The Theta Thread

It seems there is not a Theta DAC or products thread and many SBAF members I know have them due to the connection with Mike Moffat at Schiit and given that all of us also have love for vintage DACs, I thought it appropriate for Theta to have it’s own thread.

https://www.thetadigital.com/legacy-products/

https://www.stereophile.com/content/mike-moffat-re-creating-musical-event

Here is a list of DAC chips in the Theta units:

THETA CHROMA 396 DAC: 1 x PCM67P-K – CXD1244 / PMD100
THETA COBALT 307 DAC: 1 x PCM67P-K – CXD1244 – CS8412-CP
THETA DS PRO: 2 x PCM56P-K + 2 x Ti DSP – YM3623B
THETA DS PRO BASIC: 2 x AD1860 / PCM61P-K – Motorola 56001
THETA DS PRO BASIC II: 2 x PCM67P-K + 2 x Motorola XSP56001
THETA DS PRO BASIC III: 4 x PCM1702-K + 2 x Motorola DSP56001
THETA DS PRO GENERATION II: 2 x AD1860N-K + 2 x Motorola XSP56001
THETA DS PRO GENERATION III: 2 or 4 x PCM63P-K + 3 x Motorola 56001
THETA DS PRO GENERATION V: 2 or 4 x PCM63P-K + 3 x Motorola 56001
THETA DS PRO PRIME: SAA7350GP + Motorola DSP56001
THETA DS PRO PRIME II: 2 x PCM67P-K + Motorola DSP56001
THETA DS PRO PROGENY: 1 x PCM67P-K + Motorola DSP56001

 

Review of the Theta DS Pro Basic II

Features and Specs



This DAC was the 2nd tier down from the top of the line DS Pro. This particular DAC has two PCM67 chips (K grade I might add) with balanced and unbalanced out. Now the PCM67 is a 2-channel output chip, so one chip is used for each L and R channel in a balanced +/- configuration. It means doing balanced and unbalanced the hard way, but the right way.

The PCM67 is also a hybrid chip, meaning it is both multibit and 1-bit. It is a 10-bit mutibit and then for the lower part it is 1-bit for the rest of the bits. Here is a link to the datasheet if you want more info. And yes, it was one notch below the beloved PCM69, which also was in the Theta DS Pro II.

http://pdf.datasheetcatalog.com/datasheet/BurrBrown/mXrstqv.pdf

Here is what Theta has to say about the Pro Basic II on the Theta Legacy page:

“The research that was invested into the Prime and DS Pro Generation II Balanced paid dividends in other products as well. The Basic II was released in late 1991, offering sound quality many thought comparable to the Pro II. Balancing was available as an option, which was by this time becoming a standard for many digital based systems. It was, of course, balanced “the hard way” as previously described. It also featured a new DAC from Burr-Brown, the PCM 67. This was an 18-bit combination DAC that operated as a multi-bit DAC for the upper portion of its range and as a one bit DAC for the lower portion. This DAC is still used today in the Prime II, Progeny and Cobalt. New op-amps, the Analog Devices AD829 and AD707 were also utilized. The design team continued to delve into sources of dissatisfaction with digital sound. Again they found that increased processing power and digital filter accuracy was essential for further resolution enhancements. New op-amps that had faster slew rates and settling times were investigated. Improvements to the digital section’s power supply were found to decrease harshness and interference between different parts of the digital circuit.”

That is from Theta’s page, but given the style of writing seems to be Mike’s writing (uncredited)

Either way, this particular DAC I have has 1992 on the board and has AD797’s, not AD707’s, and no AD829’s. It looks like it has AD797, then a LF351N, and the final buffer handled by the outdated TO-99 package BUF03FJ.


Now we also do know that it is the muticomboburrito filter and Motorola DSP. It also has Mercury Magnetics separate transformer power rails for the digital rails and the analog rails (much like Gungnir).

As far as features, it is pretty basic (it is has “Basic” in the item name, duh), but this particular unit has:

• 2 coax S/PDIF inputs
• 1 AT&T or SP optical input
• 1 S/PDIF coax output
  
• 1 stereo unbalanced output
  
• 1 stereo balanced XLR output
  
• Phase reversal switch

The front panel just has two switches and two LED’s. The left toggle is a 3-way input toggle and the light next to the switch verifies the source. The right LED is a power LED only. And the right toggle switch is the Polarity switch marked as Phase.

There is no power switch. Once you plug in the IEC power cord it is on. Unplug it, it is off. I can’t imagine what kind of calls Schiit would get now with this kind of setup, but anyway…

The only thing I find intriguing besides the lack of a power switch is the fact that the box is one rack size, however the front anodized aluminum panel has rack looking ears, but no holes and is actually just slightly larger than one rack space.

I will say it is also hard to see what input you are in because the only indicator is the switch location (up, center, down), and that small switch can be hard to tell at a quick glance.


Review

Headphones: HD650, LCD-2C
Amps: Cavalli Liquid Carbon, Gilmore Dylalo
Sources: Etir, HiFi Digi+

Now, how does this thing sound? Uhhhhh….quite freaking amazing!

I have always seen descriptions and reviews of Theta gear as warm or very clear and thundering bass. I will say that the low end is detailed and strong. You cannot confuse this for a lean output at all.

However, the highs are also there, clear and detailed. It has a very non-fatiguing sound for sure. Really it is as warm as my Bifrost Mutibit and my Modius. One of the most musical sounding DACs I might add.

The most glorious thing about this DAC is the space and detail. The space and blackness between instruments is outstanding. It clearly passes my Bifrost Mutibit by a good bit and does not have that muted feeling I get with the Bifrost. It completely sounds open and clear, effortless, and just outright dreamy. It is very wide and deep and so easy to get lost in this thing and get “into” the music. I don’t want to spend too much time singing the praises of this, but this is THE best DAC I have ever owned. Granted I did let it have to warm up for a whole day, but that is like most multibit DACs. Sometimes I have to pinch myself that I am listening to a digital file.

Going between the Bifrost Mutibit and the DS Pro Basic II, I get that bigger sense of realism and more defined edges. More authoritative than the softer and leaner Bifrost, especially in the low end department. Lately, I have noticed a kind of muted sound to the Bifrost - this started to happen after I got Modius. Modius did not have this muted quality, but Bifrost still had more space and blackness, more 3D, and less glare. However, this Theta takes all that muted quality out of the picture and then makes it sound even wider and more spacious. I could go on, but I digress...

My only real complaint, if it is even a complaint at all, is that as full and rich it can sound, it also has a tendency towards clinical on certain tracks. Yes, it is bold and fast, yet on things like 80’s new wave, can lean towards lacking and thin, maybe even slightly edgy. I dunno, maybe I am just hearing too much details.

On sources, it is much more forgiving than other Schiit gear I have tried. The Etir only sounded slightly more hazy and soupy than the HiFi Digi+ from my Pi, but still solid. Even optical output of my computer, through an optical to coax converter was still very close to the other two. No USB, but solid on the input.

The polarity switch also has some effect on tracks and some do not. There is no delay like there is switching inputs, but it is interesting as some things did sound better and more spacious 180 degrees out, and others made no difference at all.


SPDIF Upgrade

Now the AT&T optical input is rather pointless these days. It is part of the reason Schiit went with upgradeable DAC’s so your DAC can keep up with the times as far as inputs and analog outputs as IC’s and other circuits improved.

In searching for a Theta DAC, I did see a few DS Pro’s with three coax inputs instead of one SP and two coax. So I knew there was a way to do it without a lot of fuss. I open the board and there sits the positive and negative spdif inputs. However, how to use this?

Then, I find on the board J1 that looks like a jumper soldered to the “AT&T” side and open is the “RCA” side.



I move the jumper to the coax side, take out the optical connector and wire up an RCA connector, hook up a coax feed, and boom! Now I have three coax inputs to choose from.

 

Lol, your review makes me second guess selling it to you for so little!

I agree with most of what was written. It definitely was a bold dac compared to the Modi Multibit V2 I had on hand, with more of everything. In some ways, it would have been an ideal partner for the Asgard 3 I now have on hand since the Asgard feels very mellow to me.

Glad you are enjoying it.

 

A year or two back I borrowed @Clemmaster 's Theta Gen V and ever since I've been chasing that sound. Shoulda bought it when he sold it for $600 here, though it had developed a transformer hum.

Monarchy M22B (PCM63) is like the poor man's Gen V in terms of the slam and color, but is a bit edgier and less refined overall. EAD DSP 9000 III (PCM63) is more like a souped up Progeny in terms of tone, doesn't quite have the slam of the Gen V, though it does image and resolve similarly.

Progeny feels kind of weaksauce compared to the Gen V (nerfed dynamics, not as smooth, not as spacious) but does compare favorably from a technical standpoint against some of the previous gen lower-level MB Schiit DACs (Bifrost and Modi). I haven't heard the newer Modi Multibit or Bifrost 2.

Those three DACs are all I own, using Lynx E22 in my desktop as a digital transport, and I don't find myself chasing for much more in terms of performance from a digital source. That being said, if I could get my hands on a V or Va, I probably could settle for that DAC alone and ditch what I have now. The discrete output stage is absolute magic.

 

One other thing I will add is that I made that change with the extra SPDIF input, but that was not an auditory upgrade, just a feature upgrade. I thought about what kind of changes would I make to improve it and I am almost too scared to change it because it sounds so dang good as it is. Sure, there might be some better op amp and buffers out there, but I am not one to try to tinker with a good thing if it does not need it.

There are also a ton of those mustard tantalum caps and makes the board smell when you open the case. Though, I think those were chosen for their low ESR. Not sure if a film cap would really be an upgrade there. I am sure one day I will get to replacing the big power caps since this thing has to be on pretty much ALL the time.

Yes, I really do appreciate you offering to the SBAF community for a non-inflated price to keep it "within the family." I started this thread as kind of a payback of sorts.

Who knows, I might get get bitten by the upgrade bug at some point, but this one is going to be hard to let go...at least for now.

 

I have no doubt the Pro Prime and Pro Gen stuff with the PCM63. It seems reading the history, Mike was learning and taking advantage of not only what he learned, but of new technology as well.

 

I do wish I had been able to get a Bifrost 2 in at the same time to see how old Mike vs newest Mike tech sounded compared to each other.

 

Just joined. My trusty old Data universal transport is acting up and the tray wont open. Bummed it has been with me for decades playing through a DS Pro Gen III.

Any recommendations on who could service the transport? i am pretty sure it is a souped up Pioneer LD player inside (have one of those also).

I appreciate your feedback....... Kind regards, Juan Florida USA

 

Big, dumb question incoming! Theta Gen V(a) vs Yggdrasil A2?

 

Hi, was wondering how do you tell apart the Gen V vs Gen Va versions?

Thanks..

Btw, which Theta Gen has the biggest Bass Slam definition?

 

From the big 'A' sticker in the back.

I used to own the Gen Va and Basic IIIa and no question the former had the biggest and bestest bass of the two.
Never heard a non-A Gen V.

 

Yggdrasil is the more modern version: cleaner, tighter (both bass and imaging) and more transparent.
The GenV is thicker, slams harder, stages bigger but a bit more diffuse. It's more 'fun' overall.

 

Any audio review of a detailed blow by blow account of a slug out between Gen Va vs Yiggy+?

Very curious to read about that.

Have you ever heard Eric Clapton Tears in Heaven unplugged where you hear the kick drum being played in the background? I honestly feel the Theta does something to the retrieval, no other source I have heard before.. yet with the kick drum it is distinct and not boomy and can hear the vocals and guitar clearly.. I think it's Mike's Noise shaping in the DSP that gives that distinct kick drum bass capture.

This is very different from an EQ boost where everything gets boosted like a Disco mix.

Can the Latest Yiggy+ do that?

 

Are you sure you don’t just need a belt replacement? Most of the time when a CD tray won’t open, it could just be a simple rubber belt.

 

Great thread! I own several Theta Dacs and a Pearl transport. My Pro Basic IIIA has a socket for the input receiver chip. I bought a CS8414 from ebay a few years back and now it plays 24/96 files.

 

Okay, you inspired me to purchase a WM8804 to CS8412 adapter board from eBay. It is supposed to do 192K. It likely won't be here until June, but this should be a quick pop out chip, put in new chip upgrade, and will report back.

For record, most Theta DAC's have a CS8412 receiver that only goes to 24/48. The CS8414 is pin compatible (when put on a straight adapter) to get to 24/96.

 

So the WM8804 to CS8412 adapter did not work in the Theta. The input light stayed lit no matter what input and just digital pulses on the analog output.



I bought a CS8414 and hopefully that will work.

PS - I put back the CS8412 and everything still works just fine.

 

I have not tried the WM8804 module. I used a CS8414 on a DIP adapter board on my Pro Basic IIIA.

 

Confirmed that my Theta is playing up to 24/96 files thanks to a CS8414 on an SOIC to PDIP adapter replacing the CS8412.



Anyone with a vintage DAC that has a CS8412 should try this.

My question would be that if you have a chip capable of high res, why would you limit it with the input chip. And the only think I can think is higher cost, added function when no one asking for it, or could have just been that the 8414 came out too late to change and then two reasons above. Plus, I don’t even think there IS a PDIP version of the 8414, so it would have had to come out later and would have required a board redesign.

The PCM67 is only capable of 394f, and since this DAC is likely employing 4x oversampling, so 96K input is the max I’m going to get anyways. And the CS8414 is limited to 96K anyway.

PS - trying to play a 24/192 file is dead silent. The 8412 would just pass through whatever it got and high res files would be a garbled digital mess on output. It seems this 8414 knows it can’t handle it and does not pass on the bitstream.

 

hello, I wonder what kind of switch I need to replace the input selector, it doesn't seem as a 3pole switch, I am puzzled and need to replace them in a DS Pro Generation V, and a gen II. I found a rare switch, which I might guess maybe, it's the one to use . can`t uplaod it here, it's a 3 position but not 3 pole, it's not an on-off-on, can send image upon request, TIA