Twisted Pear Audio Opus DAC

[Nebby]

Quote:

Originally Posted by philodox /img/forum/go_quote.gif The Zapfilter is just a high quality analog output stage.

Ah I see. That ought to be interesting

I've done a little reading and searching on head-fi, and from what I've read it seems like it's rather on the bassy side. If so, I definitely won't be using that for my opus, since listening to it through the Apache, the D5000's have gobs and gobs of bass already. I think adding any more would be too much for my ears

 

[philodox]

I wouldn't say it is bassy personally... the bass is definately there, but has good definition.

 

[Nebby]

I must say....you've piqued my interest, philodox. I found the Opus stock to have plenty of detail esp compared to the Oritek zhaolu, so it makes me wonder how it would sound zapfiltered.

 

[philodox]

Quote:

Originally Posted by Nebby /img/forum/go_quote.gif I must say....you've piqued my interest, philodox. I found the Opus stock to have plenty of detail esp compared to the Oritek zhaolu, so it makes me wonder how it would sound zapfiltered.

I'd wait until after swt61 has his built. They are going to try it out with and without the zapfilter to decide.

 

[Nebby]

That's what I meant by "wonder"

I am definitely going ahead with the sigma upgrade, just need to find out the resistor values I need to get 7.5...though I might just go for 9v since those values are already provided on Ti's page.

 

[swt61]

Quote:

Originally Posted by philodox /img/forum/go_quote.gif Are you building yours with the OPUS PSU or something else? Might be cool to use one of AMB's power supplies, the o22 or o11.

fierce_freak thought the stock power supply was adequate, but I am interested in an upgraded power supply. Better to do it all at once than send it back again.

Quote:

Originally Posted by Nebby /img/forum/go_quote.gif I think the sigma22 is more appropriate for the opus since it has dual rails, and the opus dac boards require separate rails for the analog and digital stages. What exactly does a zapfilter do? I keep hearing about it and I'm curious to hear how it affects the sound.

What's the cost of building a Sigma22? Do you need to buy the board and the parts seperately, or do they have a kit?

The Zapfilter definitely has strong bass, but it's not at all overexagerated. It's tight, well controlled, accurate bass. It's just the ticket for the K340 I own, but doesn't overwhelm my 600Ω DT990 either. The way it transforms the Zhaolu is amazing, so it's worth a try in the Opus. If it doesn't yield substantial gains I'll have it installed in my Parasound DAC instead.

 

[n_maher]

Quote:

Originally Posted by swt61 /img/forum/go_quote.gif What's the cost of building a Sigma22? Do you need to buy the board and the parts seperately, or do they have a kit?

I'd budget around $125 for it if you need an enclosure. Kit's can be found here.

 

[FallenAngel]

Quote:

Originally Posted by swt61 /img/forum/go_quote.gif The Zapfilter definitely has strong bass, but it's not at all overexagerated. It's tight, well controlled, accurate bass. It's just the ticket for the K340 I own, but doesn't overwhelm my 600Ω DT990 either. The way it transforms the Zhaolu is amazing, so it's worth a try in the Opus. If it doesn't yield substantial gains I'll have it installed in my Parasound DAC instead.

Just looked at the schematics of the ZapFilter 2, it looks quite a bit like PPL's diamond buffers as per the PPAv2 and the ones used for the Millet Hybrid. Definitely should be a great output stage.

 

[swt61]

Well it's decided, fierce_freak PM'd me and we're going with the σ22 power supply just to play it safe. He was also gracious enough to offer me his Opus parts so that I don't have to wait a month. His will be dormant until he gets a new amp anyway, but the offer was very nice, and greatly appreciated. So I'll be an Opus owner before long.

 

[looser101]

I don't believe you can use the sigma22 with the opus dac as intended. I've read that it's dedicated to provide + and - rails (tracking) and not two positive rails. The opus needs two positive rails, one for analog supply and one for digital supply. So you would need two sigma11. A dual (individual) secondary winding transformer would be good, two individual transformers may be even better. Somebody correct me if I am wrong.

 

[swt61]

Hmmm, I need to figure this out, as the parts order goes in soon. I don't doubt you though Renato. So do you think two σ11's will be a nice upgrade from the stock power supply? Is that all that would be needed?

 

[looser101]

Quote:

Originally Posted by swt61 /img/forum/go_quote.gif Hmmm, I need to figure this out, as the parts order goes in soon. I don't doubt you though Renato. So do you think two σ11's will be a nice upgrade from the stock power supply? Is that all that would be needed?

You have PM.

 

[swt61]

Thanks Renato!

 

[Nebby]

Well the schematic for the sigma 22 board is here:
http://www.amb.org/audio/sigma22/s22_sch_small.png

I'm still a relative beginner when it comes to DIY, but to me it looks like it should be fine. I see the two secondaries being connected to the rectifier diodes which smooth it into two seperate dc rails with + and - in each rail, then all the power supply fun....and then two terminal blocks per rail. I know that's a rather rudimentary interpretation.....so excuse my lack of technical knowledge

But am I wrong in thinking the sigma22 appropriate for the Opus dac?

 

[looser101]

Quote:

Originally Posted by Nebby /img/forum/go_quote.gif Well the schematic for the sigma 22 board is here: http://www.amb.org/audio/sigma22/s22_sch_small.png I'm still a relative beginner when it comes to DIY, but to me it looks like it should be fine. I see the two secondaries being connected to the rectifier diodes which smooth it into two seperate dc rails with + and - in each rail, then all the power supply fun....and then two terminal blocks per rail. I know that's a rather rudimentary interpretation.....so excuse my lack of technical knowledge But am I wrong in thinking the sigma22 appropriate for the Opus dac?

Well, almost. The output opamp for the negative rail tracks the voltage of the positive rail to generate the negative rail. I've read somewhere - the headwize thread? - that it can not be used for dual positive rails.

Not sure there would be an improvement from the twisted pear supply. The dac board has regulators for digital and analog supplies onboard. Most psu noise would be from the onboard regs as long as a reasonably quiet psu is used to power the dac IMO. Obviously the sigma psu's are much quieter, I'm just not convinced they would be an improvement. But if you want to try then use 2 sigma11's (or 1 for the analog supply only) with separate transformers and let us know.

Renato