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Why no 4 ohm loads on a Yamaha CA-2010?

wajobu

wajobu

Boing Boom Tschak
Hi all,

I have a question...in moving some equipment around last weekend I suddenly realized (dealing with some 4 ohm and 8 ohm speakers) that my Yamaha CA-2010 will only accept a minimum total load of 8 ohms for speakers, why?

Almost all of the other Yamahas that I have will accept 4 ohm loads with either a single pair of speakers or combined 8 ohm loads (CR-2020, CR-1000, CA-810, CA-1000, A-1, B-2, etc.). What's different about the CA-2010 amplifier's design?

Just curious--thanks. :scratch2:
 
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Many of the Yamaha's (especially later models, going into the early 80's) only show ratings for 8 ohm loads. Some of them will drive 4 ohms just fine, read the fine print if you have an owner's manual. I went through the same thing with an R-700. Turns out it will push a 4 ohm load just fine. YMMV!
 
Read the sticky on same at the top of the Vintage Solid-State Forum. Current = heat. And the CA-2010 runs hot in any event. While I've not owned one, my guess is that the CA-1010 is the same. Both have Class A capability, as well. They may have what the engineers who designed them think is marginal heat-sink area for the current needed to drive a 4-ohm load. Gotta love those cooling fans. I always have one running on the vent on my CA-2010.
 
Above the speaker terminals on my 1010 it says
"A OR B: 4-16Ω/SPEAKER A + B: 8-16Ω/SPEAKER"
so apparently it's rated for 4Ohm speakers. My KEFs are 6Ω nominally; running in Class A gets that top grille mighty warm, even at low levels.
Tom
 
Tom - What does the owner's manual state? The CA-2010 states only the 8-16ohm ratings. Does the CA-1010 have a 4-ohm rating in the spec's? I'm guess that the heatsinks on the CA-1010 and CA-2010 are the same. Witht he higher power rating of the CA-2010 they would limit the current draw (heat) by having no 4-ohm spec.
 
All I gots is the Service Manual which says:

Output 20Hz 20kHz
"B class 8Ω 100W + 100W (0.02% AUX IN)
B class 4Ω 120W + 120W (0.02% AUX IN)
B class 8Ω 20W + 20W (0.02% AUX IN)"... and I'm pretty sure that should say "A class", not "B".
No spec given for A class at 4Ω.

Tom
 
I have the CA1010 service manual also and it has the same typo. I got it from Echowars and he or the person he got it from changed the B to and A.

I have an instant read thermometer on the top grill and mine runs 140f in class A during average use. Also, I read somewhere that a class A amp runs the hottest at idle. Where none of the energy is turning to music just heat.
 
CA-2010 reads above the speaker terminals:
A or B: 8 - 16ohm speaker A + B 16ohms speaker

Service manual reads:
B Class 120W @ 8 ohm
B Class 140W @ 4 ohm
A Class 30W @ 8 ohm

Like the CA-1010, there is no rating for Class A @ 4 ohm.

Thanks for pointing out the 4ohm rating in the service manual. This is the first (and only) place I've seen any 4ohm rating for the CA-2010.
 
Yamaha B-2 said:
CA-2010 reads above the speaker terminals:
A or B: 8 - 16ohm speaker A + B 16ohms speaker

Service manual reads:
B Class 120W @ 8 ohm
B Class 140W @ 4 ohm
A Class 30W @ 8 ohm

Like the CA-1010, there is no rating for Class A @ 4 ohm.

Thanks for pointing out the 4ohm rating in the service manual. This is the first (and only) place I've seen any 4ohm rating for the CA-2010.
Click to expand...
With this in mind, then, it would appear that our friend Wajobu could indeed run some Class B 4Ohm speaker loads on his 2010. :scratch2: But does the protection circuitry protect the amp only from short-circuits, or from excessive current and/or overheating as well?
Tom
 
Personally, I run a fan on the exhaust vents on my CA-2010 and would recommend that for longevity. But, I'm a 'heat-freak'. That is, I run a fan on my B-2 amps, as well and same with the Class A BX-1. IMHO, with a fan, the 4ohm speakers should be just fine on the CA-2010 unless one is rocking-out for several hours. Even without a fan, the CA-2010 can most likely drive 4ohm speakers at 'reasonable' levels without problems. And, EW doesn't mind a bit of heat with his gear. Up to 55C. But.....I like fans.
 
I think I'll finally get that PC Power & Cooling Silencer out of my junkbox and connected to a wallwart I have and see what happens. It's surely quiet enough to be overwhelmed by music.
Tom
 
Even our central HVAC unit on the other side of the cinder-block wall knocks out any sound coming from the fan I use. Certainly isn't a problem.
 
Oh that's interesting...failed to notice the 4 ohm rating in the SM. Thanks guys...I'll proceed with caution...perhaps it's time for a muffin and wall-wart :D
 
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