Sansui AU-20000 vs AU-9900

[KeithD]

I don't actually know the seller, I just know the person "in the middle" who did the service on the 20000. So all info on the amp I have is from the service guy. My understanding is the seller has mention to the middle person that he wants to sell the amp and has asked him if he is willing to buy it. So, I believe he (middle guy) is thinking about a price to offer the seller. I think the seller is an older gentleman, and I think is very likely to take whatever price the middle guy offers him. So, I suspect the way this will go is the middle guy will buy the amp for whatever he is willing to pay, then will have it for sale in his "shop" at a marked up price. He is frequently buying/selling gear from/to people who come to his "shop", so this is his normal mode of operation as far as I can tell.

Thanks for the further thoughts on the 20000 @Bright_Star , I do enjoy hearing (reading) other people's opinions. It doesn't make the decision for me, but it does help inform my decision.

 

[bolero]

I'd go check it out, if only to satisfy my curiosity & hear one in person. Heck if I had the money I'd love to own one. They are one of the most visually striking Sansui's.

In my dreams I'd be seated on my throne in some castle, while a fire roared, food & wine flowed, and my AU-20000 supplied the music.

 

[Monicker1]

I'd go check it out, if only to satisfy my curiosity & hear one in person. Heck if I had the money I'd love to own one. They are one of the most visually striking Sansui's.

In my dreams I'd be seated on my throne in some castle, while a fire roared, food & wine flowed, and my AU-20000 supplied the music.

It sounds like you would like to open up a members' only lounge somewhere. Tell me. Are there any Gentlemen's Clubs in Magrathea?

 

[bolero]

If anyplace in the universe deserved high end Sansui gear, it would be Magrathea!

Custom made, luxury planets deserve good sound too

 

[KeithD]

I should add that I remember when I looked at the AU-20000 when the guy was servicing it and at least one of the driver boards had a pin connector removed such that wires were directly soldered to the pins. Anyone know if these connectors are available? Standard size?

 

[bolero]

IMO that may not be such a bad thing. I got sick of pulling my AU-7700 apart to reseat & clean connectors, it's probably worse in an AU-20000

Heresy, I know

 

[KeithD]

IMO that may not be such a bad thing. I got sick of pulling my AU-7700 apart to reseat & clean connectors, it's probably worse in an AU-20000

Heresy, I know

It appears all of the connector contacts and pins are gold plated on the 20000, so oxidation should not be an issue. I suppose a pin could loose contact if the mating female connector was completely not making contact. I had an issue on my 9900 where one channel was dropping, and it did turn out to be dirty pin/connector on one plug in board. However, the pins/connectors on the 9900 are not gold plated, so oxidation is likely the issue there. If one is not moving the amp around, I would think internal connections would not be an issue.

The big issue with soldering the wires directly (other than it being non-original) is when you come to service the unit. Sansui wisely designed these to be easily serviceable, and that is ruined when one removes the board connectors. I think this is the work of cheap/inexperienced repair people "solving" a connection issue by just soldering the wires to the boards.

 

[KeithD]

I've been informed of the price on the AU-20000 by the service guy (assume I can't post it here - needs to be in $ & cents forum). He's planning to pick up the amp in the next few days. Should be able to give it a listen once he gets it to his shop.

 

[KeithD]

Coming back to the question of the tone controls, I looked in the AU-20000 manual, and it shows the range in dB that each control is operating at followed by a frequency: Bass ±10dB (30 Hz), Midrange ±5dB (1.5 kHz), Treble ±10dB (20 kHz). How does one interpret the frequency values? For example, for Bass, does the control affect frequencies of 30Hz and lower? For Treble is it 20 kHz and higher? Or is the effect centered on these frequencies and cover a range on either side?

The same values are listed for the 9900 tone controls but in addition the Bass control lists a "turnover frequency" of 150, 300, 600 Hz. Again, I'm wondering if the control affects frequencies of these values and lower depending on the button pushed? My assumption is that is how the controls work because that's what it sounds like it is doing to my ears when I choose difference turnover frequencies on the 9900. Insights or confirmation or a link to an explanation would be appreciated.

 

[bolero]

Good questions I've wondered the same thing. You'd think they'd also mention the slope. Say it's -10dB at 30Hz, what is it at 60Hz? And 100Hz?

 

[CrSens]

On Au-20000 it is the max. amount (rise or cut) and at what frequency, there is no turnover freq listed, or where the slope on the curve starts. Turnover means at what frequency the control slope starts, or it has already some effect. Some controls are "shelving" controls, the curve bumps up at the certain frequency and stays up the same level for all freq up or bellow. It is possible 9900 has such controls (for bass and treble, mid is different), the bump occuring at turnover frequencies. Have to look at reviews of the time or company brochures if they show tone control graphs to be sure.

 

[KeithD]

I guess I should have looked in the 9900 OM, where this explanation is given for the Bass and Treble controls:



If I understand this right, the turnover frequency is the point at which the tone control adjustment takes effect. For Bass it is the selected frequency and below, and Treble is the selected frequency and above. It does still make me curious about the listing at the end of the manual:



Just wondering what is intended by listing Bass adjustment at 30 Hz and Treble at 20 kHz, but maybe as @CrSens suggests, we would need frequency response curves to know for sure. I wonder what the width of affected frequencies is about 1.5 kHz in the Midrange?

As for the 20000, the OM description does not appear very useful:



Since there is no turnover adjustment on the 20000, it seems all one can adjust is the very extremes of the audible range (30 Hz and below, 20 kHz and above?) For anyone who likes to adjust the tone, this seems very limiting.

 

[bolero]

Ah, yes it changes the center freq the knob affects. Makes sense. I did a quick search here on AK too:

150hz/400hz bass turnover switch

I have seen it some what explained but its still mirky to me. Kenwood ka-7300: Bass Turnover switch set to 150hz explained, Bass Turnover switch set to 400hz explained, Thanks for any input.

audiokarma.org

And then the +/- 10dB is the amount the pot will affect, min to max

Graphs would still be useful to see, meanwhile we can just use our ears

 

[Monicker1]

Imagine a perfectly flat line straight frequency response at the 0db level. The frequency turnover for the AU 20000 is probably at 300 Hz for the bass and 4KHz for the treble. At +2 db for the bass, the curve coming down from 1000 Hz (Midrange) is flat, but just starts to bend up at about an octave higher. 600Hz, Sloping to +2db at 300 Hz. And continuing on a gentle slope down to 20Hz. Likewise the - 2db has similar characteristics. Likewise with the treble control the inflection point starts to bend at the point an octave lower than the 4KHz point or at the 2KHz level. I believe the AU20000 uses the middle settings of the frequency selection of the AU-9900 / AU 11000, but don't quote me on that.



Everything is underlined. Don't know how that happened. Anyway higher settings adjustments on the tone controls result in more exaggerated curves.

Picture source is the brochure for the AU 7700 in the discussion of tone setting options available. Note the inflection points on the curve all differ depending on the turnover setting. Sorry for the quality of the picture.

It is kind of hard to explain... especially when everything gets underlined.

 

[Monicker1]

The reference frequencies of the AU 20000 are 300Hz and 4Khz. Midrange also has a reference frequency around 1500Hz but let's not worry about midrange. I am 90% certain these are the frequencies. When you set the bass control to, say +2db, it means that at 300 Hz, the audio signal is 2db boosted. The curve is bi-nodal meaning it has two inflection points - a positive and a negative. At 2 db, the beginning of the modification occurs within an octave upwards of 300Hz. If the bass control is set to +/- 8 for example, the inflection starts at a higher frequency to accommodate the more exaggerated adjustment. Perhaps at around 700Hz. The same type of geometry applies for the treble control. All tone controls are shelving types. Filters use more of a high and low pass configuration which means they do not flatten out at the extremes.

OK Correction. 300 and 4K are the inflection points. At 150Hz and 8K, a 2db setting on the controls changes those frequencies by the set amount. The trouble is, 30Hz and 20KHz are outside the hearing range of nearly all of us. The shelf flattens out to +-10db at those extreme ends. This should be properly explained in the literature. They are vague about it.

 

[KeithD]

Thanks for that explanation @Monicker1 and that figure for an AU-7700. It reminded me that I've seen those curves in other manuals, so looked at the AU-999, which has two turnover points for Bass, Midrange, and Treble. The manual has figures showing the response curves for the two settings on each control:



So, as you stated, the curve starts at a point closer to 1 kHz and then smoothly moves up (or down) for Bass or Treble. When the turnover point is set to a frequency further away from 1 KHz, the curve moves up more gently to the endpoints. Looks lkie the listed Bass and Treble frequencies in the manual (20 Hz and 20 kHz, respectively) are just the points of maximum effect of the tone control, and setting the turnover point just shifts were the tone curve starts the enhancement (decrement) of the sound.

Also have the manual for the AU-777, which has no turnover options (like the AU-20000), and the differences can be seen:



Viewing all of this makes it clear that having turnover options give more versatility for "shaping" the sound. I guess it's just one small step closer to having a true multi-band equalizer.

 

[Monicker1]

Sometimes, with technical products invented and developed in foreign countries, documentation comes to us through translation which is vague, imprecise or just plain wrong. We see this with owner's manuals written today in Chinese and loosely translated to English. I think the owner's operation manuals were written at a simplistic level which avoided proper explanations and descriptions of the product. This was also true in the 60s 70s etc. with Sansui equipment which was conceived by the Japanese. Subtlety and nuance get lost in translation.

As for the width of the midrange, I am again guessing the AU-20000 is similar to the AU-7700 which was the prototype for this entire generation of amps.
You can see it is pretty wide, peaking at the set 1500Hz but extending down to 100Hz at the low extreme and up to nearly 10KHz at the upper end of the spectrum - which is in effect almost the entire audio range. Perhaps the AU-20000 has a tighter notch.



I hope this helps. Again sorry for the poor resolution.

 

[bolero]

Yeah those graphs are perfect. I have seen them in the manuals, just forgot about it lol

Thanks!!

 

[KeithD]

As for the width of the midrange, I am again guessing the AU-20000 is similar to the AU-7700 which was the prototype for this entire generation of amps.

Unclear to me why you say the AU-7700 was the "prototype" for the AU-9900/11000/20000. The 7700 has no boards in common with any of the professional series amps. Internal layout and components used are completely different. If you follow Sansui's progression in the solid state integrated amps, for TOTL of the AU series, the progression seems to be 777, 999, 9500, 7700, 7900, 717, 919. Agree the 7700 shares many of the functions of the professional series, but internally they are quite different. It seems to me the "Professional" and "Definition" series were Sansui's attempt at "upping their game" to a higher level.

Unfortunately, the resolution of your image is too low to be readable. What is the source of that image? I'm not seeing it in the owner's or service manuals.

 

[bolero]

I might be the person who stated that claim. If you read the Sansui promo material for the 7700 it is clear they were excited about developing a new generation of amplifer, and stated such in the marketing material. It predates that whole generation of amps, and they all have similar specs and sound signature.

If you compare 7700 & 9900 schematics, they are very similar, in an evolutionary way:

phono preamp boards:
F-2092 7700
F-2570 9900: looks like it has an extra gain stage, but uses the same architecture as the 7700


tone control boards
F-2095 7700
F-2574 9900
Again very similar, same 2sc1313 transistors, probably a more advanced circuit in the 9900

Preamps & tone controls both use 2sc1313, 2sa726 transistors liberally throughout


power amp sections are
F-2097 7700
F-2580 9900

The architecture is nearly identical, even though different transistors are used.

The 9900 has it's final pairs of transistors on extra boards F-2581 while the 7700 has those included on the F-2097 board. F-2581 boards have a slightly different, probably more evolved circuit.

The 9900 & 11000 share the same service manual, so they are basically the same circuits.