SDA 2A with vintage Sansui 1000A tube receiver

hifidoctor

Hi Group,


Need some help with a vintage Sansui tube receiver I would like to run with a pair of SRA 2A speaker with inter connects. Can I do this? with no problems.....Sansui is rated at 35 watts into 8 ohms, has output for 4 to16 ohm speakers. Need some help with this before I hook up.


Thanks
Don

F1nut

Your main concern is to make sure the Sansui is common ground. If so, use the 4 ohm tap as the 2A's are 4 ohm nominal.

tonyb

Plus don't be pushing it with that Sansui. The old girl is more than likely in need of some refurbishing. Not the balsiest of their receivers either.

mhardy6647

The 1000A will need to have all of those grey coupling capacitors replaced if they haven't been already.

It is also, as implied above, fairly low powered (pp 7591A for about 25 wpc continuous).

The 1000A, although it has excellent output iron, really isn't a great receiver (although they are attractive in a 1960s way).

DSC_9817 by mhardy6647, on Flickr

EDIT: FYI, if the OP doesn't have docs for the 1000A, they're available at http://www.hifiengine.com/manual_library/sansui/1000a.shtml

westmassguy

The stock 2As will drop well below 4 ohms at certain frequencies. I hope the Sansui has output protection.

tonyb

It was my polite way of saying it's on the lightweight side for pushing those speaks. Plus if the Sansui is still in vintage form, your asking for trouble.

hifidoctor

Hi Everybody,


Thanks for the input. The 1000A has been completely rebuilt by a tube person in Canada. He does a lot of HK tube amplifiers. Here is what he has done on the 1000A


1. New power supply.  All electrolytic caps and diodes are new and very good parts.  The voltage doubler caps are now 560 uF Panasonics instead of the original 200 uF value.  The diodes are the same very quiet ones we use in the Citation II amps.  The filter caps are now an F and T and a JJ with two Nichicons underneath.  Very good caps and the filter capacitance is easily 3-4 times the original value in all spots.  The power resistors are original, but in great shape and all measure right on spec.  The result is an amp with a very black background and very quick transient response.  Bass is pretty stunning.
2. 2. New bias supply.  New diode and all electrolytic caps replaced with very good parts.  Filtering capacitance is much higher than stock.  The small resistors are original, but were good parts and all measure right on spec.  This unit has the more desirable four individual bias pots, one for each tube. 
3. 3. All signal path coupling caps replaced.  There are K40 oil caps on the four output tubes and a mix of nice film caps and small oil caps up front.
4. 4. A number of key signal path resistors are new and all the small electrolytic caps in the unit are new, including the key cathode bypass caps on the preamp tubes which many people forget to replace.
5. 5. I have installed 10 ohm cathode resistors and 274 ohm Dale screen resistors on all four output tubes.  This makes biasing easy, and more importantly it protects those wonderful output transformers in the event of a tube failure.
6. 6. I installed new modern gold plated rca jacks on the two high level inputs at the rear.
7. 7. The two 6AN8 driver tubes are NOS Tungsols, very, very nice tubes.  The outputs are a brand new quad of EH 7591a tubes.   I have rebuilt dozens of 7591 based vintage units and these tubes sound as good as the old Westinghouse or Toshiba 7591 to me.  I have many of the EH tubes out in the field and have never heard of a failure.  They are very tough and sound great.  They are biased perfectly, idling at 15 watts per tube, where they sound great and will last a LONG time.  The amp sounds much better with a perfectly matched and biased set of new output tubes than a mismatched used quad of old ones of various types.   The preamp tubes are the original Japanese 12ax7 and test strong.
8. 8. Of course all switches and pots have been cleaned and work well.  The volume and balance pots are original and of very good quality. This amplifier is dead quiet at idle, even on 99 dB horn speakers.  There is hardly any noise at all, even idling at full volume.  It has 8 and 16 ohm speaker taps.  It will certainly drive a 4 ohm speaker load, but you are probably better off with 6+ ohm speakers with a Sansui 1000a.  The tuner section works very well.  Even the stereo indicator light is working perfectly.  The amp section will easily output over 35 watts/ch which is enough to drive most any reasonable speaker load.  The sound is big and bold. The phono section is transistor based.  It is working well.  That said, I have rebuilt 5 or 6 of these over the years and all but one had a bit of transistor noise at idle.  This one does too.  They use old germanium transistors with no modern equivalent.  I could re-engineer the phono section to work with a modern transistor, but it takes quite a bit of time and it is not easy to work on, and therefore would be expensive.  If the buyer wishes, then I will rebuild the phono section, but it will add at least $100-$150 to the cost as it takes a number of hours to do.  In my opinion, if phono is important to you then you would be better served to buy a small outboard phono preamp and use the tape monitor loop.  This is a fantastic receiver and I will warrant it for one full year.  If you have any problems I will repair it for free provided you ship it to me.  Really, it should be trouble-free for many years.

Thanks
Don

motorstereo

I'm sure he did a great job rebuilding your 1000a and they are nice sounding vintage tubed receivers (I've had a couple of them). But if you try some quality separates on your sda's you'll forget all about trying to use the Sansui on them. Save the Sansui for something that will compliment it nicely like some high efficiency speakers from the same era.