Am I reaching the max power / amplitude of my Rotel RB-951 power amp?


I'm currently using a Rotel RB-951 power amp to run some vintage 3.8D Fuseliers. They are pretty beefy and require a 4 ohm load, with a range of 50-125 watts as far as I can tell (information is slim on these online). 

 

However, with my Eskinsin bluetooth adaptor plugged directly into the amp, or using a Kenwood Kr3130's tuner plugged into the amp, I am only able to get up to a maximum of 70 decibels with the meter in between the speakers. The clipping indicator on the amp does not come on at any point. 

Since I seem to have such a distinct cutoff in volume, regardless of the input method, I'm thinking that I must be reaching the power limit of my amplifier. Does that sound right?

 

The Rotel does not offer power specifications on 4 ohm loads (but it can do them, per the manual). At 8 ohms it's rated at 50w/ch continuous and 100 watts in bridged mono. 

thatguyyouknow

Okay great! So I need to explore a way to play media through my amp that doesn't involve the kenwood or the eskinsin. I'm assuming through a media player such as a modern AVR I can connect to, a streamer such as bluesound (expensive!) or some or streaming option I don't know about yet. I'll start researching.. thanks!

 

I looked at the specs for your amp... the high level setting has an input sensitivity of 775mV. The Kenwood receiver specs show a tuner output of 160mV. That's why the amp is not playing loud, the tuner's max output is -14dB lower than the voltage required to drive the amp to max power.

I'll bet if you put a scope to the Eskinsi output to a 0dBFS test signal you will see the same thing -- an output voltage way lower than 775mV.

@gs5556 the levels screws do turn down the volume, but it does not go up past the limit I am at, leading me to believe that it is set to maximum.

@imhififan yes those level adjustments are set to maximum. I was hoping that was it when I came across those a few months back but alas. Thanks for the suggestion.

Is the input level pot adjusted to maximum?

There are also internal jumper settings for input sensitivity.

RB-951-OM.pdf

 

I’d love to say I’ll just keep tinkering with it, but i’ve been tinkering with the problem off and on for the better part of 6 months now. The only thing I have left at this point is to start buying other alternatives and switching things out, unless anyone has any suggestions with the equipment I already have.

You’re right, it’s not the best place to measure. It happens because I’m sitting on the ground with the units pulled out to mess with them so that’s where I’ve been measuring from. I’ll take an accurate measurement this evening to see where I’m actually at, but regardless of the number my volume is still limited to below where I would like to be able to listen to it at times.

Thanks for taking the time to help. This issue has frustrated me for a while and I just want to sit down and enjoy my set up haha. Sorry if I come off as frustrated.

your speakers are 5ohm, 88db not overly sensitive but not bad either your amp has 150wpc so i would not expect it to run out of power. I suspect something else is the issue. Like Cleeds mentioned it may be not enough gain in the preamp/source. The kenwoods pre-out may not be up to the task. Or another issue that's not easily determined from the information available. Like is muting on. 

One thought though your meter is between your speakers? is this directly between them as that's not the ideal place to measure from. 

Hey, thanks for the response. So I’ve tried two different sources. One, bluetooth into the eskinsin receiver which is plugged directly into the amp.

Two, playing the tuner in the kenwood stereo receiver, plugged directly into the amp through the kenwood's pre-out.

So you think both of these sources have an insufficient level to drive the amplifier?

 

thatguyyouknow

I am only able to get up to a maximum of 70 decibels with the meter in between the speakers. The clipping indicator on the amp does not come on at any point. Since I seem to have such a distinct cutoff in volume, regardless of the input method, I'm thinking that I must be reaching the power limit of my amplifier. Does that sound right?

No. It sounds like your source has insufficient level to drive your amplifier to full output.