Back in the day, Sansui was known for their dodgy power designs. They even got called out for the chassis being hot on one of their amps not being separated from mains by Stereo Review, I think. A little trick I use when replacing lamps with LED's is to put 2 of them head to toe with an appropriate dropping resistor when supplied be an AC tap off the xformer. Haven't seen too much in repairing Sansui's. Really enjoyed your video.
I used to own one of these. The el-cheapo build quality (plastic sides, cardboard bottom) was evident in the amount of stray noise and buzz. But, they looked nice and sounded pretty good. The slots in the sides was for a Sansui-specific stereo cabinet where the components slid into.
Makes sense why the filter caps were poo.... Right up against the heatsink almost and if that thing has the tendency to run hot easily, there goes your capacitor life (looked pretty crowded in the area where the main filter caps are, limiting the ventilation some what too)
Strangely the a-80 is one ive never gotten.generally there hard to get for a great price.the blacks are less common than silvers mostly.i collect sansui.the a-40 is so bare bones its nearly not a amplifier.lol.the a-80 improves upon by adding a op amp servo loop from output for feedback.i love the big eighties look to them.not a fan of hardboard bottom with shielding tape and plastic sides though.after several years of rebuilding them my personal favorite is the au-d5 or d7 do to its high slew rate and build quality.nice video.
Even back in the day Sansui didn't have a great reputation but was considered a cheaper brand. I avoided their products but your analysis now justifies my gut instincts. I have an old Rotel RX-402 and Pioneer SX-6 running still from that era with little maintenance save a vacuuming or two. That said, the Rotel volume switch does need the contacts cleaned. Besides running this ancient gear I now have a Yamaha running a full Polk Audio array of speakers for my home theater setup. Nice content and I'm subscribed to your channel.
The 'Loudness' control was to make up for the fact that at lower volume the tone would drop out and sound too flat. You could turn down the volume and turn up the loudness and still get a reasonably full sound without having to fiddle with the tone controls, the downside was that at higher volume it would add distortion or 'over saturate' the speakers so you had to turn off the loudness. Not everyone used them unless they were forced to listen at low levels all the time.
Si amigo, he reparado los tres, el A-40 el A-60 y el A-80 y son bonitos en apariencia, pero Sansui tiene otros amplificadores mucho mejor que estos, no se escuchan mal, pero lo que usted dice es verdad, ese A-80 para dar la potencia que da, ese disipador es muy pequeño y para sumar mas problemas es para ambos canales, pero a su favor es que son bastantes económicos, nada que ver con la serie AU de Sansui, por compararlo con un AU- 519 la diferencia es abrumadora tanto en sonido como en construcción.
Hey Trevor, Enjoyed all 39 minutes. That Power switch is scary, no other word to describe it. When Sansui went hybrid in early 1980's, the downward spiral began, Ill take a AU 717. Very interesting with correct BIAS and idle current. That Red indicator LED light looked better with your modification.
Also, a higher bias current will have less crossover distortion. Class A amps are fully biased on and they have zero crossover distortion. Like most things in audio, it's a trade off. Do you prefer a little better sound quality, or do you prefer a cooler amp? My mono blocks are biased to 25 watts of pure class A and eat up 300 watts idling (each), but I only listen to music about 3 hr/week. For me it's worth a few more cents/week to have better sound.
@@paulb4661 Nonsense. You think transistors can turn on and off seamlessly and quickly enough, to avoid crossover distortion? It's not going to happen. There is a time lag for transistors to ramp up, thus during switching duty between the positive and negative waveform, A/B amps WILL be susceptible to crossover distortion. The higher the bias current, the less distortion. 99% of A/B amps have piss all for bias current, thus will have considerable crossover distortion. Class B amps aren't even suitable for audio due to the plethora of crossover distortion they make when each transistor turns fully off between the negative half and positive half of the waveform. At 20kHz transistors are switching back and forth 20,000 times/sec. Only class A amps have both transistors fully on at all times, thus have zero crossover distortion. It's called crossover distortion because it happens at the dead spot between the positive and negative swings, when transistors need time to ramp up to full speed. Only class A amps don't have this problem because the receiving transistor at the crossover point is running at full speed. To use a relay race as an analogy: Class B amp Runners would stop and pass the baton. Class A/B amp The baton would be passed off at a walk or a jog (according to the level of bias current). Class A amp The runners would be sprinting side by side and passing the baton back and forth seamlessly without any lag time.
@@gordthor5351 What do you mean both transistors on at all times? Since when does canonical interpretation of class A duty involve more than a single device? Fundamentally different in terms of characteristics, NPN/PNP or P/N channel devices handle respective halves of the precious signal? Or is it a quasi-complementary?
Hello mister! I want to know how names the final tranzistors ,i have one this amplifier and i think the final tranzistors are not the original, please tell me if you want how names the final tranzistors.thank you
If you like to push the amplifier I would not run 4 ohms. The design is lacking in cooling and efficiency so it will run hot if you ask it to do a little work. On my test, the heatsink got quite hot in 90 seconds at 8 ohm load. I'd expect a 4 ohm load to be worse. If you like your music quiet then go for it.
@TrevorsBench hi Trevor! What's your opinion on having a usb fan hooked up to the switched ac outlet. That's how I have my set up , but somewhere in in the past I heard someone said that it was wrong to do it...? Imo, that's almost equal to having the lid off the amp, and just letting my air conditioner do the cooling. I'm a sub. and your opinion rules.
