Sansui AU-11000

A

Andronikos

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New member here, nice to find you all!
I bought an AU11000, it arrived last week. Everything works. Some small noises with the switches suggest cleaning. The real problem is that it is too quiet for its watts, even compared to much weaker amps I have. I need to turn the volume after 12 o'clock to listen normally. This happens with all sources, and also with headphones. The volume is linear, as opposed to the AU11000A model, but this doesn't excuse the problem. I checked all RCA cables, they work fine. And of course it's not on Mute. My speakers are at 6ohms. Any ideas as to what to check? Thanks!
 
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I would start with cleaning all the controls and switches. I have personally had amps and receivers I would have sworn had bad transistors and it was just dirty controls. Tape loop switches are always highly suspect as well as speaker protect relay contacts. Just remember Deoxit D5 for switches and Faderlube F5 for pots. After that its systematic troubleshooting by eliminating the different sections. I can guide you further but need to know what type of test equipment you have.
 
First, watts vs weaker amps, ... not a valid comparison. Many cheaper amps have lots of gain (loud) without the current capacity to back it up. You turn up the Volume knob and it gets loud quickly, by the 12:00 point there's nothing left but distortion. Better quality amplifiers often are designed better and have maybe the same gain available with twice the current and are therefore at the same SPL "volume" at the same point on the Volume knob, but actually have something left above that without distortion. 6Ohms (nominal) shouldn't be a problem either.

If the two channels are equal, I would doubt that there's a serious gain problem within the amplifier as only the power supply is common to both channels, ... it is rare for components to fail on both channels exactly the same. The linear Volume control is a different beast, I have the 11000A in my office and prefer the A version's Volume control.
 
creeve said:
I would start with cleaning all the controls and switches. I have personally had amps and receivers I would have sworn had bad transistors and it was just dirty controls. Tape loop switches are always highly suspect as well as speaker protect relay contacts. Just remember Deoxit D5 for switches and Faderlube F5 for pots. After that its systematic troubleshooting by eliminating the different sections. I can guide you further but need to know what type of test equipment you have.
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Thanks Creeve! Electronics isn't my forte (I'm a musician...) so I gave it to a friend who does this professionally. He's working on it now, he has already cleaned switches. The relay looks fine. Problem persists. He has all the equipment we should need, so please advice.
 
The AU-11000 has a Linear volume control, (as does the AU-9900), meaning that you have to turn it quite a bit more to get a similar volume from an amp with a Logarithmic volume control. Nothing wrong with the amp OR the pre-amp if it behaves in this way. When they released the AU-11000A, (and the AU-9900A), they reverted back to a Logarithmic volume control because some people didn't like the linear effect. :)
 
SaturationPt said:
First, watts vs weaker amps, ... not a valid comparison. Many cheaper amps have lots of gain (loud) without the current capacity to back it up. You turn up the Volume knob and it gets loud quickly, by the 12:00 point there's nothing left but distortion. Better quality amplifiers often are designed better and have maybe the same gain available with twice the current and are therefore at the same SPL "volume" at the same point on the Volume knob, but actually have something left above that without distortion. 6Ohms (nominal) shouldn't be a problem either.

If the two channels are equal, I would doubt that there's a serious gain problem within the amplifier as only the power supply is common to both channels, ... it is rare for components to fail on both channels exactly the same. The linear Volume control is a different beast, I have the 11000A in my office and prefer the A version's Volume control.
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Thanks for the reply
Hyperion said:
The AU-11000 has a Linear volume control, (as does the AU-9900), meaning that you have to turn it quite a bit more to get a similar volume from an amp with a Logarithmic volume control. Nothing wrong with the amp OR the pre-amp if it behaves in this way. When they released the AU-11000A, (and the AU-9900A), they reverted back to a Logarithmic volume control because some people didn't like the linear effect. :)
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I thought that linear is louder at the start than logarithmic. In any case, having to turn the knob at three o'clock to listen properly can't be normal for this amp.
 
Have you tried sending the signal through the tape loop? Not sure if the AU does this but on some older Sansui's the Aux passed through the phono stage. Just something quick to try. What I would have your friend try next is if he has dummy loads and a scope, see if the preamp will drive the amp into clipping at its rated power. I will have to pull a schematic later tonight and take a look. In the mean time have your friend verify b+ voltages at the preamp boards are within spec and your power supply is healthy.
 
I use an AU-11000. The linear volume is not louder upon turning the pot from the start position than the logarithmic. It does not have that ramp up in volume from say 7:00 to the 10:00 position like most other amps.
 
Zekeman said:
I use an AU-11000. The linear volume is not louder upon turning the pot from the start position than the logarithmic. It does not have that ramp up in volume from say 7:00 to the 10:00 position like most other amps.
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That is due to it being a Log ( Audio) taper Pot.
 
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billyz said:
That is due to it being a Log ( Audio) taper Pot.
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Except I don't think the AU-11000 was fitted with a Log volume control as standard.

I am not sure why this confusion has arisen, the way people are explaining the increase of volume with a Linear volume control seems odd to me. :dunno:

I speak as someone who used to own an AU-9900 which definitely had a Linear volume control. :)
 
Take a 1 meg linear taper potentiometer, imagine a dial label that goes from 1-10 . 270 degrees of rotation.

At 1 the control pot will theoretically measure 100k , at 5 it will measure 500k to ground.

Now take 1 meg 10% log or Audio taper pot. At 1 it might measure 100 ohms to ground. At 5 it should measure 100k to ground.

How is it possible for the Audio taper control to bring the volume up faster than the Linear taper pot ?

You can also do a simple experiment. Insert a 1 meg linear pot from the output of your preamp to the input of your power amp. Make the adjustments and record your results.

Then perform the same experiment with a 1 meg audio(Log) taper control pot.

You will quickly discover that the Linear control raises the volume much more rapidly than the Audio taper pot. After 50% of rotation the results become less apparent.
 
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