Measuring Amplifiers - Page 7

I just saw one on Cult this morning!

FS: Buttkicker BKA 1000-4A Amp
« Thread Started on Yesterday at 7:51pm »

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I'm selling my 1 month old BKA. Can't use it for my sub (only used it for 1 hour anyway). Asking $200 + shipping. Pay via M.O. or PayPal (add 3% for PayPal fee).

If you look at post 152, I did do a 1% THD test and that was at nominal line voltage (no variac). This amp has very poor FR so it is not really worth it to do it at any other frequency and 100 Hz was somewhat of a stretch for it. I believe it put out 'most' power between 30 & 40 Hz.

[quote=staffcurtis]chasw98, I was considering sending an Adcom GFA-585 for you to test. I would like to know your thoughts on the powe
I have tested 2 Adcom amps that Yuriv brought over one afternoon a while back. They were classic old school class AB amplifiers that have very low distortion and their rated wattage is usually exceeded by 20% or more in bench testing. They are exellent amplifiers but they are looked upon as 'under powered' in todays world.
The GFA 585 is seen as one of the best ever built by Adcom and still holds its vaue very well. Just look here .

If you would like for me to test it, I would absolutely do it for you. PM me for details.

Chuck

I am not sure I would place it below integrated receivers. The EP1500 is a dedicated power amp and produces 'mo better' power than an integrated receiver can because of a dedicated power supply, usually only producing 2 channels instead of 5 or 7, and no possible interference from other sections of the unit. To compare the power amp sections of an EP1500 to an HK235 is not really fair to either of them. But if you were to compare the L/R channels of an EP1500 to the L/R channels of an HK 235, I think you would find that the EP would sound better mostly because of increased headroom. You kind of have to get back to common sense and take the measured numbers as only one piece of the puzzle. The EP1500 measures 1%+ THD at 20 Khz at full power. The THD number quickly drops to inaudible (and unmeasurable) levels at normal usage. If, for instance, you are cruising along using 25 watts (a lot!) of amp power from both the HK or the EP and a 6 db transient comes in the music, which amp has the headroom to reproduce it? Not the HK according to numbers. That 6 db transient has just called for 100 watts from the amplifier for a time duration of as long as the transient lasts (could be short or long). If you were to measure the EP1500 and the HK 235 at 100 watts per channel (only 2 channels each) distortion and noise in the HK would be much worse than the EP. I would have to say that the EP1500 would run circles around almost any 100 watt/channel multichannel receiver out there. But then you would need 3 or 4 EP1500's to be equivalent and the space to put them in. Which means a multichannel receiver can sometimes be the easiest most convenient unit for a particular user and some will want a rack of dedicated power amps.

Oh and I have run tests on many receivers over the years (not too many lately), and I would have to say that every power amplifier, even the worst ones, are usually better than a receiver. Not always, but usually!

Chuck

The QSC amps are very good. But you will have better redundancy with 8 amps versus 2 amps. You would probably also tend to run 8 amps at less gain than 2 amps with more gain. That would depend on the use and the load you are going to drive. For instance if you had 8 drivers that would be driven by 8 mono bridge mode EP2500's, then you are looking at a nominal 4 ohm load per amplifier (2 ohm load per amplifier channel). If each amp had the gain set to the 50% mark, then you would relatively be working the amp very easy. With only 2 QSC amps, you would have 4 channels of amplification and therefore you would be running 2 drivers per channel. Each amp channel would see 2 ohms just like the EP2500's but you would only have 2 power supplies to feed those 4 channels of amp instead of 8 power supplies. I also would think that you would be running the QSC's at a higher gain level even though they produce more power. Don't forget your electric bill. The 8 EP2500's will draw some power, probably more than 2 QSC's that are more efficient.

This assumes 4 ohm drivers to be used in a subwoofer. Since you didn't tell every little nuance about the situation, I can only make broad conclusions. This is a Thylantr disclaimer lol

4 subs = 4 physical cabinets
A) dual 4 ohm coils = 1 driver with a dual 4 ohm voice coil per cabinet?
or B) 2 drivers with dual 4 ohm voice coils per cabinet equaling 4 total voice coils between 2 drivers.
or C) 4 subs having 2 each 4 ohm coils so that would mean 2 amps per sub.

With 4 subs and 2 EP2500's per sub running in bridged mono mode, you will get 4800 watts per cabinet "according to specs".
With 4 subs and 2 QSC PLX 3602 amps, you will get 1 channel per cabinet for a total of 1800 watts per cabinet "according to specs".

Even with the EP2500 not able to produce 2400 watts at steady sine wave, it will still put out as much as a single channel of the QSC. You will get tremendous headroon using 8 amps and 4 subs with 2 4 ohm drivers per sub.

Using the QSC, you will not get as much headroom and you will not get the flexibility to turn off some cabinets when you are watching I Love Lucy reruns.

Redundancy and headroom with EP2500 PLUS
8 amps wiring complexity and electricity used MINUS

Efficiency and simplicity with 2 QSC PLUS
Lack of headroom, redundancy, and flexibility MINUS

That is how I see it. If you were going to choose between 4 EP2500's and 2 QSC's, I would 100% say get the QSC's, but 8 EP2500's affords so much headroom that the amp will be running well below its limits and ratings. The wiring complexity will only occur when you set it up and should not plague you forever so that is a "one time" minus. Using a lot of electrcity is an "all the time" minus unless you only turn them on when needed. If you burn up or damage an amp, you are only out 1/8 th of your system with the EP's, whereas you are out 1/2 of your system with the QSC's.

What do you think?