My Big Ugly PA Amp: Yamaha P2250-C

DonQuixote99

DonQuixote99

just give me some truth
I wanted a big PA Amp--mainly, just because, though I think it will come in handy if I ever get the big 4-ohm Infinities I'm gonna get some day. Anyway, this critter caught my eye on e-Bay, based on it being a Yamaha amp available at less than $1 a watt. Makes a difference given my cash flow.

Bigness: it's rated at 175 WPC @ 8 ohms, 250 wpc @ 4-ohms. I figured that would do.

I'd love to know if it's really in shape to put out that sort of power, but not having any speakers that could remotely handle 175 watts, that's a bit of a problem. What I did for performance measurement was:
1. Set attenuation to 0 (maximum gain).
2. Set the pre-amp vol control @ -30 db (pretty loud).
3. Played the 1000 hz test tone from the Command test LP I've got.
4. Measured the voltage output on each channel.

Then for comparison, I did the same thing with my Adcom GFA-5300 (80 wpc).

The results basically, were in the same ballpark: around 3.3V for the Yamaha, 3.7V for the Adcom. A little surprising that the Adcom was a bit higher; guess it's a little more efficient at that level of input.

One thing I'm wondering: how to set the gain controls. For 'high quality music reproduction,' the owner's manual describes a process sttarting with a 1 khz signal at 'line level--1.23V.' Would that mean setting the preamp wide open--0 db attenuation, volume cranked all the way to the right, in other words? Anyway, I'm supposed to then advance the gain until I see clipping, then back off 20 db for headroom.
 

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I love those Yamaha power amps! Got a few of them, and I'd like quite a few more.

They're the most under-rated audiophile deal out there, IMO.

This is my new bedroom power-rack:

yamaha%20power.jpg~original


D2040
P2075
P2100
PC-5002M
 
OK, I did the procedure as I described it above: set preamp wide open, played 1000 Hz test tone, turned up gain until I say the clipping light start to flicker, backed off a bit. That was at 8 db attentuation on the gain control.

Before I did anything else, the woofer burned out on the test speaker I was using. Big stink! It was an Infinity RS-2001, an undistinguished unit that I've long used for hazardous things, like testing unknown amps for the first time. It has stood up to a lot, but this was too much.

I figured that taking that amp to clipping was risking something like that, and I was right....

Anyway, per the manual, I then backed the gain off to -28 db. With that setting, and the preamp set at about 90%, I played the first movement of Mahlers 'The Titan' as a dynamic range test. Speakers in use are Optimus T-70s, that have 90 db sensitivity.

Sounded great, and never had to adjust the volume, which is atypical for me when listening to Mahler. I'm always cranking it up for the soft parts, and dialing down in the loud parts. In this case, I found the soft parts audible, and the loud parts good and loud, a little louder than one would want for sustained listening, which is proper.

With more sensitive and heavy-duty speakers, one could really party, and still have the great dynamic range capability!
 
Adjustment of the gain controls isn't particularly critical (unless perhaps, you're setting up a major system for professional use).

Generally, though, it's better to use more range of the preamp volume control and lower gain setting on the amp than vice versa.
 
I used the same method as I do with a proper pa

Pro amp , both channels to the max, volume controlled by the preamp.

Works fine for me.
 
DonQuixote99 said:
Very nice! I assume you sleep in Madison Square Garden?
Click to expand...

10'x12' suburban bedroom. The speakers to be driven by it come home from my storage Sunday :)

DonQuixote99 said:
OK, I did the procedure as I described it above: set preamp wide open, played 1000 Hz test tone, turned up gain until I say the clipping light start to flicker, backed off a bit. That was at 8 db attentuation on the gain control.

Before I did anything else, the woofer burned out on the test speaker I was using. Big stink! It was an Infinity RS-2001, an undistinguished unit that I've long used for hazardous things, like testing unknown amps for the first time. It has stood up to a lot, but this was too much.

I figured that taking that amp to clipping was risking something like that, and I was right....

Anyway, per the manual, I then backed the gain off to -28 db. With that setting, and the preamp set at about 90%, I played the first movement of Mahlers 'The Titan' as a dynamic range test. Speakers in use are Optimus T-70s, that have 90 db sensitivity.

Sounded great, and never had to adjust the volume, which is atypical for me when listening to Mahler. I'm always cranking it up for the soft parts, and dialing down in the loud parts. In this case, I found the soft parts audible, and the loud parts good and loud, a little louder than one would want for sustained listening, which is proper.

With more sensitive and heavy-duty speakers, one could really party, and still have the great dynamic range capability!
Click to expand...

Regardless of what the manual says, I would *never* ever set gain this way. I set gain by ear, or just leave it wide open. I prefer to have the amp down low and the preamp up, which I know can "throw away" signal, but if something bad happens ahead of the preamp, the amp is already padded down.

With pro amps (or amps with level controls), I'm inclined to use the level controls for volume when not in a bi/tri/quad amped setup, and leave the preamp well enough alone, unless I need a drastic change.
 
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vinyldavid said:
I prefer to have the amp down low and the preamp up, which I know can "throw away" signal, but if something bad happens ahead of the preamp, the amp is already padded down.
Click to expand...

Uh, that's exactly the condition I am operating in. Amp is padded down, at -28 db. Preamp is run where I want up to and including fully up.
 
If i understand what the user manual for this amp is saying, the reason for finding the point just before clipping for a reference signal, then backing the gain down, is to get what they call headroom. They suggest 20 db of headroom for hi-fi music reproduction. What this headroom gives you, I think, is the ability to handle an input 20 db higher than the reference signal without clipping. Such very powerful signals occur as peaks corresponding to music reaching 120 db spl.
 
vinyldavid is the pro here but for me the question is whether the preamp can handle the signal swings with gain wide open. Preamp output stage is like a mini 2V amp and can compress and color just like a full blown amp.
 
DonQuixote99 said:
...not having any speakers that could remotely handle 175 watts, that's a bit of a problem...
Click to expand...

I don't think anyone's hearing could remotely handle 175 watts. :) You don't intend to use it fully cranked, do you? I have two Yorkville PA amps that sound pretty good.
 
SoCal Sam said:
vinyldavid is the pro here but for me the question is whether the preamp can handle the signal swings with gain wide open. Preamp output stage is like a mini 2V amp and can compress and color just like a full blown amp.
Click to expand...

I use really high efficiency speakers (for the most part). Volume knob stays between 8:00 and 12:00, most of the time. I doubt I'm running the preamp very hard at all. Though, there is one school of thought that throwing away the signal coming from the preamp is bad, I find that I get too much noise with my preferred speakers running everything wide open.
 
DonQuixote99 said:
OK, I did the procedure as I described it above: set preamp wide open, played 1000 Hz test tone, turned up gain until I say the clipping light start to flicker, backed off a bit. That was at 8 db attentuation on the gain control.

Before I did anything else, the woofer burned out on the test speaker I was using. Big stink! It was an Infinity RS-2001, an undistinguished unit that I've long used for hazardous things, like testing unknown amps for the first time. It has stood up to a lot, but this was too much.

I figured that taking that amp to clipping was risking something like that, and I was right....

Anyway, per the manual, I then backed the gain off to -28 db. With that setting, and the preamp set at about 90%, I played the first movement of Mahlers 'The Titan' as a dynamic range test. Speakers in use are Optimus T-70s, that have 90 db sensitivity.

Sounded great, and never had to adjust the volume, which is atypical for me when listening to Mahler. I'm always cranking it up for the soft parts, and dialing down in the loud parts. In this case, I found the soft parts audible, and the loud parts good and loud, a little louder than one would want for sustained listening, which is proper.

With more sensitive and heavy-duty speakers, one could really party, and still have the great dynamic range capability!
Click to expand...
Mahler sure can be problematic. Set a level that seems right for the quiet passages and the loud ones blow you out of the room.
 
Good find. I never manage to find Yamaha pro amps locally. You got really good amp.

Like dave, I just set gain according my ears. On my crown ce2000 I have it -33 (9 o'clock). While lot think that's low, it's more then enough to balance out noise and output. My speakers are 101db@1w with max spl of 150db@full output and my mixer puts out 9v rms even at the rca/unbalanced jacks and my source/audio interface is set at +4bu (1.4v) so even set at such low input on the amp itself it will gracefully still manage full output transition peaks and high output. An amp is capable of reaching full output even if input gain controls are near all the way down. It matters how rest of the system is. It's how the overall system is tune.
 
vinyldavid said:
I use really high efficiency speakers (for the most part). Volume knob stays between 8:00 and 12:00, most of the time. I doubt I'm running the preamp very hard at all. Though, there is one school of thought that throwing away the signal coming from the preamp is bad, I find that I get too much noise with my preferred speakers running everything wide open.
Click to expand...

I will experiment with turning down the preamp and turning the amp gain up. Since both controls are calibrated in db, turning the pre down 10db and turning the amp up 10db should result in similar performance to the way I've got it, I would think. But the preamp will not be up against it's limits, and adjustment up or down for program level will be available.

Speaker efficiency is a variable I don't recall being addressed in the owner's manual discussion. I'm sure the way I've been running things would knock the house down with 100 db spl speakers.
 
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