View Full Version : Tandy PSSJ Low-pass Filter Comparison (TL/2 vs. Sensation!)

January 7th, 2012, 02:39 PM
Here's something that 99.9% of you guys won't have any interest in, but that Dan Tsatsanis asked about in the recent Tandy 2500 RSX thread.

Original WAV:

Asia - "Aqua, Pt. 1" (excerpt) (http://www.symphoniae.com/elw/tandy/Aqua.WAV)

Per Frank Durda IV, and the recorded example and diagram below, a normal PSSJ has a fixed roll-off output filter that attenuates frequencies above ~5 KHz.

Tandy 1000 TL/2:

Asia - "Aqua, Pt. 1" (excerpt) (http://www.symphoniae.com/elw/tandy/Aqua_TL2.WAV)

The first-model Sensation! on the other hand, appears to have a (ridiculous) roll-off value of ~1 KHz.

Tandy Sensation!:

Asia - "Aqua, Pt. 1" (excerpt) (http://www.symphoniae.com/elw/tandy/Aqua_Sensation.WAV)

I'm not entirely positive, but I suspect the additional filtration in the Sensation! is likely due to the built-in telephony functions. That is, that either the PSSJ DAC is being filtered for use with the answering-machine functionality, or that the output from both the PSSJ and modem is multiplexed and then filtered (presumably for the benefit of the latter) into a single "mixer" input.

And yes, the filter affects all PSSJ output, including that of the PSG:

Tandy 1000 TL/2:
Conquests of Camelot - "Gwenhyver" (excerpt) (http://www.symphoniae.com/elw/tandy/Gwenhyver_TL2.WAV)

Tandy Sensation!:
Conquests of Camelot - "Gwenhyver" (excerpt) (http://www.symphoniae.com/elw/tandy/Gwenhyver_Sensation.WAV)

This isn't an effort to make the Sensation! look bad, mind you, since the output from its Yamaha MMA chipset (both DAC and OPL3) sounds fantastic; it's just not an ideal model if you're looking for that classic "Tandy" sound.

January 10th, 2012, 06:06 PM
That is indeed ludicrous! Thanks for the examples.

Dan Tsatsanis
January 11th, 2012, 10:42 AM
Thanks for the comparison.

January 23rd, 2012, 10:23 AM
According to http://groups.google.com/group/comp.sys.tandy/msg/aeebdb7a946608ee?dmode=source the Tandy Sensation! is Adlib Gold compatible. Has anyone tested this? (like, going into a game and selecting Adlib Gold as the sound device to see if it works)

If it does work, I'm curious if it has the great output of the AG, or if the above-mentioned filtering affects it. (I seem to recall the Adlib Gold having very clean noise-free output, but maybe I'm wrong)

January 23rd, 2012, 07:56 PM
I'll have to revisit this, but I recall that detection routines specifically looking for an Ad Lib Gold card would fail, but that anything offering support for the "Gold Sound Standard" worked.

The Yamaha chipset output is - and this is super-scientific - pretty sweet, and not-at-all filtered like the PSSJ output.