Help a brother out, Amp question

[Shayne]

I just bought a set of Magnepan 1.6's and was using my little Onkyo A-9555 class D amp with them until my new Emotiva amps arrived. Well, the Emotiva's arrived today and I quickly hooked them up only to discover a discrepancy.

Ok, so the Onkyo was producing a nice listening level with the dial at around 1-2 o'clock. The Emotiva setup is producing the same output at around 4 o'clock. What gives? Onkyo is rated 85wpc, 8 ohm vs. the Emotiva at 300wpc, 8 ohm, 500 at 4 ohm. The Maggies are 4 ohm. I should have gobs of headroom with that kind of power. Suggestions?

[SunnyDaze]

You may still have gobs of headroom. The amps could have an entirely different gain factor. What type of preamp are you running with the Emo's?

Also, never discount the quality of Onkyo! The 9555 has a reputation for sounding almost magical for the price.

[thuffman03]

It might be just the sensitivity of the gain for the amp. 

But does it really matter were the volume knob is?  On my Sunfire tube preamp the gain knob is almost 45% and I have a Sunfire Signature 600 which puts out lots of power.

[Shayne]

You're right about the Onkyo. It's an amazing amp and I'll never sell it.

I'm using the Emotiva USP-2 preamp. It really does seem like there's a low pre output situation going on. Maybe it's the phono pre in the Emotiva or possibly the magnepans are just eating the power. It sounds good but it doesn't seem to be creating the same db's. I'm gonna double check everything tonight and i'll report back.

It doesn't really matter to me where the volume knob is but pegging the amp doesn't seem good either. One thing I will say for sure, the amp is clean all the way up. Maybe it's just my inexperience. I've never owned a decent set of separates or Magnepan speakers. I've always been an integrated amp, high efficiency speaker guy.

[MacGeek]

Is just the power amp new to your rig, or both the power and pre-amps?  If they are both new, try swapping the old power amp to see what happens.  Also, what happens with a high level input into the pre-amp? Or, try running a CD player, if it has a volume control, directly into the power amp.

 I have some pre-amp/amp combos that require I run the volume control near 100% (full right on the knob) to get full output from the power amp.  As thuffman noted, as long as you can get full power, the volume control setting does not matter.

Some pre-amps, especially Japanese made, achieve full gain before reaching the 12:00 setting.

[BrianT]

It might be just the sensitivity of the gain for the amp. 

But does it really matter were the volume knob is?  On my Sunfire tube preamp the gain knob is almost 45% and I have a Sunfire Signature 600 which puts out lots of power.

Tom

That's about where I run my volume knob 45% to 50% with 500 tube watts

Brian

[SunnyDaze]

I must say, I agree on the gain argument. When I play with any Carver / Sunfire rig, I notice that the gain on the preamp is usually nowhere near as sensitive as it is with my Onkyo Integra gear. 50% volume with the Amazings and the Bob Cherry's produces a sound level that is significantly less than my P-304 / M-504 / Paradigm 9seMk3 setup.

I think you might be getting used to the less drastic gain on your preamp. 

[Shayne]

I'm going to agree that it's just a difference in gain structure. The emotiva stays clean and the knob also turns a good bit more than I expected. I tested it while it was off. It will pretty much turn til the led indicator is almost straight down, between 5 - 6 o'clock position.

I'm coming around to the sound. It almost seems like everything needed some time to acclimate. It's just my ears getting used to what i'm hearing, but it really seems to be getting better the more I listen. It is obvious that I'm going to miss my tone controls. I never used them for anything but to take the edge off a bright recording but the Emotiva gear is direct signal path. We'll see about that. May eventually have to do something about that.

[Anders]

It may not just be your ears getting used to the sound.
Its well known that alot of High-End gear take quite awhile to break in and sound their best.
After I modify Acoustat amps the sound is amazingly dynamic but the sound is not right.
You can hear the sound change all over the place as the new caps break in.

Differences in volume control settings to reach clipping are just gain differences and speaker efficiency differences.

I don't own an equalizer (excepts whats in my computer) and my system has no tone controls.
If a recording is bright you just listen past the brightness to what is good in the recording.

[Shayne]

A good friend let me borrow a little Yaqin tube phono preamp this weekend. This made the phono signal closer to line level, still doesn't match my cd player output, but closer. So there's more headroom there. Most importantly it tamed some of the high frequencies and the bass is more pronounced. I'm sure it's not a primo phono pre, but it's better than whats built into my preamp. I'm impressed. We are gonna try some new tubes later this week. He said he'd sell it to me if I liked it.

[Reverend]

Yaqin (China) makes good inexpensive phono pre's/tube buffers.  Swapping out the stock tubes have made vast improvements in sound.

[wkhanna]

It is a familiar story, and a lesson I learned after too many years.
Never underestimate the importance of the pre-amp.

Most people seem to concentrate on speakers and amps when they start down the rabbit hole that is this disease….err…..I mean hobby. One will often be illuminated to the truth when, as in your case, upgrading speakers and power amplification don’t seem to deliver the improvement promised or expected.

The poor neglected pre is a vital ingredient to building a good system.

As always, JMHO YMMV 

[tube_dan]

Agreed WKHanna.  Discussing just preamps and power amps, the preamp magnifies the signal millions of times more (figurative, but Anders/T/et al. know the math)  than the power amp.

Great point, Anders, about "listening past the brightness."  :thumbup

[SunnyDaze]

Gain is a ratio of output power to input power:

Gain (Measured in dB) = 10 x log(PowerOut / PowerIn).

Looking at this definition, in order to achieve a positive gain, PowerIn must be less than PowerOut, but greater than 0. That should be rather intuitive, as otherwise, you will defeat the purpose of amplification.

Suppose we let PowerOut be 20 Joules, and PowerIn be .5 Joules. Our gain would then be: Gain = 10 x log(20J/.5J) = 16.02dB

Now, suppose we let PowerIn be 3.5J. Gain = 10 x log(20J/3.5J) = 7.56dB

Consider the opposite case, if we do not change PowerIn, but only change PowerOut, as in Shayne's case. Again, the same rules of logarithms apply. PowerIn must be less than PowerOut but greater than 0.

First, let PowerIn be fixed at 1 Joule.

Now, let PowerOut = 125J. Gain = 10 x log(125J/1J) = 20.97dB

Next, let PowerOut = 175J. Gain = 10 x log(175J/1J) = 22.43dB

This explains why your volume dial must be increased more to achieve the same SPL. By definition, increasing the output power of an amplifier when maintaining the same input power will result in a lower rate of gain. The output power on your new amplifiers is significantly high. The outputs on your Pioneer may not be at a level that is common to most high end preamplifiers, a condition that is far from optimal, thus causing the seemingly drastic lack of gain when adjusting the volume. This is why you need a lot of knob to give you a little bit of sound increase with the Pioneer / Emo setup.

Additionally, the Onkyo 9555's internal preamplifier is factory optimized to produce the maximum safe level of gain with respect to the amplifier section, hence why a little bit of knob gave you a lot of sound.

Enjoy your new stuff.

[bmwr75]

@SD - take breath bud.....you are going to pass out!!  Think I read this thread closely......and see no mention of a Pioneer preamp anywhere.  Did I miss this?

@OP -  there is no such thing as an Emotiva USP-2 preamp (per a Google search).  Maybe that is the problem.  Please list the actual Emotiva preamp and amp models you purchased.  I'm an Emotiva fan and own an XPA-2 amp and XDA-1 dac.