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The Sansui sweep tube siblings

Pio1980

Pio1980

AK Member
For no particular reason, the 25E5 powered models SM-80 and the 1000 are the only Sansui recievers I own/ ever owned. The 80 is a recent arrival out of a local barn and is reasonably complete and restorable. How desirable/collectable are these considered to be?

I've added an internal pic of the 1000 as the FM front end differs from the example at the historical Sansui site, this one being nearly identical to that of the SM80 and the other a modular "add-on" at the end of the MW/BCB AM tuner. The tuners' IFs are also differently laid out, mine again is nearly identical to the SM-80.
http://www.tube-amps.net/Sansui_Tube_Era_Products.htm
 

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Love that sparkly stuff on the larger receiver! What is the second variable capacitor for, AM?

I have no idea about its desireability, but it's great to see some tubes here on the forum. I would love to hear them, since I know Sansui got its audio origins in tubes and that their transformers are legendary. Are you into tubes, good sir?

Collin
 
noveltone said:
Love that sparkly stuff on the larger receiver! What is the second variable capacitor for, AM?

-snip-
Collin
Click to expand...

There is a second independent BCB/MW tuner on the left side. The SM-80 is a "simulcast" stereo reciever, simulcast stereo pre-dated the standardization of multiplex stereo FM. It was designed to recieve two stereo channels being simultaneously broadcast (simulcast) on an AM BCB/MW station and an FM station, 2 BCB/MW AM stations, an AM BCB/MW station and a short-wave broadcast station, or FM via an outboard add-on multiplex FM stereo adapter. It is somewhat complicated to get the switching order right to achieve the desired result.

The 1000 dispensed with all the simulcast capabilities and SW reception for an internal hand-wired FM multiplex unit. Otherwise it is technically nearly identical. The styling was changed from what I'd call the "International/Continental" styling to the American styling and the size reduced to something more like the U.S made recievers.

I do like good tube gear but generally prefer the stable reliability of good S/S. My phono pre is homebrewed tube however, I have yet to hear an S/S unit that comes close.
 
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Hi there, cool looking Sansui's!:thmbsp: I have a Sansui SM18 tube receiver which has the same styling as your SM-80 but just down scaled. I would like to add some more tube sui's to my collection, but finding them in this neck of the woods are like hens teeth! You certainly have a couple of treasures there. :)

Cheers
Glen
 
I have both working now to some extent, the SM-80 much better than the 1000. I doubt the '80 has been powered up for at least the last 20 yrs or more, it needed 3 tubes, a resistor, and a mica cap to restore all the tuner and audio functions. Interesting that the original e'lytics and coupling/blocking/bypass caps seem to be fine otherwise. Still haven't checked it on phono but it rocked the house thru the baby AR check-out speakers on "Who's Next" CD thru "AUX" in.
The FM and audio on the 1000 still has problems, dunno if I have the resources to solve the radio problems. The audio is a tonal imbalance between channels in the pre-amp ckt. That should be find-able.
 
Pio1980 said:
My phono pre is homebrewed tube however, I have yet to hear an S/S unit that comes close.
Click to expand...

Would you care to share your design and fabrication of this amp? I would be pretty interested in this as a first tube diy project. Also I am making a Pass Pearl Phono Stage (solid state) and it would be fun to compare. Thanks for your consideration.

Collin
 
It's based on the Dynaco PAS, with a different line stage. The PAS is a 12AX7 2-stage phono preamp with RIAA comp in the global NFB, followed by a 12AX7 2-stage line amp with the tone controls in it's global NFB loop. The mods/upgrades usually reconfigure the phono RIAA NFB, upgrade parts, and fiddle with component values as well as voltages. The line stage mods generally dispense with tone controls and can be anything from the upgraded stock set-up without the tone controls to a pair of dual triode based cath followers, or a single dual triode cath follower buffer for both channels, or a totem pole SEPP line stage. My present unit uses a fiddled and upgraded Dyna based RIAA phono section followed by a totem pole SEPP line driver.
Frank Van Alstine and others do some very fine & economical Dyna mods, Joe Curcio "The Dynaco Doc", does more extensive mods with drop-in boards in graduated states of completeness. The basic 12AX7 global RIAA phono front end is a big-bang-for-the-buck approach, followed by the line stage approach of choice. It was probably the most widely used approach for a mag cart phono stage in it's era.
 
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Pio1980, I just saw this thread, linked to from the tube forum. I have the 1000 just like yours, but haven't recapped it yet. I WISH I had a SM-80, those things just look so cool on the inside, especially the potted transformers. :yes: You're fortunate, having both, congrats. :thmbsp: BTW, if I understood right on one of the sites, the transformers on these 2 units are essentially the same, but they just stopped potting them. Do you know if that's true, or do you think there's any noticable difference in their sound? Thanks. :smoke:
 
I can't say for certain about the output xformers but I'd think that they were ident except for packaging. The schematics show identical implementation.
The output ckts differ apparently due to safety margin considerations. The SM-80 has 400k grid resistors, the 100 250k. This reduces the likelihood of a 25E5 with slight grid emission causing run-away and destruction of the OPT and possibly the PS iron as well.
Otherwise I'd expect them to sound substantially similar when rebuilt/recapped. They both have bad cathode baypass e'lytics in the audio stages, the 1000 recapped. I've apparently had the '1000 for at least 15 years and did extensive work in it in the past that I barely recall, the SM-80 is somewhat cosmetically grungy but otherwise basically complete and original except for the resistor and mica cap previously mentioned. I'm tempted to leave it as-is as a un-used but restorable example and put effort into getting the 1000 fully refurbed, except I cannot do FM sweep alignments and that whole section needs it to do multiplex again.
These units presently reside in the "someday" dept as does a bunch of other stuff, tube and otherwise.
Another post coming onto a pair of forgotten Kenwood twins that also re-appeared in that storage bldg. Funny I still can't find the Heathkit AA-100 that urged the search and discovery of the tube Japanese receivers.
 
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This is very interesting, & I'll watch for your thread on the Kenwoods. :yes: I have a Fisher 600 receiver that uses that "simulcast" setup, & it doesn't sound bad at all, using just the FM in mono. I've never tried it with an MPX adapter yet, but I have an Eico MX-99 now, so I'll have to give that a try sometime soon. :yes: I've used the MX-99 with a mono Sherwood tuner, after changing the RCA outputs, so I know it works well. :smoke: Kinda related, I recently got a Sony R2R, that uses SS diodes & input transistors, but otherwise all tubed, & it sounds awesome. The Japanese definitely made some major contributions to the tubed audio world, not just solid state. :yes:
 
noveltone said:
Would you care to share your design and fabrication of this amp? I would be pretty interested in this as a first tube diy project. Also I am making a Pass Pearl Phono Stage (solid state) and it would be fun to compare. Thanks for your consideration.

Collin
Click to expand...
Hi Collin. I saw your post and I'm not sure if you are refering to the amp that I'm planning to build from parts salvaged from a scrap Sansui sm320m. I'm new to AK and I'm not sure how everything works yet. Regards, Joe
 
noveltone said:
Love that sparkly stuff on the larger receiver! What is the second variable capacitor for, AM?

I have no idea about its desireability, but it's great to see some tubes here on the forum. I would love to hear them, since I know Sansui got its audio origins in tubes and that their transformers are legendary. Are you into tubes, good sir?

Collin
Click to expand...
I just finishing up my restoration of my SM-80 receiver. The dual AM tuners was an attempt at AM stereo.
I have one last issue to resolve. One channel sound different from the other, a little thinner.
I’m guessing it’s putting out about 28 watts.
The one good channel really rocks.
Some of the tube sockets are a little loose. I’m still waiting on some tubes, hopefully it will clear up the weak channel.
Finally I am looking for a FM MPX decoder and how to integrate it into the system.
If anyone has some knowledge of how to accomplish this, I would appreciate it
 
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