preamp output levels

[Ohmen]

I would like to buy a external amp for my two front speakers. I have a Yamaha RX-v2700 receiver that I would use as a preamp. Looking at the review of this receiver here on Audioholics the following was written:

"The RX-V2700 preamp output drive was a bit disappointing and a step backwards from its predecessor

The Inputs can handle 2.7Vrms unclipped!

Outputs Deliver nearly 3Vrms output before the receiver shut down, but FFT distortion becomes very high once output exceeds 1.25Vrms.

Editorial Note on Preamp Clipping
We would prefer to see Yamaha employ a preamp capable of delivering 2Vrms unclipped to ensure a wider variety of power amplifiers can be mate well. If for example you choose a power amp with the typical 29dB gain structure (THX standard), you would only be able to deliver about 155wpc (1.25 * alog(29/20)) continuously unclipped into an 8 ohm load. A preamp capable of delivering 2Vrms unclipped would allow the amp to deliver over 400wpc into an 8 ohm load!"

My question is. Does all this mean that I will get a less than worthy output? It mentions that because of this lower distortion level that I may need to purchase a amp with particular characteristics for it "to mate well". Does it come down to this receiver just not being a desireable receiver for using as a preamp?

 

[MDS]

My question is. Does all this mean that I will get a less than worthy output? It mentions that because of this lower distortion level that I may need to purchase a amp with particular characteristics for it "to mate well". Does it come down to this receiver just not being a desireable receiver for using as a preamp?

An amplifier will have a spec that says something like 'N volts input for rated output'. So if the amp is supposed to deliver 200 wpc and requires an input voltage <= 1.25 you will get the full rated output.

The review is just pointing out that the most the receiver can do without the distortion level rising to high levels is 1.25 Vrms. So if the amp requires say 2 Vrms to deliver its full rated output the receiver can supply that much voltage (review said it is capable of almost 3 Vrms) but the distortion level will be higher.

 

[jcPanny]

Amp Upgrade

Ohmen,
What is missing from your current setup? Your Yamaha receiver is very capable of driving your efficient 8-ohm axiom speakers. Unless you have a huge room and like it really loud, you probably wont benefit from an amp upgrade.

 

[Ohmen]

I do like to turn it up at times. When I turn it up to around +8 the receiver goes into shutdown. I really can live within that limit but I figure if it is going into shutdown than there probably is not enough wattage to provide extra headroom at right under +8. The room is average size at about 15x12 but it does open up into a kitchen. So the reason is to have some excess power at full volume

 

[jcPanny]

Receiver shutdown

Those higher end Yamaha receivers run pretty hot and require plenty of ventalation. Check the temp of the receiver and make sure you have room for airflow on the sides, above, and behind the receiver. You might need to add a couple fans to the cabinet or set the receiver to the "high altitude" mode so that the receiver fan runs more often.

Before you add an amp to get louder than +8 on your Yamaha you might check the volume levels w/ an SPL meter to verify that you aren't doing perminant hearing dammage!

You would probably want 200 Watts per channel or more for a reasonable upgrade from the Yamaha. A couple Behringer A500s ($180 each) in bridged mode can deliver 500 Watts into 8 ohms. You also might consider upgrading to the Axiom M80s which should sound the same as the M60's but play louder and handle more power.

 

[Ohmen]

Those higher end Yamaha receivers run pretty hot and require plenty of ventalation.

Yeah, it gets plenty warm in my cabinet. Do you think the receiver shuting down could be eliminated with some cooling fans and better ventilation? I guess it is worth a shot. I like the Behringer amp you referred to. Is that a pretty good amp? Seems pretty reasonably priced to. Thanks for the responses.

 

[zildjian]

Just to give a little more explaination in how to determine what level preamp output you need for an amplifier to perform ideally. Of course an amp is designed to perform ideally with a certain signal input level from the preamp, obviously if it's too low, then you have to turn the gain up on the amp beyond what it should be to achieve a certain volume, and conversely if you over driving the preamp, that wouldn't be good either. If you already have an amp, look at the specs for the amp, find the input sensitivity for the type of input (either balanced or unbalanced/direct) and there should be a voltage value such as... 0.6V rms (just an example value, look for your amp's specific value). In this case that means your amp is designed to perform ideally with an input signal of 0.6V from the preamp. Then to set your preamp level, play a pink noise source through your preamp and measure with a sensitive voltmeter at the outputs the voltage level with the volume on the preamp set to it's reference, "0 dB" or whatever it is on your preamp. Adjust your preamp's gain for each channel so that it's the corresponding input sensitivity of the power amp you're going to use, like in the example above 0.6V.
After you do that, then you worry about the level at which your amp gain is set, and then, it's whatever volume you want out of it (of course within it's capabilities...).
Brad

 

[Rickster71]

Yeah, it gets plenty warm in my cabinet. Do you think the receiver shuting down could be eliminated with some cooling fans and better ventilation? I guess it is worth a shot. I like the Behringer amp you referred to. Is that a pretty good amp? Seems pretty reasonably priced to. Thanks for the responses.

I agree with jcPanny.
I have a Yamaha RXV1 I use to power 4 speakers on my patio & backyard.
During a BBQ, some CD cases were accidentally left on top of the RXV1, by one of my guests.
It shut itself down.
I now keep two pancake fans on top of it. We haven't have the problem since.
Good Luck

 

[Ohmen]

zildjian, that process seems to add a whole new complexity level to balancing the system. I had not thought of these additional complexity's.
Rickster, I am going to try to cool it down. The only fan's I am aware of that would work are computer fans. The quietest one I have found so far is 17db. I supose I would just use an old extra wall transformer of the correct voltage/current to power it. I'm going to order one in the next few days.Thanks

 

[mtrycrafts]

I do like to turn it up at times. When I turn it up to around +8 the receiver goes into shutdown.

Besides the heat mentioned, this level is very high indeed and coupled with your speaker sensitivity and impedance, you may be driving it beyond its capability, not to mention that you will loose your hearing with those levels prematurely.

 

[Ohmen]

bought a fan today. 120mm, 17db, 1000rpm . It was the quietest one I could find. Hopefully it will have enough flow to do the job. Now I just have to find a power supply. I think if this works I will have to figure a way to conviently have it turn on and off with the receiver.

 

[Adam]

I think if this works I will have to figure a way to conviently have it turn on and off with the receiver.

I'd suggest plugging the fan power supply into one of the outlets on the back of the receiver.