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  #1  
Old 10-14-2009, 09:52 PM
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Sansui b-2101, any thoughts?

Have a chance to buy a Sansui b-2101 power amp for $150. The seller says it great cosmetic and working condition. Anyone have experience with this amp and/or opinions.

Thanks!
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Old 10-14-2009, 10:11 PM
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Looks pretty beefy. I say BUY.
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Old 10-14-2009, 10:47 PM
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I have been looking for just a power amp to bi-amp my speakers someday. Don't know much about early to mid 80's Sansui. I also have an old Nakamichi pre-amp, somewhere, from around that same era. May make for a good second system.
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Old 10-14-2009, 10:57 PM
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Not my ad, and no affiliation:
http://www.canuckaudiomart.com/detai...mp_with_issues
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Yamaha NS-670, NS-690II, NS690III, T-80, T-70, M-50, C-50, CD-S700
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Bozak MB80
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Old 10-14-2009, 11:16 PM
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Thanks for the info. It does look like it has some beef! What one would expect from a vintage Sansui! I am going to check it out tomorrow morning. He also has a Realistic STA-2290 for $80. Don't really want that as I'm sure I wouldn't use it.
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Old 10-15-2009, 12:25 AM
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Robisme Robisme is offline
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I have a B-2102. Same amp with different front.

The build is not the best, but it sounds wonderful.

That is a reasonable price. The matching preamps are part of the great sound.





Rob
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Old 10-15-2009, 02:17 AM
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Thanks for the info. Rob and that's a nice looking rig! I'm sure it sounds as good as it looks. I'm a bit cautious as he said he "restores" vintage gear but had the model number and power rating wrong in his ad. He also said he sometimes paints vintage gear to make them look better! Needless to say, my expectations are not very high. The good thing is it will be easy to say no as I really have no use for it at this time. It is just hard for me to pass up local quality gear as it rarely shows up where I live.
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Old 10-15-2009, 04:03 AM
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Arrow The B-2101 is bridged and will effectively drive 16 ohm speakers.

I remember when Sansui's series of "X-Balanced" amplifiers first appeared, the B-2101 being one of them. The service manuals to both the B-2101 amplifier and C-2101 pre-amplifier are available currently online at HiFiEngine.

The Sansui B-2101 is a _bridged_ amplifier. There are actually four (4) amplifiers on the chassis. The black speaker terminals are very deceiving because in reality they should all be RED as all the speaker terminals are hot with none of them being grounded.

On the downside this amplifier will most likely have trouble being stable into a four (4) ohm load and possible problems with any speaker that is not really a true eight (8) ohm load i.e. eight (8) ohm "compatible" speakers that are actually contain six (6) ohm drivers and/or have dramatic impedance drops at various frequency points.

On the up side, this amplifier should able to effectively develop high amounts of voltage and thus power into a sixteen (16) ohm load. Just last week I was inspecting the internals of this very amplifier and then studying the service manual / schematic to identify a mystery impedance switch that appears on the back panel.

This switch allows the selection, albeit unknowingly to the average end user, of different voltage taps on the secondary, yes, the secondary of the power transformer. In four (4) - eight (8) ohm mode, the secondary is fifty (50) volts, in eight (8) - sixteen (16) ohm mode, the secondary is fifty-nine (59) volts. This coupled with the fact that four (4) not just two (2) amplifiers are having their rail voltages changed will have a dramatic effect on total output power. This switch is found on service manual numbered page fourteen (14) on the secondary of the power transformer as oS2a and oS2b.

Another interesting, novel item and rarely seen, at least to me anyway, is the fact that the front panel volume controls are not pot controls, but rather are ten (10) position switches, selecting different fixed resistors to change input gain, seen in the service manual, numbered schematic page thirteen (13) in the upper left hand corner. Pot controls can be a problematic on several different grounds and in this case, the problems are all effectively eliminated.

I believe this amplifier should be able to bring [inexpensive] enjoyment to high impedance speakers that many people including myself could not find a suitably high enough voltage - power amplifier to drive, other than very old tube amplifiers with their tapped output transformers, the most expensive and powerful of which typically are fifty (50) to seventy (70) watts per channel, OTL Futterman high end designs old and new aside, all of which are expensive to exceedingly expensive and fragile compared to this amplifer. Yes, I have have experienced tube based output secondary transformer failures several times, much to my dismay.

In the past, more than two (2) decades ago I had four (4) General Electric woofers with a twenty (20) ohm DC coil resistance that I really liked, but could not drive to sufficient power levels because all the solid state amplifier technology even then, cerca nineteen eighty three (1983) continuing until now are optimized for low impedance loads i.e. eight (8) ohms and lower.

In short, if my guess is correct, this amplifier should be able to achieve at it's full rated output of two hundred (200) watts RMS output per channel into a high impedance sixteen (16) ohm load.
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Old 10-15-2009, 06:00 AM
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Quote:
Originally Posted by Jenkster View Post
Have a chance to buy a Sansui b-2101 power amp for $150. The seller says it great cosmetic and working condition. Anyone have experience with this amp and/or opinions.

Thanks!
I have one of these which I am currently restoring and it is second only to the top of the line and rare B-2301 which you never get to see

It is a much better amp than earlier amps such as the BA series. The technology in it is superior and the semiconductor devices are much better than previous amplifiers.

You will most likely need to replace the filter capacitors as these usually leak electrolyte.
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  #10  
Old 10-15-2009, 06:09 AM
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Quote:
Originally Posted by cbottorff View Post

In short, if my guess is correct, this amplifier should be able to achieve at it's full rated output of two hundred (200) watts RMS output per channel into a high impedance sixteen (16) ohm load.
This is not true. The B-2101 is rated to deliver 200 watts continuously into 8 ohms and it has IHF dynamic power rating of 600 watts into 2 ohms. It is switchable for 4 ohm operation which should make it OK for hard to drive speakers such as the Infinities. The output stage use 8 output devices per channel and because it is a bridged output stage configuration each output device only sees half the voltage compared to a split rail output stage configuration.

I use a Harman Kardon PA2400 amp which is switchable between 8 and 4 ohms and it quite happily drives my Infinity RS4.5's in the 4 ohm setting


Last edited by rabbit; 10-15-2009 at 06:48 AM.
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  #11  
Old 10-15-2009, 01:56 PM
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Well I bought it for $80. It's in very good condition cosmetically save for the rattle can paint job on the top cover. Actually it doesn't look too bad. The face plate and rear are very clean, binding posts in excellent condition. The meters work as they should and it sounds great! He hooked a CD player directly to the inputs as it has level controls for both channels. He played them through some baby Advents which was cool. Not the way I would hook it up but it worked. I look forward to putting it though its paces over the weekend. Curious to see how it will drive the big JBL 4430's. I will post pictures tonight if I have time.

Thanks to everyone of your input!
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  #12  
Old 01-03-2013, 03:32 AM
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Thumbs up B-2101 & B-2102 similiar but not the same...

Just for a bit of clarification if anyone reads these old threads. The B-2101 amp and C-2101 preamp are not the same internally as the B-2102 and C-2102. They are similar but not the same.
The 2101 Series is not as built proof or as hardy as the 2102. I own 3/ 2101's and 2/ 2102's and I am intimately familiar with their internal parts and processes and only say that because I thought I had the service manual for the 2102 and I needed the service manual because they are not the same. I can't find that service manual and the ones on line say they are for the B2102 but the one's I have found are for the B02101's

If anyone has one or any updates to service manuals, anything at all... if you could please post it it would be greatly appreciated or drop me a note. I post everything I can find because as these things get older information becomes more and more scarce and it has on a couple of occasions had problems that have taken a year to figure out. One i just figure out and I finally took it to the shop and the tech charged me $450 to fix it and he didn't even replace the caps that had obviously boiled out.

To say I wasn't happy...

Thanks to everyone that posts to help your fellow audio geek seeing it keeps this great old gear State of the Art Equipment from the Golden Era of Analog to today.
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  #13  
Old 01-03-2013, 08:04 AM
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Quote:
Originally Posted by mpowered View Post
Just for a bit of clarification if anyone reads these old threads. The B-2101 amp and C-2101 preamp are not the same internally as the B-2102 and C-2102. They are similar but not the same.
The 2101 Series is not as built proof or as hardy as the 2102. I own 3/ 2101's and 2/ 2102's and I am intimately familiar with their internal parts and processes and only say that because I thought I had the service manual for the 2102 and I needed the service manual because they are not the same. I can't find that service manual and the ones on line say they are for the B2102 but the one's I have found are for the B02101's

If anyone has one or any updates to service manuals, anything at all... if you could please post it it would be greatly appreciated or drop me a note. I post everything I can find because as these things get older information becomes more and more scarce and it has on a couple of occasions had problems that have taken a year to figure out. One i just figure out and I finally took it to the shop and the tech charged me $450 to fix it and he didn't even replace the caps that had obviously boiled out.

To say I wasn't happy...

Thanks to everyone that posts to help your fellow audio geek seeing it keeps this great old gear State of the Art Equipment from the Golden Era of Analog to today.
You should have checked our database
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  #14  
Old 01-03-2013, 10:38 PM
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I had the B-2101 and C-2101 since new and they have worked very good with no problems
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  #15  
Old 01-26-2013, 12:04 PM
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These are great undervalued amps IMO. And wascley wabbit is right,these amps are designed to handle low impedance loads down to 2 ohm,it was actually included in selling lit back in the day.Tremendous amount of headroom,detailed,fast and lotsa "oomph" to the sound. Different certainly to the old BA series but still a wonderful piece of Sansui design,and though there are nods to the cost cutting in effect,as it was for all Japanese manufacturers heading into the plastic late 80-90's with plastic in places where it twern't before,the deisgn folks ignored that contraint and built it like it still mattered how it would perform.And perform it does,enjoy it,200 watts don't come much cheaper(or a whole lot better).
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