Pioneer sx-850 Preamp?

2spike

Member
seems i should of gotten a more powerful receiver, i want to run 4 speakers how does a preamp work connected to my receiver. Love music just dont know much about audio.:confused:
 
seems i should of gotten a more powerful receiver, i want to run 4 speakers how does a preamp work connected to my receiver. Love music just dont know much about audio.:confused:
Your receiver contains a preamplifier in it.
 
You can use the preamp-out connections on the back to feed a power amplifier, thereby using the 850 as a preamp only (volume control, tone control, source selection, etc).

You can then run all four speakers from the power amp, or you can choose to run one pair from the power amp section of the 850 and one pair from the second power amp. In this scenario, you would want the separate power amp to have its own gain controls, so as to be able to match the output of the speakers (the pair connected to the 850 and the pair connected to the separate amp).

Note that the the SX-850 can handle a 4 ohm load (2 pairs of 8 ohm speakers). If you choose to go with a separate power amp, make sure it can accommodate the intended speaker load (the combined impedance of multiple speakers). Also, if you go this route, I would suggest you move up significantly in power capability. A doubling of power provides only 3dB in headroom/loudness.

If you are contemplating this change only because the impedance load of your particular speakers is lower than the 850 can handle, another alternative would be a standalone speaker selector with impedance protection. These units are inexpensive, and generally use resistors or autoformers to assure that the load doesn't drop below a specified value (usually 4 ohms).

One last point...if you end up using a separate power amplifier, note that many of them (most) do not provide speaker selection capability. In fact, most only have one pair of speaker terminals. You can of course hook two speakers to each terminal (again, assuming the amp can handle the combined impedance), but both pairs will always be active.

The solution to this issue is a separate speaker selector box (same as described earlier, above). If impedance is not an issue, use a selector box that does not include impedance protection...it's always good to keep additional components out of the circuit if possible.
 
Last edited:
probably blow up your speakers.

Tell us what you have, what you want to do and the minds here on AK will help you get things right.

Explain why you are having trouble with the four speakers as there may be something not quite right and folks can help clear that up.

The posts in this thread don't give us much info to help you out.
 
I believe that there are some important service bulletins and protection mods that may be needed before putting an 1801 to use. I know that there are some members with a lot of experience and knowledge as regards these amps. Perhaps you should start a new thread with Bose 1801 in the title to get their attention, or search for past threads and contact the experts via the AK messaging (conversation) function.
 
As posted i have a 850sx and a pair of bose 10.2 v2 speakers iam currently re doing new foam and caps on. I also have a pair of advent Heritage speakers. Have been looking for a 1250sx but price are through the roof so i thought maybe adding a amp to Boost Power!!
 
Good idea spark1! The guy that has the amp says it works fine he has owned it for 5 years but does not use it, says he just want to get rid of it too much vintage gear but for 700 bucks should be top notch i would think.
 
A-Ha we have some needed info.

The Bose are 8Ω speakers the Advent are 6Ω nominal, 4Ω minimum.

The Pioneer needs an 4Ω minimum to keep it happy, lower operating temperature, less chance of damaging the unit.

The use of a set of 6Ω and 8Ω speakers on the A+B setting gives you a conservatively HIGH number of 3.63Ω because I used 6 and 8, not 4 and 8. You are asking too much of your amp if you are playing it loud. Expect problems.

Get a pro amp. Crown XLS in whatever size you think you might need. 200-400-600-800 watts per channel or some such thing and they don't give a crap about the load impedance, generally and your load will be nothing for them. Cheaper than the Bose, too, which should work. can't find low impedance load ability for that amp.
 
A cheap easy fix would be to use a simple speaker selector box... Adcom 333 maybe.

Not a big fan of speaker selector boxes but they can be useful...
 
It depends on what problem the OP is trying to solve. A selector with impedance protection will address impedance problems, but if he needs more power than the SX850 can deliver, the selector will not help.

Unfortunately, he has not said if the problem is lack of power, load, or both.
 
The Advent Heritage sensitivity spec is 89 dB for 1 watt. The smallest loudness difference that everyone will recognize is 3 dB. To get a 3 dB louder difference requires doubling the power supplied, so:

1 watt = 89 dB
2 watts = 92 dB
4 watts = 95 dB
8 watts = 98 dB
16 watts = 101 dB
32 watts = 104 dB
64 watts = 107 dB * current capability
128 watts = 110 dB
256 watts = 113 dB
512 watts = 116 dB
1024 watts = 119 db * now we are in jet-engine territory

Your system should be able to go quite loud as it is. Prolonged exposure to loud sounds WILL damage your hearing. We all want what we want, but you may wish to reconsider your sonic goals.
 
Of course those numbers are at a listening distance of 1 meter, and for one speaker. For a more realistic starting point, I would suggest 80-82dB. I would guess that a good recording would start clipping that amp at around 90dB of continous/average output. That's loud but not LOUD.

Also, while any clipping adds harmonic distortion, minor clipping is not a big issue unless running a much higher-end system ( in my humble opinion). But as clipping goes up, distortion increases exponentially.
 
The least expensive route is to get a power amp and use the 850 as the preamp and power amp for one set of speakers and the second amp for the second set. You can run either set or both at the same time that way. No sense wasting the 850's internal amp by plugging all your speakers into a new amp which will have to be powerful to handle the load or it will run out of gas as well.

RCA Y-cables on the PRE-OUT are what you need to add a separate amp.

Should not cost you $700 to do this. Although there's nothing wrong with the 1801, it's a beast most would be happy to own.
 
Again, it depends upon what problem the OP is trying to solve. If he needs more power (so he can play his speakers louder), running both pairs off of a separate, higher-powered amp may well be a better solution, assuming it can handle the load (impedance).

If the issue is the 850's ability to handle the impedance of his two pairs of speakers when running simultaneously, splitting the load between the 850 and the separate amp may make better sense. It would give him the ability to listen to just one pair, just the other pair, or both pairs simultaneously without the need for a separate speaker selector unit. On the other hand, if the separate amp can handle the load of both pairs of speakers running in parallel, I'm not sure why it would be better to split the speakers between the two amps (other than for the aforementioned speaker switching).
 
I can't argue with that. It would only be better if buying more watts = proportionately more $. Of course amp prices are not linear in terms of $/watt so it may not save a lot. It just seemed like a waste to let the 850's capable amp sit there unused. :D
 
Back
Top Bottom