Low Voltage Stereo Receiver

[daxhobo]

So I find myself in a conundrum...I have an Integra DTM 40.7 Stereo Receiver that has a preout that is line rated for output voltage (1.0 volts) and I have 2 ML Motion 60XT's (4ohm). I am looking for an amp to fill the gap between the 2 that will give me a fuller warmer sound and kick some juice into by floor speakers. After hours of research I have only found a couple power amps that have decent wattage output into 4 ohm speakers and are able to perform at the lower input sensitivity. I am currently looking at the Outlaw 5000 and the NAD C275bee. Any opinions or advice as to the better of the two ... or am I missing an amp out there with low input sensitivity?

 

[ski2xblack]

Crown xls1502 has adjustable input sensitivity that should not only work for you (0.775v), but save you a few ducats over the Outlaw and NAD.

Also, the Integra may actually put out more than 1v unclipped, key word being 'may'. Some other manufacturers with 1v specs put out more voltage, so it's possible.

 

[lovinthehd]

Onkyo pre-out level generally measures at a higher output voltage than their nominal spec so you're likely good with a variety of consumer amps, however I'd also suggest the Crown amp (have several myself), and they're good even at 2ohm. I wouldn't expect an amp to provide particular tone control-like "warmth" tho....

 

[slipperybidness]

I'm on the same page as lov and ski.

But, I always want to throw this out there--Is that 1V spec that you mention actually 1Vrms or 1Vpeak???

Without specifying rms vs peak voltage, you really have not supplied us any useful info. Part of the problem is that the actual manufacturer may not specify if that is rms or peak either.

For reference, if that is 1Vrms that = 1.4Vpeak

Personally, if I'm looking at these sensitivity numbers for stuff like calculating gain and figuring out the proper input to hit my desired gain structure, then I work in Vpeak, easier for me to visualize.

 

[M Code]

What many fail to grasp is that pre-amp output voltage is also a function of source input level..
If the input source is a high level such as CD player, DVD player more likely it will swing a higher level..
However if the input source input is a turntable/magnetic phono cartridge, these tend to be on the low side and built-in phono preamp is lacking enough gain so the pre-amp output level may be low....

Just my $0.02...

 

[Johnny2Bad]

You shouldn't read too much into that 1V out spec (and it will be RMS, not peak). By that I mean it does not mean the receiver cannot output more than 1V; it means that the measurements from the rest of the spec sheet were taken at 1V RMS out, unless otherwise noted.

Also, the input sensitivity of a power amp is the RMS voltage needed to output full rated power. Assuming that represents the onset of clipping, it simply means the amp will be operating at much less than that value almost all of the time.

Now, generally speaking, your preamp as a Solid State device will probably be able to output perhaps 10V cleanly to accomodate transients (a vacuum state preamp may be able to output even more). There are exceptions to those generalities (I know of at least one SS preamp that can output 40V cleanly) but the point is that 1V rating is not a hard ceiling.

The power amp probably has headroom above it's input sensitivity rating, and may be able to output even more than that continuous output power for brief transients.

M Code correctly points out that the output of the preamp is ultimately determined by the input (source) voltage output; for digital sources that is supposed to be 2V and often is higher by a small amount, and I've seen 3V+ in some cases. For something like an FM tuner or a Phono preamp it might be 0.775V.

So, in order for the preamp to output 1V it will be attenuating the digital source and amplifying the line level sources. From that you can see that the volume control on your preamp represents a *relative* level; it does not mean that when it's cranked "to 11" that only then will it generate the 1V output spec. It is most likely more, perhaps much more, than 1V at that volume control position.

Broadly speaking, when the input sensitivity of the preamp is met by a source, the volume control is typically around 2:00 (as in 2:00 on a clock face) and there is more volume control available if more output is needed to get your power amp up to maximum power.

You are absolutely correct to check these specifications to insure compatibility, but for the most part it's not an issue.

 

[slipperybidness]

What many fail to grasp is that pre-amp output voltage is also a function of source input level..
If the input source is a high level such as CD player, DVD player more likely it will swing a higher level..
However if the input source input is a turntable/magnetic phono cartridge, these tend to be on the low side and built-in phono preamp is lacking enough gain so the pre-amp output level may be low....

Just my $0.02...

You make a valid point.

I did implicitly get this when I say "gain structure". That is really the key here, you need proper gain structure to get to reasonable volume levels AND to avoid clipping.

Pre-amp outputs can be clipped too. You sure as heck don't want to feed a clipped signal to a power amp.

I think we pretty much have the OP set straight at this point.

 

[Johnny2Bad]

Having a closer look at the spec sheet note the following:

Input Sensitivity (47Kohms) Line: 200mV Phono 3.5mV

The Integra 40.7 should have no problem outputting more than 1V with almost any line level source. The Phono Overload specification is 70mV. Compare that with the Phono input sensitivity of 3.5mV for 1V output. That seems to support the assumption that is plenty of headroom for any amplifier you are likely to find to hook up to the Pre Outs.

We do have to make educated guesses on these points, as it's rare to get a full measured review of any but a top-line AV receiver, for a couple of reasons (one, it's what the distributor is going to send to a reviewer over a lower tier unit, as they want to showcase their best unit, and two, these receivers receive frequent model updates, which makes the window for a topical review narrow, typically less than two years and sometimes even less). But I personally would not be worrying about it; you are almost certainly just fine.

 

[daxhobo]

Thank you so much for the help. That makes me feel better about looking for a power amp.

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