Twisted Pear Audio Opus DAC

[swt61]

I think they were getting together this weekend.

[soloz2]

I've gotta get ahold of Jim, I was hoping to meet tomorrow, but I haven't heard from him.

[ast]

Any impression of the Opus with headphones ?

[Clutz]

And I'm curious if anyone has used this DAC without the Ballsie with a headphone amp. They say that the benefit of using it is that it isn't a very good current source (i.e. amps < 1K impedance) - but my Beta22 (almost done) and Dynalo have 50K impedances, so, it seems like it would be unnecessary.
Brad

[OverlordXenu]

I wish I could DIY. I want an OPUS so much...

Also, what's the difference between using one DAC module, or running it in a dual-mono configuration?

[Jambo]

Better SNR because of the higher output levels and, one would imagine, better seperation between the channels...

[MrMajestic2]

Did anyone have problems with the PS for the DAC? Im running both the digital section of the DAC and the SPDIF receiver on out2 on the LCDPS and R4 on the PS is turning very hot and smells burned. When running it unloaded its fine and pumping out 7.5V on both channels.

[MrMajestic2]

Hmm, it seems like when the Ballsie with PS is plugged in to the same toroid it gets overloaded. I took them out and its now up and running. Sound fantastic by the way Apparently my 15VA 2x15V toroid is not strong enough for all modules.

[BrianDonegan]

If I understand what you correctly, you have a single 15VA transformer powering both supplies... this is the problem.

The DAC's LCPS (LCDPS) cannot use a center tapped transformer, because the center tap will become the + rail of first supply, and the - rail of the second supply (two distinct supplies on the board). When you connect them to the DAC, the grounds from each supply meet, and you are basically shorting + and -.

The Ballsie's Dual Supply (now LCBPS) does the opposite. The two center secondaries of your dual secondary transformer are joined to form a virtual center tap, and the center (Ground) rail of the supply.

Therefore, when you attach your transformer to both supplies, the Ballsie's power supply is turning your transformer into a center tapped transformer, and that causes a problem on the DAC supply. In the end, you need separate transformers.

The alternative, is use the single transformer to power the Ballsie supply, then use a single set of its secondaries to power both sides of the DAC supply - this will prevent the center tap shorting situation.

[MrMajestic2]

Originally Posted by BrianDonegan

If I understand what you correctly, you have a single 15VA transformer powering both supplies... this is the problem.

The DAC's LCPS (LCDPS) cannot use a center tapped transformer, because the center tap will become the + rail of first supply, and the - rail of the second supply (two distinct supplies on the board). When you connect them to the DAC, the grounds from each supply meet, and you are basically shorting + and -.

The Ballsie's Dual Supply (now LCBPS) does the opposite. The two center secondaries of your dual secondary transformer are joined to form a virtual center tap, and the center (Ground) rail of the supply.

Therefore, when you attach your transformer to both supplies, the Ballsie's power supply is turning your transformer into a center tapped transformer, and that causes a problem on the DAC supply. In the end, you need separate transformers.

The alternative, is use the single transformer to power the Ballsie supply, then use a single set of its secondaries to power both sides of the DAC supply - this will prevent the center tap shorting situation.

Aha, I see. Didnt realise that this would happen. So the solution for this is to run both secondaries to the Ballsie PS, and then run a single secondary from the Ballsie supply to the DAC supply? But all four power inlets on the DAC supply must be populated I guess, so Ill just jumper between them, right? Hmm, maybe I will run dual transformers anyway, even though the umbilical will be huge Anyway, thanks for the swift reply and thanks for a great sounding DAC. Now I just need the upsampler module

[MrMajestic2]

Ok, decided to go with dual transformers. Dual umbilicals actually looks pretty cool The DAC sounds fantastic with the Ballsie up and and running. Now I just need a bigger case to house all the modules. The Galaxy GX243 is getting kind of cramped.

[swt61]

Sounds pretty nice. How is the soundstage?

[MrMajestic2]

Originally Posted by swt61

Sounds pretty nice. How is the soundstage?

Little early to give a review, but to my ears its very wide and detailed. Im not set up to A/B with and without Ballsie yet, but I will be later when my B22 is built Im listening though a pimped out Pimeta at the moment since my Millet Max is undergoing some modifications. Im betting that it will sound even better with another amp.

[luvdunhill]

^^ synchronized bump (or not... must wait 30 seconds between posts?) ^^

any more impressions?

Also, can any of the twisted pear goodies be configured to operate in non-oversampling mode?

[Clutz]

Originally Posted by luvdunhill

^^ synchronized bump (or not... must wait 30 seconds between posts?) ^^

any more impressions?

Also, can any of the twisted pear goodies be configured to operate in non-oversampling mode?

No, because the DAC chip that they have used has both the oversampling filter and the DAC itself integrated into a single chip solution. In order to make use of a non-oversampling DAC, you need to use a DAC chip that doesn't have a digital filter integrated. To the best of my knowledge, all current DAC chips have the digital filters integrated, except maybe the AD1853?

Brad