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Sansui QRX 7001 and 4 Ohm speakers?

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BeoProf

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Hi Everyone, could anyone confirm that the Sansui QRX 7001 can handle a 4 ohm load per channel? I want to hook it up to 4 Bang&Olufsen Beovox P45 speakers which are rated at 4 ohms.
In the user manual for the receiver (available easily online) in the section on speakers (page 10) it states explicitly you can have 4-16 Ohm per channel.
However, on the specifications page (p. 18) of the manual it says "Load impedance: 8 Ohm". I am planning to purchase this receiver, but of course would prefer to avoid blowing it up...
Any help will be greatly appreciated!!!
Thanks in advance,
Peter
 

BeoProf

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Thanks! I was hoping that this is just a measurement, but I want to be ultra safe, I would feel like a fool if I broke the receiver for such a stupid reason :)
 

Quadzilla

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You're welcome. It is a very nice receiver, probably my favourite quad unit ... and a much better (and simpler) design than the 8001 and 9001. I had mine recapped a few months ago, so it should be good for a while.
 

BeoProf

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Thanks! That is actually precisely my reasoning behind choosing the 7001 -- it seems to be a great deal without many of the issues plaguing the higher models in this series.
I have one more question: in the 7001 there is a "2 channel direct front" and "plus back" buttons to have stereo only, through front or front+back. Do you know if this setting alone requires 8 ohm speakers?

In the 9001 and 8001 there is a bridged version of this, within a speaker selection there is 2x power setting for stereo only -- but this one actually does require 8 ohm speakers!
 

Quadzilla

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Unlike the 8001/9001, the 7001 does not bridge power amplifiers. The 'Plus Back' switch does exactly what you think it does. It sends the same stereo signal to the front and rear channels. No need to worry about using 4 ohm speakers with this setting, although unless your speakers are in different rooms, why not just use the quad synth mode for stereo sources? It is fantastic on this receiver. I also have a Sansui SD-3030 reel to reel deck (stereo record/play, quad playback). Sansui make great gear. The Marantz guys really don't know what they are missing, just to get blue dial lights and a few bragging rights.

SD-3030.JPG
 
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BeoProf

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Wow, what a great photo! And an excellent piece of equipment!
I am definitely not planning on using the stereo setting too often, only asking to make sure I don't bridge the amps and break it just by pushing that button.
Thanks a lot for all the information, I really appreciate it!!! I might be closing a deal on a fully restored 7001 this week, so fingers crossed :)
 

BeoProf

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I am going to see it tomorrow, but I only have more questions... :) I posted another thread about testing the CD-4 demodulator with a signal generator. Another piece of information from the seller (a professional audio restorer) is that 4ohm speakers will cause harmonic distortion at much lower volumes than 8ohm speakers in the QRX 7001. This is what he measured at least.
Anyway, I'm going to see it in person tomorrow.
 

Quadzilla

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Like I said, I am using 4 ohm speakers and it sounds fine to me. I can't comment on testing a demodulator with a signal generator, but it sounds a bit risky since it requires a phono-level signal ... around 5 mV. You can damage it if you overload it. I don't use the demodulator in mine. I have never been able to dial it in properly. I suspect that the controls are dirty, but they are buried so deep that you have to remove circuit boards to get to them. Using an outboard demodulator also allows me to use a stand-alone (Rega) phono preamp for matrix LPs.
 

BeoProf

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I agree, I find it unlikely I will every try CD-4, given how much effort goes into it... however, I'd like to have the option and of course to know if the asking price is OK. The seller is a professional tech, he does wonderful stereo restorations, however he's not a quad guy and the state of the quad boards in this piece he's selling is a bit of unknown. He does however have all the equipment and knowledge so that we could possibly test it without blowing the preamp, the demodulator itself etc.

Can I ask what outboard demodulator you're using or could recommend? I was wondering about this solution with the quad receiver I already have, the Beomaster 3400. It has an SQ demodulator based on the MC1312 chip, or it can take a discrete 4-channel input from an outboard demodulator.
 

Quadzilla

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I am using a JVC 4DD-5 with the QRX-7001. In my main system I use a Marantz CD-400B. The Marantz is a bit more convenient because the separation controls have knobs, instead of recessed screwdriver adjustments. It also has a 4-channel line input for another quad source. The JVC does not.

Where are you located? You should add that to your profile.
 

BeoProf

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OK, added my location. I am in Warsaw, Poland, and my guess is that there is no tech in the country, or probably even the whole Eastern Europe, that specializes specifically in quad gear. Of course, quad never made it here in the 70's through the iron curtain, so gear is scarce, and if anyone is using it then probably mainly in stereo.
In any case, great suggestions with the decoders! I'll research this a bit more and perhaps hook it up to the Beomaster (on the photo below).
IMG_20180130_083125.jpg
 

Mistisal

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Jan 31, 2018
Messages
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Hi Everyone, could anyone confirm that the Sansui QRX 7001 can handle a 4 ohm load per channel? I want to hook it up to 4 Bang&Olufsen Beovox P45 speakers which are rated at 4 ohms.
In the user manual for the receiver (available easily online) in the section on speakers (page 10) it states explicitly you can have 4-16 Ohm per channel.
However, on the specifications page (p. 18) of the manual it says "Load impedance: 8 Ohm". I am planning to purchase this receiver, but of course would prefer to avoid blowing it up...
Any help will be greatly appreciated!!!
Thanks in advance,
Peter
Quadzilla is absolutely right, the specs are under 8 ohms, but the receiver handles 4 to 16 ohms, I have the same receiver! Finally some people who have knowledge that I can talk with!!! Woo Hoo!!! I presently have it driving my monstreous 2 pairs of Snell's type Aiii !!!!
20180331_183020A.jpg
 

Quadzilla

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Quadzilla is absolutely right, the specs are under 8 ohms, but the receiver handles 4 to 16 ohms, I have the same receiver! Finally some people who have knowledge that I can talk with!!! Woo Hoo!!! I presently have it driving my monstreous 2 pairs of Snell's type Aiii !!!!View attachment 32586
Nice setup Mistisal, but you would be quite alone here in thinking that I have any knowledge.
Not many here think that I have anything intelligent to say. Thank you for the kind words though.
 

Mistisal

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I am using a JVC 4DD-5 with the QRX-7001. In my main system I use a Marantz CD-400B. The Marantz is a bit more convenient because the separation controls have knobs, instead of recessed screwdriver adjustments. It also has a 4-channel line input for another quad source. The JVC does not.

Where are you located? You should add that to your profile.
Sorry Quadzilla, why would you add a CD-4 demodulator? doesn't the QRX works with all formats? or at least someone told me it would? Am I incorrect? thanks!!!
 

Mistisal

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Nice setup Mistisal, but you would be quite alone here in thinking that I have any knowledge.
Not many here think that I have anything intelligent to say. Thank you for the kind words though.
HAHAHAHA, I dont think so honestly, for me knowledge and experience are 2 diff things, you have experience with the QRX, so it is in fact knowledge!!!

In my mind I was thinking about gettin the 9001 one day so that I have more power for my Snells, but its not the first time i read that those 2 after the 7001 are problematics.... how much did it cost you to service yours? did it really made a difference? sorry for all the questions!
 

Quadzilla

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Most CD-4 demodulators are based on the same design, whether they are stand-alone or built into a receiver. I have never been able to get the one in my Sansui working properly, and I suspect that the separation and subcarrier control pots are dirty. They are pretty sticky to turn, but they are VERY difficult to get at without removing the (very large) bottom circuit board. I didn't want to go to all that trouble when I had the JVC sitting around with nothing to do. Also, the phono input in the receiver is pretty mediocre, and using a separate demodulator allows me to use a better phono preamp connected to a line input on the Sansui ... and a better preamp will give you better matrix decoding as well.
 

Mistisal

New member
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Jan 31, 2018
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Hum... yes of course, yes I have seen pictures of where the control boards are , and yes again, you almost have to split it open completely, then you can adjust it or verify the voltage coming out for the quad thing... man it must sound like heaven with your tape reel, bit jealous here! hahahaha
 
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