Author Topic: Sansui-AU 111 revisited  (Read 9880 times)

Offline King_Julian_S

Re: Sansui-AU 111 revisited
« Reply #30 on: July 01, 2015, 11:45:59 AM »
Got it tx and noted
Non audiophile music lover...

Offline Ampdog

Re: Sansui-AU 111 revisited
« Reply #31 on: January 04, 2017, 01:40:49 PM »
Still, Julian, it seems a waste to just leave a front panel switch as a decoration. As said previously, it is quite simple to incorporate the same feature in one of the pre-amp stages, at least giving a real 'presence' feature.

One should not condemn something without leaving an alternative. Thus, after a few - mmmm, days - I have now done the necessary!

Reading up, I found that for some 'Presence' alludes to increased deep bass; apparently that is the sensation with the listener closer to the instruments (??). The more common feeling is that a shelf increase in h.f. from 1 KHz upward brings one 'closer' to a speaker/singer, and I support this view.

Technical, for those wishing to make such a change in their amplifiers (I describe for one channel only; the equivalent components in the other are easily identified):

Firstly the original function is disabled by replacing C65-R81 with a short, as when the 'Presence' switch is in the "OFF" position. [Part of the screened cables to the switch S9(a + b) can be used in the alteration]. That leaves R73 (4K7) as the only NFB resistor in place.

A good place to cause the increase of h.f. as explained, is by placing a frequency dependant network over R40 (2K7) in the V4-V5 pre-amp stages. This will decrease feedback of that stage, with resultant shelf rise in h.f.

 A series combination of 2,7 NF and 3K3 ohm resistor across R40 will give some 6 dB rise in h.f. above 1KHz. The shielded cable from the 'Presence' switch S9 may conveniently be used shortened. One connects the series R.C network permanently to pin 3 of the appropriate triode, switching the earthy side to common. (Better to use the switch at the 'earthy side' of the particular network.)

NOTE:  In the opriginal application the S9 works in its "contacts short" mode for 'Presence off', now they must short for 'Presence on'. Thus at the switch the centre terminals and the previously unused terminals (at the opposite end) are now utilised. Screened cable shield is connected at any earth, the earthy lead only at a 'signal earth' near V4-V5.

To eliminate an audible click at engaging S9, the 2N7 cap must be pre-charged. This can be done by placing high value resistor (say >470K) over the switch contacts.



 
Audio must be the only branch of engineering where lack of basics' knowledge is considered a superior form of wisdom. (Anon)

Offline Raj Nair

Re: Sansui-AU 111 revisited
« Reply #32 on: December 11, 2017, 12:53:33 PM »
i have just got my au111 back from a mate who passed on but but in need of some tlc.

Offline IlkoAlexandrov

Re: Sansui-AU 111 revisited
« Reply #33 on: July 14, 2018, 03:49:21 PM »
i sorry ampdog, can you pls help me out :

Hi everyone

Im sorry, guys please, can someone help me how to send a message here ?! Trying to sell few Tounshends super tweets and stuff .. I still love this site, even if it is 1995 in its dsign .. Thank you


Nothing other than a Exclame must come between you and the music

Offline kenvanraas

Re: Sansui-AU 111 revisited
« Reply #34 on: July 15, 2018, 12:10:35 AM »
bump  :thumbs:

Offline Ampdog

Re: Sansui-AU 111 revisited
« Reply #35 on: July 16, 2018, 01:34:51 AM »
Apology Ilko!

I did not read here over the weekend.

If I understand correctly, you should go to the "Classifieds" section, under 'Items for sale'. You have a more than high enough post count (minimum required = 50). There are other rules listed  there which should be clear.

If you are trying to reach a particular member in this regard, click up on his name/avatar and send a PM.

Is this what you were looking for?
Audio must be the only branch of engineering where lack of basics' knowledge is considered a superior form of wisdom. (Anon)