Just got a Sansui AU-555a, what should i do first, and is it suitable for headphones?

[HenkBok]

Hi guys,

I was just gifted a Sansui AU-555a (and some other audio equipment) by my father, who inherited it from my grandpa some time ago.

It's in awesome condition without any scratches or broken buttons, and after fiddling around with it a bit, i got it set up and working pretty well. I don't yet have the appropriate cables to use my dac (ODAC) with it, so i'm just using an CD player i got for the moment.

My main questions are: What should i do with it first (in terms of maintenance), and is it suitable for use with headphones?

I did a bit of listening with my HD600s plugged in, and i pretty quickly noticed that the noise floor was pretty high compared to modern equipment. At the max level i'd ever listen to music, you heard noticeable noise when not playing anything. Other than that, anything above level 2 on the volume knob would be extremely loud, and 10 would no doubt blow my headphones up instantly.
Are these things a result of it being meant as a speaker amplifier?

Eagerly awaiting your guys's response.

 

[Hyperion]

There are plenty of AK members who have more experience of the AU-555a than me, but just a few general observations to get you started.

Yes, you will find that there is a higher noise floor, particularly noticeable with headphones. It is not an amplifier only intended to be used only with speakers, headphones are a valid choice, except that headphone sensitivity has improved immeasurably since the amplifier was designed.

The amplifier will definitely benefit from being reconditioned, when the noise problem can be addressed, perhaps by the careful changing of a few transistors which can become noisy with age. The noise can be very much reduced by this method but not eliminated completely, but I think enough to allow you to enjoy headphone listening with this amplifier.

The AU-555a is a great amplifier, a highly sought after model, well worth any effort to recondition it. I'll leave it there as there are members who have reconditioned and owned one (or more!), I'll leave it to them to explain more about this little gem.

BTW: Welcome to AK! - and especially the Exclusively Sansui forum.

 

[HenkBok]

There are plenty of AK members who have more experience of the AU-555a than me, but just a few general observations to get you started.

Yes, you will find that there is a higher noise floor, particularly noticeable with headphones. It is not an amplifier only intended to be used only with speakers, headphones are a valid choice, except that headphone sensitivity has improved immeasurably since the amplifier was designed.

The amplifier will definitely benefit from being reconditioned, when the noise problem can be addressed, perhaps by the careful changing of a few transistors which can become noisy with age.

The AU-555a is a great amplifier, a highly sought after model, well worth any effort to recondition it. I'll leave it there as there are members who have reconditioned and owned one (or more!), I'll leave it to them to explain more about this little gem.

BTW: Welcome to AK! - and especially the Exclusively Sansui forum.

Thanks Hyperion! I'll look into it. Perhaps some other members here can lead me in the right direction.

 

[HenkBok]

@Hyperion By the way, i am not knowledgeable about any kind of electronics repair. If i were to ahve this reconditioned by someone, how much do you reckon that will cost me? Are we taking about a couple hundred euros?

 

[Hyperion]

@Hyperion By the way, i am not knowledgeable about any kind of electronics repair. If i were to have this reconditioned by someone, how much do you reckon that will cost me? Are we talking about a couple hundred euros?

Where are you located? Europe?... we always find that the best results are almost always achieved if an AK member does the reconditioning. There are very very few high street retailers (who advertise that they do electronics repairs) who are 'Vintage aware' enough or competent enough, to understand what is needed and execute the work properly. I guess up to a couple of hundred Euros would be about what I would expect.

I just looked at your profile, and saw how old you are, you must be one of the very youngest here, congratulations

 

[HenkBok]

Where are you located? Europe?... we always find that the best results are almost always achieved if an AK member does the reconditioning. There are very very few high street retailers (who advertise that they do electronics repairs) who are 'Vintage aware' enough or competent enough, to understand what is needed and execute the work properly. I guess a couple of hundred Euros would be about what I would expect.

I just looked at your profile, and saw how old you are, you must be one of the very youngest here

Probably am. I think i input the wrong date because i don't especially care to put my correct date on a random audio site, but i'm 18, close to 19.

I've been getting more and more into audio in the last while, but i've been using a pair of HD600s that i got from by brother for a couple of years. That's how i got into it.

Unfortunate that it will cost a couple hundred euros though. I'm not sure if i'm willing or able to pay that for a vintage amplifier, even though it has a lot of charm.

 

[LBPete]

The AU-555a is a great little amp. A real workhorse. I've been using one as a computer amp for more than 10 years. Aside from periodic cleaning It's all original. Nothing has been changed or updated. It's on for hours every day and it's as quiet as a mouse. It's outlasted at least two computers.

So, all yours may need is a good cleaning. That's something that any reputable shop can do.

- Pete

 

[HenkBok]

The AU-555a is a great little amp. A real workhorse. I've been using one as a computer amp for more than 10 years. Aside from periodic cleaning It's all original. Nothing has been changed or updated. It's on for hours every day and it's as quiet as a mouse. It's outlasted at least two computers.

So, all yours may need is a good cleaning. That's something that any reputable shop can do.

- Pete

Hi Pete, that's good to hear!

Mine has been operational for over 40 years without any repairs AFAIK, so it sure is durable.

I still have things I'm trying to understand, so maybe you can shine some light on it.

First one is whether the high noise floor could be connected to old capacitors, and the second one is if the sound of (very slight) electric buzzing could be caused by old capacitors? I've started to notice buzzing today. I don't believe it was there yesterday.

 

[stereofun]

Welcome and congrats on the Au-555a. First up, you've got a little gem of an amp - even if you cant afford a rebuild now or don't have the time skills to take it on - then by all means hang on to it until you do. These amps, in great condition like yours, are becoming more rare as well as more expensive.

Whenever you have electronics that are 40+ years old, there will be some degree of degraded performance - it may come from transistors, especially the smaller ones or it may be capacitors - it is really hard to say, so the optimum course of action is to eventually have it restored, that is to have all caps replaced perhaps some or all of the smaller transistors (here some models have transistors that looks like UFO's - those are especially prone to become noisy and unreliable)

As LBPete mentions, the usual first step and recommendation, is to have the unit cleaned - many time this alone will significantly reduce scratchiness or uneven/intermittent channels - it is not likely to reduce a persistent high noise level - but hey anything is possible with old electronics There are many tutorials on how to clean an amp, the search terms here on AK and as well on youtube would be "how to deox" - in essence you buy a can of electronic cleaner (craigs deoxit is a good one) and optionally a can of pressurized air. Unplug the amp, remove all covers, and then begin to blow dust out from nook and crannies, next you squirt a little bit of cleaner into/onto turn knobs, switches rotary dials then operate them vigorously. (see/read some tutorial first) Let the amp dry a bit before you reconnect. If you have solder skills, a basic cleaning could also include a thorough visual inspection, looking for cracked or dis-colored solder joints, that is then re-flowed. But lets do one thing at a time.

P.s one thing to try, is to reverse the power plug (just turn it 180 degrees and re-insert), this may sometimes lower buzzing a bit by minimizing the voltage drop between the amps floating ground and the outlets earthed ground - difference can be in excess of a volt.

 

[HenkBok]

Welcome and congrats on the Au-555a. First up, you've got a little gem of an amp - even if you cant afford a rebuild now or don't have the time skills to take it on - then by all means hang on to it until you do. These amps, in great condition like yours, are becoming more rare as well as more expensive.

Whenever you have electronics that are 40+ years old, there will be some degree of degraded performance - it may come from transistors, especially the smaller ones or it may be capacitors - it is really hard to say, so the optimum course of action is to eventually have it restored, that is to have all caps replaced perhaps some or all of the smaller transistors (here some models have transistors that looks like UFO's - those are especially prone to become noisy and unreliable)

As LBPete mentions, the usual first step and recommendation, is to have the unit cleaned - many time this alone will significantly reduce scratchiness or uneven/intermittent channels - it is not likely to reduce a persistent high noise level - but hey anything is possible with old electronics There are many tutorials on how to clean an amp, the search terms here on AK and as well on youtube would be "how to deox" - in essence you buy a can of electronic cleaner (craigs deoxit is a good one) and optionally a can of pressurized air. Unplug the amp, remove all covers, and then begin to blow dust out from nook and crannies, next you squirt a little bit of cleaner into/onto turn knobs, switches rotary dials then operate them vigorously. (see/read some tutorial first) Let the amp dry a bit before you reconnect. If you have solder skills, a basic cleaning could also include a thorough visual inspection, looking for cracked or dis-colored solder joints, that is then re-flowed. But lets do one thing at a time.

P.s one thing to try, is to reverse the power plug (just turn it 180 degrees and re-insert), this may sometimes lower buzzing a bit by minimizing the voltage drop between the amps floating ground and the outlets earthed ground - difference can be in excess of a volt.

Thanks for the detailed response!

As you suggested, i've already cleaned the insides a bit. Not that thoroughly, just with with a cloth, a brush and my lungs, but clean enough.

I've looked around and found a reputable shop that specializes in vintage audio equipment, and it's pretty close to where i live. Prices are surprisingly affordable for recapping (~24 euros per half hour), and the same price for restoration. Score!

Is there anything else you can give me as sort of a pro-tip while i start getting this set up as my main amp?

 

[HenkBok]

Here are some shots of my unit

 

[stereofun]

Looks very clean, inside out. I see you do have the UFO / flying saucer transistors. As for now I would not worry too much about them, just keep in mind that if you experience a fair amount of background noise post recap, then these are likely culprits.

Before you commit to the shop I'd just get a total estimate for replacing all electrolytic capacitors. This amp only has some 30-35 of them, so it's one of the easiest amps in that regard, also considering access. The. estimate should include adjustment pr service manual.

 

[gslikker]

Some like to use a bigger smoothing cap to get less hum, if the case then the two rectifier diodes need to be replaced or paralleled to take care of possible bigger current during switch on the amp. They are one amp diodes which is on the edge, anyway.
There is one big power smoothing cap and three more for preamp power smoothing.
Some want to have bigger output capacitors, too. Original ones may be 1500 or 2200 uF according the schematics which are around, using 2200 uF or more is recommended. Mine were 1500 uF so I replaced by a bigger value.

Input sensitivity is high by design. CD player output is usually much too high to be a good match.

One can poke with sensitivity using resistors. (maybe divide 5:1 for voltage using 39k in series and 10k to ground before the volume pot).

(Noise lowering and making input sensitivity much lower could be accomplished by a modification of the preamp input stage between volume pot and tone controls, by eliminating its gain and modify to a impedance converter only. (although probably considered not done by most). Myself, I was thinking about it but I sold the amp before trying...)


Guess the circuit is noisy by design, but use of modern transistors in the preamp will give probably half the noise level by just replace those in the tone/preamp, and in the turntable preamp (if a TT is used).
First, decide if the noise is really a problem when listening to the quietest music you will listen to.


btw according the photographs the main amp is already worked on, on one channel.


It looks quite nice, well worth preserving it!

(mine I sold when a 666 came around)

 

[smurfer77]

You have a beautiful example of a beautiful looking and sounding amp. One of the best amps ever IMO. I don't really have much to add beyond what others have said. If the buzz is audible via speakesr at normal volumes that's something I would fix, but if its just heard via headphones at high volume it could be quite normal. If you dont hear noise via the speakers, maybe just give a clean and enjoy the amp until your ready to try some work on it later or find a good tech.

The headphone output from the amp doesn't come from a dedicated headphone amp; it's basically taking from the speaker outlets and knocked down a bit via resistors. The pros are that the headphone output will drive any headphone easily. The downside is that you can hear a bit of hiss unless you headphones are high sensitivity, that you wouldn't hear through speakers from he listening position. I have reduced this hiss significantly by replacing transistors in some, but not all of my sansui. Some of the transistors in the 555A are known to be a bit noisy, especially as they start to fail. As other mentioned it could also be caps.

If you have time and inclination, I bet you could do a few transistor replacements with some advice from the forum . Otherwise, try to find a reputable tech.

Anyway, congrats. great amp. I will never be without at least one 555A in my house!

 

[BLAH BLAH]

Or two....

 

[gslikker]

And an accompanying tuner, just for the looks..

 

[HenkBok]

And an accompanying tuner, just for the looks..

Yeah i've seen the units Sansui makes. They look veeeeery retro.

Also, hello fellow Dutchman!

 

[gslikker]

I already thought so because of your name ;-)

In case you want somebody else to work on your unit, there are some reputable guys on the Dutch audiofreaks forum, you can ask around. At least one of them is on AK, also.

Myself I do not do repairs/restorations for other people since it has to remain a hobby, not work...

 

[HenkBok]

I already thought so because of your name ;-)

In case you want somebody else to work on your unit, there are some reputable guys on the Dutch audiofreaks forum, you can ask around. At least one of them is on AK, also.

Myself I do not do repairs/restorations for other people since it has to remain a hobby, not work...

Do you have any experience, or have you heard anyone's experience with the company "hifistereo"?

 

[gslikker]

No, I don't. Apart from chatting here on AK and very sometimes on the audiofreaks or hififorum forums (not that much activity there) I have no contacts about audio stuff at all, people nor businesses.