TACT RCS 2.0 Users Group

I've recently purchased the TACT RCS 2.0 unit. As I've been wrestling with getting the optimum performance out of it, I keep thinking there must be other owners out there that have ideas to share, as well as those who could benefit from what I've learned.

I was hoping this thread would provide a forum to introduce us to each other.

Anyone interested in sharing what you've learned?

I for one have found the unit difficult to get a true grasp of how to optimise, but once learned, it has produced the best sound of any component I've ever added to my system. My system currently consists of a Sony SCD1 to the TACT 2.0 RCS with internal DAC and D/A converter. Signal is then fed from the TACT in analog format to my Art Audio Jota and then to the Avantgarde Duo Hornspeakers.
I'll start by stating I've found the suggestions in the TACT documentation for speaker placement to be contra to good sound. I've gotten the best results by using George Cardas's Near Field logic and using the TACT Nearfield target curve as the beginning point to custom build my personal target curves.

This resulted in a sound stage this is awesome and the clarity of the frequencies is without compare in my experience.

However, it took over 100 hours of experimentation to reach this result - a lot of lessons learned. At this point, I feel I know just enough to be dangerous!
I am really interested in any response to the use of this unit. I have heard that the A/D and D/A section of this unit is not good, and it adds coloration/ hurt the sound. I have read reviews which were favorable, but feel that they may be biased. please enter your personal experience and list of you system. thanks.
I am a big believer in DSP correction. I had the Tact unit in my system for a week comparing it to the Sigtech. I believe that one of the greatest short comings of the Tact unit is insufficient instrumentation power built into the unit to effectively set it up without hours of trial and error. To start with, several of the Tact correction curves have ridiculous bass boosts below 30HZ. But more importantly when I measured the in room response with independent professional real time analysis equipment, what the Tact displayed as the correction curve did not track the measured frequency response. The Sigtech did. By fiddling around and iteratively using the real time equipment to take frequent measurements, I did get a decent correction curve from the Tact although I strongly prefer the Sigtech. However, set up for the Sigtech was accomplished in 2 hours using the supplied Sigtech instrumentation. I’m afraid that most Tact users will not be able to get the optimum performance out of their units due to the challenges of set-up. I believe that Tact should offer additional set-up processing power or a service as does Sigtech. The speakers I use are Dunlavy SC-V’s
I agree completely with PLS1. If Tact would add the ability to run an impulse signal (like the SigTech does) through the filter to see if you get the actual corrected measurements you think you should have, it would allow the user to actually get closer to a desired target through an interative process. Since I have a SigTech as well, I can use it for that purpose but most folks are not going to have that luxury (there is some third party software that can be run from a PC that could serve the purpose)

I also agree that it is nowhere near the SigTech in sound quality. The SigTech does a MUCH BETTER job of presenting an even spectral balance and does a much better job of correcting high frequency anamolies. It just sounds much more like live music through the SigTech. To be fair, however, the Tact cost a lot less. For $3000 for the basic unit, you do get a digital preamp and room correction. If the SigTech did not exist, I could be happy with the Tact because it sure beats not having any room correction at all.

I used to think the SigTech user interface for setup was ugly. However, after playng with the Tact (which won't work on my laptop as I can't see the whole screen and there are no scroll bars !!!)I have decided that the SigTech is not so bad after all. It appears to me that the Tact user interface was designed by engineers for engineers and there is a lot of "gobbledygook" that does not need to be there. Maybe the next release of the software will address some of these issues.
I agree that the set-up documentation and proceedure listed in the Tact users guide needs alot of work. I also have the TacT 2.0 DA. I use a Sony 9000ES for a transport through a Harmonic Tech digital coax cable to the Tact. The Tact analog output then goes through my VAC Standard Ltd. Ed. preamp. The VAC PA100/100 tube amp drives Von Sch. VR5's.

I've tried various eq. curves with different room correction tests. The sound changes with each time I perform a correction session. I'm not even sure I've done the proceedure correctly. I'm sure that if I spend another 20-50hrs. I would be able to improve further on the sound, which right now is the best I've ever heard from my speakers. Before I bought the Tact I was considering buying a different kind of speaker to get the sound I wanted, but now I feel with enough tweeking I may be able to dial them in!
I have had a Tact 2.0 for about 6 months. All told, it has been a wonderful addition to my system. I can't bear to listen the system without the Tact running (and I thought my system sounded great BEFORE the Tact). The associated computer software for the Tact leaves much to be desired -- it's not even friendly to engineers such as myself with training in digital signal processing. I also wish that it were possible to do a post-compensation check of the equalized response. I also wish that the output format allowed for 24/96 given a 16/44.1 input... the scaling applied to the compensation filters appears to be overly conservative and can cause several bits of resolution loss (the scaling is why one has to back off the gain of the "bypassed" signal in order to level match a compensation channel with a bypassed channel). All in all, I think it's a breakthrough product for $3K, and it is real and here today, as opposed to other perpetually promised technologies. The other piece of hope is that Tact continues to refine the product through additional software releases. The application software running in the Tact box is downloadable from the PC that runs the compensation filter, so there may be potential for continued product improvement. Sure wish they'd fix their web site though...
I've had an RCS 2.0 for about 8 months, and have found it
to be the biggest improvement in my system of ANY component.
Maybe the A/D and D/A converters are not of Levinson 360S
quality, however I think they're decent, and the overall
improvement in sound is astounding. One problem with the
SigTech as I understand it is that you need a sound engineer
to come to your room with a signal generator and associated
equipment to obtain optimal results. That can get expensive.
At least with the TacT, I can do a measurement/adjustment in
a few minutes on my own.
Concerning speaker placement with the Tact... I also tried following their advice concerning moving the speakers towards the back wall for increased room coupling. I have full-range reflex-loaded speakers (PSB Stratus Gold-i), and found that getting close to the wall is counterproductive: even after compensation by the Tact there's too much residual room boom. (The configuration of my room doesn't permit me to go wider with the speakers, so I can't comment on that). I've found I obtain the best result by starting with speakers in the position that gives the best sound *unprocessed*, and then using the Tact to do the room compensation.
I'm considering getting a Tact 2.0 so that I can put speakers in a bookshelf and still get good sound. Currently I have Audio Physic Virgos in the middle of the room and I can't stand the clutter anymore.

Am I being too optimistic that with good bookshelf monitors and a subwoofer plus the Tact that I can get really good sound?

Also, any other opinions about what is the best DSP out there - Sigtech etc.?

To Boliver@onlineinteriors.com,

If the placement of the bookshelf speakers have a restricted area you can be experimenting with placement, and I assume you are restricted, then I would be cautious about expecting too much.

At this point in my "Tact Adventure", if I were going to start with the restrictions you've defined, I would be sure to do two things:
1. Learn how to build a lot of custom target curves. Be very conservative in my movement of "frequency control points" and start with the flat Nearfield target curve. It is very easy to overdrive your speakers, and possibly do damage to them.
2. Be sure that the dealer I purchased it from had a clear 30 day refund policy he would honor. If not, buy direct from Tact and be sure they understand your challenge.

However, done correctly and with the investment of experimentation, I would be surprized if you did not experience a pleasant improvement.
To those who have the Sigtech and have directly compared it to the TACT, particularly Pls1, would you please give us a little more detail on what you sonically hear as an improvement in the Sigtech over the TACT? I'd appreciate it. Also, do you own the latest incarnation of the Sigtech, or the original version?

From the postings, it is obvious we all feel the user interface and software toolset needs dramatic improvement. Nice to see I'm not alone on that issue!

It is my understanding, TACT will have an upsampler upgrade available in the near future - this should address 1439bhr's valid comments. I'm hopeful that the upsampler will be executed with elegance. However, it will require a motherboard upgrade as well.

To my knowledge, the price for the full blow Sigtech with correction software, cal. mic, etc. is well over $10K.

For the difference in price between the TACT and the Sigtech, I've been willing to spend my evening hours working to get the Tact to give me the sound I want, albeit an unnecessarily frustrating adventure if the software interface and toolset was properly implemented.

I have the requirement in my thinking about room correction that I must have the ability to personally recalibrate the room and adjust as I change system components (try different tubes, pieces of gear in the signal path, etc.) and not have to call in the Sigtech engineer to do this for me at a cost of $400 a shot, or what ever they want to charge, every time.

I have also found that I personally like to build custom target curves for different types of music, tube sets, and even certain artist. The nine filters in the TACT are nice to have, and I use all nine!

Yeah, I'm a perfectionist who is fascinated with the scientific side of our obsession as much as the actual music. This is an interest that can literally blend the artistic and scientific appreciation elements of each of us. And that is one of the big reasons I'm personally insisting on having the tools under my control, not an outside engineer.

Naturally, this is not an approach for everyone. And I admit, there were moments in my first 100 hours with the TACT that I wished I could remove that facet of my personality! LOL!!
To tao. With the Tact alone you are not in control because the curves that you see do not track the actual in room measurements as measured by a professional impulse based instrument with full MLSSA capabilities. With the SigTech you do. If you want to use the SigTech instrumentation but not their D to A the total cost is about $7500. You can have 4 curves in memory. The Tact was in my system 1 year ago. There was a noticable digital glare when I added it into the system, even in bypass mode. I can't detect any with the Sigtech. I was using a Theta ProGen Va. I currently have the MSB Platinum and the dCS Elgar/972 combo. From looking at the chip sets in both the Sigtech and the Tact there are multiples of raw computing power in the Sigtech. When I finally got it set up, the Tact was a decent DSP but what bothered me is that do DID NOT give the correction that you thought you were getting. If you are as perfectionistic as you say you should really buy a real time analyzer. They aren't that much compared to a lot of high end gear.
For those who purchased the TacT 2.0 more than a few months ago, you may want to make sure you have the current software. It is available as a free download on the TacT site. There are some directions and suggestions for download on Audioasylum.
Sigtech vs. TacT... there's a few things which are not clear to me: Does the Sigtech support 24/96 - if not, can it be upgraded. Does any of the units offer upsampling ?
The Sigtech unit does not yet support 24/96. I just spoke to Sigtech and they are waiting for the dust to settle on the format wars. The do have a 24/96 design. What I do is take to output of the Sigtech and run it into my dCS 972 upsampler and then into the Elgar DAC. My transport and DMX Satellite outputs go to the Sigtech. They recommend that you use outboard A to D and D to A units
Having used the TacT 2.0 for the last year together with the TacT Millenium digital amplifier I must say that I am stunned by the negative comments from PLS1 and Audioguy123. The TacT in my opinion is very easy to use, there are actually only 3 steps in the setup procedure. Furthermore TacT has recently upgraded the software with additional very useful features (at no cost to the users)
With the TacT I have been able to get very excellent results from the very first day, although further experimentation with the target curves certainly can give even better results.
With regards to digital glare I can say that I have heard no such thing. Did you maybe run the volume control to above the O dB level? Anyway in my system the TacT 2.0 is completely transparent.
Over the last year the topic of Tact vs. Sigtech has come up several times. In looking back at my posts on this thread I see that I didn't post here that my experience with the Tact was one year ago which I believe was one major software release ago. From my discussions with others, the glare seems to have been removed and I will certainly eliminate that comment since I have no further first hand info. However, I understand that the setup software is the same so I believe that the problems with correction curves are probably still there.
I have had a full blown TacT (room correction, A/D, D/A, all inputs and outputs)since 1999. I have been very happy with the sound. I lost most of the room reflections and the sound seems "easier" and a lot more musical. I also found I listened at lower levels (I measured the spl).

I still have not totally figured out how to set all the curves I could want. I find the instructions confusing but TacT is willing to stay on to phone to answer questions. I have Maggie 3.5s and TacT say planars and ESLs pose a problem (I'm not sure what that problem could be).

After living with the 2.0 for almost two years I have only one complaint and it is growing into a major issue. The TacT has no record out capabilities. This means that, while I can connect a recording device to the output, I can't adjust volume or presets without altering the recording. TacT has no plans to offer tape loops, etc.
Hey Pearl,
I would not be stunned about negative comments, you'll see that about any great produc. You have to take the good with the bad I guess. Both are superb products that will only get better: the RCS will hopefully be upgraded to the 6 DSP version soon, and the Millennium will be mkIII this summer. But anyway, I also have the 2.0 (1 year) and the Millennium mkII (over 2 years) and was curious if you did extensive transport comparisons and if so what did you end up with? Also what digital cables and speakers are you using?
Does anyone have any info concerning future product upgrades to the Tact 2.0? Wonder how Tact is doing as a company, between their, um, modest website and low-key advertising, I'm wondering if they're going to lose the high ground to other companies (such as Perpetural Technologies) that do a much better job at promoting, yet don't (yet) have the goods to deliver.
Now that I've had the RCS 2.0 in my system for two days, I want to chime in and echo everyone else's enthusiasm. At this early point, it seems to me that the TacT truly dwarfs a lot of other "significant" upgrades I have made. Cables, power cords, PLCs, isolation products, they're all minor league by comparison. I think it is an even bigger upgrade than SACD, though of course SACD is moot in an RCS system. The world needs a great, affordable A-D converter now!

Something I find curious is that many previously bad-sounding recordings are now rendered quite respectable, if not downright excellent. For example, Beth Orton's Central Reservation, one of my favorites of the last few years, always sounded bleached and hazy. Now it sounds most definitely like music, with plenty of tonal color. The improvements in the "poor" recordings are more dramatic than the improvements in the audiophile stuff. Why would that be so? -Dan
Short answer,many "poor" recordings aren't that bad. They just have significant musical info in frequency bands that are distorted by room interactions. It is EXACTLY like removing distortion. As I have said in previous posts, most audiophiles will never really hear the caopabilities of their systems without digital room correction systems.
But why is there not also significant musical info in those same frequency bands on "good" recordings?
Thanks, ever so much. I was hoping to here from an SCD-1 owner who has successful integrated the TACT. As I can't treat my room (Unless I want a divorce), the Tact seems like a logical choice.

Regards, Lorne Cherry
I don't know the recordings you refer to and I can't hear your room but there are several things that COULD be going on. I say could because it would take careful measurement and listening to determine it. The most general reason is that those recordings with the most improvement have sensitive musical info at the frequencies that your room and/or speakers are most "off" combined with placement of those instruments on the left to right soundstage so that the effect of the room interactions are most noticeable. Also, the musical info is not buried in the mix. I will use an example from my situation with a Sigtech and Dunlavy V's. I have asymmetric bass response in several narrow bands starting at 80 and ending around 200hz due to a large Middle Eastern style arched door in the plaster wall. If I listen to a well-recorded string quartet with the cello in its normal position on the right of the sound stage the cello sounds thin and hazy. Reverse the channels and the quartet sound fine. Kick in the Sigtech and it sounds fine. Play a quartet recording with an extra wide soundstage or a tight soundstage and the effect almost goes away. Second possibility, you may have a general rise in response from the lower midrange (room or speaker). Recordings mixed with a similar rise in response (not uncommon with pop and rock) will sound bad. Recordings without the rise will sound OK. Both will sound better with the DSP turned on and correcting for that rise. These are the real effects I've heard and measured. Of course this may have nothing to do with your specific situation. and correcting for that rise.
One simple test is to play the recordings in question in mono or on headphones and note the difference.
Guys, great post and feedback! I've been considering buying a TacT and this is great information. Thanks!
In the Users Group spirit of this topic, let me pose a few questions to those with some experience under their belts. As a new TacT user, I'm bursting with questions.

1. Which of the taget curves have you found most to your liking?

2. Are you finding that the supplied target curves do the job, or have you ended up editing to make one of your own creation?

3. Are there any tricks to the measurement process that users should know about?

4. It's very easy to take a measurement and fit a curve. What do you recommend as the next step or steps to get more out of the system?

5. Do you find you need to re-measure every time you try a new component, such as an interconnect, for example? (I wonder what the TacT can teach us about the nature of component differences.)

I'll stop there. I think a true on-line users group would be an excellent idea.

For any DSP room correction system:

For 5: Remeasure only when things that impact the time behavior or gross frequency behaviours of your system change. That includes new speakers, new pieces of furniture, moving your speakers, moving your furniture, or moving your listening position.

For 4: the answer should be to take a true time domain measurement after each curve fit to see that you actually achieved your desired response but that is the limitation discussed above.

Let me address a few of the questions you raised based on my experience to date with the Tact:

Your questions 1 & 2;
First, as to the Tact supplied target curves - my experience was to throw all of them away except the Near Field (NF) curve. Also, ignore the placement of the speakers that Tact recommends and go with the formula that George Cardas recommends.

Then, using the NF curve, and ideally a NF listening position (measure the distance between your speakers and move your listening position out from the face of the speakers that distance) and begin to make very small incremental changes of just 1/2 db in the frequency areas you feel need modification.

A lot of trial and error is what worked for me. Actually, the target curve I ended up with that sounds the best took very little modification from the NF default curve, but the changes were effective.

Question 3;
I have not found any tricks to the measurement process. I place the mic exactly where the center of my head will be positioned while listening, then have my computer and myself on the floor behind the listening chair.
I have experimented with sitting in the listening position and quickly swinging the mic from where my left ear is to where my right ear is during the measurement cycle, but I did not like the results I got.

Question 4;
Next step to get more out of the system is, IMHO, to have all of us push Tact to release the enhanced software that they said they would in the last issue of Absolute Sound under the Manf. Comments area on the article Robert Green wrote reviewing the Tact with the Sigtech. That plus support for running the software on a laptop in 600x480 res would be nice.

Question 5;
Actually, I have found I do remeasure after changing any element in the system. Now, bare in mind, I'm the Poster Child for the Anil Retentive of North America, but I can see in the measurement graph and hear a difference. In my experience it is worth the extra effort.

I have recently been testing different digital cables and analog interconnects and found it necessary to remeasure and reload the target curves to get the best sound from my system.

In closing, I would like to suggest that each of us begin pushing Tact to satisfy some of the user needs that this thread has brought to light. Collectively we have a lot more clout than any one of us does alone.
One additional suggestion which is a substitute for indpendent measurement. Get a good Mercury Living Presence CD that was recorded in Mono. A stereo recording played in mono won't work because you do't know the actual left right time response. I recommend the Dorati recording of Tchaikovsky's Swan Lake with the Minneapolis Symphony. It doesn't matter if you don't like classical this is a test record. Listen to the last 15 minutes with your eyes closed. If your curves succesfully correct for the room and speaker anomolies, the image should be rock solid between the speakers. If the instruments wander depending on what is playing or how many other instruments are playing, you should check your speaker placement and remeasure. This should work with just about any reasonable target frequency response curve.
I would also recommend that people looking to understand the response of their room try ETF 5.x. Look at http://www.etfacoustic.com/. It is some times simpler (and cheaper) to correct the response this way.
Question 1: I found the TactG1 best suited my taste in terms of the provided target curves. I have a PSB Stratus Gold-i speakers (full range). Other curves would work better for speakers with a more restricted LF response.

Question 2: TactG1 was a good starting place, but what I'm running now is a hybrid of TactG1 and TactF1 (I spliced the HF portion of TactF1 in place of the highend of TactG1), and I tweaked the midrange (500 -1500 Hz) up a bit, with a max rise of about 1 dB at 1 kHz for a bit more presence, and boosted the upper bass / low midrange a a skoche for a tad more warmth and bass oomph. I find the Tact curves just a little too dry (I add ed 0 dB boost at 250 Hz rising to about 2 dB boost at 100 Hz, then smoothly sloping to match target curve at around 50 Hz). I'd be happy to e-mail my target curve to anyone who's interested.

Question 3: Get the house as quiet as possible. I wait until everyone's gone to bed (although St. Bernards snoring in the mudroom carry a long way), turn off the central heat, and wait 'til the refrigerator stops running. Turn up the preamp volume to a LOUD listening level, and use a lot of averaging (I use 20 averages, but 100 would be better -- an effective SNR increase of 7 dB in the measurement).

Question 4: tweak and listen. An experiment I'd like to do is to program a Fletcher-Munson equal loudness curve as a target curve. See, for example,
http://www.sfu.ca/sca/Manuals/ZAAPf/e/equal_loud_cont.html The curve describes the relative power level needed for a sound at any frequency to sound as loud as a
reference tone at 1 kHz. In effective, it's an equalization curve for the "typical" human ear. It shows that at moderate levels (say 80 dB SPL at 1 kHz) significant
boost and buck (a few dB to over 10 dB) of various frequencies is needed for those frequencies to sound as loud as the reference 1 kHz tone. So even though the target
curve is decidely unflat, using this target should result in a systems that SOUNDS flat. By the way, see the Stereophile archives for J. Gordon Holt's article on why "Flat is Bad" (or similar such title).

Question 4, cont'd -- I'm also suspicious that the Tact inverts polarity (am running in DD mode)... I found that with the Tact in the signal chain, my systems sounds a bit more open if I switch on polarity inversion in my preamp (this effect passed the "honey, do you hear this?" A/B blind test). I suppose what I ought to do next time I calibrate is turn polarity inversion on, calibrate, and then turn polarity inversion off and run the system that way as a matter of course.

Question 5: I remeasure every time the room configuration changes. I've found that once I've calibrated the room, even relatively small changes are audible degradations
in sound quality -- a large pile of books on the coffee table for example changes things noticeably. I've changes some components ranging from cables to preamps and not
recalibrated. If these components do not have flat frequency response, then any sonic impact they provide will be (or should be) washed out the next time I recalibrate.
I am in complete agreement with you on the Fletcher-Munson thing, 1439bhr. The high end has eschewed equalization for good reasons, but if Fletcher-Munson is true, we are giving up a lot for the sake of purity of signal. I happen to listen mostly at lower levels. Am I trying for Fletcher-Munson compensation in my choice of components? Could be.

As I understand it, F-M compensation varies by volume. So an F-M target curve for 80 db would be different from one for 70db. Can of worms. If the software could adjust variably for volume, now that would be something!

Which raises another question. Is the volume of the system at the time of TacT measurement something to be concerned with? The TacT literature suggests not, but I wonder. With no preamp in the system (using the TacT as the only preamp), the test signal is pretty freaking loud. Should it be calibrated to normal listening levels (can it be?) or does it not matter?
Drubin, quite right about the F-M curves being indexed by reference SPL level... you'd have to program a set of target curves (no problem-o with TacT's 9 EQ memories). I think what happens in real life is that room gain gives the bass boost which is a key feature of the F-M curve... so even a speaker that measures flat anechoically will approximate a F-M curve. I think a lot of what goes on with system matching (including cable-ology) is an indirect attempt to equalize the system frequency response (to an actual F-M curve? actually, to the actual response of thatindividual's ear)

As far as volume level goes, it affects the SNR of the calibration measurement, so higher volume is better from that standpoint. On the other hand, I could see that loud pulses could start driving an amp and speaker into dynamic compression, which would alter the measured frequency response (the amplitude-compressed pulse would have differenct spectral content than the assumed spectral content of the digitally generated reference pulse). I haven't experimented with this issue; I simply set my preamp gain to what corresponds to a fairly loud listening level.

I've been using the Behringer Ultracurve room correction system with positive results and I am looking to move to the full TACT AA.

However, I have a question about the analog to digital conversion. When using the Ultracurve and feeding it a variable analog in from my prepro, there is a distinct quantization distortion at low volume levels.

This is caused by the low level of the signal the unit receives.

Has anyone found this to be a problem with the TACT?

Does anyone see any drawbacks when using the Tact as a preamp, i.e. sonic degradation? This is a common complaint with other digital preamps, e.g. Wadia 27ix. As a point of reference, I'd be eliminating a BAT VK-50SE.
I assume from your question that you would be using the Tact as a DAC also. The DAC portions of the Tact or the Sigtech are not as good as the best DAC's out there. The combination of a DSP and an MSB Platinum DAC (which I used for the last year) will give you a better sound. Th choice of volume control could be in the preamp or a Z-Systems (which is also an excellent unit).
Actually, I will be using a Tact RCS 2.0 AD with an external DAC (Sonic Frontiers Processor 3). This means that all volume control will be through the Tact. I spoke to Tact yesterday and they said that they add bits so that lowering the volume does not affect things. However, this is also what Wadia says and many owners feel that Wadias sound OPTIMAL over a narrow volume range.
If you can, hang on to your BAT preamp for a while and try it in and out of the system, see what you think.
I plan on hanging on to the BAT until I'm sure the Tact (delivered Weds.) works well in my system. However, keeping both is a pricey propostition when the costs of isolation, interconnect, digital and power cables is factored in.

I'm very happy with my system right now. I have a relatively large room so room interactions may not be hurting my sound. However, I wanted to see what all the hubub on the Tact is about. I'm also a techno dweeb so this is right up my alley.
Has anyone compared other Analog to Digital converters with the Tact on-board unit, e.g. Wadia 150 or dCS? I just bought a unit with the ADC, but want to know if it would be worth upgrading to an outboard ADC since I'll be feeding in a pretty good analog front end.
As per above, I compared the Tact to outboard DAC's and it isn't as good. The digital volume control is best over a limited range. I use a shunt to ground volume control in my monoblocks to allow for setting the output from the digital volume control in the Z-Systems (which has a better digital volume control than the Tact) to its best range.
My question was about ADC not DAC. Thanks.
Comment to Pls1, 031701

Re: Measurement with TacT 2.0 versus MLSSA.

It is absolutely true that the measurement performed and displayed by the 2.0 does not match the response when you measure with other measurement systems. In fact no two measurement systems will concur unless you set all the parameters for the measurements to identical parameters.
When you make in-room measurements there are a number of variables that will influence the measured result:

1. Microphone – is it well calibrated and corrected
2. Gating – how long a window for the measurement
3. What kind of windowing filter, Hamming, Hanning etc.etc
4. What kind of smoothing is applied

The TacT measurement system is designed to be used with the TacT correction system. The measurement uses proprietary frequency dependant gating, windowing filter and smoothing, and the measurement also takes into account the way the sound decays in the room.
It stands to reason that at very low frequencies – where the wavelength is long, it is desirable to correct for all the variation in frequency response imposed by the room while at higher frequencies it can be total nonsense to correct for small variations, simply because the measured results can be completely different if you move the microphone 1”. So the TacT measurement will surely differ a lot from measurements that are designed for steady state response measurements with no regard for what the measurement will be used for.
It fact a lot of the research leading to the TacT Correction systems have gone into the design of a suitable measurement system.
It would have been much easier just to adopt an existing measurement system and use it for correction, and in fact that was what we did in the early trials of RCS, sometimes with reasonable results but more often with rather terrible results.
Re: The comment on number of chips. Yes TacT 2.0 uses 3 very fast 48 Bit DSP’s while the Sigtech uses many more. However the DSP’s used in the Sigtech are ancient designs so it is really irrelevant to compare.
Re: Sigtech versus TacT

In response to comments from a Sigtech owner who have tried the TacT 2.0 without immediate success I would like to explain why the Sigtech owner – initially - is less likely to achieve good results with the TacT 2.0 than other customers.

In no way do we want to belittle the fantastic achievemet made by Sigtech when they brough out their correction system in 1992. However it is important to understand some of the fundamental differences between our products.

The Sigtech approach to correction is to find the speaker position that gives the flattest possible response in the bass region and then apply correction.

The TacT approach to correction is to place the speakers where it is suitable for the utilisation of the living space, and if possible where they produce a lot of bass, and then do correction.

The difference in approach comes from the correction capability of the systems. The Sigtech has a correction resolution of 20 Hz and 50 milliseconds throughout the bandwidth which extends to 20 KHz. The TacT 2.0 has a correction resolution of 2 Hz and 500 milliseconds in the bass region and the correction resolution is then reduced to about 10 Hz in the midrange and further to much less than that at higher frequencies, while the frequency bandwidth extends to 45 KHz.

With the limited resolution of the Sigtech at lower frequencies the correction can not be accurate below 200 Hz. Then one could argue that that is only 1 % of the frequency bandwidth – yes, but that is not how we hear it! 200 Hz and down to 16 Hz is almost 4 octaves – approximately half of the fundamental tones used in music! Furthermore below 200 Hz is where most of the energy is in an average piece of music. Sigtechs´s solution to this problem is to find the position where the speaker system itself will have the best possible frequency response in the region below 250 Hz and then apply correction.

The problem with the Sigtech approach is the following: To achieve a relatively flat response in a listening room in the region below 250 Hz you will have to find a placement of the speakers that randomise the standing waves and pathways of sound from the speaker to the listening position to the greatest possible extent. Unfortunately this also means that the time-coherence is randomised as much as possible. Technically speaking: That the least amount of energy received in the listening position is minimum phase while the greatest amount is non-minimum phase. What is minimum phase and non-minimum phase ? Well it is not so difficult to understand: the signal that has minimum phase in the listening position relative to the speakers own response is the part of the sound that comes directly to the listening position, while the non-minimum phase is the part of the signal that is delayed because it has bounced from a back wall, sidewall etc. ( every time the sound chage direction it also change the phase )
So Sigtech can achieve good results in terms of frequency response throughout the bandwidth if you are very careful placing the speakers where the inherent response is flat already at low frequencies – but the penalty can be a lack of time coherence in the fundamental range of music.

Once the speakers have been placed for flat response – meaning least amount of minimum phase from the speakers / greatest amount of time smear – then the options for correction is limited. Why is that ? Simply because no correction system – even theoretically – can change the way the low frequencies radiate from a speaker box. (without putting DSP power on each drive separately). So once time coherence is lost it can not be re-established.

With TacT correction systems we encourage to experiment a little with speaker placement as well. But now with the intent to find a position of the speakers relative to the listening position that yields the greatest amount of energy from the speakers and then apply correction. That usually means placing the speakers closer to the back wall, and closer to the corners. Yes, that will increase the bass level – but what does that mean ? It means that a greater amount of sound travels directly to the listening position without delay and phase shift, so the time coherence is better. Obviously the frequency response is much worse but that is easily corrected with the TacT system. (The TacT operates with 48 bit internal resolution so any amount of correction can be performed without noise or distortion).
So with the TacT correction units you have the ability to achieve both a good frequency response and a good time coherence. Once you have heard what that does to the palpability to the music you will have little doubt that we are barking up the right tree !

Peter Lyngdorf , TacT Audio.
Mr Lyngdorf is incorrect.

I have both units and have long term experience in this area.

Fact: With the Tact you have no way of knowing what the end result is after correction. When looking at the actual measurements after correction using industry standard mesurement tools (MLSSA, it will be clearly demonstrated that the end result does NOT look like the target curve. Transalated--you are guessing when you pick a target curve.

Doing the exact same thing with the SigTech, you get what you expect---that is, if you tell the SigTech you want a flat response, you get a flat response (that is flat in the sense that the FFT of the time domain is flat).

In addition, the SigTech does NOT require that you place the speakers where you get the flattest bass response. While there may be some benefits to that approach, I can assure you that most of the SigTech installs I am familiar with (hundred of them) have the speakers where, in no particualr order (a)they fit within the rooms decor (b) the optimization between bass response and image depth (usually determined by the distance from the front wall) is considered and (c) customers personal placement preference.

On a more subjective basis, Mr Lyngdorf's comments notwithstanding, I could argue that the bass correction of the Tact sounds worse that the SigTech. I can demonstrate that from about 300Hz up the SigTech give MUCH BETTER response.

All of that said, I would summarize as follows: (a) for a fully function digital preamp with a good D to A converter and the ability to do your own room correction, you pay about $3500. The equivalnet (almost) SigTech (new) cost 3 times that (b) with some care (and some external measurement software) you can get much better sound (MUCH, MUCH, MUCH BETTER)with the Tact than you will EVER get with out one in 98% of the rooms.

While I can (and will) argue that the SigTech is the superior product in terms of sound quality, the Tact beats the pants off of no room correction and in terms of dollars per unit of sonic gain, the Tact wins against the SigTech.
If you can afford a SigTech, get one. If you can't, run, don't walk to your local Tact dealer.
Audioguy123, can you give a general description of the TacT's variation from target correction (which frequencies, how much, etc.) in your experience of measuring it? Thanks.
Drubin--it is not consistent. The one place where it is consistent is in the low end. If you use one of the curves with the boosted base, you actually get flatter base but the problem (as I stated in an ealier post) is that you don't know how much to boost the bass in the target curve (and what slopes to use) to get the correct flat response.

Sorry I can't be more help. There is some stand alone software that you can use with a Tact that by an iterative process you can get the desired result. Try www.ETFacoustics.com.

Now I have been working with the TacT for app. 1½ year, I have some experiences on that product. It seems to me, that especially in the bas the improvement in sound is huge. Besides that it is also improving the general sound in terms of naturalness, coherens between bas, midrange and treble, and the general balance between left and right.

It may be right, that the target curve is not telling you the total truth. And so what? As long as you are able to change the sound temperature by just adjusting the target curve I dont see any problems. Do you really think the right system will actually have a totally flat frequency response? Probably not. Because the system is only performing, what you want to measure. Think of f.x. Mark Levinson, which excellent product do have an equalized bass, even that the frequency curve is very flat. The frequency response is unfortunately only the half truth. Or trying different cables. Different sound, but still the same frequency response. A lot of other things counts.

It is important to notice, that according to my experience it is essential, that the correction is based on the same propriety measurement system, not a external system. It is during the design of the measurement system necessary to select between several solutions, and to decide how to measure what we exactly are hearing, is very, very complicated. A lot of AES-papers can document that. And on this very point, the TacT system is indeed very good. Very good similarities between what is measured and how it will sound. From that point of view it is not important how the resulting target curve will look like. The TacT system is NOT a measurement system, but a sound system.

In short, I find the system very hard to live without, because it - to put simple - solves the interaction problems with my listening room, which I never had solved. It will not do a bad speaker perfect, as it requires a very good and expensive speaker to make it possible to registrate the full benefits. By the way the system is also working very well with dipolar speakers fx MartinLogan Prodigy.

Kim Kruse Petersen, High Fidelity, Denmark
In response to Audioguy 123 on the subject of Sigtech versus TacT, I have to maintain that there is no way the Sigtech with the limited time and frequency resolution can accurately correct for low frequency variations. Then obviously in your case it seems to be desirable to have less correction at lower frequencies. This could be due to some room anomalies that we have not experienced in the many different setups we have made with the 2.0. With regards to the sound quality we have only 3 times heard of customers preferring the Sigtech over the TacT in direct comparison. One of the obstacles we have encountered when selling the 2.0 into studios have been that many studios have tried the Sigtech without success. In every single instance we have demonstrated 2.0 to professionals with previous experience with Sigtech the comments have been hugely in favor of TacT 2.0. Therefore maybe we have become a bit arrogant, just dismissing the Sigtech as old fashioned and obsolete. My apologies for that. But not to the real issue: Anything the Sigtech does the 2.0 can be programmed to do with higher accuracy, except that the Sigtech can correct with higher resolution above 4 KHz – where little or no correction is needed. So when you have a situation where the Sigtech works better in real
life then I would really like to get to the bottom of this. If you send me the measurements for left and right channel made by the 2.0, and also the Mic. Cal. file then I will get some idea. If you like you can
also send the measurements made by your MLSSA measurements system on the Sigtech correction and the TacT correction I will be able to help you get better results. With regards to the TacT not following the measurements made by the MLSSA it is just a question of how the parameters are set on the measurement system. If you tell us how exactly you would like to measure, then we can correct to something that will look flat on that particular set of measurement parameters. I am sure though, that the sound would be worse that when measured with the TacT system.
Please send the measurements to: Lyngdorf@tactaudio.com

Peter Lyngdorf, TacT Audio
Regarding sound quality of the digital volume control in 2.0. How do you actually evaluate the sound quality of a digital volume control? If you use it with an external DA converter and a preamplifier then it is very difficult to say if the changes you hear at lower digital settings are due to the digital volume, the DA converter, the preamplifier or some combination of these units.
At TacT audio we have made extensive listening tests on our digital volume control, and we have a tool which give us much more reliable information about the effect of digital volume: The TacT Millennium digital amplifier.
The TacT is still the only amplifier in the world where the volume control is done at the power supply rails. This means that the actual resolution and signal/noise remains absolutely constant over the upper 40 dB of the operating range of the volume (voltage) control. Therefore we can reliably compare the effect of the digital volume control over a very wide range without altering other parameters. When the 2.0 volume control is tested in this way we have not found that anyone could hear any degradation on a blind testing. Therefore our opinion is that the volume control in 2.0 is extremely good, and certainly in respect to linearity – distortion etc. it is superior to volume controls in analogue preamplifiers. Also we can add that nobody have made any complaints whatsoever in the many reviews on our digital preamplifiers.

Peter Lyngdorf