? I have my monica for quite a while now, and that thread was posted in April 07. How about doing a search and getting other users comments? If the portability issue is now gone, its hard to pass a Zhaolu for the money - not much more than a Monica and already done for you. Change a few things like opamnps and the caps mod and you have a pretty decent DAC. You will also have a HP amp that you can compare with your pimeta.

Oh yeah - I bought mine pre-built, but cased it myself.

Fran

 

[srobertson]

Quote:

Originally Posted by fran /img/forum/go_quote.gif Anyway you could get one to try out or something before you buy? Those posts on the forum link posted are pretty vehement, aren't they? I have my monica for quite a while now, and that thread was posted in April 07. How about doing a search and getting other users comments?

That's a good idea, and if I had more time I'd definitely want to try it myself. However, I have a feeling that once I pick a DAC it'll be a couple years before I upgrade again, and I'm not yet discerning enough (or perhaps motivated enough) to spend hundreds testing several. I'll definitely look deeper for more reviews, though.

Quote:

Originally Posted by fran /img/forum/go_quote.gif If the portability issue is now gone, its hard to pass a Zhaolu for the money - not much more than a Monica and already done for you. Change a few things like opamnps and the caps mod and you have a pretty decent DAC. You will also have a HP amp that you can compare with your pimeta.

The Zhaolu has received a lot of positive attention, and is definitely on my short-list, although I personally would prefer building it myself (even if it adds $100 due to low quantity orders - yeah, I'm dumb).

Another one I'm interested is the Opus, which looks like it could be really nice. Still hunting down some reviews, though.

If you've got any more suggestions for a DAC (either DIY with a premade board or fully assembled) that takes at a minimum S/PDIF, please share. Free time is overrated.

 

[fran]

Don't know about the opus, but I have a darwin source selector from twisted pear and I can tell you they are most helpful, well beyond the call of duty. I don't think you can go too far wrong. Wouldn't mind one myself!

Fran

 

[threEchelon]

I didn't reed through the whole OPUS thread at diyaudio but from what I did read, it seemed like people, after looking over the PCB's, thought that the DAC was good but that the SPDIF receiver could definitely be improved.