Had a lucky timing to grab a McIntosh MSD4 I was casually hunting for the past 5 years (they almost never pop up for sale in Japan without being badly used or having a broken face-plate).

Not the latest generation of DD/DTS decoding by any stretch -- they were selling from 1998 to 2000 -- but a nice fit for a LD-centered 5.1 setup.





Clean modular design that seems to have a separate AC3RF demodulator add-on board as well as a serviceable/upgradable DD/DTS decoding board. This is likely how they added DTS to the previous McIntosh MAC-3 board, keeping everything else identical.





To be tested... when received.

Julien

Very nice! Interesting to see the rear inputs and facia input selector knob labelled as LV?

Typical on McIntosh gears.

From the manual => Laser Video Disc Player (LV)

Julien

Interesting unit. It's actually using the Sample Rate Systems RF Demod board that I acquired some years ago. I had a feeling it was used in some company's processor design and now I know.

I think this model is also marketed as a MAC-3. They appear the same.

As explained above, the McIntosh MAC-3 was DD and was upgraded with DTS for the McIntosh MSD4.

I added the internal pics on each entry.

MAC-3


MSD4


Julien

For some reason I missed that. Thanks for the clarification. Learn something new .

Decoding works just fine!



Must test the audio outputs now.

Was curious to find out which 24-bit DACs are used internally but, even after removing the screws, I can't figure out how to remove the cover.

Julien

All good, smooth sound (still don't know which DACs!).

Both DTS and AC3RF.





Julien

Same RF daughtboard has been confirmed in McIntosh RFD2, McIntosh MAC-3 and McIntosh MSD4. It has the Pioneer demodulating chip like most other designs.

I presume the other McIntosh gears with AC3RF decoding capability around that time were also using it.

I made a wrong assumption that MSD4 just "added DTS" to the MAC-3.

Actually the differences are:

• New decoding daughter board added DTS decoding
• New decoding daughter board added THX Timbre Matching for AC3
• ADC was upgraded from 20-bit to 24-bit
• DACs were upgraded from 20-bit to 24-bit

No need to source the HR034 vintage remote control from McIntosh for the MAC-3 or MSD4.
The updated HR093 will work for both when selecting "Page 9 codes" to be compatible with the HR034.

Julien

After playing with it for a little while (aka "tech torture"), I found this behavior:

• DTS CD => OK
• DTS LD => OK
• AC3RF => OK
• AC3 (from another AC3RF demod) => OK

However, if the decoder is in Stereo Digital mode (Surround = off), then:

• DTS CD => Left and Right channels only
• DTS LD => No sound
• AC3RF => Left and Right channels only (could be a stereo down-mix?)

Julien

That seems odd that DTS LD would mute in stereo mode but be fine for DTS CD; they both should be the same thing. I could understand if it was DTS from a DVD having odd quirks.

As for AC3, that’s pretty normal. All my processors will downmix the 5.1 to stereo when set to two channel mode.

DTS specs are slightly different for CD (1,411kbps) and LD (1,235kbps).
Headers are also slightly different.

Since the decoder is using a custom decoding board, it's possible the behavior is also different.

DTS starts decoding almost instantly, but AC3 has a slight delay before playing.

Julien

Most curious; I’ll have to test this out on my Denon AVR to see if I get similar results.

Let you know when I can

As for the AC3 delay, seems normal to me due to the mute control kicking in when it does.


Follow up......

No issues w/ decoding DTS from LD and CD in stereo or surround when playing back through my Denon AVR-2808CI (fed from Sony SDP-EP9ES and Pioneer CLD-3030). So the issue might simply be a design choice on the McIntosh or programming mistake as this was an early DTS decoder.