rail voltage on the old sansui's

[ozzy.46]

hi im ozzy.46 im new to this site i have a lot of old sansui amps au 719 g 8700db 9090 db is there a way to change the rail voltage on the old sansui's im haveing over heating problems the speakers im useing are cerwin vega 4ohm all the old stuff used 8 ohm ive tried 4 ohm resitors wireing in series andthey just dont sound good and they are not as loud can some one help me i was thing about just getting an amp for 4 ohm speakers from parts express thanks ozzy.46

[marlboro]

Areyoulearningdisabledordoyouhaveareligiousconvict ionagainsttheuseofperiodsspacesandspostrophiesando therstufflikethataswellasaspellcheckermarlboro

[ozzy.46]

Don't make fun of me. I'm just looking for some help .I shop at parts express an thought you guys could help me and yes im 46 and type with one finger

[ozzy.46]

Areyoulearningdisabledordoyouhaveareligiousconvict ionagainsttheuseofperiodsspacesandspostrophiesando therstufflikethataswellasaspellcheckermarlboro

wellsomeonewillhelpmeitdoesnothalfttobeyouBUBA

[killa]

No expert but i think it would be easier just to get a new stereo. Most new amps will handle 4 ohms. The only thing about new amps is they dont have phono input which means you would need a phono pre amp. I think they are pretty cheap though.

[ozzy.46]

No expert but i think it would be easier just to get a new stereo. Most new amps will handle 4 ohms. The only thing about new amps is they dont have phono input which means you would need a phono pre amp. I think they are pretty cheap though.

thanks that's what i was thinking .Can i build a pair of 8 ohm speakers that will stand up to a 4 ohm pair

[philiparcario]

Bro sometimes we get prankster's with false posts that look to cause fights. So you have three older sansui amp's.

Did they ever work with your speakers? Your power caps are they original? Power caps are the big ones that are feed from the transformer. this order is the simple version.


transformer
rectifier
power caps.

If the caps are old (over 20 years) and the amp overheats the caps may have leaked. Open the amp up and look at the big caps see if they are misshaped or if fluid has come out of them. You may need to replace them. The easy way to reduce the rail voltage is use a variac transformer and give the amp 100 volts.


here is one on ebay.

http://cgi.ebay.com/WH-CURTIN-POWERSTAT-10-AMPERE-AC-VARIAC_W0QQitemZ290354716429QQcmdZViewItemQQptZLH_ DefaultDomain_0?hash=item439a7d5f0d&_trksid=p3286.c0.m14#ht_500wt_1182

[davidl]

Just over look Marlboro he seems to be in a pissy mood.:rolleyes: The onlty way to change rail voltage would be a complete revamp of the power supply which isn't going to happen. Your Sansui is current limited, that is why it over heats with 4 ohm speakers. Inserting a 4ohm resistor in series is futile since half the watts are now going to the resistor and prob heating up a lot as well. Looks like a new amp is the answer that can handle 4 ohm loads

[philiparcario]

what is budget for a new amp? lots out there.

[mzisserson]

Hi Ozzy,
Older Sansui's should be able to drive the hell out of a 4 ohm cerwin vega without overheating issues. My thoughs are the following:

1. There is an issue with one, or both, of the speakers.
2. YOu listen too loud, mabye with an eq? Bass turned up? You may be clipping the amp and not knowing it.
3. Please gove soem more detail as to your listening habits. Mabye this issue is you do not have enough something in your system that you need.

[ozzy.46]

Bro sometimes we get prankster's with false posts that look to cause fights. So you have three older sansui amp's.

Did they ever work with your speakers? Your power caps are they original? Power caps are the big ones that are feed from the transformer. this order is the simple version.


transformer
rectifier
power caps.

If the caps are old (over 20 years) and the amp overheats the caps may have leaked. Open the amp up and look at the big caps see if they are misshaped or if fluid has come out of them. You may need to replace them. The easy way to reduce the rail voltage is use a variac transformer and give the amp 100 volts.


here is one on ebay.

http://cgi.ebay.com/WH-CURTIN-POWERSTAT-10-AMPERE-AC-VARIAC_W0QQitemZ290354716429QQcmdZViewItemQQptZLH_ DefaultDomain_0?hash=item439a7d5f0d&_trksid=p3286.c0.m14#ht_500wt_1182

Ok i'll check it out when i get in from work and i'm for real not looking for a fight just looking for people that share the love of musis thanks

[dubbreak]

hi im ozzy.46 im new to this site i have a lot of old sansui amps au 719 g 8700db 9090 db is there a way to change the rail voltage on the old sansui's im haveing over heating problems the speakers im useing are cerwin vega 4ohm all the old stuff used 8 ohm ive tried 4 ohm resitors wireing in series andthey just dont sound good and they are not as loud can some one help me i was thing about just getting an amp for 4 ohm speakers from parts express thanks ozzy.46

Well the resistor is eating nearly half of your power, hence it not being as loud. It may also be rolling off the top end depening on the resistor. I'm surprised it can't handle the 4ohm load. I have an old sansui that handles 4ohm loads fine (mind you it's not the same model, also it is rated to make less power into 4ohms than 8...).

As mentioned by someone else getting something else that will run the 4ohm load is probably the easiest solution (possibly the most cost effective). Not a lot of amp heads here, so I don't think anyone will be able to recommend how to modify your current amp. How about looking at craigslist and other sites for something used that fits your needs? Or get some different speakers.

Also if you want people to be able to read and understand your question you should make it clear and concise. That generally includes the use punctuation.

[ozzy.46]

Hi Ozzy,
Older Sansui's should be able to drive the hell out of a 4 ohm cerwin vega without overheating issues. My thoughs are the following:

1. There is an issue with one, or both, of the speakers.
2. YOu listen too loud, mabye with an eq? Bass turned up? You may be clipping the amp and not knowing it.
3. Please gove soem more detail as to your listening habits. Mabye this issue is you do not have enough something in your system that you need.

hi i'm useing a adc eq and i like bass they are re38's

[cpcarter]

Ozzy,
Welcome to the forum, punctuation and spelling aside, you will be made to feel welcome here. You will find mutual courtesy and respect with some serious ribbing and even some knowledge to be shared.

Having said that I don't have a clue how to help you!
My opinion is that changing the voltages inside the receiver is not an option without redesigning the entire amp. I owned some old Sansui stuff and always thought it was pretty robust. Questions:

Driving a 4 ohm load causing overheating- How hot? Does it shut down or just feel warm to the touch?
What SPL are you trying for? Did this just start? Could the Receiver heatsinks be clogged or if fan cooled is the fan operating? What Cerwin Vegas? Are those speakers that hard to drive normally or could a crossover capacitor have changed causing a drop in Impedance? Measure the DC resistance across each Speaker terminal and see what you get.
If speakers and amp are within spec then I guess, as you suggest, another amp/ speaker combination is needed.

CC

[ozzy.46]

Hi Ozzy,
Older Sansui's should be able to drive the hell out of a 4 ohm cerwin vega without overheating issues. My thoughs are the following:

1. There is an issue with one, or both, of the speakers.
2. YOu listen too loud, mabye with an eq? Bass turned up? You may be clipping the amp and not knowing it.
3. Please gove soem more detail as to your listening habits. Mabye this issue is you do not have enough something in your system that you need.

thank's i guess i need to put it on the bench and start looking

[ozzy.46]

Ozzy,
Welcome to the forum, punctuation and spelling aside, you will be made to feel welcome here. You will find mutual courtesy and respect with some serious ribbing and even some knowledge to be shared.

Having said that I don't have a clue how to help you!
My opinion is that changing the voltages inside the receiver is not an option without redesigning the entire amp. I owned some old Sansui stuff and always thought it was pretty robust. Questions:

Driving a 4 ohm load causing overheating- How hot? Does it shut down or just feel warm to the touch?
What SPL are you trying for? Did this just start? Could the Receiver heatsinks be clogged or if fan cooled is the fan operating? What Cerwin Vegas? Are those speakers that hard to drive normally or could a crossover capacitor have changed causing a drop in Impedance? Measure the DC resistance across each Speaker terminal and see what you get.
If speakers and amp are within spec then I guess, as you suggest, another amp/ speaker combination is needed.

CC

hi it get's real hot and then shuts off no fans

[philiparcario]

did the amp's ever work with this set of speakers?

[neildavis]

I'm surprised it can't handle the 4ohm load.

That amp is only rated for 8 ohm operation. I've got one that a neighbor had set out as garbage...saw it and brought it home. It looks like new and powers OK, but I haven't tried it beyond that. When I was looking up the specs for it, Sansui claimed to be using some unique output configuration to reduce TIM distortion. Some of that was hype, of course, but I got the feeling that it wouldn't be a workhorse amp that you could abuse. It's a nice looking amp and built very well, so it's a shame to not use it, but it's not the right amp for high volumes with 4 ohm speakers.

[romanbednarek]

Since it hasn't been brought up yet, using a 4 ohm resistor in series with a speaker "can" change the frequency response, especially if the impedance of the speaker has large swings above (and below) the nominal impedance rating of 4 ohms. (The resistor will act as a voltage divider with the impedance of the speaker, and only if the speaker had a purely resistive 4 ohm impedance would the amount of attenuation through the added resistor be equal across the entire frequency range).

I thought that I would mention this based on the intial comments of a change in the sound of the speakers with the series resistors added (beyond an overall drop in sensitivity across the entire spectrum).

I'm not sure if an impedance matching volume control (transformer driven) would work better or not but it may be a different option other than a series resistor (assuming that there aren't any other issues with the amp).

[mzisserson]

hi i'm useing a adc eq and i like bass they are re38's


Ozzy,

EQ'ed bass can be EXTREMELY stressful to an amp. If you are cranking up the bass you may be overdriving the amp without realizing it. Mabye a subwoofer is in order. I owend some old Jensen speakers with 15" woofers and it was funny because they had no deep bass. So a big speaker with large woofers does not always equate to strong deep bass. I may be wrong but the CV's I can recall listening too were always "punchy" with lots of midbass. They were more impacting than deep. A sub could cure that issue if and only if the speakers are good.

Phil's question is extremely relevant. Did they ever work with this/these amps. This may really find the root of your issues. :confused::confused::confused:

[romanbednarek]

Ozzy,

EQ'ed bass can be EXTREMELY stressful to an amp. If you are cranking up the bass you may be overdriving the amp without realizing it. Mabye a subwoofer is in order. I owend some old Jensen speakers with 15" woofers and it was funny because they had no deep bass. So a big speaker with large woofers does not always equate to strong deep bass. I may be wrong but the CV's I can recall listening too were always "punchy" with lots of midbass. They were more impacting than deep. A sub could cure that issue if and only if the speakers are good.

Phil's question is extremely relevant. Did they ever work with this/these amps. This may really find the root of your issues. :confused::confused::confused:

Good point on the boosted bass as well as the characteristics of CV speakers. I have an old CV passive 12" vented subwoofer that seemed to have a stress in the midbass region as you mentioned (I bought it on clearance in the early 90's and haven't used it in quite a while partially because it seemed more like a "woofer" than a "subwoofer").

[JRT]

hi im ozzy.46 im new to this site i have a lot of old sansui amps au 719 g 8700db 9090 db is there a way to change the rail voltage on the old sansui's im haveing over heating problems the speakers im useing are cerwin vega 4ohm all the old stuff used 8 ohm ive tried 4 ohm resitors wireing in series andthey just dont sound good and they are not as loud can some one help me i was thing about just getting an amp for 4 ohm speakers from parts express thanks ozzy.46

For test purposes, try one channel at a time. Wire both speakers in series for an 8_Ohm load and connect them to the right channel output. Disconnect the left channel input, and put a 32_Ohm resistor across the left channel output. Give it a listen. Use a CD with mono content, not stereo. It should sound normal with mono content.

If it sounds wrong, shut it off. If it smells wrong, shut it off. If it starts leaking any smoke, shut it off.

Ease the volume up, and it should go very loud without big issues. Then swap sides, inputs and outputs, and give it another listen.

Do not have an input attached to the channel that has the resistor attached to the output or else you will cook the resistor and you might burn up some output transistors with it.

Wiring both speakers in series means that you connect the black/negative terminal of one speaker to the red/positive terminal on the other speaker. The other terminal on each speaker gets connected to one channel on the amplifier. That doubles the load impedance seen by the amplifier on the connected channel. The other channel goes unused.

There should be very little output voltage on the unused channel, just what leaks through in crosstalk. The resistor provides a path for the corresponding current, very low level (might be unecessary, but better safe than sorry).

Everything should be off before you start playing with any of the connections. These are not designed to tolerate any hot swapping.

If the amp proves good, I suggest you keep the amp and replace the speakers with something more suitable. Loudspeakers have come a long way.

Welcome to the board.



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