Manuals for a Technics SU-G91 amp?

January 6, 2008 3:01 PM

Old-skool AmpFilter: Who can provide links and/or guidance for us to find manuals / technical info for an older Technics amp and 5-CD changer?

Neither AskMeFi nor Google has been of any help.

Specifics: The amp is a Technics SU-G91 New Class A Stereo Integrated Amp. The CD player is a Technics SL-PD845 5-CD changer.

Both components appear to have serial# / manufacture dates of 1993. From the (very) sparse info I was able to locate on the web, Technics was apparently taken over by Panasonic at some point, and neither site has any info on these 2 components that I could locate.

mr. lfr was the beneficiary of a friend's move, and picked up these 2 components. Both appear to be in pristine shape, however it's a little flaky trying to figure out how to set up the amp for surround mode with satellite rears.

I think (I'm not that knowledgeable about All Things A/V) that this system may predate Dolby 5.1 Surround. It does have a Dolby ProLogic button on the front of the amp.

I've tried various google searches and the information on these things is not easy to find. A smattering of forum posts on diy sound forums is about all I could find, and they mainly concerned stuff like how to re-solder leads to the heat sink on damaged amps.

Specifically want to figure out how many channels the amp has, and how many watts per channel - I see some references to 130 wpc, but is this for all channels, or only the front? Don't want to fry the satellites or blow the amp.

A link to a .pdf of an user manual for one or both of these components would be ideal. Failing that, someone who knows where we can find links to (preferably free) schematics online, or can otherwise give insight. I would imagine there's someone on MeFi who knows enough about older rack system componentry to provide assistance.

Thanks AskMeFi!

posted by lonefrontranger to technology (8 answers total)

This place seems to sell the amp manual you want for $30 (ouch). Search on "SUG91".
posted by itchylick at 3:29 PM on January 6, 2008

You can buy a Sams Photofact for the CD Changer by searching on SLPD845, as here. Please deposit another $30.
posted by Wet Spot at 3:38 PM on January 6, 2008

Based on the vintage and your description, you're most likely right that the amp doesn't support true surround sound. The original Dolby ProLogic is basically a reverb effect that does some processing on the stereo audio signal and tries to simulate different room configurations. Dolby ProLogic II is an actual 5.1 surround standard, where instead of stereo there is actually information for all the speakers encoded on the source DVD, and the amp just plays the appropriate channel through the corresponding speaker, which allows for real surround effects like objects passing from front to back, voices from behind you, etc. Personally I like the old ProLogic I a lot less than the perfectly good 2-channel stereo it "enhances", but ymmv.

I wouldn't worry about the watts per channel figure, unless you're looking for bragging rights. Most any modern amplifier has enough headroom to go louder than you'd ever want, and the speakers will start to distort the audio noticeably if you're pushing them too hard. Just make sure the impedance on the speakers is 8 Ohms (8Ω), which is true for almost all speakers sold for the home market, both presently and going back well before 1993. Occasionally you'll run across 4Ω speakers, and if these are what you've got you'll need to make sure the amp can handle them. There might be a label next to the speaker connectors on the back stating what speaker impedances it's compatible with.

For details about the specific models you have, try asking around AVS Forum before shelling out $60 for information about your free, 15 year old equipment.
posted by contraption at 5:02 PM on January 6, 2008

I've always found audiokarma.com to be a wealth of knowledge on most pre-surround sound stuff.
posted by gofargogo at 11:48 PM on January 6, 2008

Specifically want to figure out how many channels the amp has, and how many watts per channel - I see some references to 130 wpc, but is this for all channels, or only the front? Don't want to fry the satellites or blow the amp.

Power rating means virtually nothing. Instead, go by the mass on the unit, or the AC power draw specification printed on the back. These are only guidelines of course, but..

Dolby ProLogic is really a 4 channel standard. The two rear speakers are wired in series, and there is no subwoofer. I've no idea about comparative performance of ProLogic vs. ProLogic II, but I'm skeptical. Dolby Digital is yet another standard beyond either pro logic.

That said, I'm planning to list a whole passel of ~90s consumer electronics service manuals in a rent or buy arrangement on my website. I haven't started listing yet, but it just happens that I have a copy of the service Manual for the SU-G91.

From the manual, the centre output is rated at 15W into 8ohms, and the rear is rated at 10W into 16ohms (8ohms for each of two speakers wired in series). These two channels are actually generated from a stereo chip though, so they are likely identical in actual power output capability. The main left and right channels are rated at 130W each.


Sooner or later I will post an AskMe about the technical issues around listing my service manuals. On the business side, I'm thinking of charging $15 for a manual, and then refunding $10 if the manual is returned within a certain time frame. Perhaps that is too cheap? Any comment or suggestion is welcome!
posted by Chuckles at 12:51 AM on January 7, 2008

thanks Chuckles.

that said, sorry but there's no way we're going to bother paying for manuals for a free, old stereo set like this - it was basically one step from getting freecycled when we took it off the guy's hands. we'll just muddle thru and figure out how to set it up so it sounds ok. Maybe someone on those diy nerd boards who's into fixing up these old components might want to.

the only reason he's bothering to mess with these is that his main speakers were shot, his CD changer was b0rked, and these components also came with 2 (huge, working, nice sounding) Pioneer cabinet speakers.
posted by lonefrontranger at 6:38 AM on January 7, 2008

Sure.. Other than the specifications, a service manual isn't going to give you any of the information you want anyway. It is mostly assembly drawings and schematics, and a few descriptions of what signal should be present at certain points. There is very little information about operation.

My question was about the general issue :)
posted by Chuckles at 8:21 AM on January 7, 2008

And your reply was about the general issue too.. d'oh!
posted by Chuckles at 8:25 AM on January 7, 2008