The Halo JC 2

[Peter Nielsen]

Is max level with respect to the speakers or the amplifiers or unity gain of the pre-amplifier?

In the TacT true digital system: All ones in the music data (i.e. 0dB on the CD) means the amp outputs peak power. (It is impossible to go beyond this in a TacT true digital system).

The TCS (Tact room Correction System) preamp has no gain (it's a computer, no analog paths, all digital). 0dB in is 0dB out (however the room correction will of course reduce levels at certain frequencies to compensate for the room - which in practice means that if one frequency needs to be amplified 10dB, it is left at 0dB and other frequencies are muted by -10dB). In any case, the gain is zero. You cannot input more than 0dB and you can't get out more than 0dB. When all bits are one, they are one. It's like trying to fit a larger value than 255 in a 8-bit variable. Impossible.

The power amps are hardcoded at the factory to output full power at 0dB digital input signal. (They ONLY accept digital input signal, either S/PDIF or AES/EBU). Thus, at 0dB in, they will output the max power. There is no way to exceed this, as you cannot exceed 0dB digital level. Computationally impossible.

The power amps are fed with full digital level at all times (to keep full digital resolution regardless of listening level). User volume control is done by lowering/raising the voltage to the amps. Of course full voltage is required to achieve full power output at 0dB input.

The MG20.1 are rated for 500W, the amps are 400W, i.e. below max. recommended speaker power. (However, I do bi-amp with 2x400W, so it is not clear how that translates to Magnepans recommendation in practice).

Peter, now that the JC2 is out why haven't you gone back to running the MG20.1 with a pair of JC1 for two channel stereo?

That's partly a financial decision. The TacT Boz system is nearly impossible to sell, unless I'm willing to sell it really cheap, say below 30% of MSRP (which I of course will not do). Also, the TacT system has several intriguing features, like no need to worry about ADCs or DACs. (D/A conversion is done by computationally transforming the digital signal to pulse witdth without any analog conversions in between. The digital signal drives the PWM directly. The crossovers are of course also digitally implemented).

In my next home I will have a dedicated listening room. Yes, I have been considering the JC2 + a pair of JC1s with the MG20.1s. But when that day comes, it is possible that I go with a pair of Soundlab Majestics and a pair of Classé Omegas just to experience something different.

I will most likely keep the TacT for many years, but the Maggies will be replaced with speakers more suited for theatre use. Maybe three Dynaudio Munro M5 for the front stage... Or possibly JBL Pro Cinema speakers... Another possiblity is a Genelec active speaker system, but that would mean I will have no use for my TacT amps...

Peter

[Chris D]

Peter, you'll have to put me on the list of potential buyers for your Maggies, whenever you do sell!