[Brucemck]

I've had a pretty heavily modded DEQX for a couple of weeks now.  Steve added USB and i2s inputs, a SuperClock, modded the single ended and balanced analog outputs, modded the balanced analog inputs, modded the power supply and internal cabling ... among other things.

It's still burning in, I'm using an old multichannel Sherbourn amp and cheap (almost zip cord quality) interconnects and speaker wire, and haven't even begun the tweaking process.  But even at this very early stage ....

This is an extremely impressive unit, particularly via the USB input (source is FLAC via J River MC12 running at 24/96) and the modded single ended outputs.  It's got tremendous power and impact, coupled with deep black quiets and nuanced tonality.  Imaging is amazing.  Details galore.  Dynamic range that's startling.  Everything I'd hoped for, and a whole lot more.

It's appreciably better than my Meridian 861v4, which is no slouch in the D/A and preamp departments.  It reminds me, a LOT, of the AR Ref2 Mk2 preamp I had a couple of years back, only better. 

The balanced analog inputs are pretty good, but not amazing.  The balanced analog outputs are a lot better, actually pretty nice, but not really close to the single ended analog outputs which are very special indeed.

Thanks Steve.

[richidoo]

It reminds me, a LOT, of the AR Ref2 Mk2 preamp I had a couple of years back, only better. 

Wow, that's saying a lot Bruce. Congrats, nice piece. I hope you enjoy it!

I wish more people understood and appreciated what these processors can do, especially when modded as yours. There is a still a lot of fear about digital processing in purist audio fantasyland. Mostly caused by the proliferation of cheap and lousy sounding processors with $3 opamp output stages and $10 power supplies, but the 32bit DSP gets blamed. A high resolution digital crossover of this level of refinement is far less "harmful to the signal" than any analog filter could ever hope to be, plus it can "think" to figure out your room in seconds.... haha   
Rich

[Brucemck]

I was very positively surprised by the sonics of going to an active digital crossover, even without any room correction.

Used solely as a DAC and preamp Steve's moddes DEQX is terrific, on a par with my 861v4 or AR Ref2 Mk2.  But when you add in the crossover functionality it's really in another league.  (And it's not like it was replacing a weak crossover.  My passive crossover had Mundorf caps, etc. ... all top of the line ... and was very well done.  I thought it sounded impressive before I added the DEQX.  Afterwards I realized what I'd been missing!)

Other than a bit of PEQ for the subs I've barely tapped the room eq functionality of the DEQX.  That'll come later.

[TomS]

Can you share what the active speaker setup is?  Thanks, Tom

[JoshK]

Did you have all the opamps replaced?  That is a lot of work. 

Its funny that you mention that the SE outputs sound better than the XLR's.  I too have both sets on my DEQX but I wasn't really able to compare as the SE outputs created a ground loop with my bass amp at the time so I had to switch to XLR which did the trick. 

I trust that Steve does good work and I was really curious about some of the mods.  However, the price of admission was more than I could afford. 

[Brucemck]

Speakers are line arrays from Selah Audio, with 5" Accutons for mids and Foutek ribbons for the highs:

http://www.audiocircle.com/index.php?topic=43722.0

Amp is currenty an old Sherbourn.  I'm having custom 300B SET amps built by 3d Audio:

http://www.3d-audio.com/

Low end is handled by two Seaton Submersives as a single mono sub:

http://www.websitetoolbox.com/tool/post/seatonsound/vpost?id=1942660

I cross the Accutons to the Founteks at 2k with 96db/octave slopes.  Earlier I tried 3k with 24db slopes.  Both sound good, but there's slightly more detail and speed crossing lower and steeper.

I cross the Accutons to the Submersives at 90hz.  I add 12db/octave to the Accutons, which added to the sealed boxes natural 12db rolloff gives me 24db/octave.  I set the Seatons at 24db/octave to match.

I use Room EQ Wizzard to measure and PEQ the low end.  One Submersive is at the front of the room and centered, the other is on a side wall and is approximately one foot off center.  I found those locations via trial and error using REQ.

Once I get a bit more time I expect to shift the subs from mono mode to stereo subs.  I've got several other subs (two James EMB15s and a Def Tech SuperCube) and a QSC30 PEQ that I'll likely blend in down the line.

[Brucemck]

JoshK ... yes, I did have the op amps replaced.  I had Steve do everything he could think of, other than upgrading the volume control chip which was going to push the unit out by several weeks.

I had a single ended ground loop too, but inserting a Jensen isolation transformer in front of the subs solved it.

[JoshK]

Impressive system you have there. 

[audioengr]

The balanced analog inputs are pretty good, but not amazing.  The balanced analog outputs are a lot better, actually pretty nice, but not really close to the single ended analog outputs which are very special indeed.

Thanks Steve.

I'm really pleased that you like it.  This is what makes it all worthwhile for me.

During this mod, I discovered some things about the balanced output board.  I had seen some strange behavior before on previous mods, but I shrugged it off as bad op-amps, as it seemed to get better when I replaced them.  This time I discovered that the balance board does appear to have some problems in the design I think.  We have reported these to DEQX, but no real debugging feedback yet.  The individual outputs for the balanced board seem to vary in amplitude over frequency, each output being different.  It seems to depend on the tolerance of the capacitors and resistors.  The voltage on the differential pairs is always fine, the same on all outputs.  It also has relatively high DC offset, in the 5-10 mV range.  The voltage variation would not be a problem for a transformer-coupled amplifier, but a direct-coupled amplifier input could have problems with it, such as distortion and clipping.  The DC offset is not good for transformer-coupling either.  Seems like it could be problematic in any situation.  I do not plan to recommend it anymore.  They have a new version that has transformers on it, and is a lot more expensive.

The cable from the main board to the balanced output board is also really cheesey.  I have shortened these in previous mods, but on this one, I developed a new silver-teflon cable to improve the quality.  I guess it wasn't enough to bring it up to the SE outputs.  Oh well.

Thanks again,

Steve N.

[glaesemann]

What model Deqx is this?

[audioengr]

What model Deqx is this?

It is essentially a PDC2.6 w/preamp and balanced output board.  It does not look like a PDC though because it is mounted in a taller chassis along with a linear medical power supply.

Steve N.

[fu_man]

I do not plan to recommend it anymore.  They have a new version that has transformers on it, and is a lot more expensive

Steve,

...are you saying  you no longer  plan to  recommend the DEQX? or the  balanced output ( or  blanaced output mods)?
sorry  I'm lost at the problems  with the  "DC offset..."?

I've been dreaming of a  SB3  - Pacecar - DEQX  combination...  but the crossover solution and  speaker corrections are my first  must haves.  I know a couple of other digital crossover options( mostly  pro gear)   but not without critcisms/ difficulties expounded on this AC forum.
Yours  are the first real  criticisms  I read of  the DEQX so it's got me  reconsidering....
 

[JoshK]

I think Steve was trying to say that he didn't recommend the balanced output option.

[audioengr]

I do not plan to recommend it anymore.  They have a new version that has transformers on it, and is a lot more expensive

Steve,

...are you saying  you no longer  plan to  recommend the DEQX? or the  balanced output ( or  blanaced output mods)?
sorry  I'm lost at the problems  with the  "DC offset..."?

I've been dreaming of a  SB3  - Pacecar - DEQX  combination...  but the crossover solution and  speaker corrections are my first  must haves.  I know a couple of other digital crossover options( mostly  pro gear)   but not without critcisms/ difficulties expounded on this AC forum.
Yours  are the first real  criticisms  I read of  the DEQX so it's got me  reconsidering....
 

I think given the problems with the old balanced board, that anyone considering this should get the newer, more expensive balanced board instead.

The DEQX is still the best-sounding active crossover on the planet, with Empirical Mods of course.  When used as a preamp and DAC, it beats practically everything, even only running 2 channels.  Highly recommended.

Steve N.

[doug s.]

what would the mods cost be for a deqx w/o the preamp, & w/no balanced outs?

thanks,

doug s.

[audioengr]

what would the mods cost be for a deqx w/o the preamp, & w/no balanced outs?

thanks,

doug s.

The costs are approx:

USB interface - $1K
I2S interface (internal) - $1500
Dual op-amp upgrade - $450
Turbomod (~100 caps) - $1500
Coupling cap replacement (Sonicap Plat. or V-Cap Teflon) - $400
Linear Power supply (separate Chassis) - $800

The typical cost for all of the above is around $5500.00

Without the USB interface, around $3500.00

Steve N.

[doug s.]

thanks,  it will probably be a while before this happens.  mebbe my next life...   

doug s.

what would the mods cost be for a deqx w/o the preamp, & w/no balanced outs?

thanks,

doug s.

The costs are approx:

USB interface - $1K
I2S interface (internal) - $1500
Dual op-amp upgrade - $450
Turbomod (~100 caps) - $1500
Coupling cap replacement (Sonicap Plat. or V-Cap Teflon) - $400
Linear Power supply (separate Chassis) - $800

The typical cost for all of the above is around $5500.00

Without the USB interface, around $3500.00

Steve N.

[Brucemck]

Worth every penny.  An amazing audiophile toy.

[doug s.]

for ~$1k, i might be interested.  otherwise, i think it's ok as-is, & my dollars would be better spent elsewhere.  like losing my hearing on another vintage ducati?   

doug s.

Worth every penny.  An amazing audiophile toy.