I have two vintage Sansui receivers that I am looking to use as a pre and power amp.

Hello,

I'm looking at using my Sansui AU-717 as a pre-amp (because I might like the phono section a little more) while connecting it to my Sansui G8000 as a power-amp (because it has more power). I am also doing this just for fun lol.

Both of the units have the same goinzas as seen below.



My understanding is they both need to be set to separated (2) capacitor coupled.

I would run standard RCA cables from the pre-amp out of the AU-717 to the power amp in of the G8000? The speakers would be connected to the G8000 (power amp)? Does this sound right?

A few random questions.

Would all the tone controls and volume of the G8000 be bypassed and all controls are active only on the AU-717?

Any other traps to look out for?

Any specific order they should be powered up and down?

 

Yes, it will work as you think
You could try direct coupled ... might be better
Run good cables, not just standard ones
All controls of the G8000 are in the preamp and will be bypassed
I also use my Pioneer SX1250 as a power amp only (but I use a real preamp in front)
No specific order to power them up

Have fun!

 

Thanks I do have these RCA cables coming. Should be good enough eh? I have no problem upgrading if you think it's beneficial. I got ~6ft to be safe as I'm low on options in my rack....I my reduce to 3ft if it will work.

https://www.amazon.com/gp/product/B073GTXFCZ/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1

I did some reading and I couldn't really grasp the concept but my takeaway was direct coupled MIGHT be SLIGHTLY better but could create some issues.....where capacitor coupled was "safer". I have no idea what the were getting at though. I'm running a pair of JBL 4412s or a pair of Infinity WTLCs.

 

The manual says either way:
-C coupled filters out DC
-direct does not but it will be detected and the protection circuitry will shut the amp down

 

Be careful. I almost blew out my speakers doing something like this. Make sure you're not somehow running from a "line" out rather than a true pre-amp.

 

Just try what sounds better, direct or cap coupled
Can’t imagine what should not be safe, preamp voltage is max 2Volt or around there
The caps are there to prevent external disturbances (I think)
You might hear the kitchen mixer

The cables look okay, later comes the question if something shall be improved
Then maybe silver cables come into the game

 

Thanks! Can you elaborate on this for dummies? I'm running the two receivers mentioned with LBL 4412 or Infinity WTLC speakers. The source is either a Denon turntable or streaming tdal via a DAC.

 

Thanks. I'm only using the gonizas in the picture I linked so it should be good eh?

 

What cables would you recommend out of curiosity? If this works out well it could be my permanent set up for awhile so I'm OK spending a little within reason....

 

No recommendation at the moment, try it out for a month or two
If you then would like to have more details or better treble, we discuss
If you are happy, you are happy
I am not on the cable hype train, most are absolutely overpriced
A better cartridge might be the better investment- or a CD Player

 

I looked at the manual and service manual schematic.
When C coupled caps are switched in series with the signal to filter DC

When direct no caps so DC could leak thru and be amplified to the speakers, but the amp has a circuit that senses this and shuts the amp down to protect the speakers.

I looked at the pre out and is direct, no filter caps.

I would use the C coupled to be safe, it should only affect freq below 20 Hz

the source does not matter

 

Here is the schematic section for the input selection mode.
Input signal on the left (pre out) and output on the right (amp in)
Top is right ch, bottom is left ch

I ran the HP RC filter thru a calculator.
Its cutoff < 1 Hz, no reason NOT to use the C coupled imho.

cutoff = 1/(2 Pi R C) Hz

 

Thanks!

 

Power supply leakage, bad filter capacitor, incorrect bias, several different sources

 

Yaya all good haha
Basically everything is broken all the time or could be

 

Just don't do any connecting or disconnecting when the G8000 is on, just a touch of the RCA cable on the wrong place and all the power of the amp will go to the speakers putting in danger both (speakers and amp) plus your ears. I will try direct coupling first.

 

Correct, the power amp should be off all the time when changing connections
Statics can be pretty nasty

 

Careful not to let the "coolness" factor of running two vintage beauties color your perception of what sounds better. I deceived myself this way when I started running a Onkyo pre-amp into my Sansui 2000X. When I finally sold the Onkyo and went back to the 2000X on it's own the veil was lifted, lol.

 

Seems you are overlooking the true input load and other factors.

The capacitors are likely not serial, but instead cheap electrolytics back-to-back to become a bipolar cap. Would still have the same value as a single one. Whereas Audio Note will sell you their next tier with snake oil capacitors for $1000 more, here, you can simply not use the capacitor coupled option and avoid any signal degradation.

 

Consider comparing using the one receiver with the phono pre you prefer vs both connected together. My new philosophy is to keep things simple. If the amp section in receiver A works to your liking, super! Then you can sell the other one to buy music!

BTW, I have a Kenwood KA 7100 integrated amp that is DC coupled. Never felt it sounded any different than any other amp I used.

 

the caps are bipolar and in series.
The ones that are not have polarity markings on the schematic. That is a standard convention.

 

You’ll need to ask someone smarter than me. Good luck! I love vintage gear. That’s my setup.

 

I had a Sunfire 300 amp that I ran Direct Coupled from the preamp. I was able to do this since the pre had a blocking cap at its output. There was an improvement in the quality of the bass.

@Oberon313 ,
I agree to use capacitor coupled in your situation for the reasons stated by Ingenieur.
Btw, those are two beautiful amps from the golden age of Japanese electronics.

 

thanks they are awesome amps. I was lucky to get them both from a friend for pretty “cheap”.

I will run cap coupled based on the input here.....but I love bass heavy music (old funk to bass heavy modern pop) so I am interested in the dynamics you mentioned.

I’m struggling to keep up with the technical lingo here.

what is the risk of running direct coupled? Like what is the worst case scenario ?