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Any way to boost power output of vintage quad receiver?

hnash53

hnash53

Super Member
I am curious: Is there a way to increase the RMS output wattage per channel of my receiver... without changing receivers?

If the obvious answer is NO... then stop reading. If "maybe," the reason I'm asking is below.

I'm considering upgrading the 4 speakers in my quad system. But the upgrades I am looking at are all rated at 4 ohms and are 2-4 dB less efficient. My current speakers are 8 ohms, 89dB efficiency.

My receiver is a Sanyo DCX3300KA and detailed specs for this receiver seem hard to come by. I have both the operating instructions and service manual for this unit. But neither says what the RMS wattage per channel is. The only spec I read is that it says under "Audio Section" that the "Power Output" is 20 W. Investigations elsewhere suggest RMS wattage per channel is 16 to 25 watts for this receiver.

The service manual says the speaker and headphone are rated at 8 ohms.

My previous front speakers were Infinity RS 5b's, and they are 4 ohm. My receiver ran them fine along with an 8 ohm pair of rears. The links below are to prior discussions I initiated when I first got the Infinity's (and I do not wish to rehash any of that here, so that's why I am citing them here):
http://www.audiokarma.org/forums/in...phonic-receiver-is-there-such-a-thing.686231/
http://www.audiokarma.org/forums/index.php?threads/infinity-rs-5b-speakers-ohmage-question.686136/

My listening habits are such that I never go over 90dB peaks from my listening position about 10 feet away.

4 ohm speakers obviously require more power from my receiver than 8 ohm. But I've run 4 ohm speakers before as mentioned above and I never noticed any "stressing" of my receiver.

I've recently recapped the quad receiver and am not interested in changing receivers. Just wondering if I could increase its RMS wattage output.

Thanks.
 
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its mainly governed by the power transformer and the output devices .
firstly to get x power out you need x power in . plus the power devices need to handle it .
 
No, you can't...but keep in mind that if the receiver is putting out x watts at a certain volume setting into an 8 ohm load, and you switch the load to 4 ohms, all else being constant, the receiver will output 2x watts into the 4 ohm load. Now, some receivers are better than others at doing that all the way to the max power output. I would not assume if yours is 20W into 8 ohms that it will put out 40W into 4 ohms, but the point is, it WILL have more output power into the 4 ohm speakers.
 
Maybe...

One can put a big engine in a small car with enough resources (time, money, skill, and patience). Whether or not it's practical is another matter.

Without major redesign it's unlikely there is a practical way to materially increase the power output.
 
just dave said:
Does it have pre-outs? If so slap a couple power amps on the back.
Click to expand...

No, if the pictures I looked at were of the correct model. There is the possibility of speaker to line/pre out level converters, if external amps are a possibility. Or, perhaps modification of the receiver to add pre outs.

I've known some people to use the headphone outputs to feed external amps in other cases.
 
Some quad receivers/amps can be bridged to stereo. I had a Pioneer SQ-939 (or somesuch), bridged it to stereo, and it sounded like it had bottomless reserves of power.
 
Splatter Pak said:
Some quad receivers/amps can be bridged to stereo. I had a Pioneer SQ-939 (or somesuch), bridged it to stereo, and it sounded like it had bottomless reserves of power.
Click to expand...

OK... I'll try to understand bridging on my own. But how does one tell if one's quad receiver is "bridgeable"?
 
In the case of the Pioneer, there was a plate with electrical contacts on the back panel. I unscrewed it, turned it 90 degrees, and plugged it back in: stereo.

Be aware that not all quad gear has that feature.
 
it should say in the manual of bridgeable . p.s it then becomes one channel .. but then again if real quad you lose the quad bit and have 2 channels ..so 2 bridges needed ..not something i would recommend on unserviced vintage gear as it happens .
 
I've been running an external amp on my quad receivers for many a moon, and most didn't have pre out. That's what they make tape loops for, with the help of a Y adapter to close the loop and allow additional post processing.

For example, here's 200wpc courtesy of a McIntosh 2125 off a couple different Sansui quads ...

tapeloop-mc2205.jpg


I built the Y adapter right into my custom tube amp ...

assembly-back.jpg


That's only 70wpc, but tube watts are bigger. <G>

You DO usually lose any tone and volume controls on the receiver hooking them up via the loop. Not an issue here as all my amps have their own volume/balance controls, and I use EQ and PEQ for adjusting the tone.
 
I would not try to bridge that receiver, and I would advice against using it with 4 ohm speakers. This Sanyo has STK0231 outputs on heat sinks that are a joke, barely larger than the STK modules themselves. If you search for pics "1975-sanyo-dcx-3300-ka" there is a photo of the receiver with cover off, it tells the whole story. In any case, the DCX3300KA it does not have a bridging switch. DCX3300KB does, but I would not try to bridge that one either, the main difference between the two seems to be the switch and STK0241 outputs.

Maybe it could be modified to add pre out jacks for external power amps. You'd need a schematic to figure that out, I can't tell based on pics alone.
You can also try adding a power amp with built-in attenuator (input level pot) by connecting it to front channels tape out jacks. You will get more power, but you'd have to control volume of the front channels on the power amp and you lose all preamp functions for front channels except for source switching and phono stage.

If you need more power AND a quad, I would suggest a different that has either more power or pre out jacks (or both). And if you want to use 4 ohm speakers, I would also suggest to steer away from receivers with STK outputs (in quad receivers this generally means Sanyo and Technics).

If you like this Sanyo (and I agree it looks nice), I also that you should consider different speakers, preferably 8 ohm and efficient.
 
Thanks for all the comments. I'm staying with this receiver. Would it make a difference if had TWO of these, and somehow configured/connected them where one of them powers the front speakers and the other one powers the rear speakers?

Can that be done some way?
 
hnash53 said:
Thanks for all the comments. I'm staying with this receiver. Would it make a difference if had TWO of these, and somehow configured/connected them where one of them powers the front speakers and the other one powers the rear speakers?

Can that be done some way?
Click to expand...
Yes, two of them would do that for you. I know they don't make them anymore, but you might find them at reasonable prices on the used market.
 
Not sure what you'd accomplish there. Even the QRX 9001 doesn't allow bridging other than the built in "X2" feature, and that redirects all power to the front channels anyway. What you'd end up with is the exact same power on the rears as you'd have just using one quad receiver.

Once again, on rears ... I just use them for ambiance here, so a lot depends on what all you're trying to accomplish. My room has two sets of smaller speakers mounted in a hafler array driven off the rear channels of the quad through a Dynaco Quadraptor. That allows me to put the drivers closer to the primary seating position and effectively increases the SPLs at that point. Also makes for an extremely wide sound field on the rear of the room.

Therein may lie the solution in your system as well ... just move the rears closer to compensate for what you feel is missing. If you're not getting the bottom you desire, go with a powered sub and satellites instead.

PS ... common misconception is that quad needs four identical speakers equidistant from the listener ... not true. Put em where you want em, and tune the room accordingly. Another standard solution is to put the rears in FRONT of the listening position and to the sides.

speakers-2-2-setup.jpg
 
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That ^^ would probably do the trick. As would connecting an external power amp to the Sanyo's headphone output (sorry, forgot about that one before) - this line level converter is probably just a bunch of resistors in a box, which is exactly how a headphone output is made in most receivers. In both cases you will have 2 power amps in the signal path (meaning a bit more noise and distortion), but it is an easy solution and should be safe for all devices in play.

And no, buying another DCX3300 to power the other speakers will not help, the problem is in the outputs that have insufficient power and should not be bridged. Adding 4 more channels will only mean 4 idle channels, the ones you use will still have 20 W power and be less than ideal for 4 ohm speakers.

There actually are quad receivers in which you can boost the power of front channels without bridging if you switch off rear channels. They take advantage of using the entire power supply to feed the front channels' outputs when the rears are turned off. It works if the receiver's power is limited by its power supply and not by the power amp section. Bang&Olufsen Beomaster 3400 is an example of this solution. But in the case of your Sanyo, the problem is in the power amp section, not in the power supply.
 
OK...again thanks for the help. I already have a matching DCX3300 except it's just the "K" instead of the "KA" version... that's why I asked if this could be done if I have two identical receivers. But I don't think I'm going to do anything that has been suggested... not that they weren't good suggestions. They were and I appreciate the efforts made to answer my question.

skizo... you have the 9001 and you run it with just the Hafler circuit for the rears? Seems you're missing a lot of the quad effect with that. I have a 5500QRX and my Sanyo blows it away in terms of quad separation front to back and left to right. So my NOS 5500 is now in moth balls.

musichal... I keep clicking on the link but it's going nowhere. What is that product called so that I can look it up?

So, I guess all of this is academic now. My current 8 ohm speakers probably are close enough in audio quality to the 4 ohm varieties I was looking at. I keep wondering if I'm missing anything in terms of audio quality with my current setup. Sure I could spend $500/1000 on a pair of speakers but would I get an equivalent improvement in sound quality over my $200 pair of speakers? My gut tells me no. I've posted a question about this elsewhere but the replies indicate that I wouldn't. Maybe my system is as good as it's gonna get unless I move up 10X in price. Oh well...

Thanks again.
 
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