Twisted Pear Audio Opus DAC - Page 9

Hello, sorry I missed this conversation so far. Some points if I may.

1) The Opus works wonderfully single ended even without the Ballsie module as others have pointed out.

2) The Ballsie is a bit more than a BAL/SE converter. The output of the DAC is not conducive to driving very current hungry loads, it has a minimum load of 1K. In those cases where the load is < 1K the Ballsie acts a buffer (both balanced and SE). Notice that the Ballsie has balanced AND SE outputs at the same time. I have been listening to the DAC with Ballsie in place for a couple weeks now. I truly like it better in the mix especially with single ended power amps like the "MyREF".

3) The Ballsie is an implementation of Wolfson's own recommended filter circuit that has been tweaked just a tad. In this respect it can be viewed as a stand in for something like a zap-filter. The opamps we are using are incredibly low distortion and low noise, and work very well for the role. The design was blessed by the Wolfson engineers I submitted it to. Call it peer review.

4) The USB module was really intended to simply be another I2S source for the Opus stack, in which case it sounds incredibly good. But, Brian and I have found that also despite being bus powered, it actually sounds very good on its own (much better than I expected) using its internal DAC and analog outputs.

5) I have a lot of tricks up my sleeve, The Opus stack is by no means complete yet , look for some very very cool things coming soon... I would say more but Brian will shoot me. One thing I will mention is our ASRC module(possibly more than one ASRC module).

You can look at the Opus stack as an expandable project. You can start out as basic as you please, and add to it as you like. Start with just the REC/DAC and later add USB, Ballsie, ASRC, etc.

Cheers!
Russ

ASRC?

ASRC = Asynchronous Reclocker. It can up-sample 44.1 to 192,96,48khz whatever, or even down-sample. Because it can host the master clock, it can provide a nice clean clock solution. How much better it is than the other clock sources remains to be seen. But at least it will be an option.

Cheers!
Russ

Thanks for the clarifications Brian and Russ. I'll be using the balanced outputs 99% of the time, and my Opus build has a Zapfilter discrete output stage, but you did make things clearer for me.

Can't wait to hear your Joshua Tree on my ϐ22 build.

ASRC? whicked! looking really forward!!!!
You do awesome stuff!

Greetings,
and thanks a lot for your statement, russ! Now the Opus is on the top of my own list ... which you could call "My first DAC". Well, perhaps an AlienDAC at first - as a "warm up".

best regards,
bearmann

like more Joshua Tree boards?

like more Joshua Tree boards?

edit: nevermind, just checked your website....

Could you expand? Thanks.

Expanding:

First, let me describe two setups for loudspeakers.

I2S(USB, SB, CDP, DVD, etc..) -> Opus -> Power Amp (TXO) 1K impedance.
I2S(USB, SB, CDP, DVD, etc..) -> Opus -> Ballsie -> Power Amp (TXO) 1K impedance.

There is no preamp currently in the mix. I have firmware written to control the volume direct from the Opus. The voltage gain of the power amps is low(about 10X) so I can run the DACs without much attenuation (usually around 18db) Both setups above work well, but as I said earlier the current drive of the DAC chip itself is not exactly beefy. The TXO power amp as I have it configured uses fully symmetric current feedback and the source sees a load of around 1K. This is right at the DAC's minimum. While it sounded fine, I was anxious to try it with the Ballsie in place. Well lets just say it is staying... The music is just more alive and dynamic, there is more punch. Also, with the filter caps in place on the ballsie, the presentation of the DAC become a bit warmer, sweeter, while still leaving the excellent dynamics of the DAC. I can't decide if I like it better with or without the filter caps, but I am glad it is easy to use it either way.

Here is the other side benefit, the SE output of the ballsie is the same level as the differential output. This worked out great for me as I have a very good subwoofer amp with only SE inputs, and before I was simply feeding it half the differential signal directly from that DAC, the problem with that being that then the DAC was asymmetrically loaded. While that does no serious harm, it is not optimal, especially when you are using it balanced too, the balanced output is then not quite quite as balanced if you follow.

Also, I like to run the DAC in mono mode (dual differential) where both differential outputs are in parallel. The Ballsie allows for this and provides series resistance so that the parallel outputs are evenly loaded and do not drive each other. Dual differential mode is definitely the way to go for absolute optimal performance from the WM8740.

I hope that helps.

Cheers!
Russ

I think I'm going to get to hear one soon! Fierce and I are planning to get together for a little listening session

Thanks Russ.

mmmm .... multi-dac modules ..... drool

Doh! You'll get to hear my DAC before me. Remember that one has a Zapfilter installed, but Jim has heard it without the ZF as well. I'm dying to hear about it!

If I'm lucky I'll get to hear spacemanspliff's Beresford too

and I have my modded Zhaolu 1.3 andmy Bereford MKIII

^^bump^^

any impressions?