Increase wattage during amp servicing worth it ?

larry777

I plan to send off my Sansui AU 717 two channel stereo Amp for servicing. You know, the normal adjustments for bias and offset....having all the dials and switches lubed.....probably new caps etc to bring the Amp back to factory spec. As an additional service these amps can have the wattage increased from 85 watts per channel to 125 watts per channel or higher in the same case,with different and higher grade components and tweaks. Is this an option that is recommended ? Additional cost would run $195. I am told that the amp will retain the Sansui Sound but would play louder and be more efficient. What do you think about this option while the Amp is on the bench ? Would it be worth it ? I don't plan on selling this amp.

stuwee

Tough call, if you really love the amp and plan on keeping it for many years and have 2 bills laying around with nothing to spend them on, I'd do it. The amp won't play much louder than it does now, the increase from 85 to 125 isn't that much to your ears, but if it runs more effeciently as they said, sounds like a good deal for the amp down the road.

DON73

You would have to increase the power to 170 watts for an increase in sound level of 3db. Increasing to 125 watts is not worth it in my opinion.

DarqueKnight

Go for it!

Music is full of transient spikes that require a large amount of power in a short amount of time. Increasing the power by 40 watts will mean more power on reserve for these spikes. The ability to reproduce musical transients results in cleaner, higher fidelity, less fatiguing sound.

Higher power is not just about playing louder. It is primarily about playing with greater overall sound quality at any level.

heiney9

As long as you trust the rebuilder and he has sufficiently explained to you that the stock unit can handle it. I would assume one of the major tweaks will be to increase the bias through the output devices. Be absolutely sure they can handle the increase and that there is sufficient heat sinking available for the increased heat that will result w/larger bias currents. Many, many older vintage stuff had very poor heatsinks or just barely enough heatsinking to run at normal spec.

It's not easy to increase wattage by just a few tweaks here and there especially going from 85wpc to 125 wpc. As far as transient information I would also assume an increase in output capacitance. Just increasing bias to gain more wattage doesn't mean larger transient response if the current cap size can't deliver, etc, etc.

I say go for it as well, but make sure you do the homework and ask the right questions.

H9

heiney9

I'd have to know alot more about the current design and what they were doing to it. Modifications many times are worth it simply because technology has changed and there are options available today that weren't 20-30-40 years ago.

If you trust the guy and he is the real deal for Sansui gear, I'd say go for it. The increase in wattage is only part of the story, I have a feeling.

H9

sda2mike

me? i'd stay stock...it's gotten down the road this far..

larry777

I don't know the person as the ads are listed on E-Bay.....under service55 ( Name Ben ) with great overall feedback score. Two listings available....1 Professional Repair Service (aprox $180) and.... 2 Professional Upgrade Service ( this one more expensive at $250 ) Their is a very detailed discription with these ads showing what will be done for each procedure....... You can go to E-bay and in the search engine put in Sansui AU and you will see these services for this Sansui AU 717 Amp.... to long to show here " YOU ALSO SEE A VERY GOOD PICTURE OF THIS AMP WITH THE TOP OFF",SO DETAIL CAN BE SEEN INSIDE. Its double monoblock construction and each channel has its own seperate power supply. Ben and I passed e-mails back and forth a couple of times and in addition to the regular work....... for the extra $195 the Power Caps are replaced ($40 each ) which would cost $225 total installed but are included in the Regular/upgrade service. A NEW power Board would be installed or existing one would be used ( Stripped of its components ) and rebuilt with new parts. I am told all parts are High Quality.
I also traded e-mails with Terry Dewick from Dewick Repair Service ( Authorized repair dealer for McIntosh and others ) and he said Caps alone would be $150-$200....so Ben is in line here. H9,does this give you enough detail to reinforce your previous comments ?

madmax

If it were me I'd give it a try but in the back of my mind I would be willing to lose the amp if something happened. If I were not willing to take a chance I would not up the wattage.

larry777

Thanks for the comments guys. I definately don't want to lose this amp after all this time. Is it really safe to have the Caps replaced,the switches and Pods cleaned and lubed and having the Amp brought back to factory spec....kepping the same wattage ???
Or is there still a danger something could go wrong and ruin the Amp. All this being done by a qualified professional that is.....and not me.

FTGV

Is the rebuilder claiming an increase in continuous or just short term dynamic power?To increase the continuous power by that amount would require that the voltage on the DC rails be increased substantially.This would require a higher voltage transformer.However a healthy increase in filter capacitance can aid in the short term power reserves dept.Brock,merely increasing bias will not increase the total power output ,only the percentage that will be in Class A.

larry777

I believe it is continuous power as they state from 85 watts per channel to 125 watts per channel. Factory 85 WPC is "continuous".....although these stock amps have been bench tested at well over this factory rating and are likely already putting out this 125 WPC now anyway,or very close. This is a well known fact, so it may take less work than one would think to confirm a rating of 125 WPC. If they were talking another 40 Sansui Watts Per Channel that would be a big improvement.....but the increase is likely 40 wpc period. I would ask to be e-mailed the full procedure and parts required for this increased wattage before making any commitment...then I would be able to give more detail.

FTGV

larry777 wrote: »

Factory 85 WPC is "continuous".....although these stock amps have been bench tested at well over this factory rating and are likely already putting out this 125 WPC now anyway,or very close.

It's certainly possible Sansui under rated it but that would be very unusual as most of the mainstream Japanese manufacturers would want to put the highest number they could on the spec sheet.Especially so back then when they were having a power war of sorts.

FTGV

Have you inquired further on the finer details of what the mod entails?

larry777

Just what I explained in post # 8. The guy is out of the Country for a couple of weeks so no contact lately. Thanks for the Interest.

FTGV

larry777 wrote: »

Just what I explained in post # 8. The guy is out of the Country for a couple of weeks so no contact lately.

Sorry I missed that little detail:redface:

Thanks for the Interest.

Just curious.

mhardy6647

The DC "rails" (secondary voltages) will determine the maximum power output before clipping. The AU-717 has a commendably beefy (dual) power supply; I don't know what it is up to, though. I can't say I like the sound of "overclocking" these old beasts; just doesn't sound very prudent.

The AU-717 is a pretty nice amplifier.

FTGV

FTGV wrote: »

Is the rebuilder claiming an increase in continuous or just short term dynamic power?To increase the continuous power by that amount would require that the voltage on the DC rails be increased substantially.This would require a higher voltage transformer.However a healthy increase in filter capacitance can aid in the short term power reserves dept.Brock,merely increasing bias will not increase the total power output ,only the percentage that will be in Class A.

mhardy6647 wrote: »

The DC "rails" (secondary voltages) will determine the maximum power output before clipping.

Correct as I mentioned in post #11 higher voltages from the tranny would be required.
As for increasing the bias while increasing the percentage of Class A output,it may in fact reduce the maximum power output as the increased constant current draw may cause some voltage sag on the supply rails.

mhardy6647

oops, read right through that.